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 ∼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