Photocurrent spectroscopy of lattice-matched superlattice electrodes in photoelectrochemical cells

Abstract
Photocurrent spectra of GaAs/Al0.38Ga0.62As lattice-matched superlattice electrodes were obtained in photoelectrochemical cells containing nonaqueous liquid electrolyte; spectra were compared for two electron acceptors, cobalticinium and ferrocinium, having redox potentials (energy levels) that differ by 1.33 V. The spectra were found to be independent of acceptor energy levels, in sharp contrast to previous results with GaAs/GaAs0.5P0.5As strained-layer superlattices. These results indicate that for lattice-matched systems hot-electron transfer from upper quantum states in the quantum wells is not a dominant process. This is explained by the much lower surface trapping rates in lattice-matched superlattices compared to strained-layer superlattices.