Fabrication of p-CuGaS2/n-ZnO:Al heterojunction light-emitting diode grown by metalorganic vapor phase epitaxy and helicon-wave-excited-plasma sputtering methods

Greenish-white electroluminescence (EL) was observed from the heterojunction light-emitting diodes (LEDs) composed of p-type (001) CuGaS₂ chalcopyrite semiconductor epilayers and preferentially (0001)-oriented polycrystalline n-type ZnO thin films. The CuGaS₂ layers were grown on a (001) GaP substrate by metalorganic vapor phase epitaxy and the ZnO films were deposited by the surface-damage-free helicon-wave-excited-plasma sputtering method. The n-ZnO/p-CuGaS₂ LED structure was designed to enable an electron injection from the n-type wider band gap material forming a TYPE-I heterojunction. The EL spectra exhibited emission peaks and bands between 1.6 and 2.5 eV, although their higher energy portions were absorbed by the GaP substrate. Since the spectral lineshape resembled that of the photoluminescence from identical CuGaS₂ epilayers, the EL was assigned to originate from p-CuGaS₂.