High quality GaN grown on polycrystalline diamond substrates with h-BN insertion layers by MOCVD

[Display omitted] •The monocrystalline GaN on polycrystalline diamond is successfully obtained.•The h-BN layer is used to alleviate the mismatch between GaN and diamond.•The full width at half maximum of (002) plane of GaN is as low as 1.20°. The single crystal GaN film was successfully grown on the polycrystalline diamond substrate using a h-BN insertion layer by metal–organic chemical vapor deposition, which solved the problem that GaN and diamond are difficult to combine due to the lattice and thermal mismatch. After using h-BN and optimizing the growth process of AlN nucleation layer, the full width at half maximum value of (002) plane of GaN is decreased from 4.67° to 1.20°. The root mean square roughness is decreased from 31.5 nm to 1.07 nm, and the yellow luminescence caused by carbon impurity is obviously suppressed. The successful preparation of single crystal GaN film on polycrystalline diamond provides a new solution for the heat dissipation problem, which has plagued the development of GaN-based power devices for a long time.