Controllable regulation of diamond nucleation and growth on GaN substrates through pulse bias duty ratio

Abstract

GaN/AlN/diamond composite structures were prepared by the pulsed-DC bias-enhance nucleation (BEN) technique. Smooth diamond interface on GaN surface obtained for the first time by BEN technique. Different bias duty ratios (30%–70 %) can regulate the nucleation of diamond. The nucleation density increases and then decreases with the increase of duty ratio. The highest nucleation density was 1011 cm−2 which enough to grow a dense diamond layer on GaN. The effect of BEN treatment on the interface was investigated and some positive and negative results were obtained. After diamond deposition, GaN layer was protected by amorphous carbon and dielectric layers from hydrogen plasma, which implies that the BEN technique has the potential to be applied to grow diamond on GaN surfaces. A smooth and complete interfacial structure was obtained after diamond deposition. After the BEN treatment, 10 nm AlN layer was carbonized into an amorphous structure. BEN duty cycle can modulate GaN/AlN/diamond interface structure, which may reduce interfacial thermal conductivity. These results demonstrate the potential of BEN technique for diamond deposition on GaN substrates and provides a reference for further optimization.