Photoluminescence study of Al doping in GaAs grown by molecular-beam epitaxy

Abstract

A detailed photoluminescence investigation of the effects of Al doping on GaAs grown by molecular-beam epitaxy is reported. Materials with 0.1%, 1%, and 3% Al doping have been studied. Viewed as an AlxGa1−xAs alloy semiconductor, our study on these materials presents results on the optical characteristics of the lowest Al composition material reported to date. Photoluminescence spectra show three major peaks. Detailed measurements on the dependence of these spectra on temperature and excitation power have been carried out to characterize the various transitions responsible for the luminescence peaks. A near-band-edge exciton peak, a carbon acceptor-related free-to-bound transition, and a defect complex-related luminescence peak, probably involving silicon, are identified as the main features of our luminescence spectra. The integrated luminescence intensity shows a strong quenching with the increase in Al doping, thus supporting the increase of nonradiative deep-level centers with Al doping, concluded from our earlier reported deep level transient spectroscopy study. The relative intensity of the excitonic peak shows a stronger decrease than that of the other luminescence features. New data on the shift of the excitonic transition energy with Al content x in AlxGa1−xAs, for the lowest x values yet reported, are provided by our photoluminescence study.