Ultraviolet electroluminescence properties of the p-NiO/n-GaN-based heterojunction diodes

Diodes based on NiO/GaN and NiO/MgO/GaN heterojunctions were fabricated on commercially available n-GaN/u-GaN/Sapphire substrates using a radio frequency magnetron sputtering system. Electroluminescence (EL) measurements revealed that the diode with the MgO layer exhibited fairly pure ultraviolet emission peaking at similar to 370 nm with a full-width at half maximum of about 9 nm, while no EL was detected from the diode without the MgO layer. By choosing a proper thickness of the insulator MgO layer, the EL performance of the devices could be greatly improved. The results were discussed in terms of the I-V characteristics and the band diagrams of the heterojunctions.