Band Gap Measurement of P – Type Monocrystalline Silicon Wafer

Available online at www.banglajol.info Bangladesh J. Sci. Ind. Res. 53(3), 179-184, 2018

Here, light emits from a tungsten-halogen lamp which is then And ni is the intrinsic carrier concentration of silicon = 1 x 1010 cm-3 From the highlighted color at least 3 wavelengths along with horizontal axis all these points will be in the same line use an equipment rather than its primary purpose. As spectral Sze S and Ng K (2007), Physics of Semiconductor Tauc J, Grigorovici R and Vancu A (1966), Optical focused onto the entrance slit of the monochromator using a (Vivien and Pavesi, 2013; NSM Archive Website) A.U (Arbitrary Unit) are needed to from a straight line. Here and slope will be the same. response measurement system can measure the band gap of Devices, 3rd Ed., John Wiley & Sons, Inc. New Properties and Electronic Structure of Amorphous condenser lens. Furthermore, a stepper motor is attached to Therefore, conduction band voltage Ec = 0.02584 ln it can easily be done using Microsoft Excel software. Just silicon the primary purpose of this work has been fulfilled. Jersey. Germanium, Phys. Stat. Sol. 15(2): 627-637. Band gap Measurement of P – type Monocrystalline Silicon Wafer the monochromator which rotates and varies the selecting and then removing the unnecessary points Furthermore, from spectral response of polished P-type monochromator output wavelength between 400 nm to 1200 (wavelengths) will easily form a straight line, which is monocrystalline silicon wafer absorption, reflection and Tauc J (1968), Optical Properties and Electronic Structure Vivien L and Pavesi L (2013), Handbook of Silicon nm. Also a SR540 optical chopper is placed at the exit slit of actually the negative slop (shown in Fig. 4). The negative transmission has been observed and the result has been of Amorphous Ge and Si, Mat. Res. Bull. Pergamon Photonics, CRC Press, Taylor and Francis Group, 1 2 2 1 the monochromator to provide reference signal to the SR510 G. Hashmi *, M. K. Basher , M. Hoq and M. H. Rahman slop formation wavelengths and associated A.U. are tabulated theoretically verified using Planck–Einstein relation. Press, Inc., USA 3: 37-46. DOI.org/ New York, USA. lock-in amplifier to ensure all the stray light is rejected by the in Table III. Now, extension of the negative slop will 10.1016/0025-5408(68)90023-8 1 system and enhance system sensitivity from nV to mV Department of Electrical and Electronic Engineering, University of Dhaka, Dhaka-1000 intersect the horizontal axis and will give away the required Acknowledgment range.The output from the monochromator is directed to the 2Institute of Electronics, AERE, Bangladesh Atomic Energy Commission, Savar, Dhaka wavelength. Lastly, by putting the value of the wavelength in material (silicon wafer) with a simple rotatable mirror. After The authors thank Bangladesh Atomic Energy Commission that, the reflected Planck-Einstein equation the band gap of P-type monocrystalline silicon wafer can be determined. for granting access to one and only solar cell fabrication Abstract laboratory at Atomic Energy Research Establishment, Savar, Bangladesh and to do research with Spectral Response Band gap of P-type monocrystalline silicon wafer has been measured using spectral response 1.12 eV, absorption decreases and reflection increases. At Measurement Equipment. This work has been supported by measurement system. To see the spectral response a SR510 lock in amplifier, SR540 optical chopper, 975 nm, peak is observed, where reflection is highest. After the scholarship program of the ICT Division, Ministry of monochromator (400nm-1200nm), optical detector and lab view software has been used. From infrared region photon energy is lower than band gap of Now putting the wavelength value in equation 2 Posts, Telecommunications and IT, Government of spectral response of polished P-type monocrystalline silicon wafer absorption, reflection and happen it will depend upon refractive index, absorption silicon (1.12eV) so transmittance happen, so roll off of (Planck-Einstein equation) we get, Bangladesh. Finally, the authors also express their gratitude transmission has been respectively seen from 400nm-550nm, 550nm-1050nm and 1050-1200nm. coefficient, thickness, surface roughness etc. of the spectral response is seen. Procedure of Band gap measurement to the Faculty of Engineering and Technology and Assuming band gap of silicon is (1.12eV), this result has been theoretically verified using Band gap measurement semiconductor material. Moreover, if һf = Eg then electron Band Gap = = 1.127907 eV ; which is the Department of Electrical and Electronic Engineering, Planck–Einstein relation. Moreover, theoretical band gap of silicon has been calculated (1.127362 hole pair is created and light is efficiently absorbed. Whereas, Literature review and theoretical calculation of band gap of To determine the band gap of P-type monocrystalline University of Dhaka for taking such initiative to do this kind silicon From the spectral response measurement system, the data band gap of P-type monocrystalline silicon wafer. Received: 07 August 2017 eV). The band gap measurement process uses partial concept of Tauc’s downhill negative slop and if һf < Egthen light interact weakly and pass through the polished silicon wafer, the spectral response of P-type of research. Planck–Einstein relation. Experimental result shows that, the band gap of silicon is 1.127907 eV. semiconductor as if it was a transparent material. So to see, of P-type monocrystalline silicon wafer has been Revised: 08 October 2017 Although most of the books and journals specified band gap monocrystalline silicon wafer needs to be drawn first. From these relationship, the Planck-Einstein equation has been successfully obtained and tabulated in Table II. References Accepted: 31 January 2018 the Table II data the spectral response curve has been drawn However, the theoretical calculation shows the band gap of used to determine the photon energy of different wavelength of silicon as 1.12 eV, literature review of band gap of silicon Moreover, with that data the spectral response curve has Keywords: Spectral response; Band gap; Planck-Einstein equation; Silicon wafer; Intrinsic suggested that the band gap of silicon varies from 1.11 eV to silicon is 1.127362 eV. So the error is by the following equation. been proficiently drawn in Microsoft Excel. However, in Microsoft Excel. Next, drawing of a negative slope along Darmont A (2009), Spectral Response of Silicon Image DOI: http://dx.doi.org/10.3329/bjsir.v53i3.38263 carrier concentration 1.13 eV. This is due to the fact that, as temperature varies, the the experimentally obtained data directly does not provide the downhill part of the spectral response of P-type Sensors, White paper, Aphesa. intrinsic carrier concentration (n ), effective density of states E = һf …. (1) i the band gap of silicon. monocrystalline polished silicon wafer is necessary, as × 100 = 0.04834%, which can be of the conduction band (N ) and effective density of states of Introduction c shown in Fig. 3. Dharma J and Pisal A (2009), Simple Method of Where һ is the Planck constant, E is the photon energy and f the valance band (N ) also varies. The theoretical and v There are various techniques like UV-VIS spectroscopy, considered negligible. So from spectral response easurement Measuring the Band Gap Energy Value of TiO2 in is the associated wave frequency. experimental of these values are considered different in One of the most important properties of a semiconductor theoretically calculated which is 1.127362 eV. There are light falls upon a large convex lens close to the surface of the Tauc’s plot and equation, reflection, and absorption books and journals and that’s why the band gap of silicon system band gap of P-type monocrystalline silicon can be the Powder Form using a UV/Vis/NIR which distinguish it from metals and insulators is band various techniques like UV-VIS spectroscopy, Tauc’s material thus collecting the reflected and scattered light coefficient or spectra, four point probe etc. are used to varies from 1.11 eV to 1.13eV. However, it is suffice to say successfully measured. Spectrometer, PerkinElmer, Inc., U.S.A. gap. Band gap is defined as the energy difference (in eV) plot and equation, reflection, and absorption coefficient which is then focused onto an optical detector. The optical determine the band gap of semiconductor. Nevertheless, detector (which converts optical signal to electrical signal) is that the band gap of silicon will always lie between 1.11 eV between the top of upper band (valence band) and the or spectra, four point probe etc. are used to determine the in all the band gap measurement cases the technique and McEvoy A, Markvart T and Castaner L (2012), Practical connected to SR510 lock-in amplifier for measurement to 1.13eV. Conclusion bottom of the lower band (conduction band) in insulators band gap of semiconductor. But here only partial the data used to find the band gap of semiconductor are Handbook of Photovoltaics: