Analysis of Crystalline Defects Caused by Growth on Partially Planarized Spalled (100) GaAs Substrates

Jacob Boyer, Anna Braun, Kevin Schulte, John Simon, Steven Johnston, Harvey Guthrey, Myles Steiner, Corinne Packard, Aaron Ptak

Research output: Contribution to journalArticlepeer-review

1 Scopus Citations

Abstract

We analyze the effect of growth on non-(100) surfaces resulting from incomplete planarization of spalled GaAs wafers on the defect structure of GaAs solar cell layers grown by hydride vapor phase epitaxy (HVPE). Controlled spalling of (100)-oriented GaAs has the potential to reduce substrate costs for III-V epitaxy; however, it creates regularly faceted surfaces that may complicate the growth of high-quality III-V optoelectronic devices. We leverage the anisotropic growth rate of HVPE to planarize these faceted GaAs substrates, reducing the surface roughness and degree of faceting. We observe degraded solar cell performance and material quality in sample areas where facets are not completely removed. We used dark lock-in thermography and photoluminescence to identify recombination in areas that were not fully planarized. We used cathodoluminescence to identify the presence of extended defects in these regions, which are correlated with bandgap fluctuations in the material. We hypothesize that these defects were created by strain from compositional fluctuations in ternary alloys grown on the faceted surfaces. This work elucidates the potential issues of solar cells grown on faceted surfaces and builds understanding toward realizing high performance III-V photovoltaics with the cost-reduction potential of controlled spalling.

Original languageAmerican English
Article number681
Number of pages13
JournalCrystals
Volume13
Issue number4
DOIs
StatePublished - 2023

Bibliographical note

Publisher Copyright:
© 2023 by the authors.

NREL Publication Number

  • NREL/JA-5900-85683

Keywords

  • crystalline defects
  • device characterization
  • HVPE
  • III-V
  • photovoltaics
  • spalling

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