GaAs Solar Cells Grown on Unpolished, Spalled Ge Substrates: Preprint

Alessandro Cavalli, Steven Johnston, Dana Kern, John Simon, Kevin Schulte, David Young, Aaron Ptak, Brett Ley, Corinne Packard

Research output: Contribution to conferencePaper


Decreasing the cost of single-crystal substrates by wafer reuse techniques has long been sought for III-V solar cells. Controlled spalling of III-V devices is a possible pathway for epitaxial liftoff, which would help reduce costs, but chemo- mechanical polishing after liftoff tends to limit the potential cost savings. Growth on an unpolished spalled surface would be an additional step toward lower costs, but it is crucial to show high efficiency solar cell devices on these unprocessed substrates. In this study, we spalled 2-inch Ge wafers using a Ni stressor layer, and then grew GaAs solar cells by HVPE on the spalled Ge surface without any other surface treatment. We show a 12.8% efficient single-junction device, without anti-reflection coating, with quantum efficiency very close to identical devices grown by HVPE on non-spalled GaAs substrates. Demonstrating a high carrier collection on unpolished spalled wafers is a step toward reducing substrate-related liftoff and reuse costs.
Original languageAmerican English
Number of pages7
StatePublished - 2018
Event2018 World Conference on Photovoltaic Energy Conversion (WCPEC-7) - Waikoloa, Hawaii
Duration: 10 Jun 201815 Jun 2018


Conference2018 World Conference on Photovoltaic Energy Conversion (WCPEC-7)
CityWaikoloa, Hawaii

Bibliographical note

See NREL/CP-5K00-73680 for paper as published in IEEE proceedings

NREL Publication Number

  • NREL/CP-5900-71591


  • controlled spalling
  • epitaxial lift-off
  • gallium arsenide
  • germanium substrate
  • photovotaics
  • solar cells


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