DOCSLIB.ORG

Khatiwada-Dissertation-2019

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Khatiwada-Dissertation-2019 ©Copyright by Devendra Khatiwada 2019 All Rights Reserved Fabrication and Optimization of Single-Junction GaAs Thin Film Solar Cells on Epi-ready Flexible Metal Tapes for Low-cost Photovoltaics A Dissertation Presented to the Faculty of the Department of Mechanical Engineering University of Houston In Partial Fulfillment for the Requirements of the Degree Doctor of Philosophy in Materials Science and Engineering by Devendra Khatiwada August 2019 Fabrication and Optimization of Single-Junction GaAs Thin Film Solar Cells on Epi-ready Flexible Metal Tapes for Low-cost Photovoltaics Devendra Khatiwada Approved: Chair of the Committee Venkat Selvamanickam, Professor, Mechanical Engineering Committee Members: Haleh Ardebili, Associate Professor, Mechanical Engineering James K.Meen, Research Associate Professor, Chemistry Jae -Hyun Ryou, Associate Professor, Mechanical Engineering M e c Alamgir Karim, Associate Professor, h Material Science and Engineering a n i c Suresh K.Khator, Associate Dean, Alamgir Karim, Professor and a Cullen College of Engineering Director, Material Science and l Engineering E n g ii i n e e r Acknowledgements Firstly I would like to acknowledge my thesis advisor professor Venkat Selvamanickam for his persistent help, guidance and offering me opportunities to involve in various interesting project. The last four years has been an outstanding experience to work with him. His patience in research, scientific knowledge, hard work and technical skills always inspired me to continuously work in different projects. I am very lucky to have him as my advisor. It was a great pleasure to work with the excellent members in our research group. Special thanks to Dr.Pavel Dutta, Dr.Monika Rathi, Sicong Son, Carlos Favela, Sahil Sharma, Sara Pouladi for their great help during my research work. Special thanks to Sicong Son who was always enthusiastic to help me at any time. I appreciate help and guidance from Dr.Jae-Hyuan Ryou in each step of my research work. I would like to thank my committee member Dr.Alamgir Karim, Dr. James K.Meen and Dr.Haleh Ardebili. Thanks to Dr.Alamgir Karim for providing all the support needed from the department. I would specially thank to my family member for their immense support. My lovely wife, Yojana Ghimire has been extremely supportive in all the circumstances and through this entire process. Without her it would have been impossible to complete my goal of research. v Fabrication and Optimization of Single-Junction GaAs Thin Film Solar Cells on Epi-ready Flexible Metal Tapes for Low-cost Photovoltaics An Abstract of a Dissertation Presented to the Faculty of the Department of Mechanical Engineering University of Houston In Partial Fulfillment for the Requirements of the Degree Doctor of Philosophy in Materials Science and Engineering by Devendra Khatiwada August 2019 vi Abstract Properties like high efficiency, flexibility and light weight, resistance to UV radiation and moisture and a low temperature coefficient make gallium arsenide (GaAs) more favorable than the ubiquitously-used silicon for solar cells. In spite of their high efficiency, GaAs solar cells have found limited use in various application due to high cost of the GaAs or Ge wafer used. In an approach to produce low-cost GaAs solar cells, we have developed a technology to grow epitaxial semiconductor thin films on low-cost flexible epi-ready metal tapes that can replace the expensive wafers. The template layers on the epi-ready metal tapes are grown via a roll-to-roll process using Ion Beam Assisted Deposition (IBAD). Metal organic chemical vapor deposition (MOCVD) is used to epitaxially grow GaAs solar cells structure on ‘single-crystalline-like’ germanium film on epi-ready metal foils. These epitaxial GaAs films exhibit excellent crystalline alignment with high carrier mobility, excellent crystalline alignment and optoelectronic properties. These grown thin films were processed via photo-lithography, etching and contact deposition to fabricate single-junction (1J) GaAs solar cell devices. The fabricated solar cell underwent a process of cap layer removal (passivation) and anti-reflection coating. Efficiency greater than 6% with open circuit voltage (VOC) of 566mV, fill factor (FF) of 68%, short circuit 2 current density (JSC) of 17.4mA/cm was obtained. Steps were taken to improve the quality of p-n junction by improving the quality of Ge template and incorporating an intrinsic layer with p-i-n solar cell structures. A 2 device efficiency of 11.5 % with VOC of 566mV, FF of 68%, JSC of 17.4mA/cm was vii obtained at 1 Sun on improved Ge template, using CVD germanium instead of sputtered germanium used before. Solar cells fabricated with the improved p-i-n structure showed a −2 device efficiency of 13.2% at 1 sun with VOC of 650 mV, JSC of 28 mA cm , and FF of 72 %. These thin film GaAs photovoltaics, with further improvement in quality, can potentially lead to light-weight, inexpensive and scalable solar cell manufacturing. viii Table of Contents Acknowledgement……………………………………...