Suppression of Cu diffusion from a bulk ZnSe substrate to a homoepitaxial layer by Se-beam irradiation as a pregrowth treatment

Cu diffusion of homoepitaxial ZnSe was investigated through low-temperature photoluminescence (PL) spectra and secondary ion mass spectroscopy. Though Cu in ZnSe normally diffuses easily, we found that Cu in a ZnSe substrate did not diffuse into the homoepitaxial layer when the substrate was heated under Se-beam irradiation prior to growth. Cu-related emissions, such as Ideep1 and Cu-green, disappeared from the PL spectrum of the homoepitaxial layer grown on the Se-beam irradiated substrate. This suppressed Cu diffusion can be explained by site transformation of interstitial Cu atoms in the ZnSe substrate into Cu atoms occupying the Zn lattice site. This treatment is very useful for improving the purity of homoepitaxial ZnSe layers.