Surface photovoltagespectroscopy of pulsed laser deposited undoped ZnSe/n+GaAs

Abstract

We report surface photovoltage (SPV) spectra of ZnSe thin filmsdeposited on n+GaAs substrates in the wavelength rangeof 400-800 nm. In the above bandgap region of ZnSe(below 450 nm), we find that the major contribution to SPVcomes from trapping and re-emission from the slow states atthe ZnSe surface and ZnSe/GaAs interface. The effect of interference of light on the SPV spectra, has been analysed forsubbandgap wavelength excitation of ZnSe (470-800 nm). Inspite of the presence of a large number of subbandgap statesin ZnSe, the major contribution to SPV in this wavelength rangecomes from the substrate. The difference in the magnitudes ofthe SPV between the bare n+GaAs and the ZnSe/n+GaAs is due to the reduction of surface recombination velocity(SRV) of the minority carriers in n+GaAs.