……………………..…...….…..v Abstract………………………………………………………………….……………….vii Table of Contents………………………………...………………………..………….…..ix List of Figures……………………………………..………………....................…...…..xiv List of Tables……………………………………………...……………………...……..xix List of Abbreviation……………………………………………..…...…………….........xxi Chapter 1 Introduction ........................................................................................................ 1 1.1 Introduction to Solar cells ............................................................................. 1 1.1.1 Background............................................................................................. 1 1.2 Photovoltaics (PVs) ....................................................................................... 1 1.2.1 Semiconductors as photovoltaic materials ............................................. 3 1.3 The p-n junction in semiconductors .............................................................. 6 1.3.1 Mechanism and characteristic curve for p-n junctions under bias ......... 9 Chapter 2 Solar Cells: Structures and Characterizations .................................................. 13 2.1 Solar or Photovoltaic Cell ........................................................................... 13 2.2 Solar Cell Structure ..................................................................................... 15 2.3 Solar Cell Characteristics ............................................................................ 18 2.3.1 Equivalent circuit for solar cells ........................................................... 19 2.4 Solar cell parameters used for measurements ............................................. 21 ix 2.4.1 Short circuit current density (Jsc) .......................................................... 22 2.4.2 Open circuit voltage (Voc) .................................................................... 23 2.4.3 Leakage current (Io) ............................................................................. 24 2.4.4 Maximum power point (Pmax) ............................................................... 25 2.4.5 Fill Factor (FF) ..................................................................................... 25 2.4.6 Efficiency ............................................................................................. 25 2.4.6.1 Air Mass (AM) .............................................................................. 26 2.5 Series and shunt resistance in solar cell ...................................................... 27 2.6 Loss mechanism in solar cells ..................................................................... 29 2.6.1 Optical Loss .......................................................................................... 29 2.6.1.1 Absorption loss ............................................................................. 29 2.6.1.2 Reflection Loss ............................................................................. 31 2.6.2 Recombination loss .............................................................................. 33 2.6.2.1 Direct recombination .................................................................... 34 2.6.2.2 Auger recombination .................................................................... 34 2.6.2.3 Trap-assisted recombination ......................................................... 35 2.7 Conclusion ................................................................................................... 35 Chapter 3 III-V semiconductor material and solar cells fabrication and characterization 36 3.1 Introduction ................................................................................................. 36 3.2 Growth Methods of III-V Semiconductor ................................................... 37 x 3.2.1 Liquid-encapsulated Czochralski (LEC) Method ................................. 37 3.2.2 Float Zone and Bridgman ..................................................................... 38 3.2.3 Liquid Phase Epitaxy (LPE) ................................................................. 38 3.2.4 Molecular Beam Epitaxy ...................................................................... 39 3.2.5 Metal Organic Chemical Vapor Deposition (MOCVD) ...................... 40 3.3 III-V Single-junction Gallium Arsenide Solar Cells Structure and Design 42 3.4 III-V Multi -junction Solar Cell Structure and Design ............................... 44 3.5 Characterization tools for characterizing III-V materials and
Load more

Recommended publications
  • Communications
