Epitaxy and Characterization of Metamorphic Semiconductorsfor III-V/Si Multijunction Photovoltaics

Bibliographic Details
Main Author:	Boyer, Jacob Tyler
Language:	English
Published:	The Ohio State University / OhioLINK 2020
Subjects:	Materials Science Heteroepitaxy metamorphic semiconductors III-V on Si dislocations epitaxial growth electron channeling contrast imaging photovoltaics MOCVD GaP on Si GaAsP on Si TDD
Online Access:	http://rave.ohiolink.edu/etdc/view?acc_num=osu1607042647720476

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spelling	ndltd-OhioLink-oai-etd.ohiolink.edu-osu16070426477204762021-10-02T05:10:33Z Epitaxy and Characterization of Metamorphic Semiconductorsfor III-V/Si Multijunction Photovoltaics Boyer, Jacob Tyler Materials Science Heteroepitaxy metamorphic semiconductors III-V on Si dislocations epitaxial growth electron channeling contrast imaging photovoltaics MOCVD GaP on Si GaAsP on Si TDD III-V/Si multijunction photovoltaics possess the potential for high power conversion efficiencies (surpassing the single-junction limit) at low cost by leveraging the inexpensive and scalable Si platform. Both space and terrestrial markets can benefit from this technology; however, multiple materials-related obstacles must first be overcome in order to truly demonstrate this potential and enable adoption of this new technology. For terrestrial usage, low-cost III-V deposition techniques are necessary to remain cost competitive with current photovoltaics. Given a Si bottom cell, the optimal series-connected dual-junction photovoltaic efficiency for both space and terrestrial solar spectra is achieved with a 1.7-1.8 eV top cell, which is most conveniently provided by GaAs<sub>y</sub>P<sub>1-y</sub> (y ~0.7-0.8) at around 3% lattice mismatch to the Si substrate. While epitaxial integration of GaAs<sub>y</sub>P<sub>1-y</sub> alloys on Si is favorable over high-cost and non-scalable wafer bonding or stacking techniques, controlling (minimizing) dislocation content within the strain-relaxed metamorphic materials, and/or minimizing its impact on top cell performance via careful device design, is key to achieving optimal performance. Materials challenges related to the heterovalent, lattice-mismatched GaP/Si interface and the thermal expansion coefficient mismatch of GaAs<sub>y</sub>P<sub>1-y</sub> to Si all complicate the production of low-defect density GaAs<sub>y</sub>P<sub>1-y</sub> materials.To this end, we have undertaken metalorganic chemical vapor deposition (MOCVD) growth studies of GaP/Si nucleation layers and GaAs<sub>y</sub>P<sub>1-y</sub> step-graded buffers, demonstrating substantial progress by reducing defect densities by over an order of magnitude in the course of this recent work. These efforts have largely been enabled via rapid feedback regarding crystalline defect populations obtained from electron channeling contrast imaging (ECCI). From these experimental studies, a deeper understanding of dislocation dynamics in these metamorphic materials is reached via quantitative analysis and modeling. As a result, successful demonstration of defect density reductions over an order of magnitude have been demonstrated in GaAs<sub>y</sub>P<sub>1-y</sub>/GaP/Si materials tailored to the requirements of III-V/Si photovoltaic devices. This achievement in material quality enables further production and development of high efficiency III-V/Si photovoltaic devices with rapid improvements at the newly achieved defect levels. 2020 English text The Ohio State University / OhioLINK http://rave.ohiolink.edu/etdc/view?acc_num=osu1607042647720476 http://rave.ohiolink.edu/etdc/view?acc_num=osu1607042647720476 unrestricted This thesis or dissertation is protected by copyright: all rights reserved. It may not be copied or redistributed beyond the terms of applicable copyright laws.
collection	NDLTD
language	English
sources	NDLTD
topic	Materials Science Heteroepitaxy metamorphic semiconductors III-V on Si dislocations epitaxial growth electron channeling contrast imaging photovoltaics MOCVD GaP on Si GaAsP on Si TDD
spellingShingle	Materials Science Heteroepitaxy metamorphic semiconductors III-V on Si dislocations epitaxial growth electron channeling contrast imaging photovoltaics MOCVD GaP on Si GaAsP on Si TDD Boyer, Jacob Tyler Epitaxy and Characterization of Metamorphic Semiconductorsfor III-V/Si Multijunction Photovoltaics
author	Boyer, Jacob Tyler
author_facet	Boyer, Jacob Tyler
author_sort	Boyer, Jacob Tyler
title	Epitaxy and Characterization of Metamorphic Semiconductorsfor III-V/Si Multijunction Photovoltaics
title_short	Epitaxy and Characterization of Metamorphic Semiconductorsfor III-V/Si Multijunction Photovoltaics
title_full	Epitaxy and Characterization of Metamorphic Semiconductorsfor III-V/Si Multijunction Photovoltaics
title_fullStr	Epitaxy and Characterization of Metamorphic Semiconductorsfor III-V/Si Multijunction Photovoltaics
title_full_unstemmed	Epitaxy and Characterization of Metamorphic Semiconductorsfor III-V/Si Multijunction Photovoltaics
title_sort	epitaxy and characterization of metamorphic semiconductorsfor iii-v/si multijunction photovoltaics
publisher	The Ohio State University / OhioLINK
publishDate	2020
url	http://rave.ohiolink.edu/etdc/view?acc_num=osu1607042647720476
work_keys_str_mv	AT boyerjacobtyler epitaxyandcharacterizationofmetamorphicsemiconductorsforiiivsimultijunctionphotovoltaics
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Epitaxy and Characterization of Metamorphic Semiconductorsfor III-V/Si Multijunction Photovoltaics

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