Fundamentals and through the LabVIEW interface. Here, LabVIEW interface is and semiconductors (Streetman, 1993). Furthermore, concepts of Tauc’s method has been used. Additionally, different as the data are not collected form spectral nd used for system control, data acquisition and to view the Although the relative reflectivity is normally measured by Applications, 2 Ed., Academic Press, Elsevier, band Gap measurement has a significant role in spectral response of polished P-type monocrystalline response measurement system. spectral response of the material. The primary purpose of the spectral response measurement system, it is seen that band UK. semiconductor, nanomaterial and solar cell fabrication silicon wafer has been investigated. Then this result was spectral response measurement system is to plot the spectral So, a new approach has been applied to measure the band gap of polished P-type monocrystalline silicon wafer can also industries (Dharma and Pisal, 2009). As band gap theoretically verified after calculating the photon energy Neamen D (2003), Semiconductor Physics and Devices: response of a material and then from the plotted graph gap of P-type monocrystalline silicon using spectral be measured by this system. Experimental measurement measuring equipment’s are very pricy sometimes with Planck–Einstein relation and relating the photon From equation (2) photon energy of different wavelength Basic Principles, 3rd Ed., McGraw-Hill, New York. relative reflectivity (in respect to mirror) can be obtained. along with its corresponding frequency and color are Where K is the Boltzmann constant, T is the temperature in Kelvin response measurement system. Apart from spectral shows band gap of silicon is 1.127907eV. Whereas, resource management is necessary. For this purpose, the energy with band gap of silicon (1.12eV). Results and discussion calculated and tabulated in Table I. and q is the electron charge in coulomb. response measurement system’s data, partial concept of theoretical calculated value is 1.127362 eV. As error is main goal of this research work has been to utilize an Spectral response of polished P - type monocrystalline silicon Now, the conduction band energy at intrinsic level is determined by NSM Archive, http://www.ioffe.ru/ SVA/ NSM/ Description of spectral response measurement system Tauc’s band gap measurement process is used in this band By extending the negative slope, it interests a point in 0.04834%, it can be considered as negligible. With this Semicond/ Si/ bandstr.html equipment rather than its primary purpose. Although, the wafer Now, the band gap of silicon is 1.12 eV (Sze et al., 2007; the following equation gap measurement process. Major difference between the horizontal axis.This intersection point in the spectral response measurement system the absorption primary purpose of spectral response measurement The spectral response measurement system, as shown in NSM Archive, Website). So, photon energy more than 1.12 Tauc’s band gap measurement process (Tauc, 1968) and horizontal axis is the required wavelength.To find out coefficient cannot be determined, so direct and indirect band Rogers B, Adams J and Pennathur S (2015), system is to measure the spectral response of a material, Figure 1, is composed of a SR510 lock in amplifier, Figure 2 shows the spectral response of polished P-type eV will get highly absorbed. Therefore when 400-550nm this work is that, Tauc’s band gap measurement process gap semiconductor identification is not possible. But, it can Nanotechnology: Understanding Small Systems, 3rd this system has been used to measure the band gap of SR540 optical chopper, monochromator monocrystalline silicon wafer. To interpret the spectral (violet to green, photon energy 2.75-2.50 eV) wavelength the intersection point of horizontal axis, it is uses the photon energy (eV) vs. absorption coefficient be concluded that spectral response measurement equipment Ed., CRC Press, New York. P-type monocrystalline silicon wafer. The measurement response one has to understand about the relationship falls on the P-type wafer, these wavelength is highly considered that P1 (1050, 2.840405); P2 (1075, (400nm-1200nm), optical detector and lab view software. plot of the material whereas here, arbitrary unit (A.U.) shows that, the band gap of polished P-type between photon energy and band gap. It is seen that, if the Now, to draw the negative slop along the downhill spectral 1.890594); P (λ, 0) these three points are in the same can be used as a band gap measurement equipment if the This system emits and directs lights upon a material and absorbed. As the wavelength increases (from red to infrared 3 rd Where, Nc is the conduction band state concentration (at intrinsic) = and wavelength (λ) of the material has been used to semiconductor material spectral response lies between 400 Streetman B (1993), Solid State Electronic Devices, 3 monocrystalline silicon wafer is 1.127907 eV. form the reflected lights it determines the spectral (photon energy) һf > Eg (Band gap) then absorption will wavelength (550-1050nm)) the photon energy eV becomes response, downhill part spectral data are selected from Table line. It is only possible if and only if the slope for both 2.86 x 1019 (cm-3) (McEvoy et al., 2012) determine the band gap of semiconductor. Ed., Prentice-Hall of India, New Delhi. Furthermore, the band gap of silicon has been response of a material (Darmont, 2009). happen (Rogers et al., 2015). How much absorption will lower and as photon energy become close to silicon band gap II (Highlighted by yellow color). the lines are same. As λ is the intersection point of nm to 1200 nm. The main purpose of this work has been to

*Corresponding author e-mail: [email protected] 180 Band gap Measurement of P – type Monocrystalline Silicon Wafer 53(3) 2018

Here, light emits from a tungsten-halogen lamp which is then And ni is the intrinsic carrier concentration of silicon = 1 x 1010 cm-3 From the highlighted color at least 3 wavelengths along with horizontal axis all these points will be in the same line use an equipment rather than its primary purpose. As spectral Sze S and Ng K (2007), Physics of Semiconductor Tauc J, Grigorovici R and Vancu A (1966), Optical focused onto the entrance slit of the monochromator using a (Vivien and Pavesi, 2013; NSM Archive Website) A.U (Arbitrary Unit) are needed to from a straight line. Here and slope will be the same. response measurement system can measure the band gap of Devices, 3rd Ed., John Wiley & Sons, Inc. New Properties and Electronic Structure of Amorphous condenser lens. Furthermore, a stepper motor is attached to Therefore, conduction band voltage Ec = 0.02584 ln it can easily be done using Microsoft Excel software. Just silicon the primary purpose of this work has been fulfilled. Jersey. Germanium, Phys. Stat. Sol. 15(2): 627-637. the monochromator which rotates and varies the selecting and then removing the unnecessary points Furthermore, from spectral response of polished P-type monochromator output wavelength between 400 nm to 1200 (wavelengths) will easily form a straight line, which is monocrystalline silicon wafer absorption, reflection and Tauc J (1968), Optical Properties and Electronic Structure Vivien L and Pavesi L (2013), Handbook of Silicon nm. Also a SR540 optical chopper is placed at the exit slit of actually the negative slop (shown in Fig. 4). The negative transmission has been observed and the result has been of Amorphous Ge and Si, Mat. Res. Bull. Pergamon Photonics, CRC Press, Taylor and Francis Group, the monochromator to provide reference signal to the SR510 slop formation wavelengths and associated A.U. are tabulated theoretically verified using Planck–Einstein relation. Press, Inc., USA 3: 37-46. DOI.org/ New York, USA. lock-in amplifier to ensure all the stray light is rejected by the in Table III. Now, extension of the negative slop will 10.1016/0025-5408(68)90023-8 system and enhance system sensitivity from nV to mV intersect the horizontal axis and will give away the required Acknowledgment range.The output from the monochromator is directed to the wavelength. Lastly, by putting the value of the wavelength in material (silicon wafer) with a simple rotatable mirror. After The authors thank Bangladesh Atomic Energy Commission that, the reflected Planck-Einstein equation the band gap of P-type monocrystalline silicon wafer can be determined. for granting access to one and only solar cell fabrication laboratory at Atomic Energy Research Establishment, Savar, Bangladesh and to do research with Spectral Response Fig. 2. Spectral response of polished p - type Measurement Equipment. This work has been supported by monocrystalline silicon wafer 1.12 eV, absorption decreases and reflection increases. At 975 nm, peak is observed, where reflection is highest. After the scholarship program of the ICT Division, Ministry of infrared region photon energy is lower than band gap of Now putting the wavelength value in equation 2 Posts, Telecommunications and IT, Government of happen it will depend upon refractive