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Published December 23, 1993 | public
Journal Article

Effects of metal ion chemisorption on gallium arsenide surface recombination: picosecond luminescence decay measurements

Abstract

n-GaAs/KOHSe^(-/2-)(aq) contacts have been studied using real time photoluminescence decay techniques. This system is of interest because metal ion chemisorption improves the steady-state current-voltage properties of GaAs/KOH-Se^(-/2-)(aq)/Pt cells, yielding 16% efficiency under simulated 1-sun illumination conditions. In this work, the luminescence decay dynamics of thin epilayer GaAs samples under high level injection conditions were monitored in contact with KOHSe^(-/2-)(aq) solutions. The photoluminescence signals decayed more rapidly after metal ion chemisorption than after a fresh etch, indicating that the metal ion treatment induced a more active recombination and/or charge-transfer process than the etch. A finite-difference simulation was used to model the decays and to extract a minority carrier surface recombination velocity, S_(min), for these systems. For etched GaAs surfaces, S_(min) = 5 X 10³ cm s⁻¹, while GaAs surfaces that had been etched and then exposed to 0.010 M Co(NH₃)₆³⁺ (pH = 11) solutions displayed S_(min) = 2 X 10⁵ cm s⁻¹. Qualitatively similar behavior was observed for Rh-, Ru-, and Os-treated GaAs surfaces as well. These data are fully consistent with prior suggestions that the primary effect of metal ion chemisorption is to increase the rate of hole transfer to the Se^(-/2-)(aq) electrolyte, as opposed to decreasing surface recombination processes at the GaAs/liquid contact.

Additional Information

© 1993 American Chemical Society. Received: September 1, 1993. We gratefully acknowledge C. L. R. Lewis, H. MacMillan, L. Eng, and A. Yariv for supplying the GaAs samples that were used in this work. We are also grateful to Steve Feldberg for discussions regarding the finite-difference calculations, to J. Winkler of Caltech and J. Perry of JPL for invaluable assistance with the laser experiments, and to A. Heller of the University of Texas, Austin, for helpful discussions. This work was supported by the U.S. Department of Energy, Office of Basic Energy Sciences, through the Fundamental Interactions Branch.

Additional details

Created:
August 20, 2023
Modified:
October 18, 2023