    COMMUNICATIONS dihydroxynaphthalene or 3,4-dihydroxybenzoate (extinction of blue qualify for Zintl phases when a broader definition is used. The l fluorescence at em 440 nm upon oxidation to the quinone). Nor- latter includes compounds of transition metals with filled or adrenaline reacts similarly to adrenaline down to pH 5. Adreno- empty d shells, that is the late transition metals of the Ni, Cu, chrome (2) is unstable and polymerizes to brown and finally insoluble [2] black products upon prolonged standing in solution. and Zn groups, and the early transition elements of the Ti, V, [14] a) M. Simmel, M. Turunen, J. Piironen, T. Vaara, VTT Symp. 1991, 122, and Cr groups at maximum formal oxidation states.[3] There 145 ± 161; b) R. J. Wodzinski, A. H. J. Ullah, Adv. Appl. Microbiol. are only two Zintl compounds containing a transition metal 1996, 42, 263 ± 302. with partially filled d shell, both based on manganese, [15] B.-L. Liu, A. Rafiq, Y.-M. Tzeng, A. Rob, Enzyme Microbiol. Technol. 1998, 22, 415 ± 424. (AE)14MnPn11 (AE alkaline-earth metal, Pn pnictogen) [4] [16] A. H. J. Ullah, D. M. Gibson, Prep. Biochem. 1987, 17, 63 ± 91. and Sr21Mn4Sb18 . Perhaps only they should be called true [17] Several kits for the titration of inorganic phosphate based on the ™transition metal Zintl phases∫ although the name is contra- reaction with ammonium molybdate are available commercially. dictory in itself. All but two of the d0 compounds contain Methyl-umbelliferyl phosphate and 4-nitrophenyl phosphate are isolated tetrahedra [MPn ]nÀ (M Nb, Ta, W, Ti).[5] The two general fluorogenic and chromogenic substrates for phosphatases 4 but do not enable phytases to be distinguished from other phospha- exceptions are Na5HfAs3 with dimers of edge-sharing tetra- 10À tases, in contrast to assays based on phytic acid.
    [Show full text]
  • The Reaction of Pyridine Witb Sulfur Dioxide In
    The Reaction of Pyridine witb Sulfur Dioxide in Benzoyl Chloride (55 letters) J THE REACTION OF PYRIDINE WITH SULFUR DIOXIDE IN BENZOYL CHLORIDE by James R. Watson A Thesis submitted to the Faculty of Graduate Studies and Research in partial fulfilment of the requirements for the degree of Master of Science Department of Chemistry McGill University Montreal, Canada August, 1965 • - i - ACKNOWLEDGMENTS I wish to thank Dr. J. T. Edward for his helpful guidance during my stay at McGill University and in the preparation of this manuscript • • TABLE OF CONTENTS ACKNOWLEDGMENTS. • . • • . • . • i LIST OF FIGURES........................................ ii LIST OF TABLES.. • • . • • . • . • . • 1 v INTRODUCTION•••••••••••••••·•·••••••••••••••••••••••••• 1 A. Reactions of Acylpyridinium Halides.............. 2 B. Partial Reduction to Dihydro and Tetrahydro Pyridine.................................. 6 C. Ring Opening Reactions........................... 8 EXPERIMENTAL. • • • • . • . • • • . • . • • • • • . • • . • • • . • • • . • 11 A. Reagents............... .. ... .. 11 B. Reaction of Pyridine with Sulfur Dioxide in Benzoyl Chloride to form Compound A.............. 11 C. Measurement of the Dissociation Constant of Compound A....................................... 15 D. Attempted Reaction of Pyridine, Benzoyl Chloride and Sodium Sulfite............................... 18 E. Reaction of 2-Picoline with Sulfur Dioxide in Benzoyl Chloride ta form Compound B.............. 18 F. Reaction of 2,4-Lutidine with Sulfur Dioxide in Benzoyl Chloride to form
    [Show full text]
  • Quaternary Ammonium Compositions and Their Uses
    Europaisches Patentamt (19) European Patent Office Office europeen des brevets (11) EP 0 726 246 A1 (12) EUROPEAN PATENT APPLICATION (43) Date of publication: (51) |nt. CI.6: C07C 21 1/63, C01 B 33/44, 14.08.1996 Bulletin 1996/33 C1 p 1/62j Q21 C 5/02, (21) Application number: 96101900.7 A61 K 7/50 //C09D7/12 (22) Date of filing: 09.02.1996 (84) Designated Contracting States: • Campbell, Barbara DE DK ES FR GB IT NL Bristol, PA 1 9007 (US) • Chiavoni, Araxi (30) Priority: 10.02.1995 US 385295 Trenton, N J 0861 0 (US) • Magauran, Edward (71 ) Applicant: RHEOX INTERNATIONAL, INC. Westhampton, NJ 08060 (US) Hightstown, New Jersey 08520 (US) (74) Representative: Strehl Schubel-Hopf Groening & (72) Inventors: Partner • Cody, Charles, Dr. Maximilianstrasse 54 Robbinsville, NJ 08691 (US) 80533 Munchen (DE) (54) Quaternary ammonium compositions and their uses (57) Quaternary ammonium compositions are described which are made using diluents including soya bean oil, caster oil, mineral oils, isoparaffin/naphthenic and coconut oil. Such diluents remain as diluents in the final product and generally have a vapor pressure of 1mm of Hg or less at 25°C, and are liquid at ambient temperature. The quaternary/ammonium diluent com- positions have low volatile organic compound emission rates and high flash points, and can be tailored to partic- ular applications. Such applications include use a fabric softeners, cosmetics ingredients, deinking additives, surfactants, and reaction materials in the manufacture of organoclays. < CO CM CO CM o Q_ LU Printed by Rank Xerox (UK) Business Services 2.13.0/3.4 EP 0 726 246 A1 Description BACKGROUND OF THE INVENTION 5 1 .