index, absorption silicon (1.12eV) so transmittance happen, so roll off of (Planck-Einstein equation) we get, Bangladesh. Finally, the authors also express their gratitude coefficient, thickness, surface roughness etc. of the spectral response is seen. Procedure of Band gap measurement to the Faculty of Engineering and Technology and Band gap measurement semiconductor material. Moreover, if һf = Eg then electron Band Gap = = 1.127907 eV ; which is the Department of Electrical and Electronic Engineering, hole pair is created and light is efficiently absorbed. Whereas, Literature review and theoretical calculation of band gap of To determine the band gap of P-type monocrystalline University of Dhaka for taking such initiative to do this kind silicon From the spectral response measurement system, the data band gap of P-type monocrystalline silicon wafer. if һf < Egthen light interact weakly and pass through the polished silicon wafer, the spectral response of P-type of research. of P-type monocrystalline silicon wafer has been semiconductor as if it was a transparent material. So to see, monocrystalline silicon wafer needs to be drawn first. From these relationship, the Planck-Einstein equation has been Although most of the books and journals specified band gap successfully obtained and tabulated in Table II. the Table II data the spectral response curve has been drawn However, the theoretical calculation shows the band gap of References used to determine the photon energy of different wavelength of silicon as 1.12 eV, literature review of band gap of silicon Moreover, with that data the spectral response curve has suggested that the band gap of silicon varies from 1.11 eV to silicon is 1.127362 eV. So the error is by the following equation. been proficiently drawn in Microsoft Excel. However, in Microsoft Excel. Next, drawing of a negative slope along Darmont A (2009), Spectral Response of Silicon Image 1.13 eV. This is due to the fact that, as temperature varies, the Fig. 1. Schematic diagram of spectral response the experimentally obtained data directly does not provide the downhill part of the spectral response of P-type Sensors, White paper, Aphesa. intrinsic carrier concentration (n ), effective density of states measurement system E = һf …. (1) i the band gap of silicon. monocrystalline polished silicon wafer is necessary, as × 100 = 0.04834%, which can be of the conduction band (N ) and effective density of states of c shown in Fig. 3. Dharma J and Pisal A (2009), Simple Method of Where һ is the Planck constant, E is the photon energy and f the valance band (N ) also varies. The theoretical and v There are various techniques like UV-VIS spectroscopy, considered negligible. So from spectral response easurement Measuring the Band Gap Energy Value of TiO2 in light falls upon a large convex lens close to the surface of the is the associated wave frequency. experimental of these values are considered different in Tauc’s plot and equation, reflection, and absorption system band gap of P-type monocrystalline silicon can be the Powder Form using a UV/Vis/NIR material thus collecting the reflected and scattered light books and journals and that’s why the band gap of silicon coefficient or spectra, four point probe etc. are used to successfully measured. Spectrometer, PerkinElmer, Inc., U.S.A. which is then focused onto an optical detector. The optical varies from 1.11 eV to 1.13eV. However, it is suffice to say determine the band gap of semiconductor. Nevertheless, detector (which converts optical signal to electrical signal) is that the band gap of silicon will always lie between 1.11 eV in all the band gap measurement cases the technique and McEvoy A, Markvart T and Castaner L (2012), Practical connected to SR510 lock-in amplifier for measurement to 1.13eV. Conclusion the data used to find the band gap of semiconductor are Handbook of Photovoltaics: Fundamentals and through the LabVIEW interface. Here, LabVIEW interface is different as the data are not collected form spectral nd Although the relative reflectivity is normally measured by Applications, 2 Ed., Academic Press, Elsevier, used for system control, data acquisition and to view the response measurement system. spectral response of the material. The primary purpose of the spectral response measurement system, it is seen that band UK. spectral response measurement system is to plot the spectral gap of polished P-type monocrystalline silicon wafer can also So, a new approach has been applied to measure the band Neamen D (2003), Semiconductor Physics and Devices: response of a material and then from the plotted graph gap of P-type monocrystalline silicon using spectral be measured by this system. Experimental measurement From equation (2) photon energy of different wavelength Basic Principles, 3rd Ed., McGraw-Hill, New York. relative reflectivity (in respect to mirror) can be obtained. Where K is the Boltzmann constant, T is the temperature in Kelvin shows band gap of silicon is 1.127907eV. Whereas, along with its corresponding frequency and color are response measurement system. Apart from spectral Results and discussion calculated and tabulated in Table I. and q is the electron charge in coulomb. response measurement system’s data, partial concept of theoretical calculated value is 1.127362 eV. As error is Spectral response of polished P - type monocrystalline silicon Now, the conduction band energy at intrinsic level is determined by NSM Archive, http://www.ioffe.ru/ SVA/ NSM/ Tauc’s band gap measurement process is used in this band By extending the negative slope, it interests a point in 0.04834%, it can be considered as negligible. With this Semicond/ Si/ bandstr.html wafer Now, the band gap of silicon is 1.12 eV (Sze et al., 2007; the following equation gap measurement process. Major difference between the horizontal axis.This intersection point in the spectral response measurement system the absorption NSM Archive, Website). So, photon energy more than 1.12 Tauc’s band gap measurement process (Tauc, 1968) and coefficient cannot be determined, so direct and indirect band Rogers B, Adams J and Pennathur S (2015), Figure 2 shows the spectral response of polished P-type eV will get highly absorbed. Therefore when 400-550nm horizontal axis is the required wavelength.To find out this work is that, Tauc’s band gap measurement process gap semiconductor identification is not possible. But, it can Nanotechnology: Understanding Small Systems, 3rd monocrystalline silicon wafer. To interpret the spectral (violet to green, photon energy 2.75-2.50 eV) wavelength the intersection point of horizontal axis, it is uses the photon energy (eV) vs. absorption coefficient be concluded that spectral response measurement equipment Ed., CRC Press, New York. response one has to understand about the relationship falls on the P-type wafer, these wavelength is highly considered that P1 (1050, 2.840405); P2 (1075, plot of the material whereas here, arbitrary unit (A.U.) between photon energy and band gap. It is seen that, if the Now, to draw the negative slop along the downhill spectral 1.890594); P (λ, 0) these three points are in the same can be used as a band gap measurement equipment if the absorbed. As the wavelength increases (from red to infrared 3 rd Where, Nc is the conduction band state concentration (at intrinsic) = and wavelength (λ) of the material has been used to semiconductor material spectral response lies between 400 Streetman B (1993), Solid State Electronic Devices, 3 (photon energy) һf > Eg (Band gap) then absorption will wavelength (550-1050nm)) the photon energy eV becomes response, downhill part spectral data are selected from Table line. It is only possible if and only if the slope for both 19 -3 determine the band gap of semiconductor. happen (Rogers et al., 2015). How much absorption will lower and as photon energy become close to silicon band gap 2.86 x 10 (cm ) (McEvoy et al., 2012) II (Highlighted by yellow color). the lines are same. As λ is the intersection point of nm to 1200 nm. The main purpose of this work has been to Ed., Prentice-Hall of India, New Delhi. Hashmi, Basher, Hoq and Rahman 181

