Light Emitting Diode
Total Page:16
File Type:pdf, Size:1020Kb
Load more
Recommended publications
-
Semiconductor Heterostructures and Their Application
Zhores Alferov The History of Semiconductor Heterostructures Reserch: from Early Double Heterostructure Concept to Modern Quantum Dot Structures St Petersburg Academic University — Nanotechnology Research and Education Centre RAS • Introduction • Transistor discovery • Discovery of laser-maser principle and birth of optoelectronics • Heterostructure early proposals • Double heterostructure concept: classical, quantum well and superlattice heterostructure. “God-made” and “Man-made” crystals • Heterostructure electronics • Quantum dot heterostructures and development of quantum dot lasers • Future trends in heterostructure technology • Summary 2 The Nobel Prize in Physics 1956 "for their researches on semiconductors and their discovery of the transistor effect" William Bradford John Walter Houser Shockley Bardeen Brattain 1910–1989 1908–1991 1902–1987 3 4 5 6 W. Shockley and A. Ioffe. Prague. 1960. 7 The Nobel Prize in Physics 1964 "for fundamental work in the field of quantum electronics, which has led to the construction of oscillators and amplifiers based on the maser-laser principle" Charles Hard Nicolay Aleksandr Townes Basov Prokhorov b. 1915 1922–2001 1916–2002 8 9 Proposals of semiconductor injection lasers • N. Basov, O. Krochin and Yu. Popov (Lebedev Institute, USSR Academy of Sciences, Moscow) JETP, 40, 1879 (1961) • M.G.A. Bernard and G. Duraffourg (Centre National d’Etudes des Telecommunications, Issy-les-Moulineaux, Seine) Physica Status Solidi, 1, 699 (1961) 10 Lasers and LEDs on p–n junctions • January 1962: observations -
Wide Band Gap Materials: Revolution in Automotive Power Electronics
20169052 16mm Wide Band Gap Materials: Revolution in Automotive Power Electronics Luca Bartolomeo 1) Luigi Abbatelli 2) Michele Macauda 2) Filippo Di Giovanni 2) Giuseppe Catalisano 2) Miroslav Ryzek 3) Daniel Kohout 3) 1) STMicroelectronics Japan, Shinagawa INTERCITY Tower A, 2-15-1, Konan, Minato-ku, 108-6017 Tokyo, Japan (E-mail: [email protected]) 2) STMicroelectronics , Italy 3) STMicroelectronics , Czech Republic ④④④ ④④④ Presented at the EVTeC and APE Japan on May 26, 2016 ABSTRACT : The number of Electric and Hybrid vehicles on the roads is increasing year over year. The role of power electronics is of paramount importance to improve their efficiency, keeping lighter and smaller systems. In this paper, the authors will specifically cover the use of Wide Band Gap (WBG) materials in Electric and Hybrid vehicles. It will be shown how SiC MOSFETs bring significant benefits compared to standard IGBTs silicon technology, in both efficiency and form factor. Comparison of the main electrical characteristics, between SiC-based and IGBT module, were simulated and validated by experimental tests in a real automotive environment. KEY WORDS : SiC, Wide Band Gap, IGBT, Power Module 1. INTRODUCTION When considering power transistors in the high voltage range Nowadays, an increased efficiency demand is required in (above 600V), SiC MOSFETs are an excellent alternative to the power electronics applications to have lighter and smaller standard silicon devices: they guarantee lower RON*Area values systems and to improve the range of new Electric (EV) and compared to the latest silicon-based Super-Junction MOSFETs, Hybrid vehicles (HEV). There is an on-going revolution in the especially in high temperature environment (1). -
Towards Direct-Gap Silicon Phases by the Inverse Band Structure Design Approach
Towards Direct-Gap Silicon Phases by the Inverse Band Structure Design Approach H. J. Xiang1,2*, Bing Huang2, Erjun Kan3, Su-Huai Wei2, X. G. Gong1 1 Key Laboratory of Computational Physical Sciences (Ministry of Education), State Key Laboratory of Surface Physics, and Department of Physics, Fudan University, Shanghai 200433, P. R. China 2National Renewable Energy Laboratory, Golden, Colorado 80401, USA 3Department of Applied Physics, Nanjing University of Science and Technology, Nanjing, Jiangsu 210094, People’s Republic of China e-mail: [email protected] Abstract Diamond silicon (Si) is the leading material in current solar cell market. However, diamond Si is an indirect band gap semiconductor with a large energy difference (2.4 eV) between the direct gap and the indirect gap, which makes it an inefficient absorber of light. In this work, we develop a novel inverse-band structure design approach based on the particle swarming optimization algorithm to predict the metastable Si phases with better optical properties than diamond Si. Using our new method, we predict a cubic Si20 phase with quasi- direct gaps of 1.55 eV, which is a promising candidate for making thin-film solar cells. PACS: 71.20.