Optical studies were made of epilayers of N-doped material which had been grown by means of molecular beam epitaxy. The photoluminescence spectra of the donor-acceptor pair region at various temperatures, and for various carrier concentrations, showed that 2 donors were present in the samples. These were residual shallow donors with an activation energy of 0.026eV and deep donors, with an activation energy of 0.004eV, that had previously been attributed to a VSe-Zn-NSe complex. In the exciton region, an emission was observed (at 2.765eV) which increased in intensity when the epilayer was compensated by the deep donor. It was proposed that this transition was related to a deep-donor bound exciton.

I.S.Hauksson, S.Y.Wang, J.Simpson, K.A.Prior, B.C.Cavenett, W.Liu, B.J.Skromme: Physical Review B, 1995, 52[24], 17184-90