Here, light emits from a tungsten-halogen lamp which is then And ni is the intrinsic carrier concentration of silicon = 1 x 1010 cm-3 From the highlighted color at least 3 wavelengths along with horizontal axis all these points will be in the same line use an equipment rather than its primary purpose. As spectral Sze S and Ng K (2007), Physics of Semiconductor Tauc J, Grigorovici R and Vancu A (1966), Optical focused onto the entrance slit of the monochromator using a Table I. Photon energy of different wavelength along with (Vivien and Pavesi, 2013; NSM Archive Website) A.U (Arbitrary Unit) are needed to from a straight line. Here and slope will be the same. response measurement system can measure the band gap of Devices, 3rd Ed., John Wiley & Sons, Inc. New Properties and Electronic Structure of Amorphous condenser lens. Furthermore, a stepper motor is attached to its corresponding frequency and color Therefore, conduction band voltage Ec = 0.02584 ln it can easily be done using Microsoft Excel software. Just silicon the primary purpose of this work has been fulfilled. Jersey. Germanium, Phys. Stat. Sol. 15(2): 627-637. the monochromator which rotates and varies the selecting and then removing the unnecessary points Photon Furthermore, from spectral response of polished P-type monochromator output wavelength between 400 nm to 1200 Color Wavelength Frequency energy (wavelengths) will easily form a straight line, which is monocrystalline silicon wafer absorption, reflection and Tauc J (1968), Optical Properties and Electronic Structure Vivien L and Pavesi L (2013), Handbook of Silicon nm. Also a SR540 optical chopper is placed at the exit slit of actually the negative slop (shown in Fig. 4). The negative transmission has been observed and the result has been of Amorphous Ge and Si, Mat. Res. Bull. Pergamon Photonics, CRC Press, Taylor and Francis Group, the monochromator to provide reference signal to the SR510 violet 380 –450 nm 668 –789 THz 2.75 –3.26 eV blue 450 –495 nm 606 –668 THz 2.50 –2.75 eV slop formation wavelengths and associated A.U. are tabulated theoretically verified using Planck–Einstein relation. Press, Inc., USA 3: 37-46. DOI.org/ New York, USA. lock-in amplifier to ensure all the stray light is rejected by the in Table III. Now, extension of the negative slop will 10.1016/0025-5408(68)90023-8 system and enhance system sensitivity from nV to mV green 495 –570 nm 526 –606 THz 2.17 –2.50 eV intersect the horizontal axis and will give away the required Acknowledgment range.The output from the monochromator is directed to the yellow 570 –590 nm 508 –526 THz 2.10 –2.17 eV orange 590 –620 nm 484 –508 THz 2.00 –2.10 eV wavelength. Lastly, by putting the value of the wavelength in material (silicon wafer) with a simple rotatable mirror. After The authors thank Bangladesh Atomic Energy Commission that, the reflected red 620 –750 nm 400 –484 THz 1.65 –2.00 eV Planck-Einstein equation the band gap of P-type 700 -1050 430 THz -300 1.24 mili eV - monocrystalline silicon wafer can be determined. for granting access to one and only solar cell fabrication infrared nm GHz 1.7eV laboratory at Atomic Energy Research Establishment, Savar, Bangladesh and to do research with Spectral Response 1.12 eV, absorption decreases and reflection increases. At Measurement Equipment. This work has been supported by 975 nm, peak is observed, where reflection is highest. After the scholarship program of the ICT Division, Ministry of infrared region photon energy is lower than band gap of Now putting the wavelength value in equation 2 Posts, Telecommunications and IT, Government of happen it will depend upon refractive index, absorption silicon (1.12eV) so transmittance happen, so roll off of (Planck-Einstein equation) we get, Bangladesh. Finally, the authors also express their gratitude coefficient, thickness, surface roughness etc. of the spectral response is seen. Procedure of Band gap measurement to the Faculty of Engineering and Technology and Band gap measurement semiconductor material. Moreover, if һf = Eg then electron Band Gap = = 1.127907 eV ; which is the Department of Electrical and Electronic Engineering, hole pair is created and light is efficiently absorbed. Whereas, Literature review and theoretical calculation of band gap of To determine the band gap of P-type monocrystalline University of Dhaka for taking such initiative to do this kind silicon From the spectral response measurement system, the data band gap of P-type monocrystalline silicon wafer. if һf < Egthen light interact weakly and pass through the polished silicon wafer, the spectral response of P-type of research. of P-type monocrystalline silicon wafer has been semiconductor as if it was a transparent material. So to see, monocrystalline silicon wafer needs to be drawn first. From these relationship, the Planck-Einstein equation has been Although most of the books and journals specified band gap successfully obtained and tabulated in Table II. the Table II data the spectral response curve has been drawn However, the theoretical calculation shows the band gap of References used to determine the photon energy of different wavelength of silicon as 1.12 eV, literature review of band gap of silicon Moreover, with that data the spectral response curve has suggested that the band gap of silicon varies from 1.11 eV to silicon is 1.127362 eV. So the error is by the following equation. been proficiently drawn in Microsoft Excel. However, in Microsoft Excel. Next, drawing of a negative slope along Darmont A (2009), Spectral Response of Silicon Image 1.13 eV. This is due to the fact that, as temperature varies, the the experimentally obtained data directly does not provide the downhill part of the spectral response of P-type Sensors, White paper, Aphesa. intrinsic carrier concentration (n ), effective density of states E = һf …. (1) i the band gap of silicon. monocrystalline polished silicon wafer is necessary, as × 100 = 0.04834%, which can be of the conduction band (N ) and effective density of states of c shown in Fig. 3. Dharma J and Pisal A (2009), Simple Method of Where һ is the Planck constant, E is the photon energy and f the valance band (N ) also varies. The theoretical and v There are various techniques like UV-VIS spectroscopy, considered negligible. So from spectral response easurement Measuring the Band Gap Energy Value of TiO2 in light falls upon a large convex lens close to the surface of the is the associated wave frequency. experimental of these values are considered different in Tauc’s plot and equation, reflection, and absorption system band gap of P-type monocrystalline silicon can be the Powder Form using a UV/Vis/NIR material thus collecting the reflected and scattered light books and journals and that’s why the band gap of silicon coefficient or spectra, four point probe etc. are used to successfully measured. Spectrometer, PerkinElmer, Inc., U.S.A. which is then focused onto an optical detector. The optical varies from 1.11 eV to 1.13eV. However, it is suffice to say determine the band gap of semiconductor. Nevertheless, detector (which converts optical signal to electrical signal) is that the band gap of silicon will always lie between 1.11 eV in all the band gap measurement cases the technique and McEvoy A, Markvart T and Castaner L (2012), Practical connected to SR510 lock-in amplifier for measurement to 1.13eV. Conclusion the data used to find the band gap of semiconductor are Handbook of Photovoltaics: Fundamentals and through the LabVIEW interface. Here, LabVIEW interface is different as the data are not collected form spectral nd Although the relative reflectivity is normally measured by Applications, 2 Ed., Academic Press, Elsevier, used for system control, data acquisition and to view the response measurement system. spectral response of the material. The primary purpose of the spectral response measurement system, it is seen that band UK. spectral response measurement system is to plot the spectral gap of polished P-type monocrystalline silicon wafer can also So, a new approach has been applied to measure the band Neamen D (2003), Semiconductor Physics and Devices: response of a material and then from the plotted graph gap of P-type monocrystalline silicon using spectral be measured by this system. Experimental measurement From equation (2) photon energy of different wavelength Basic Principles, 3rd Ed., McGraw-Hill, New York. relative reflectivity (in respect to mirror) can be obtained. Where K is the Boltzmann constant, T is the temperature in Kelvin shows band gap of silicon is 1.127907eV. Whereas, along with its corresponding frequency and color are response measurement system. Apart from spectral Results and discussion calculated and tabulated in Table I. and q is the electron charge in coulomb. response measurement system’s data, partial concept of theoretical calculated value is 1.127362 eV. As error is Spectral response of polished P - type monocrystalline silicon Now, the conduction band energy at intrinsic level is determined by NSM Archive, http://www.ioffe.ru/ SVA/ NSM/ Tauc’s band gap measurement process is used in this band By extending the negative slope, it interests a point in 0.04834%, it can be considered as negligible. With this Semicond/ Si/ bandstr.html wafer Now, the band gap of silicon is 1.12 eV (Sze et al., 2007; the following equation gap measurement process. Major difference between the horizontal axis.This intersection point in the spectral response measurement system the absorption NSM Archive, Website). So, photon energy more than 1.12 Tauc’s band gap measurement process (Tauc, 1968) and coefficient cannot be determined, so direct and indirect band Rogers B, Adams J and Pennathur S (2015), Figure 2 shows the spectral response of polished P-type eV will get highly absorbed. Therefore when 400-550nm horizontal axis is the required wavelength.To find out this work is that, Tauc’s band gap measurement process gap semiconductor identification is not possible. But, it can Nanotechnology: Understanding Small