Gettered GaP Substrates for Improved Multijunction Solar Cell Devices

K. H. Montgomery, Birck Nanotechnology Center, Purdue University
C. R. Allen, Birck Nanotechnology Center, Purdue University
Isaac H. Wildeson, Birck Nanotechnology Center, Purdue University
J. H. Jeon, Birck Nanotechnology Center, Purdue University
A. K. Ramdas, Purdue University
Jerry M. Woodall, Birck Nanotechnology Center, Purdue University

Abstract

We report on the characterization of gettered p-type GaP substrates for application in high-efficiency multijunction solar cells. A commercial zinc-doped GaP substrate was divided, with one piece soaked in a phosphorus-saturated gallium-aluminum melt at 975A degrees C. Low-temperature continuous-wave photoluminescence indicated a significant decrease in deep-level impurity peaks due to oxygen and zinc-oxygen complexes after gettering in the phosphorus-saturated gallium-aluminum melt. To illustrate what effect this has on minority-carrier diffusion lengths, Au/GaP Schottky solar cells were fabricated on the substrates, and the spectral response of each was examined. A marked increase in response across all wavelengths on the gettered sample indicates an increase in minority-carrier diffusion lengths. To ensure these results were not simply due to an increase in the depletion region width resulting from a change in carrier density, C-V profiling was performed and found only a small change in carrier concentration of the gettered sample.

Discipline(s)

Nanoscience and Nanotechnology