The growth and electrical characteristics of epitaxial layers of zinc sulphide and of zinc selenide on p-type gallium phosphide†

Single crystal layers of ZnS and ZnSe have been expitaxially grown on p-type GaP using an HC1 close-spaced vapour transport system. Grown layer doping is accomplished using heavily doped source (ZnS, ZnSe) material and a zinc vapour diffusion process that reduces the number of compensating zinc vacancies. Experimental characteristics of nZnS-pGaP and nZnSe-pGaP diodes indicate dominance of the forward I-U relationship by space-charge-limited flow in the 103-104 ohm-cm ZnS and ZnSe. The reverse I-U characteristics of these devices agree qualitatively with a multistep tunnelling process but show larger than, expected reverse currents. The reverse bias capacitance is strongly frequency dependent in all devices studied. Forward injection electroluminescence was not observed from any of the nZnS-pGaP and nZnSe-pGaP devices studied.