Spatially resolved photocarrier energy relaxation in low-doped bulk GaAs

Abstract

We report on spatially resolved cw-photoluminescence studies of very-low-doped $n$- and $p$-type GaAs, which demonstrate that optically excited electrons retain significant excess energy on length scales of several tens of microns away from the excitation point. In contrast, the lattice is heated only negligibly outside the optical excitation area even for moderate excitation intensities. When diffusing away from the excitation site the photoelectrons are therefore not in thermal equilibrium with the lattice. Our results imply that it is inappropriate to describe low temperature photocarrier diffusion in GaAs with a spatially uniform diffusion constant.