OPTICAL AND ELECTRICAL-PROPERTIES OF RADICAL BEAM GETTERING EPITAXY GROWN N-TYPE AND P-TYPE ZNO SINGLE-CRYSTALS

A method has been developed for obtaining single crystal layers of ZnO on ZnS and ZnO single crystal substrates by means of heat treating the crystals in an activated oxygen atmosphere. With this method, an inversion of the type of conductivity in zinc oxide has been accomplished. The fundamental luminescence properties of these layers are investigated. In addition to A-excitons, emission bands corresponding to B- and C-excitons have been registered in the exciton regions of the photoluminescence spectra. It was found that the violet band at 400 nm ascribed to an association of the doubly-charged oxygen vacancy and the singly-charged zinc vacancy is the dominant one in the photoluminescence spectra of ZnO layers with p-type conductivity. In ZnO layers with n-type conductivity, the fundamental visible luminescence bands - green and yellow-orange - are generated by oxygen vacancies and alkali metals, respectively. Hole mobility is determined from Hall effect measurements.