LOW-RESISTIVITY P-TYPE ZNSE-N GROWN BY MOLECULAR-BEAM EPITAXY USING A NITROGEN FREE-RADICAL SOURCE

The provision of stable, low-resistivity p-type ZnSe epitaxial material, a necessary ingredient for the fabrication of ZnSe-based short-wavelength (blue/green) diode lasers, has been an elusive goal for many years. However, a recently developed doping technique which has been employed to incorporate nitrogen impurities into ZnSe during molecular beam epitaxial growth shows excellent promise in this regard. The new doping technique involves the use of an rf plasma discharge, nitrogen free-radical source which supplies highly reactive nitrogen species to the growing ZnSe surface. As will be described in this paper, the remote (to the substrate) discharge plasma contains a significant concentration of ground state N atoms as evidenced by molecular emission spectroscopy studies of the nitrogen plasma itself and it is postulated that the fraction of N(4S) atoms which emanate from the source are the reactive species responsible for enhanced nitrogen doping of the ZnSe epilayers. To date, ZnSe:N epilayers have been grown at the University of Florida having resistivities as low as 0.75-OMEGA cm using the nitrogen free-radical doping approach.