Images of the steady-state luminescence of passivated GaAs self-standing films under excitation by a tightly-focussed laser are analyzed as a function of light excitation power. While unipolar diffusion of photoelectrons is dominant at very low light excitation power, an increased power results in a decrease of the diffusion constant near the center of the image due to the onset of ambipolar diffusion. The results are in agreement with a numerical solution of the diffusion equations and with a physical analysis of the luminescence intensity at the centre of the image, which permits the determination of the ambipolar diffusion constant as a function of electron concentration.
@article{arxiv.1201.2574,
title = {Imaging ambipolar diffusion of photocarriers in GaAs thin films},
author = {Daniel Paget and Fabian Cadiz and Alistair Rowe and Francois Moreau and Steve Arscott and Emilien Peytavit},
journal= {arXiv preprint arXiv:1201.2574},
year = {2015}
}