Systems, 3rd monocrystalline silicon wafer. To interpret the spectral (violet to green, photon energy 2.75-2.50 eV) wavelength the intersection point of horizontal axis, it is uses the photon energy (eV) vs. absorption coefficient be concluded that spectral response measurement equipment Ed., CRC Press, New York. response one has to understand about the relationship falls on the P-type wafer, these wavelength is highly considered that P1 (1050, 2.840405); P2 (1075, plot of the material whereas here, arbitrary unit (A.U.) between photon energy and band gap. It is seen that, if the Now, to draw the negative slop along the downhill spectral 1.890594); P (λ, 0) these three points are in the same can be used as a band gap measurement equipment if the absorbed. As the wavelength increases (from red to infrared 3 rd Where, Nc is the conduction band state concentration (at intrinsic) = and wavelength (λ) of the material has been used to semiconductor material spectral response lies between 400 Streetman B (1993), Solid State Electronic Devices, 3 (photon energy) һf > Eg (Band gap) then absorption will wavelength (550-1050nm)) the photon energy eV becomes response, downhill part spectral data are selected from Table line. It is only possible if and only if the slope for both 19 -3 determine the band gap of semiconductor. happen (Rogers et al., 2015). How much absorption will lower and as photon energy become close to silicon band gap 2.86 x 10 (cm ) (McEvoy et al., 2012) II (Highlighted by yellow color). the lines are same. As λ is the intersection point of nm to 1200 nm. The main purpose of this work has been to Ed., Prentice-Hall of India, New Delhi. 182 Band gap Measurement of P – type Monocrystalline Silicon Wafer 53(3) 2018

10 -3 Here, light emits from a tungsten-halogen lamp which is then And ni is the intrinsic carrier concentration of silicon = 1 x 10 cm Table II. Spectral response data of P-type monocrystalline From the highlighted color at least 3 wavelengths along with horizontal axis all these points will be in the same line use an equipment rather than its primary purpose. As spectral Sze S and Ng K (2007), Physics of Semiconductor Tauc J, Grigorovici R and Vancu A (1966), Optical rd focused onto the entrance slit of the monochromator using a (Vivien and Pavesi, 2013; NSM Archive Website) polished silicon wafer A.U (Arbitrary Unit) are needed to from a straight line. Here and slope will be the same. response measurement system can measure the band gap of Devices, 3 Ed., John Wiley & Sons, Inc. New Properties and Electronic Structure of Amorphous condenser lens. Furthermore, a stepper motor is attached to Therefore, conduction band voltage Ec = 0.02584 ln it can easily be done using Microsoft Excel software. Just silicon the primary purpose of this work has been fulfilled. Jersey. Germanium, Phys. Stat. Sol. 15(2): 627-637. the monochromator which rotates and varies the λ(nm) A.U. λ (nm) A.U. λ (nm) A.U. λ A.U. selecting and then removing the unnecessary points Furthermore, from spectral response of polished P-type monochromator output wavelength between 400 nm to 1200 (nm) (wavelengths) will easily form a straight line, which is monocrystalline silicon wafer absorption, reflection and Tauc J (1968), Optical Properties and Electronic Structure Vivien L and Pavesi L (2013), Handbook of Silicon nm. Also a SR540 optical chopper is placed at the exit slit of 400 0.05 625 1.53 850 3.12 1075 1.89 actually the negative slop (shown in Fig. 4). The negative transmission has been observed and the result has been of Amorphous Ge and Si, Mat. Res. Bull. Pergamon Photonics, CRC Press, Taylor and Francis Group, the monochromator to provide reference signal to the SR510 slop formation wavelengths and associated A.U. are tabulated Press, Inc., USA 3: 37-46. DOI.org/ New York, USA. 425 0.07 650 1.78 875 3.40 1100 1.23 theoretically verified using Planck–Einstein relation. lock-in amplifier to ensure all the stray light is rejected by the in Table III. Now, extension of the negative slop will 10.1016/0025-5408(68)90023-8 system and enhance system sensitivity from nV to mV 450 0.12 675 2.13 900 3.74 1125 0.76 intersect the horizontal axis and will give away the required Acknowledgment range.The output from the monochromator is directed to the 475 0.23 700 2.63 925 3.98 1150 0.45 wavelength. Lastly, by putting the value of the wavelength in material (silicon wafer) with a simple rotatable mirror. After Planck-Einstein equation the band gap of P-type The authors thank Bangladesh Atomic Energy Commission that, the reflected 500 0.36 725 2.85 950 4.14 1175 0.25 monocrystalline silicon wafer can be determined. for granting access to one and only solar cell fabrication 525 0.55 750 2.98 975 4.19 1200 0.23 laboratory at Atomic Energy Research Establishment, Savar, 550 0.76 775 2.99 1000 4.10 1075 1.89 Table III. The three wavelengths and associated A.U. Bangladesh and to do research with Spectral Response which form the negative slope 1.12 eV, absorption decreases and reflection increases. At 575 1.024 800 2.99 1025 3.72 1100 1.23 Measurement Equipment. This work has been supported by the scholarship program of the ICT Division, Ministry of 975 nm, peak is observed, where reflection is highest. After 600 1.28 825 3.00 1050 2.84 1125 0.76 infrared region photon energy is lower than band gap of Wavelength Arbitrary Now putting the wavelength value in equation 2 Posts, Telecommunications and IT, Government of happen it will depend upon refractive index, absorption silicon (1.12eV) so transmittance happen, so roll off of (nm) unit (Planck-Einstein equation) we get, Bangladesh. Finally, the authors also express their gratitude coefficient, thickness, surface roughness etc. of the spectral response is seen. Procedure of Band gap measurement (A.U.) to the Faculty of Engineering and Technology and Band gap measurement semiconductor material. Moreover, if һf = Eg then electron Band Gap = = 1.127907 eV ; which is the Department of Electrical and Electronic Engineering, hole pair is created and light is efficiently absorbed. Whereas, Literature review and theoretical calculation of band gap of To determine the band gap of P-type monocrystalline 1025 3.724194 University of Dhaka for taking such initiative to do this kind silicon From the spectral response measurement system, the data band gap of P-type monocrystalline silicon wafer. if һf < Egthen light interact weakly and pass through the polished silicon wafer, the spectral response of P-type of research. of P-type monocrystalline silicon wafer has been 1050 2.840405 semiconductor as if it was a transparent material. So to see, monocrystalline silicon wafer needs to be drawn first. From these relationship, the Planck-Einstein equation has been Although most of the books and journals specified band gap successfully obtained and tabulated in Table II. the Table II data the spectral response curve has been drawn However, the theoretical calculation shows the band gap of References used to determine the photon energy of different wavelength of silicon as 1.12 eV, literature review of band gap of silicon Moreover, with that data the spectral response curve has 1075 1.890594 silicon is 1.127362 eV. So the error is by the following equation. suggested that the band gap of silicon varies from 1.11 eV to been proficiently drawn in Microsoft Excel. However, in Microsoft Excel. Next, drawing of a negative slope along Darmont A (2009), Spectral Response of Silicon Image 1.13 eV. This is due to the fact that, as temperature varies, the the experimentally obtained data directly does not provide the downhill part of the spectral response of P-type Sensors, White paper, Aphesa. intrinsic carrier concentration (n ), effective density of states E = һf …. (1) i the band gap of silicon. monocrystalline polished silicon wafer is necessary, as × 100 = 0.04834%, which can be of the conduction band (N ) and effective density of states of c shown in Fig. 3. Dharma J and Pisal A (2009), Simple Method of Where һ is the Planck constant, E is the photon energy and f the valance band (N ) also varies. The theoretical and v There are various techniques like UV-VIS spectroscopy, considered negligible. So from spectral response easurement Measuring the Band Gap Energy Value of TiO2 in light falls upon a large convex lens close to the surface of the is the associated wave frequency. experimental of these values are considered different in Tauc’s plot and equation, reflection, and absorption system band gap of P-type monocrystalline silicon can be the Powder Form using a UV/Vis/NIR material thus collecting the reflected and scattered light books and journals and that’s why the band gap of silicon coefficient or spectra, four point probe etc. are used to successfully measured. Spectrometer, PerkinElmer, Inc., U.S.A. which is then focused onto an optical detector. The optical varies from 1.11 eV to 1.13eV. However, it is suffice to say determine the band gap of semiconductor. Nevertheless, that the band gap of silicon will always lie between 1.11 eV detector (which converts optical signal to electrical