    [Show full text]
  • Available Online Journal of Scientific And
    Available online www.jsaer.com Journal of Scientific and Engineering Research, 2016, 3(5):281-284 ISSN: 2394-2630 CODEN(USA): JSERBR Research Article Study of toxicity of arsenic during the synthesis of new class of iron-based oxyarsenide superconductors Intikhab A Ansari, Syed S Ghani*, Iqbal Hussain General Studies Department, Jubail Industrial College, P. O. Box - 10099, Jubail industrial City-31961, Saudi Arabia Abstract The toxicity of arsenic and its severe effect on human-beings are reported in this study. The different exposure limits of various materials are described during the synthesis of iron-based superconductor as a time- weighted average (TWA) over an 8-hours workday. This report reveals that the element arsenic is found to be highly toxic in case of inhalation or ingestion by the employers amongst the starting materials during the synthesis of oxyarsenide superconductor. All the exposure limits are taken from Occupational Safety and Health Administration (OSHA) regulations. This study helps to increase the primary care provider’s knowledge of hazardous substances such as arsenic in the environment and to promote the adoption of medical practices that aid in the evaluation and care of potentially exposed patients. Keywords Iron-based superconductor; toxicity; arsenic, exposure limits, extracted Introduction The recent discovery on the new class of iron-based superconductor has broken the tyranny of copper. The innovation of 26 K transition temperature (Tc) in fluorine-doped LaFeAsO superconductor [1] marked the beginning of worldwide efforts to investigate this new family of superconductors. After several efforts the Tc has reached 55 K by replacement of Lanthanum (La) by other rare earth elements [2-4].
    [Show full text]
  • United States Patent Office Patented Dec
    3,294,827 United States Patent Office Patented Dec. 27, 1966 1. 2 3,294,827 which will remain inert during the preparative procedure. QUATERNARY AMMONIUMMETAL COMPOUNDS The term "capryly' used herein refers to the hydrocarbon Ronald R. Swanson, Minneapolis, Minn., assignor to radicals (octyl and decyl) derived from a mixture of General Mills, Inc., a corporation of Delaware caprylic acid and capric acid. No Drawing. Filed Sept. 26, 1961, Ser. No. 140,691 Another method for preparing the compounds of the 12 Claims. (CI. 260-429) present invention is by contacting the quaternary ammo nium starting material with a simple metallic salt. The This invention relates to novel quaternary ammonium quaternary and the metal salt are combined in a mutual compounds. solvent and, upon removing the solvent, the desired qua It is an object of this invention to provide novel qua 10 ternary ammonium metal compound is prepared. For ternary ammonium metal compounds. It is another ob example, if it is desired to prepare a quaternary ammo ject of this invention to provide the novel process for nium compound having an anion MnCl4, this can be the preparation of quaternary ammonium metal com done by contacting quaternary ammonium starting mate pounds. Other objects will appear hereinafter. rial with manganese chloride in a mutual solvent such as The objects of this invention are accomplished by a 5 ether or isopropanol. While the product must be com fatty quaternary ammonium metal compound wherein the pletely soluble in the chosen solvent, it is not generally anion of said quaternary compound is an inorganic anion necessary that both the starting quaternary compound and containing a metal of Group VIIB of the Periodic Table.