-b,42.79.Ek,78.20.Ci,88.40.jj 1 Due to the high stability, high abundance, and the existence of an excellent compatible oxide (SiO2), Si is the leading material of microelectronic devices. Currently, the majority of solar cells fabricated to date have also been based on diamond Si in monocrystalline or large- grained polycrystalline form [1]. There are mainly two reasons for this: First, Si is the second most abundant element in the earth's crust; Second, the Si based photovoltaics (PV) industry could benefit from the successful Si based microelectronics industry. -
CSE- Module-3: SEMICONDUCTOR LIGHT EMITTING DIODE :LED (5Lectures)
CSE-Module- 3:LED PHYSICS CSE- Module-3: SEMICONDUCTOR LIGHT EMITTING DIODE :LED (5Lectures) Light Emitting Diodes (LEDs) Light Emitting Diodes (LEDs) are semiconductors p-n junction operating under proper forward biased conditions and are capable of emitting external spontaneous radiations in the visible range (370 nm to 770 nm) or the nearby ultraviolet and infrared regions of the electromagnetic spectrum General Structure LEDs are special diodes that emit light when connected in a circuit. They are frequently used as “pilot light” in electronic appliances in to indicate whether the circuit is closed or not. The structure and circuit symbol is shown in Fig.1. The two wires extending below the LED epoxy enclose or the “bulb” indicate how the LED should be connected into a circuit or not. The negative side of the LED is indicated in two ways (1) by the flat side of the bulb and (2) by the shorter of the two wires extending from the LED. The negative lead should be connected to the negative terminal of a battery. LEDs operate at relative low voltage between 1 and 4 volts, and draw current between 10 and 40 milliamperes. Voltages and Fig.-1 : Structure of LED current substantially above these values can melt a LED chip. The most important part of a light emitting diode (LED) is the semiconductor chip located in the centre of the bulb and is attached to the 1 CSE-Module- 3:LED top of the anvil. The chip has two regions separated by a junction. The p- region is dominated by positive electric charges, and the n-region is dominated by negative electric charges. -
The Band Gap of Silicon
Norton 0 The Band Gap of Silicon Matthew Norton, Erin Stefanik, Ryan Allured, and Drew Sulski Norton 1 Abstract This experiment was designed to find the band gap of silicon as well as the charge of an electron. A transistor was heated to various temperatures using a hot plate. The resistance was measured over the resistor and transistor in the circuit. In performing this experiment, it was found that the band gap of silicon was (1.10 ± 0.08) eV. In performing this experiment, it was also found that the charge of an electron was (1.77 ± 0.20) × 10 −19 C. Introduction When a substance is placed under the influence of an electric field, it can portray insulating, semi-conducting, semi-metallic, or metallic properties. Every crystalline structure has electrons that occupy energy bands. In a semiconductor, there is a gap in energy between valence band and the bottom of the conduction band. There are no allowed energy states for the electron within the energy gap. At absolute zero, all the electrons have energies within the valence band and the material it is insulating. As the temperature increases electrons gain enough energy to occupy the energy levels in the conduction band. The current through a transistor is given by the equation, qV I= I e kT − 1 0 (1) where I0 is the maximum current for a large reverse bias voltage, q is the charge of the electron, k is the Boltzmann constant, and T is the temperature in Kelvin. As long as V is not too large, the current depends only on the number of minority carriers in the conduction band and the rate at which they diffuse. -
Wide Band-Gap Semiconductor Based Power Electronics for Energy Efficiency
