Effects of ZnSe epitaxial growth on the surface properties of GaAs

The epitaxial growth of ZnSe induces changes in the surface properties of GaAs: surface barrier height, surface recombination velocity, and Fermi level pinning. These changes were investigated with Raman and photoluminescence spectroscopies in ZnSe-GaAs heterostructures with ZnSe layer thickness D ranging from 50 to 5000 nm. The ZnSe layers were grown by molecular beam epitaxy on (100)n-type GaAs substrates. Barrier heights smaller than 0.1 eV together with lower recombination velocities were obtained for pseudomorphic ZnSe layers with no misfit dislocations at the interface (D≤150 nm). When D exceeds the critical layer thickness and misfit dislocations are present at the interface the barrier height gradually increases with D. The barrier height and the pinning position of the Fermi level depend on the surface density of the dangling bonds generated by the misfit dislocations.