    [Show full text]
  • Atomic Structure and Non-Electronic Properties of Semiconductors
    SEMICONDUCTORS VOLUME 32, NUMBER 7 JULY 1998 ATOMIC STRUCTURE AND NON-ELECTRONIC PROPERTIES OF SEMICONDUCTORS Indium layers in low-temperature gallium arsenide: structure and how it changes under annealing in the temperature range 500–700 °C N. A. Bert, A. A. Suvorova, and V. V. Chaldyshev A. I. Ioffe Physicotechnical Institute, Russian Academy of Sciences, 194021 St. Petersburg, Russia Yu. G. Musikhin A. I. Ioffe Physicotechnical Institute, Russian Academy of Sciences, 194021 St. Petersburg, Russia; Max Planck Institut fu¨r Mikrostrukturphysik, D-5120 Halle, Germany V. V. Preobrazhenski , M. A. Putyato, and B. R. Semyagin Institute of Semiconductor Physics, Russian Academy of Sciences, Siberian Branch, 630090 Novosibirsk, Russia R. Werner Max Planck Institut fu¨r Mikrostrukturphysik, D-05120 Halle, Germany ~Submitted December 29, 1997; accepted for publication December 31, 1997! Fiz. Tekh. Poluprovodn. 32, 769–774 ~July 1998! Transmission electron microscopy is used to study the microstructure of indium d layers in GaAs~001! grown by molecular beam epitaxy at low temperature ~200 °C!. This material, referred to as LT-GaAs, contains a high concentration ('1020 cm23) of point defects. It is established that when the material is d-doped with indium to levels equivalent to 0.5 or 1 monolayer ~ML!, the roughness of the growth surface leads to the formation of InAs islands with characteristic lateral dimensions ,10 nm, which are distributed primarily within four adjacent atomic layers, i.e., the thickness of the indium-containing layer is 1.12 nm. Subsequent annealing, even at relatively low temperatures, leads to significant broadening of the indium- containing layers due to the interdiffusion of In and Ga, which is enhanced by the presence of a high concentration of point defects, particularly VGa ,inLT-GaAs.
    [Show full text]
  • Relationship Between the Molecular Conformation of Choline Aryl Ethers and Nicotine-Like Stimulant Activity
    Br. J. Pharmac. Chemother. (1968), 32, 113-126. RELATIONSHIP BETWEEN THE MOLECULAR CONFORMATION OF CHOLINE ARYL ETHERS AND NICOTINE-LIKE STIMULANT ACTIVITY BY E. R. CLARK, P. M. DAWES* ANi) S. G. WILLIAMS t From the Department of Pharmacology, School of Medicine, University of Leeds, Leeds 2 (Received August 7, 1967) The introduction of one or more methyl substituents into the structure of choline phenyl ether bromide (TMl) may result in large changes, both qualitative and quantitative, in pharmacological action. Thus, whereas choline o-tolyl ether bromide (o-Me-TM1), and a-methylcholine phenyl ether bromide (a-Me-TMI) are potent ganglion stimulants, being respectively one half and twice as active as choline phenyl ether (Hunt & Renshaw, 1936), choline 2,6-xylyl ether bromide (xylocholine) and /8-methylcholine phenyl ether bromide (P-Me-TMl) are devoid of ganglion stimulant activity (Hey, 1952; Clark & Jana, 1966), and xylocholine possesses adrenergic neurone blocking activity. An examination of molecular models of xylocholine and choline phenyl ether suggested that the difference in biological action might be steric in origin. Xylocholine is very sterically hindered, rotation about its phenyl-oxygen bond is virtually completely inhibited, and the plane containing the oxygen valencies is orthogonal to the plane of the benzene ring. In contrast choline phenyl ether is completely flexible and able to adopt different conformations in which the angle between the plane of the benzene ring and the plane containing the oxygen valencies (" angle-of-twist") varies between 00 and 900. p-Me-TMl lies between these two extremes; some degree of rotation about the phenyl- oxygen bond is possible but steric hindrance occurs between the o-hydrogens and the ,B-methyl group, and the "angle-of-twist" is always >00.