signal) is in all the band gap measurement cases the technique and McEvoy A, Markvart T and Castaner L (2012), Practical connected to SR510 lock-in amplifier for measurement to 1.13eV. Conclusion the data used to find the band gap of semiconductor are Handbook of Photovoltaics: Fundamentals and through the LabVIEW interface. Here, LabVIEW interface is different as the data are not collected form spectral nd Although the relative reflectivity is normally measured by Applications, 2 Ed., Academic Press, Elsevier, used for system control, data acquisition and to view the response measurement system. spectral response of the material. The primary purpose of the Fig. 4. Negative slope spectral response measurement system, it is seen that band UK. spectral response measurement system is to plot the spectral gap of polished P-type monocrystalline silicon wafer can also So, a new approach has been applied to measure the band Neamen D (2003), Semiconductor Physics and Devices: response of a material and then from the plotted graph gap of P-type monocrystalline silicon using spectral be measured by this system. Experimental measurement From equation (2) photon energy of different wavelength Basic Principles, 3rd Ed., McGraw-Hill, New York. relative reflectivity (in respect to mirror) can be obtained. Where K is the Boltzmann constant, T is the temperature in Kelvin shows band gap of silicon is 1.127907eV. Whereas, along with its corresponding frequency and color are response measurement system. Apart from spectral Results and discussion calculated and tabulated in Table I. and q is the electron charge in coulomb. response measurement system’s data, partial concept of theoretical calculated value is 1.127362 eV. As error is Spectral response of polished P - type monocrystalline silicon Now, the conduction band energy at intrinsic level is determined by NSM Archive, http://www.ioffe.ru/ SVA/ NSM/ Tauc’s band gap measurement process is used in this band By extending the negative slope, it interests a point in 0.04834%, it can be considered as negligible. With this Semicond/ Si/ bandstr.html wafer Now, the band gap of silicon is 1.12 eV (Sze et al., 2007; the following equation Fig. 3. Negative slope drawn along downhill part of gap measurement process. Major difference between the horizontal axis.This intersection point in the spectral response measurement system the absorption NSM Archive, Website). So, photon energy more than 1.12 spectral response of polished p - type Tauc’s band gap measurement process (Tauc, 1968) and coefficient cannot be determined, so direct and indirect band Rogers B, Adams J and Pennathur S (2015), Figure 2 shows the spectral response of polished P-type eV will get highly absorbed. Therefore when 400-550nm monocrystalline silicon wafer horizontal axis is the required wavelength.To find out this work is that, Tauc’s band gap measurement process gap semiconductor identification is not possible. But, it can Nanotechnology: Understanding Small Systems, 3rd monocrystalline silicon wafer. To interpret the spectral (violet to green, photon energy 2.75-2.50 eV) wavelength the intersection point of horizontal axis, it is uses the photon energy (eV) vs. absorption coefficient be concluded that spectral response measurement equipment Ed., CRC Press, New York. response one has to understand about the relationship falls on the P-type wafer, these wavelength is highly considered that P1 (1050, 2.840405); P2 (1075, plot of the material whereas here, arbitrary unit (A.U.) between photon energy and band gap. It is seen that, if the Now, to draw the negative slop along the downhill spectral 1.890594); P (λ, 0) these three points are in the same can be used as a band gap measurement equipment if the absorbed. As the wavelength increases (from red to infrared 3 rd Where, Nc is the conduction band state concentration (at intrinsic) = and wavelength (λ) of the material has been used to semiconductor material spectral response lies between 400 Streetman B (1993), Solid State Electronic Devices, 3 (photon energy) һf > Eg (Band gap) then absorption will wavelength (550-1050nm)) the photon energy eV becomes response, downhill part spectral data are selected from Table line. It is only possible if and only if the slope for both 19 -3 determine the band gap of semiconductor. happen (Rogers et al., 2015). How much absorption will lower and as photon energy become close to silicon band gap 2.86 x 10 (cm ) (McEvoy et al., 2012) II (Highlighted by yellow color). the lines are same. As λ is the intersection point of nm to 1200 nm. The main purpose of this work has been to Ed., Prentice-Hall of India, New Delhi. Hashmi, Basher, Hoq and Rahman 183

Here, light emits from a tungsten-halogen lamp which is then And ni is the intrinsic carrier concentration of silicon = 1 x 1010 cm-3 From the highlighted color at least 3 wavelengths along with horizontal axis all these points will be in the same line use an equipment rather than its primary purpose. As spectral Sze S and Ng K (2007), Physics of Semiconductor Tauc J, Grigorovici R and Vancu A (1966), Optical focused onto the entrance slit of the monochromator using a (Vivien and Pavesi, 2013; NSM Archive Website) A.U (Arbitrary Unit) are needed to from a straight line. Here and slope will be the same. response measurement system can measure the band gap of Devices, 3rd Ed., John Wiley & Sons, Inc. New Properties and Electronic Structure of Amorphous condenser lens. Furthermore, a stepper motor is attached to Therefore, conduction band voltage Ec = 0.02584 ln it can easily be done using Microsoft Excel software. Just silicon the primary purpose of this work has been fulfilled. Jersey. Germanium, Phys. Stat. Sol. 15(2): 627-637. the monochromator which rotates and varies the selecting and then removing the unnecessary points Furthermore, from spectral response of polished P-type monochromator output wavelength between 400 nm to 1200 (wavelengths) will easily form a straight line, which is monocrystalline silicon wafer absorption, reflection and Tauc J (1968), Optical Properties and Electronic Structure Vivien L and Pavesi L (2013), Handbook of Silicon nm. Also a SR540 optical chopper is placed at the exit slit of actually the negative slop (shown in Fig. 4). The negative transmission has been observed and the result has been of Amorphous Ge and Si, Mat. Res. Bull. Pergamon Photonics, CRC Press, Taylor and Francis Group, the monochromator to provide reference signal to the SR510 slop formation wavelengths and associated A.U. are tabulated theoretically verified using Planck–Einstein relation. Press, Inc., USA 3: 37-46. DOI.org/ New York, USA. lock-in amplifier to ensure all the stray light is rejected by the in Table III. Now, extension of the negative slop will 10.1016/0025-5408(68)90023-8 system and enhance system sensitivity from nV to mV intersect the horizontal axis and will give away the required Acknowledgment range.The output from the monochromator is directed to the wavelength. Lastly, by putting the value of the wavelength in material (silicon wafer) with a simple rotatable mirror. After The authors thank Bangladesh Atomic Energy Commission that, the reflected Planck-Einstein equation the band gap of P-type monocrystalline silicon wafer can be determined. for granting access to one and only solar cell fabrication laboratory at Atomic Energy Research Establishment, Savar, Bangladesh and to do research with Spectral Response 1.12 eV, absorption decreases and reflection increases. At Measurement Equipment. This work has been supported by 975 nm, peak is observed, where reflection is highest. After the scholarship program of the ICT Division, Ministry of infrared region photon energy is lower than band gap of Now putting the wavelength value in equation 2 Posts, Telecommunications and IT, Government of happen it will depend upon refractive index, absorption silicon (1.12eV) so transmittance happen, so roll off of (Planck-Einstein equation) we get, Bangladesh. Finally, the authors also express their gratitude coefficient, thickness, surface roughness etc. of the spectral response is seen. Procedure of Band gap measurement to the Faculty of Engineering and Technology and 1239.84193 semiconductor material. Moreover, if һf = E then electron Band gap measurement Band Gap = = 1.127907 eV ; which is the Department of Electrical and Electronic Engineering, g 1099.240734 hole pair is created and light is efficiently absorbed. Whereas, Literature review and theoretical calculation of band gap of To determine the band gap of P-type monocrystalline University of Dhaka for taking such initiative to do this kind silicon From the spectral response measurement system, the data band gap of P-type monocrystalline silicon wafer. if һf < Egthen light interact weakly and pass through the polished silicon wafer, the spectral response of P-type of research. of P-type monocrystalline silicon wafer has been semiconductor as if it was a transparent material. So to see, monocrystalline silicon wafer needs to be drawn first. From these relationship, the Planck-Einstein equation