IDEAL BEHAVIOR AT ILLUMINATED SEMICONDUCTOR-LIQUID JUNCTIONS

Photocurrent-voltage characteristics that show a nearly ideal dependen ce on the concentration of a nonadsorbed, outer-sphere redox acceptor (cobaltocenium) have been achieved with a novel photoelectrode structu re that consists of a thin (30-50 Angstrom) epilayer of GaInP2 deposit ed on a thick (5000 Angstrom) p-GaAs epilayer. The thin GaInP2 layer p roduces nearly perfect passivation of the GaAs surface (resulting in a surface recombination velocity <200 cm/s), while at the same time per mitting efficient electron transfer via field-assisted tunneling and/o r thermionic emission, The electron transfer kinetics, as characterize d by quenching of the GaAs photoluminescence, also shows a systematic acceptor concentration dependence. An unambiguous concentration,depend ence of the photocurrent and electron transfer kinetics has not been p reviously reported at semiconductor-liquid junctions.