    [Show full text]
  • 10391225.Pdf
    https://theses.gla.ac.uk/ Theses Digitisation: https://www.gla.ac.uk/myglasgow/research/enlighten/theses/digitisation/ This is a digitised version of the original print thesis. Copyright and moral rights for this work are retained by the author A copy can be downloaded for personal non-commercial research or study, without prior permission or charge This work cannot be reproduced or quoted extensively from without first obtaining permission in writing from the author The content must not be changed in any way or sold commercially in any format or medium without the formal permission of the author When referring to this work, full bibliographic details including the author, title, awarding institution and date of the thesis must be given Enlighten: Theses https://theses.gla.ac.uk/ [email protected] The Use of Cationic Surfactants in Marine Anti-fouling Applications Margaret J Smith B.Sc. Submitted for the Degree of M.Sc. University of Glasgow Department of Mechanical Engineering Faculty of Engineering August 1997 © M. J. Smith ProQuest Number: 10391225 All rights reserved INFORMATION TO ALL USERS The quality of this reproduction is dependent upon the quality of the copy submitted. In the unlikely event that the author did not send a com plete manuscript and there are missing pages, these will be noted. Also, if material had to be removed, a note will indicate the deletion. uest ProQuest 10391225 Published by ProQuest LLC (2017). Copyright of the Dissertation is held by the Author. All rights reserved. This work is protected against unauthorized copying under Title 17, United States C ode Microform Edition © ProQuest LLC.
    [Show full text]
  • Vulcanizable Elastomer Composition
    ~" ' MM II II II MINI MM II Ml II I II J European Patent Office _ __ _ _ © Publication number: 0 257 640 B1 Office europeen des brevets © EUROPEAN PATENT SPECIFICATION © Date of publication of patent specification: 16.03.94 © Int. CI.5: C08G 59/40, C08G 59/68, C08G 59/32, C08G 59/34 © Application number: 87112415.2 @ Date of filing: 26.08.87 The file contains technical information submitted after the application was filed and not included in this specification © Vulcanizable elastomer composition. © Priority: 29.08.86 JP 202817/86 © Proprietor: NIPPON ZEON CO., LTD. 29.08.86 JP 202818/86 6-1, 2-chome, Marunouchl, Chlyoda-ku @ Date of publication of application: Tokyo(JP) 02.03.88 Bulletin 88/09 @ Inventor: Yaglshlta, Shlgeru © Publication of the grant of the patent: 4-23, Kalgan-dohrl 16.03.94 Bulletin 94/11 Naka-ku Yokohama-shl Kanagawa-ken(JP) © Designated Contracting States: DE FR IT © Representative: Kraus, Walter, Dr. et al References cited: Patentanwalte Kraus, Welsert & Partner EP-A- 0 142 918 DE-A- 1 912 281 Thomas-Wlmmer-RIng 15 DE-A- 1 942 898 FR-A- 2 567 899 D-80539 Munchen (DE) US-A- 3 779 949 US-A- 3 838 101 US-A- 4 144 159 00 o CO m cm Note: Within nine months from the publication of the mention of the grant of the European patent, any person ® may give notice to the European Patent Office of opposition to the European patent granted. Notice of opposition CL shall be filed in a written reasoned statement.
    [Show full text]
  • Fabrication of III-V Integrated Photonic Devices
    UNIVERSITY OF OTTAWA DOCTORAL THESIS Fabrication of III-V integrated photonic devices Author: Kashif AWAN Supervisors: Prof. Ksenia DOLGALEVA and Prof. Robert BOYD A thesis submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy Ottawa-Carleton Institute for Electrical and Computer Engineering University of Ottawa c Kashif Awan, Ottawa, Canada, 2018 ii Declaration of Authorship I, Kashif AWAN, declare that this thesis, titled “Fabrication of III-V integrated pho- tonic devices”, and the work presented in it are my own. I confirm that except where specific reference is made to the work of others, the contents of this dissertation are original and have not been submitted in whole or in part for consideration for any other degree or qualification in this, or any other university. This dissertation is my own work and contains nothing which is the outcome of work done in collaboration with others, except as specified in the text and Acknowledgements. Kashif Awan March, 2018 Ottawa, Canada iii Abstract This doctoral dissertation focuses on fabrication processes for integrated photonic devices based on III-V semiconductors. This work covers a range of III-V materials and a variety of devices. Initially, design, fabrication and optical characterization of aluminum gallium arsenide (AlGaAs) waveguides for enhanced optical nonlin- ear interactions was carried out. Based on our results, we proposed a new type of waveguide for AlGaAs integrated nonlinear optics. Photonic crystal nanocavities and waveguides are attractive components for integrated photonic devices, due to their control over spatial, spectral and dispersion properties of light. Fabrication pro- cess for high-Q GaAs photonic crystal nanocavities was developed.
