Luminescence in highly conductive n-type ZnSe

We have studied the photoluminescence of ZnSe doped by diffusion of Al at high temperature (1000–1100 °C) or by Ga at low temperature (600 °C). The diffused samples are highly conductive (0.1ρ10 Ω cm). According to the doping conditions the luminescence, at 300 °K, is dominated by the well-known self-activated orange emission (6300 Å) or by a yellow-green band that we assign to Na-Al complexes. Annealing in zinc atmosphere was found to have a large influence on the photoluminescence of the Ga-doped samples only. Thus, at 300 °K, the annealed samples exhibit a blue intrinsic emission with a strong reduction of the orange or the yellow-green bands; at 77 and 4.2 °K the photoluminescence spectra are dominated by blue lines corresponding, respectively, to free-electron–acceptor or donor-acceptor recombinations. We show that the shallow acceptor involved is Na.