Photoluminescent properties of p-GaAs electrodes related to the ‘‘photocurrent anomaly’’: Determination of surface electron-capture velocities and depletion widths in photoelectrochemical cells

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Abstract
Steady‐state photoluminescence (PL) measurements have been used to determine depletion widths W and surface electron‐capture velocities S for p‐GaAs electrodes in aqueous acidic electrolytes. Electrodes subjected to slow cycling of applied potential (10 mV/s) exhibit a hysteresis in PL intensity in the ‘‘photocurrent anomaly’’ (PA) potential regime, characterized by negligible photocurrent at voltages up to ∼0.5 V negative of the flat‐band potential (∼0.1 V versus a saturated calomel reference electrode, SCE). A marked hysteresis in S values is observed in the PA potential regime of ∼−0.1 to −0.4 V vs SCE. Estimated S values are high, approaching 107 cm/s, but decrease significantly during anodic‐going scans. Variations in W between −0.1 and −0.8 V vs SCE indicate that strong Fermi‐level pinning does not obtain. Electrode operation under a pulsed potential program (−0.05 to −1.00 V vs SCE) caused a transient reduction in S of approximately an order of magnitude.