Effect of delocalization of the donor states on the donor-acceptor recombination in zinc selenide

The effect of delocalization of donor states with increased donor concentra tion in ZnSe was considered. This effect leads to the change of recombinati on mechanism from donor-acceptor pair recombination to the recombination be tween the donor band and localized acceptor states without tunneling. The c ritical donor concentration for delocalization has been estimated to be N-e r approximate to 5 x 10(16) cm(-3) for shallow donors with E-D = 30 meV and N-er approximate to 2 x 10(17) and 5 x 10(17) cm(-3) for deeper donors wit h E-D = 44 and 55 meV, respectively. The comparison of the proposed recombi nation model with experimental results allows one to explain qualitatively without contradiction, the observed behaviour of the near-band edge impurit y recombination bands in intermediately doped compensated ZnSe : N samples. (C) 1999 Published by Elsevier Science B.V. All rights reserved.