White electroluminescence from ZnO/GaN structures

White electroluminescence (EL) from ZnO/GaN structures fabricated by pulsed laser deposition of ZnO:In onto GaN:Mg/GaN structures MOCVD-grown on Al 2 O 3 substrates has been observed. The white light is produced by superposition of the two strongest emission lines, narrow blue and broad yellow, peaked at 440 and 550 nm, respectively. The intensity ratio of different EL lines from ZnO/GaN/Al 2 O 3 structures depends on the ZnO film quality and drive current. The white EL is due to the high density of structural defects at the n -ZnO/ p -GaN interface. A band diagram of the n -ZnO/ p -GaN/ n -GaN structure is constructed and a qualitative explanation of the EL is suggested.