Molecular beam epitaxial growth of nitrogen-doped ZnSe with ion doping technique

Nitrogen-doped ZnSe layers on GaAs substrates have been prepared by an ion doping with nitrogen during molecular beam epitaxial growth of ZnSe in an attempt to obtain p-type crystals. The preliminary work using a simple ion source without a mass separator indicated that a considerable contamination of donor species occured, together with the doping of nitrogen acceptors. The low-temperature photoluminescence (PL) was dominated by a strong donor-acceptor pair (DAP) emission. A remarkable improvement was achieved by using high-purity nitrogen atomic or molecular ions generated by an ion gun system with an ExB mass separator. The best result obtained was with an N-doped layer exhibiting a PL spectrum dominated by a strong acceptor-bound-exciton emission I₁ whose peak intensity was 40 times greater than that of the DAP emission. The optimum condition for ion doping was investigated in terms of ion energy and ion current density. A temperature dependence of the PL spectrum was also reported.