Blue/green electroluminescence from a ZnO nanorods/p-GaN heterojunction light emitting diode under different reverse bias

Vertically aligned ZnO nanorods were directly grown on p-GaN film to form a ZnO nanorods/p-GaN heterojunction. Electroluminescence characteristics of the ZnO nanorods/p-GaN heterojunction light emitting diode (LED) operated at different reverse bias were investigated. Only green emission at around 519 nm could be observed at 3.5 V, and blue emission at around 468 nm gradually appeared with the increase of reverse bias. The color of the device could be turned from green (0.31, 0.39) to blue (0.16, 0.16) by varying the reverse bias voltages. The electroluminescence mechanism of the heterojunction LED was discussed in terms of interface defects and band diagram.