Photoluminescence study of Li- and Na-implanted ZnSe epitaxial layers grown by atmospheric pressure metalorganic vapor-phase epitaxy

Abstract

We have investigated p-type doping of Li and Na impurities by ion implantation into ZnSe heteroepitaxial layers grown at very low temperatures (250 °C) by atmospheric pressure metalorganic vapor-phase epitaxy. The activation rates of shallow acceptor levels, the density of self-activated centers in the implanted-ZnSe epitaxial layers (epilayers), and the degradation of crystalline quality due to radiation damage are dependent on the ion implantation and annealing conditions. As the dose density changes, so do the optimum annealing conditions for the degrees of activation and the recovery of radiation damage. Also the depth profile of the implanted ions and damage is greatly influenced by the acceleration energy. It is difficult to decide on the optimum annealing conditions at the different acceleration energies and to assess the crystalline quality of the implanted epilayers with a nonuniform depth profile of the implanted ions, because the region analyzed is restricted near to the surface and does not always coincide with the implanted region in the epilayer. We have confirmed that the high-temperature annealing does not cause the damage to propagate deeply into the implanted epilayers, although it has been a cause of much concern in II-VI compounds.