Wide Band-Gap Semiconductor Based Power Electronics for Energy Efficiency Isik C. Kizilyalli, Eric P. Carlson, Daniel W. Cunningham, Joseph S. Manser, Yanzhi “Ann” Xu, Alan Y. Liu March 13, 2018 United States Department of Energy Washington, DC 20585 TABLE OF CONTENTS Abstract 2 Introduction 2 Technical Opportunity 2 Application Space 4 Evolution of ARPA-E’s Focused Programs in Power Electronics 6 Broad Exploration of Power Electronics Landscape - ADEPT 7 Solar Photovoltaics Applications – Solar ADEPT 10 Wide-Bandgap Materials and Devices – SWITCHES 11 Addressing Material Challenges - PNDIODES 16 System-Level Advances - CIRCUITS 18 Impacts 21 Conclusions 22 Appendix: ARPA-E Power Electronics Projects 23 ABSTRACT The U.S. Department of Energy’s Advanced Research Project Agency for Energy (ARPA-E) was established in 2009 to fund creative, out-of-the-box, transformational energy technologies that are too early for private-sector investment at make-or break points in their technology development cycle. Development of advanced power electronics with unprecedented functionality, efficiency, reliability, and reduced form factor are required in an increasingly electrified world economy. Fast switching power semiconductor devices are the key to increasing the efficiency and reducing the size of power electronic systems. Recent advances in wide band-gap (WBG) semiconductor materials, such as silicon carbide (SiC) and gallium nitride (GaN) are enabling a new genera- tion of power semiconductor devices that far exceed the performance of silicon-based devices. Past ARPA-E programs (ADEPT, Solar ADEPT, and SWITCHES) have enabled innovations throughout the power electronics value chain, especially in the area of WBG semiconductors. The two recently launched programs by ARPA-E (CIRCUITS and PNDIODES) continue to investigate the use of WBG semiconductors in power electronics. -
The Field-Effect Transistor (FET) in a Field-Effect Transistor, an Applied Voltage Is Used to Change the Conductivity of an Electron Or “Hole” Channel
The Field-Effect Transistor (FET) In a field-effect transistor, an applied voltage is used to change the conductivity of an electron or “hole” channel. To understand the operation of a FET, we first should understand just a little about the chemistry and physics of semiconductor devices. Let us consider, for simplicity, only silicon devices. Some Background (this section is Explore More!...will not be tested) Silicon (Si) is an element of the periodic table that contains 4 electrons in its “outer shell”. Pure silicon can arrange itself in a diamond cubic crystal structure (ref: http://en.wikipedia.org/wiki/Band_gap) where it shares its electrons with other Si atoms. The valance band is nominally full and the conduction band is nominally empty, thus resulting in an insulating material. Within this structure, Si forms an insulating material with a band gap energy of 1.11 electron volts (1.6e-19J, the amount of energy needed to move one electron across a one volt potential) separating the valance band from the conduction band. Figure 1: Electron band gap of an undoped (intrinsic) semiconductor. When doped (or infused) with an element that contains 5 electrons in its outer shell (say, for instance, nitrogen, N), this element will displace one silicon atom. Only using 4 of its 5 outer-shell electrons to form tight bonds with the neighboring Si atoms, nitrogen has one electron that is only loosely bound to the lattice. An electron may be more easily excited into the conduction band (the dopant provides a smaller band gap). With enough dopants (often 1 doping atom per 1 thousand to 1 billion Si atoms) and energy to excite electrons into the conduction band, the material becomes less like an insulator and more like a conductor. -
An Inorganic Light-Emitting Diode (LED; Figure 1) Is a Diode Which Is Forward-Biased (Switched On)
