Photoluminescent properties of n-GaAs electrodes: Simultaneous determination of depletion widths and surface hole-capture velocities in photoelectrochemical cells

Abstract

Steady-state photoluminescence measurements performed on n-GaAs electrodes used in photoelectrochemical cells (PEC’s) employing a stabilizing, aqueous telluride electrolyte yield values for the electrode’s depletion width W and surface hole-capture velocity S. Between −1.0 V (a potential near short circuit) and −1.5 V vs an SCE reference electrode (a potential near open circuit at the photon flux of 1×1015 photons/s cm2 employed), the interface behaves ideally: virtually all of the applied potential appears in the semiconductor space-charge region. Over this potential regime S is determined to be constant to within 10% and has a value, using literature values for hole lifetime and diffusion length, of approximately 2×105 cm/s for n-GaAs electrodes having carrier concentrations of (1–4)×1017 cm−3. Similar values of S obtained in air and in the PEC suggest a common rate-limiting mechanism for hole consumption in the two media.