has been Although most of the books and journals specified band gap successfully obtained and tabulated in Table II. the Table II data the spectral response curve has been drawn However, the theoretical calculation shows the band gap of References used to determine the photon energy of different wavelength of silicon as 1.12 eV, literature review of band gap of silicon Moreover, with that data the spectral response curve has silicon is 1.127362 eV. So the error is by the following equation. suggested that the band gap of silicon varies from 1.11 eV to been proficiently drawn in Microsoft Excel. However, in Microsoft Excel. Next, drawing of a negative slope along Darmont A (2009), Spectral Response of Silicon Image 1.13 eV. This is due to the fact that, as temperature varies, the the experimentally obtained data directly does not provide the downhill part of the spectral response of P-type Sensors, White paper, Aphesa. intrinsic carrier concentration (n ), effective density of states 1.127907-1.127362 E = һf …. (1) i the band gap of silicon. monocrystalline polished silicon wafer is necessary, as × 100 = 0.04834%, which can be of the conduction band (N ) and effective density of states of 1.127362 c shown in Fig. 3. Dharma J and Pisal A (2009), Simple Method of Where һ is the Planck constant, E is the photon energy and f the valance band (N ) also varies. The theoretical and v There are various techniques like UV-VIS spectroscopy, considered negligible. So from spectral response easurement Measuring the Band Gap Energy Value of TiO2 in light falls upon a large convex lens close to the surface of the is the associated wave frequency. experimental of these values are considered different in Tauc’s plot and equation, reflection, and absorption system band gap of P-type monocrystalline silicon can be the Powder Form using a UV/Vis/NIR material thus collecting the reflected and scattered light books and journals and that’s why the band gap of silicon coefficient or spectra, four point probe etc. are used to successfully measured. Spectrometer, PerkinElmer, Inc., U.S.A. which is then focused onto an optical detector. The optical varies from 1.11 eV to 1.13eV. However, it is suffice to say determine the band gap of semiconductor. Nevertheless, that the band gap of silicon will always lie between 1.11 eV detector (which converts optical signal to electrical signal) is in all the band gap measurement cases the technique and McEvoy A, Markvart T and Castaner L (2012), Practical connected to SR510 lock-in amplifier for measurement to 1.13eV. Conclusion the data used to find the band gap of semiconductor are Handbook of Photovoltaics: Fundamentals and through the LabVIEW interface. Here, LabVIEW interface is different as the data are not collected form spectral nd Although the relative reflectivity is normally measured by Applications, 2 Ed., Academic Press, Elsevier, used for system control, data acquisition and to view the response measurement system. spectral response of the material. The primary purpose of the spectral response measurement system, it is seen that band UK. spectral response measurement system is to plot the spectral gap of polished P-type monocrystalline silicon wafer can also So, a new approach has been applied to measure the band Neamen D (2003), Semiconductor Physics and Devices: response of a material and then from the plotted graph gap of P-type monocrystalline silicon using spectral be measured by this system. Experimental measurement From equation (2) photon energy of different wavelength Basic Principles, 3rd Ed., McGraw-Hill, New York. relative reflectivity (in respect to mirror) can be obtained. Where K is the Boltzmann constant, T is the temperature in Kelvin shows band gap of silicon is 1.127907eV. Whereas, along with its corresponding frequency and color are response measurement system. Apart from spectral Results and discussion calculated and tabulated in Table I. and q is the electron charge in coulomb. response measurement system’s data, partial concept of theoretical calculated value is 1.127362 eV. As error is Spectral response of polished P - type monocrystalline silicon Now, the conduction band energy at intrinsic level is determined by NSM Archive, http://www.ioffe.ru/ SVA/ NSM/ Tauc’s band gap measurement process is used in this band By extending the negative slope, it interests a point in 0.04834%, it can be considered as negligible. With this Semicond/ Si/ bandstr.html wafer Now, the band gap of silicon is 1.12 eV (Sze et al., 2007; the following equation gap measurement process. Major difference between the horizontal axis.This intersection point in the spectral response measurement system the absorption NSM Archive, Website). So, photon energy more than 1.12 Tauc’s band gap measurement process (Tauc, 1968) and coefficient cannot be determined, so direct and indirect band Rogers B, Adams J and Pennathur S (2015), Figure 2 shows the spectral response of polished P-type eV will get highly absorbed. Therefore when 400-550nm horizontal axis is the required wavelength.To find out this work is that, Tauc’s band gap measurement process gap semiconductor identification is not possible. But, it can Nanotechnology: Understanding Small Systems, 3rd monocrystalline silicon wafer. To interpret the spectral (violet to green, photon energy 2.75-2.50 eV) wavelength the intersection point of horizontal axis, it is uses the photon energy (eV) vs. absorption coefficient be concluded that spectral response measurement equipment Ed., CRC Press, New York. response one has to understand about the relationship falls on the P-type wafer, these wavelength is highly considered that P1 (1050, 2.840405); P2 (1075, plot of the material whereas here, arbitrary unit (A.U.) between photon energy and band gap. It is seen that, if the Now, to draw the negative slop along the downhill spectral 1.890594); P (λ, 0) these three points are in the same can be used as a band gap measurement equipment if the absorbed. As the wavelength increases (from red to infrared 3 rd Where, Nc is the conduction band state concentration (at intrinsic) = and wavelength (λ) of the material has been used to semiconductor material spectral response lies between 400 Streetman B (1993), Solid State Electronic Devices, 3 (photon energy) һf > Eg (Band gap) then absorption will wavelength (550-1050nm)) the photon energy eV becomes response, downhill part spectral data are selected from Table line. It is only possible if and only if the slope for both 19 -3 determine the band gap of semiconductor. happen (Rogers et al., 2015). How much absorption will lower and as photon energy become close to silicon band gap 2.86 x 10 (cm ) (McEvoy et al., 2012) II (Highlighted by yellow color). the lines are same. As λ is the intersection point of nm to 1200 nm. The main purpose of this work has been to Ed., Prentice-Hall of India, New Delhi. 184 Band gap Measurement of P – type Monocrystalline Silicon Wafer 53(3) 2018

Here, light emits from a tungsten-halogen lamp which is then And ni is the intrinsic carrier concentration of silicon = 1 x 1010 cm-3 From the highlighted color at least 3 wavelengths along with horizontal axis all these points will be in the same line use an equipment rather than its primary purpose. As spectral Sze S and Ng K (2007), Physics of Semiconductor Tauc J, Grigorovici R and Vancu A (1966), Optical focused onto the entrance slit of the monochromator using a (Vivien and Pavesi, 2013; NSM Archive Website) A.U (Arbitrary Unit) are needed to from a straight line. Here and slope will be the same. response measurement system can measure the band gap of Devices, 3rd Ed., John Wiley & Sons, Inc. New Properties and Electronic Structure of Amorphous condenser lens. Furthermore, a stepper motor is attached to Therefore, conduction band voltage Ec = 0.02584 ln it can easily be done using Microsoft Excel software. Just silicon the primary purpose of this work has been fulfilled. Jersey. Germanium, Phys. Stat. Sol. 15(2): 627-637. the monochromator which rotates and varies the selecting and then removing the unnecessary points Furthermore, from spectral response of polished P-type monochromator output wavelength between 400 nm to 1200 (wavelengths) will easily form a straight line, which is monocrystalline silicon wafer absorption, reflection and Tauc J (1968), Optical Properties and Electronic Structure Vivien L and Pavesi L (2013), Handbook of Silicon nm. Also a SR540 optical chopper is placed at the exit slit of actually the negative slop (shown in Fig. 4). The negative transmission has been observed and the result has been of Amorphous Ge and Si, Mat. Res. Bull. Pergamon Photonics, CRC Press, Taylor and Francis Group, the monochromator to provide reference signal to the SR510 slop formation wavelengths and associated A.U. are tabulated theoretically verified using Planck–Einstein relation. Press, Inc., USA 3: 37-46. DOI.org/ New York, USA. lock-in amplifier to ensure all the stray light is rejected by the in Table III. Now, extension of the negative slop will 10.1016/0025-5408(68)90023-8 system and enhance system