Figure 1: a) examples of LEDs; b) circuit symbol An inorganic Light-Emitting Diode (LED; Figure 1) is a diode which is forward-biased (switched on). By doing so electrons are able to recombine with holes within the vicinity of the junction (depletion region) thereby releasing energy in the form of light (photons) as shown in Figure 2 a). One basic requirement for the used semiconductor is to be a direct band gap semiconductor. This means that the maximum of the valence-band and the minimum of the conduction band meet at the same k-value. Figure 2 b) and c) show the 2 types of semiconductors. Since Si is an indirect band-gap semiconductor no photons are emitted by Si-based p-n-junctions. Figure 2: a) forward biased p-n-junction b) indirect band-gap semiconductor; c)direct Figure 3: a) band diagram in a heterojunction LED; b) schematic display of a double heterostructure LED Figure 3 a) shows the band diagram of an improved LED where a heterojuncion is used. The figure shows that the central material (where the light is generated) is surrounded by a region with a higher energy gap. This allows confining the injected charge carriers inside the un-doped central region with a lower band-gap thereby increasing the emissive radiation rate. Figure 3 b) shows the configuration of a double heterorstructure LED. This type of confinement is also utilized for semiconductor lasers. The usage of a heterojunction is further advantageous to obtain a higher output of light out of the LED since the generated photons don’t have enough energy to generate an electron-hole pair within the semiconductor with wider band-gap. -
Semiconductor Science and Leds
Optoelectronics EE/OPE 451, OPT 444 Fall 2009 Section 1: T/Th 9:30- 10:55 PM John D. Williams, Ph.D. Department of Electrical and Computer Engineering 406 Optics Building - UAHuntsville, Huntsville, AL 35899 Ph. (256) 824-2898 email: [email protected] Office Hours: Tues/Thurs 2-3PM JDW, ECE Fall 2009 SEMICONDUCTOR SCIENCE AND LIGHT EMITTING DIODES • 3.1 Semiconductor Concepts and Energy Bands – A. Energy Band Diagrams – B. Semiconductor Statistics – C. Extrinsic Semiconductors – D. Compensation Doping – E. Degenerate and Nondegenerate Semiconductors – F. Energy Band Diagrams in an Applied Field • 3.2 Direct and Indirect Bandgap Semiconductors: E-k Diagrams • 3.3 pn Junction Principles – A. Open Circuit – B. Forward Bias – C. Reverse Bias – D. Depletion Layer Capacitance – E. Recombination Lifetime • 3.4 The pn Junction Band Diagram – A. Open Circuit – B. Forward and Reverse Bias • 3.5 Light Emitting Diodes – A. Principles – B. Device Structures • 3.6 LED Materials • 3.7 Heterojunction High Intensity LEDs Prentice-Hall Inc. • 3.8 LED Characteristics © 2001 S.O. Kasap • 3.9 LEDs for Optical Fiber Communications ISBN: 0-201-61087-6 • Chapter 3 Homework Problems: 1-11 http://photonics.usask.ca/ Energy Band Diagrams • Quantization of the atom • Lone atoms act like infinite potential wells in which bound electrons oscillate within allowed states at particular well defined energies • The Schrödinger equation is used to define these allowed energy states 2 2m e E V (x) 0 x2 E = energy, V = potential energy • Solutions are in the form of -
A Self-Consistent Static Model of the Double-Heterostructure Laser
IEEE JOURNAL OF QUANTUM ELECTRONICS, VOL. QE-17, NO. 9, SEPTEMBER 1981 1941 A Self-Consistent Static Model of the Double-Heterostructure Laser Abstract-A new static model of the double-heterostructure laser is even as an approximation, neglects twovery important effects: presentedwhich treats the p-njunction in the laser in a consistent first,the effect on the electricad characteristics oflateral manner.The .soiution makes use of thefinite-element method to treat complex diodegeometries. The model is valid above lasing thresh- carrier drift and diffusion and, second, the saturation of junc- old cdshows both the saturationin the diode junction voltageat tionvoltage (and carrier populations) associated with lasing thresholdas well as lateral mode shifts associated with spatial hole threshold. A more reasonable condition to apply to the diode burning.Several geometries have been analyzed and somespecific junction in the double-heterostructure laser is to assume the results are presented as illustration. continuity of the carrier quasi-Fermi levels across the hetero- junction interfaces. Thisassumption leads naturally to the I.INTRODUCTION saturationof the diode voltage at lasing threshold,and is OUBLE-HETEROSTRUCTURE injection lasershave consistent with semiconductor physics. However, the use of Drecently become objects of intense interest as compact, this model of the diode junction requires the use of a different highly efficient sources of coherent light. With this in mind, solution method from that ofprevious models. laser diode modeling is potentially a tool of great value, both Another model specifically designed to treat the behavior of to understand the effects seen in real laser diodes as well as to a narrow planar stripe laser treats the diode junction in this predict and possibly optimize the behavior of as yet unfabri- manner using a highly simplified geometry [7] . -
