White-Light Electroluminescence From n-ZnO/p-GaN Heterojunction Light-Emitting Diodes at Reverse Breakdown Bias

White-light electroluminescence (EL) from n-type ZnO (n-ZnO)/p-type GaN (p-GaN) heterojunction light-emitting diodes operated at reverse breakdown bias was reported. The n-ZnO epilayers were grown by atomic layer deposition on p-GaN. The electron tunneling from the deep-level states near the ZnO/GaN interface to the conduction band in n-ZnO is responsible for the reverse breakdown. The EL spectrum was composed of the blue light at 450 nm and the broadband around 550 nm, which originated from the Mg acceptor levels in p-GaN and the deep-level states near the ZnO/GaN interface, respectively. The chromaticity coordinate of the EL spectrum was (0.31, 0.36), which is very close to (0.33, 0.33) of the standard white light.