Influence of Photoexcitation Depth on Luminescence Spectra of Bulk GaAs   Single Crystals and Defect Structure Characterization
  The results of investigation of bulk GaAs photoluminescence are presented taken from near-surface layers of different thicknesses using for excitation the light with the wavelengths which are close but some greater than the excitonic absorption resonances (so-called bulk photoexcitation). Only the excitonic and band-edge luminescence is seen under the interband excitation, while under the bulk excitation, the spectra are much more informative. The interband excited spectra of all the samples investigated in the present work are practically identical, whereas the bulk excited PL spectra are different for different samples and excitation depths and provide the information on the deep-level point defect composition of the bulk materials. 
V. A. Yuryev, V. P. Kalinushkin, A. V. Zayats, Yu. A. Repeyev, and V.   G. Fedoseyev
cond-mat.mtrl-sci cond-mat.mes-hall physics.optics