skip to main content
DOE PAGES title logo U.S. Department of Energy
Office of Scientific and Technical Information

This content will become publicly available on November 28, 2020

Title: Guided Optimization of Phase-Unstable III–V Compositionally Graded Buffers by Cathodoluminescence Spectrum Imaging

Abstract

Compositionally graded buffers (CGBs) are essential components of high-efficiency III-V inverted metamorphic solar cells, and high-quality CGBs with low defect densities are a requirement for high device efficiencies. Here, we use plan-view and cross-sectional cathodoluminescence spectrum imaging (CLSI) to investigate the effect of growth conditions on the microstructure of Al yGa 1-x-yIn xAS CGBs with x In > 0.30. CLSI reveals significant compositional fluctuation in these materials that correlates with the distribution of threading dislocations in the CGBs. Threading dislocations are observed to collect in regions between abrupt transitions in emission energy, implying that concomitant strain fluctuations in these regions restrict dislocation motion. Thus, the compositional fluctuation leads to elevated threading dislocation densities that degrade CGB quality. We also correlate compositional fluctuation in the CGB with compositional fluctuation in subsequently grown device layers. The effectiveness of specific growth conditions at suppressing compositional fluctuation and limiting threading dislocation density is evaluated. CGBs grown at high temperatures with high Al content exhibit the lowest defect densities. The use of a high V/III ratio suppresses compositional fluctuation and defect density. In conclusion, these insights lead directly to improvements in the efficiency of metamorphic Ga 1-xIn xAs solar cells grown on AlyGa 1-x-yIn xAsmore » CGBs.« less

Authors:
ORCiD logo [1]; ORCiD logo [1]; ORCiD logo [1]; ORCiD logo [1]
  1. National Renewable Energy Laboratory (NREL), Golden, CO (United States)
Publication Date:
Research Org.:
National Renewable Energy Lab. (NREL), Golden, CO (United States)
Sponsoring Org.:
USDOE Office of Energy Efficiency and Renewable Energy (EERE), Solar Energy Technologies Office (EE-4S)
OSTI Identifier:
1580497
Report Number(s):
NREL/JA-5900-75338
Journal ID: ISSN 2156-3381
Grant/Contract Number:  
AC36-08GO28308
Resource Type:
Accepted Manuscript
Journal Name:
IEEE Journal of Photovoltaics
Additional Journal Information:
Journal Volume: 10; Journal Issue: 1; Journal ID: ISSN 2156-3381
Publisher:
IEEE
Country of Publication:
United States
Language:
English
Subject:
14 SOLAR ENERGY; 36 MATERIALS SCIENCE; indium gallium arsenide; luminescence; photovoltaic cells; scanning electron microscopy

Citation Formats

Schulte, Kevin L., Guthrey, Harvey L., France, Ryan M., and Geisz, John F. Guided Optimization of Phase-Unstable III–V Compositionally Graded Buffers by Cathodoluminescence Spectrum Imaging. United States: N. p., 2019. Web. doi:10.1109/JPHOTOV.2019.2951927.
Schulte, Kevin L., Guthrey, Harvey L., France, Ryan M., & Geisz, John F. Guided Optimization of Phase-Unstable III–V Compositionally Graded Buffers by Cathodoluminescence Spectrum Imaging. United States. doi:10.1109/JPHOTOV.2019.2951927.
Schulte, Kevin L., Guthrey, Harvey L., France, Ryan M., and Geisz, John F. Thu . "Guided Optimization of Phase-Unstable III–V Compositionally Graded Buffers by Cathodoluminescence Spectrum Imaging". United States. doi:10.1109/JPHOTOV.2019.2951927.
@article{osti_1580497,
title = {Guided Optimization of Phase-Unstable III–V Compositionally Graded Buffers by Cathodoluminescence Spectrum Imaging},
author = {Schulte, Kevin L. and Guthrey, Harvey L. and France, Ryan M. and Geisz, John F.},
abstractNote = {Compositionally graded buffers (CGBs) are essential components of high-efficiency III-V inverted metamorphic solar cells, and high-quality CGBs with low defect densities are a requirement for high device efficiencies. Here, we use plan-view and cross-sectional cathodoluminescence spectrum imaging (CLSI) to investigate the effect of growth conditions on the microstructure of AlyGa1-x-yInxAS CGBs with xIn > 0.30. CLSI reveals significant compositional fluctuation in these materials that correlates with the distribution of threading dislocations in the CGBs. Threading dislocations are observed to collect in regions between abrupt transitions in emission energy, implying that concomitant strain fluctuations in these regions restrict dislocation motion. Thus, the compositional fluctuation leads to elevated threading dislocation densities that degrade CGB quality. We also correlate compositional fluctuation in the CGB with compositional fluctuation in subsequently grown device layers. The effectiveness of specific growth conditions at suppressing compositional fluctuation and limiting threading dislocation density is evaluated. CGBs grown at high temperatures with high Al content exhibit the lowest defect densities. The use of a high V/III ratio suppresses compositional fluctuation and defect density. In conclusion, these insights lead directly to improvements in the efficiency of metamorphic Ga1-xInxAs solar cells grown on AlyGa1-x-yInxAs CGBs.},
doi = {10.1109/JPHOTOV.2019.2951927},
journal = {IEEE Journal of Photovoltaics},
number = 1,
volume = 10,
place = {United States},
year = {2019},
month = {11}
}

Journal Article:
Free Publicly Available Full Text
This content will become publicly available on November 28, 2020
Publisher's Version of Record

Save / Share: