LI+ ION-IMPLANTATION INTO ZNS EPITAXIAL LAYERS GROWN BY METALORGANIC VAPOR-PHASE EPITAXY

We have investigated the thermal stability of ZnS epilayers (epitaxial layers) with mirror-like surface morphologies, which are grown at 250-degrees-C by atmospheric pressure metalorganic vapor phase epitaxy. We have confirmed that the crystalline quality of the ZnS epilayers is maintained fully even at an annealing temperature (T(t)) of 700-degrees-C, as well as that of ZnSe epilayers. Based on the high thermal stability, we apply the post-annealing after ion implantation as a method for p-type doping. The optimum post-annealing conditions are investigated in order to remove the radiation damage and to raise the activation rate of Li acceptors without generating SA (self-activated) centers. It indicates that Li+ ions scarcely degrade the crystalline quality of the ZnS epilayers. The PL intensities of free-to-acceptor emission in Li+-implanted ZnS epilayers increase with T(t). Li forms a shallow acceptor level without SA center, and the activation rate of Li acceptor levels increases drastically with T(t).