Photoluminescence study of initial interdiffusion of SiGe/Si quantum wells grown by ultrahigh vacuum-chemical vapor deposition

Abstract

SiGe quantum wells were grown at 525 °C using a commercially available, ultrahigh vacuum–chemical vapor deposition system, in which the purity of the material and quality of interfaces have already been demonstrated. Changes in photoluminescence line energies are monitored and the extent of interdiffusion in the wells during annealing is calculated. A strong initial enhancement of the diffusivity is observed in as-grown material. Material annealed using a two-step process in which strain and Ge peak concentrations are unchanged after the first (low temperature) step, shows a much lower interdiffusion during the second step. It is argued that strain alone cannot explain the enhanced interdiffusion, which is, thus, attributed to grown-in, nonequilibrium point defects.