The effects of nitridation on properties of GaN grown onsapphire substrate by metal-organic chemical vapourdeposition

Abstract

The material qualities of GaN overlayers grown on (0001) sapphire substrates by metal-organic chemical vapour deposition were investigated as a function of nitridation time. The nitridation of sapphire surface notably affects on the properties of the GaN overlayers, such as surface morphology and structural, optical and electrical properties. The GaN overlayer with a short nitridation time of 30 s shows a good surface morphology, a relatively low background Hall carrier concentration and a high electron mobility, but the defect-related emission around 550 nm increased. Furthermore, for the GaN overlayer with nitridation for 180 s, even though it has a low (102) full width at half-maximum of the high-resolution x-ray diffraction rocking curve, other material properties were degraded owing to the long nitridation time. It was found that material properties have a trade-off relationship with the variation of nitridation time.