Light-Emitting Diodes (Leds) Teacher Materials (Includes Student Materials)
Light-Emitting Diodes (LEDs) Teacher Materials (includes Student Materials) Index 2 Curriculum Suggestions 3 Sample Lesson plans 4 Light Emitting Diodes Overview 6 More Information on Light Emitting Diodes 7 Demonstration 1 - Electron Flow within an Energy Band 17 Demonstration 2 -Changing Conductivity By Adding or Removing Electrons 20 Demonstration 3 -Investigating Electronic Properties of a p-n Junction 24 Demonstration 4 -Relationship Between Composition and Wavelength of LEDs 27 Student Follow- Up Questions 30 Investigations: What makes graphite a good conductor Teacher Version 34 Student Version 35 Investigations: The Crystal Structure of Light Emitting Diodes Teacher Version 36 Student Version 37 Experiments Teacher Version 39 Student Version 40 Review Materials Teacher Version 43 Student Version 48 Assessment Teacher Version 52 Student Version 57 Light Emitting Diodes (LEDs) Curriculum Suggestions Sample Lesson Plan LED Overview Light Emitting Diodes Demonstration 1 (Instructor copy) Demonstration 2 (Instructor copy) Demonstration 3 (Instructor copy) Demonstration 4 (Instructor copy) Student Questions after Demonstration 4 Investigation 1 (Student copy) Investigation 1 (Instructor copy) Investigation 2 (Student copy) Investigation 2 (Instructor copy) Experiment 1 (Student copy) Experiment 1 (Instructor copy) LED Review Questions (Student copy) LED Review Questions (Instructor copy) LED Assessment (Student copy) LED Assessment (Instructor copy) 2 CURRICULUM SUGGESTIONS TOPICS SOLIDS QUANTUM MECHANICS SEMICONDUCTORS Bonding Electron Configurations p-n Junctions Metals Periodic Table LEDs Metallic Bonding Periodic Relationships (Trends) (Valence-Bond Model) Band Theory Solid Solutions OVERVIEW This module would complement a unit on atomic structure and periodicity. Typically, is introduced in two chapters: one dealing with the nature of light and its use to determine the electronic structure of atoms; and another that relates this electronic structure to the periodic table and trends in properties. -
1 Semiconductors, Alloys, Heterostructures
1 Semiconductors, alloys, heterostructures 1.1 Introducing semiconductors Single-crystal semiconductors have a particularly important place in optoelectronics, since they are the starting material for high-quality sources, receivers and amplifiers. Other materials, however, can be relevant to some device classes: polycrystalline or amorphous semiconductors can be exploited in light-emitting diodes (LEDs) and solar cells; dielectrics (also amorphous) are the basis for passive devices (e.g., waveguides and optical fibers); and piezoelectric (ferroelectric) crystals such as lithium niobate are the enabling material for a class of electrooptic (EO) modulators. Moreover, polymers have been recently exploited in the development of active and passive optoelectronic devices, such as emitters, detectors, and waveguides (e.g., fibers). Nevertheless, the peculiar role of single-crystal semiconductors justifies the greater attention paid here to this material class with respect to other optoelectronic materials. From the standpoint of electron properties, semiconductors are an intermediate step between insulators and conductors. The electronic structure of crystals generally includes a set of allowed energy bands, that electrons populate according to the rules of quantum mechanics. The two topmost energy bands are the valence and conduction band, respectively, see Fig. 1.1. At some energy above the conduction band, we find the vacuum level, i.e., the energy of an electron free to leave the crystal. In insulators,the valence band (which hosts the electrons participating to the chemical bonds) is separated from the conduction band by a large energy gap Eg, of the order of a few electronvolts (eV). Due to the large gap, an extremely small number of electrons have enough energy to be promoted to the conduction band, where they could take part into electrical con- duction.