P-type doping by ion implantation into ZnSe epitaxial layers grown by metalorganic vapor phase epitaxy

Abstract

We discuss the optimum conditions (acceleration energy and dose density) of both Li + and Na + ion implantations and the problem of fast diffusion of alkali impurities in ZnSe heteroepitaxial layers (heteroepilayers) grown by atmospheric pressure metalorganic vapor phase epitaxy. Li is preferred to Na as a p-type dopant in ZnSe because Na easily generates self-activated (SA) centers. The optimum annealing temperature ( T a) for activating Na acceptor levels without generating SA center levels is lower than that of Li, so that ion damage in Na-implanted epilayers cannot recover at the low T a. Moreover, Na diffuses fast as well as Li in ZnSe heteroepilayers at T a>550°C, which confirmed by SIMS and PL with a successive etching process. Na is redistributed almost uniformly in ZnSe as well as Li after optimum annealing. Particularly, Li in ZnSe forms high concentration of shallow acceptor levels without SA center levels after annealing.