Photoluminescence properties of nitrogen-doped ZnSe layers grown by molecular beam epitaxy with ion- and radical-beam doping techniques

Molecular beam epitaxial growth of N-doped ZnSe layers on GaAs and ZnSe substrates were carried out using ion- and radical-beam doping techniques during growth to obtain p-type layers. Photoluminescence (PL) properties of these layers are mainly described in this paper. Low-temperature PL of the ion-doped ZnSe with an appropriate condition showed a dominant I₁ line with well-suppressed DAP emission, indicating that N is successfully incorporated as shallow acceptors without contamination of donor impurities. However, the layer did not exhibit measurable p-type conduction, probably due to low concentration of acceptors. Layers with higher concentrations showed degradation of both PL properties and crystallinity, caused by ion damage. Subsequent experiments using the neutral radical-beam doping technique provided p-type conduction in N-doped ZnSe on GaAs substrates, whereas the PL spectrum showed intense DAP emission. This result indicates that damage by irradiation of neutral radicals is slight in comparison with the ion damage. Use of homoepitaxial growth considerably increased the hole concentration attributed to an improvement in crystallinity compared to the heteroepitaxy.