    [Show full text]
  • Isovalent Substitution Effects of Arsenic on Structural and Electrical
    Isovalent substitution effects of arsenic on structural and electrical properties of iron-based superconductor NdFeAsO0.8F0.2 Z. Alborzi and V. Daadmehr* Magnet and Superconducting Res. Lab., Faculty of Physics & Chemistry, Alzahra University, Tehran 19938, IRAN [email protected], *[email protected] Abstract In this paper, nominal compositions of NdFeAsO0.8F0.2, NdFeAs0.95Sb0.05O0.8F0.2 and NdFeAs0.95P0.05O0.8F0.2 were prepared by one-step solid-state reaction method. The structural, electrical and morphological properties of samples were characterized through the XRD pattern, the 4-probe method and SEM, respectively. The crystal structure of our samples was tetragonal with P4/nmm:2 symmetry group. Also, the (x, y, z), occupancy of ions and lattice parameters were changed by isovalent substitution of Phosphorus (P) and Antimony (Sb)in the NdFeAsO0.8F0.2 sample. The ⍺, β bond angles and Fe-As bond length are changed from the corresponding value of ⍺ and β regular FeAs4-tetrahedron by isovalent doping P/As and Sb/As, that they are effective on the superconductivity transition temperature. The microstrain and crystalline size of samples were studied by the Williamson Hall method. The superconducting critical temperatures were attained at 56 K and 46 K for NdFeAsO0.8F0.2, NdFeAs0.95Sb0.05O0.8F0.2, respectively. The NdFeAs0.95P0.05O0.8F0.2 showed the structural transition temperature at 140 K. It seems that there is a relation between the superconductivity and shrinkage of the crystal lattice. The flake-type of grains was observed by SEM pictures of samples. Key words: Iron- based superconductor, isovalent doping, crystal structure, microstrain 1.
    [Show full text]
  • On Inp by MOVPE
    GRK 1782 "Functionalization of Semiconductors" Seminar 2017 Seminarhotel Kunze-Hof, Stadland, 02.10.2017 – 06.10.2017 Research Summaries supported by: Graduiertenkolleg 1782 „Functionalization of Semiconductors“ Seminarhotel Kunze-Hof, Stadland Seminar Program 02. – 06.10.2017 Monday, 02.10.2017 till 15:30 Arrival 15:30 – 16:00 Welcome Snack/ Coffee Break 16:00 – 17:30 Simulation Workshop I Jan Oliver Oelerich 18:00 Dinner Tuesday, 03.10.2017 08:00 – 09:00 Breakfast 09:00 – 10:30 Simulation Workshop II Jan Oliver Oelerich 10:30 – 11:00 Coffee Break 11:00 – 12:30 Simulation Workshop III Jan Oliver Oelerich 13:00 – 14:00 Lunch Break Session I Chair: Jan Oliver Oelerich 14:00 – 14:30 Lukas Nattermann: MOVPE in-situ gas phase analysis with real-time 3D quadrupole ion trap mass spectrometer 14:30 – 15:00 Lars Ostheim: Electronic transport properties of dilute N- and B-containing III-V semiconductors under hydrostatic pressure 15:00 – 15:30 Lars Bannow: A first principle based approach to optical properties of semiconductor materials 15:30 – 16:00 Coffee Break Session II Chair: Katharina Hanau 16:00 – 16:30 Johannes Völkner: Monolayer Functionalization of GaAs Surfaces 16:30 – 17:00 Mikko Wilhelm: Optoelectronic Coupling between Quantum Dots and Burrowed Quantum Wells 17:00 – 17:30 Jürgen Belz: Atomic-Scale 3D Reconstruction of Antiphase Boundaries of GaP on Silicon (001) by STEM 18:00 Dinner Wednesday, 04.10.2017 08:00 – 09:00 Breakfast Session III Chair: Jonas Hühn 09:00 – 09:30 Thilo Hepp: MOVPE growth of quaternary GayIn1-yAs1-xBix structures on InP and on GaAs 09:30 – 10:00 Vitalii Valkovskii: Peculiarities of the photoluminescence line shape in Ga(N,As,P)/GaP.
    [Show full text]