sensitivity from nV to mV intersect the horizontal axis and will give away the required Acknowledgment range.The output from the monochromator is directed to the wavelength. Lastly, by putting the value of the wavelength in material (silicon wafer) with a simple rotatable mirror. After The authors thank Bangladesh Atomic Energy Commission that, the reflected Planck-Einstein equation the band gap of P-type monocrystalline silicon wafer can be determined. for granting access to one and only solar cell fabrication laboratory at Atomic Energy Research Establishment, Savar, Bangladesh and to do research with Spectral Response 1.12 eV, absorption decreases and reflection increases. At Measurement Equipment. This work has been supported by 975 nm, peak is observed, where reflection is highest. After the scholarship program of the ICT Division, Ministry of infrared region photon energy is lower than band gap of Now putting the wavelength value in equation 2 Posts, Telecommunications and IT, Government of happen it will depend upon refractive index, absorption silicon (1.12eV) so transmittance happen, so roll off of (Planck-Einstein equation) we get, Bangladesh. Finally, the authors also express their gratitude coefficient, thickness, surface roughness etc. of the spectral response is seen. Procedure of Band gap measurement to the Faculty of Engineering and Technology and Band gap measurement semiconductor material. Moreover, if һf = Eg then electron Band Gap = = 1.127907 eV ; which is the Department of Electrical and Electronic Engineering, hole pair is created and light is efficiently absorbed. Whereas, Literature review and theoretical calculation of band gap of To determine the band gap of P-type monocrystalline University of Dhaka for taking such initiative to do this kind silicon From the spectral response measurement system, the data band gap of P-type monocrystalline silicon wafer. if һf < Egthen light interact weakly and pass through the polished silicon wafer, the spectral response of P-type of research. of P-type monocrystalline silicon wafer has been semiconductor as if it was a transparent material. So to see, monocrystalline silicon wafer needs to be drawn first. From these relationship, the Planck-Einstein equation has been Although most of the books and journals specified band gap successfully obtained and tabulated in Table II. the Table II data the spectral response curve has been drawn However, the theoretical calculation shows the band gap of References used to determine the photon energy of different wavelength of silicon as 1.12 eV, literature review of band gap of silicon Moreover, with that data the spectral response curve has suggested that the band gap of silicon varies from 1.11 eV to silicon is 1.127362 eV. So the error is by the following equation. been proficiently drawn in Microsoft Excel. However, in Microsoft Excel. Next, drawing of a negative slope along Darmont A (2009), Spectral Response of Silicon Image 1.13 eV. This is due to the fact that, as temperature varies, the the experimentally obtained data directly does not provide the downhill part of the spectral response of P-type Sensors, White paper, Aphesa. intrinsic carrier concentration (n ), effective density of states E = һf …. (1) i the band gap of silicon. monocrystalline polished silicon wafer is necessary, as × 100 = 0.04834%, which can be of the conduction band (N ) and effective density of states of c shown in Fig. 3. Dharma J and Pisal A (2009), Simple Method of Where һ is the Planck constant, E is the photon energy and f the valance band (N ) also varies. The theoretical and v There are various techniques like UV-VIS spectroscopy, considered negligible. So from spectral response easurement Measuring the Band Gap Energy Value of TiO2 in light falls upon a large convex lens close to the surface of the is the associated wave frequency. experimental of these values are considered different in Tauc’s plot and equation, reflection, and absorption system band gap of P-type monocrystalline silicon can be the Powder Form using a UV/Vis/NIR material thus collecting the reflected and scattered light books and journals and that’s why the band gap of silicon coefficient or spectra, four point probe etc. are used to successfully measured. Spectrometer, PerkinElmer, Inc., U.S.A. which is then focused onto an optical detector. The optical varies from 1.11 eV to 1.13eV. However, it is suffice to say determine the band gap of semiconductor. Nevertheless, detector (which converts optical signal to electrical signal) is that the band gap of silicon will always lie between 1.11 eV in all the band gap measurement cases the technique and McEvoy A, Markvart T and Castaner L (2012), Practical connected to SR510 lock-in amplifier for measurement to 1.13eV. Conclusion the data used to find the band gap of semiconductor are Handbook of Photovoltaics: Fundamentals and through the LabVIEW interface. Here, LabVIEW interface is different as the data are not collected form spectral nd Although the relative reflectivity is normally measured by Applications, 2 Ed., Academic Press, Elsevier, used for system control, data acquisition and to view the response measurement system. spectral response of the material. The primary purpose of the spectral response measurement system, it is seen that band UK. spectral response measurement system is to plot the spectral gap of polished P-type monocrystalline silicon wafer can also So, a new approach has been applied to measure the band Neamen D (2003), Semiconductor Physics and Devices: response of a material and then from the plotted graph gap of P-type monocrystalline silicon using spectral be measured by this system. Experimental measurement From equation (2) photon energy of different wavelength Basic Principles, 3rd Ed., McGraw-Hill, New York. relative reflectivity (in respect to mirror) can be obtained. Where K is the Boltzmann constant, T is the temperature in Kelvin shows band gap of silicon is 1.127907eV. Whereas, along with its corresponding frequency and color are response measurement system. Apart from spectral Results and discussion calculated and tabulated in Table I. and q is the electron charge in coulomb. response measurement system’s data, partial concept of theoretical calculated value is 1.127362 eV. As error is Spectral response of polished P - type monocrystalline silicon Now, the conduction band energy at intrinsic level is determined by NSM Archive, http://www.ioffe.ru/ SVA/ NSM/ Tauc’s band gap measurement process is used in this band By extending the negative slope, it interests a point in 0.04834%, it can be considered as negligible. With this Semicond/ Si/ bandstr.html wafer Now, the band gap of silicon is 1.12 eV (Sze et al., 2007; the following equation gap measurement process. Major difference between the horizontal axis.This intersection point in the spectral response measurement system the absorption NSM Archive, Website). So, photon energy more than 1.12 Tauc’s band gap measurement process (Tauc, 1968) and coefficient cannot be determined, so direct and indirect band Rogers B, Adams J and Pennathur S (2015), Figure 2 shows the spectral response of polished P-type eV will get highly absorbed. Therefore when 400-550nm horizontal axis is the required wavelength.To find out this work is that, Tauc’s band gap measurement process gap semiconductor identification is not possible. But, it can Nanotechnology: Understanding Small Systems, 3rd monocrystalline silicon wafer. To interpret the spectral (violet to green, photon energy 2.75-2.50 eV) wavelength the intersection point of horizontal axis, it is uses the photon energy (eV) vs. absorption coefficient be concluded that spectral response measurement equipment Ed., CRC Press, New York. response one has to understand about the relationship falls on the P-type wafer, these wavelength is highly considered that P1 (1050, 2.840405); P2 (1075, plot of the material whereas here, arbitrary unit (A.U.) between photon energy and band gap. It is seen that, if the Now, to draw the negative slop along the downhill spectral 1.890594); P (λ, 0) these three points are in the same can be used as a band gap measurement equipment if the absorbed. As the wavelength increases (from red to infrared 3 rd Where, Nc is the conduction band state concentration (at intrinsic) = and wavelength (λ) of the material has been used to semiconductor material spectral response lies between 400 Streetman B (1993), Solid State Electronic Devices, 3 (photon energy) һf > Eg (Band gap) then absorption will wavelength (550-1050nm)) the photon energy eV becomes response, downhill part spectral data are selected from Table line. It is only possible if and only if the slope for both 19 -3 determine the band gap of semiconductor. happen (Rogers et al., 2015). How much absorption will lower and as photon energy become close to silicon band gap 2.86 x 10 (cm ) (McEvoy et al., 2012) II (Highlighted by yellow color). the lines are same. As λ is the intersection point of nm to 1200 nm. The main purpose of this work has been to Ed., Prentice-Hall of India, New Delhi.