STRUCTURE OF FREE-EXCITON LUMINESCENCE SPECTRA IN HETEROEPITAXIAL ZNSE GAAS/

Free exciton photoluminescence (PL) and reflection spectra of MOVPE-gr own ZnSe/GaAs epilayers with thickness higher than the strain relaxati on thickness were studied experimentally and theoretically at T = 10-1 20 K. The calculations were performed using a single-and a two-oscilla tor model including spatial dispersion, in the frame of the dead layer model. The results allow us to rule out the explanation of the fine s tructure of the free exciton spectra by the thermal strain-splitting a nd by polariton effects. It was shown that this structure appears main ly due to the light interference caused by the presence of a dead laye r in the near-surface region, The dead layer thickness depends on the illumination intensity of the light used for PL excitation. (C) 1998 E lsevier Science B.V. All rights reserved.