Microscopy of nitride layers grown on diamond

GaN films were grown on three different orientation diamond substrates: (001), (110) and (111). In all three cases the hexagonal GaN is grown with (0001) direction parallel to the surface normal, but otherwise matching to diamond in a different way. The appropriate orientational relationships are determined by selected area electron diffraction. Besides threading dislocations a high number of inversion domains (ID) were formed in some GaN films. The preparation of the diamond surface and the growth conditions proved to affect significantly the formation of crystal defects such as threading dislocations and IDs. Single polarity GaN films with a low density of dislocations were achieved for the optimized growth conditions. The highest quality GaN layers were grown on AlN buffer in which two crystalline variants were nucleated, but one of them was overgrown already in the thickness of the buffer layer.