Photoelectrochemical etching of ZnSe and nonuniform charge flow in Schottky barriers

Photoelectrochemical etching of ZnSe, similar to that which was employed for cadmium chalcogenides, is found to decrease electron-hole recombinations upon photoexcitation considerably and to change the morphology of the semiconductor surface. Thus the photocurrent of a single-crystal ZnSe electrode in various electrolytes increases considerably (up to 100%) after such treatment. A unique morphology consisting of a dense pattern (${10}^9$ ${\mathrm{cm}}^{-2\mathrm{}}$) of etch pits is revealed after photoetching. This pattern is believed to reflect the dopant distribution close to the surface. Onset potential measurements show an anodic shift in the flat-band potential after photoetching which may arise from reduced pinning of the Fermi level associated with elimination of surface states. These measurements also indicate that the average dopant density close to the semiconductor surface is reduced after photoetching in accordance with our model of nonuniform hole flow in the space-charge region.