Greenish-white electroluminescence from p-type CuGaS2 heterojunction diodes using n-type ZnO as an electron injector

Greenish-white electroluminescence (EL) was observed from p-type (001) CuGaS2 chalcopyrite semiconductor epilayers grown on a (001) GaP substrate by metalorganic vapor phase epitaxy, due to the electron injection from preferentially (0001)-oriented polycrystalline n-type ZnO thin films deposited by the surface-damage-free helicon-wave-excited-plasma sputtering method. The structure was designed to enable the electron injection from n-type wide band gap partner forp-CuGaS2 forming the ZnO∕CuGaS2 TYPE-I heterojunction. The EL spectra exhibited emission peaks and bands between 1.6 and 2.5eV, although the higher energy portion was absorbed by the GaP substrate. Since the spectral line shape resembled that of the photoluminescence from the identical CuGaS2 epilayers, the EL was assigned to originate from p-CuGaS2.