Effect of enhanced reactivity in plasma-assisted epitaxial growth of ZnSe

Abstract

Plasma optical emission spectroscopy has been employed to detect active species in the plasmas used for the growth of undoped and N-doped ZnSe on GaAs substrates by plasma-assisted epitaxy. It revealed excited states of H 2, H, Zn, Se and SeH supplied onto the growing surfaces in hydrogen plasma with Zn and Se molecules evaporated from resistively heated crucibles. High purity undoped ZnSe layers, in which photoluminescent spectra are dominated by a strong emission due to free excitons, can be grown in plasma with controlled flow rate of pure hydrogen gas. For the layers grown in H 2 + N 2 mixed gas plasma, such photoluminescent emissions as I N 1 (excitons bound to neutral nitrogen acceptors) and DA (donor-acceptor pair) due to N-acceptors were clearly observed. Reactive nitrogen species of N + 2 and N 2, which seem to be responsible for N-acceptor doping into ZnSe, were detected by optical emission spectroscopy in the mixed gas plasma, but it also detected SeN produced by the reaction of N + 2 with Se or SeH and supplied to the growing surface.