High-resolution X-ray diffraction analysis of cubic GaN grown on (0 0 1)GaAs by RF-radical source molecular beam epitaxy

Cubic GaN epilayers were grown on atomic hydrogen treated (0 0 1)GaAs substrates by RF-radical source molecular beam epitaxy. The crystalline quality was characterized by a high-resolution X-ray diffractometer. It was found that high-quality c-GaN can be grown at temperatures above 680°C; the FWHM of (0 0 2)GaN rocking curve was as small as 80-90 arcsec. In order to further precisely investigate how and to what extent the h-GaN phase is included in the c-GaN layer, the X-ray reciprocal space maps were measured for the X-ray beams incident along both 〈1 1 0〉 and 〈1 1 0〉 azimuths. It was found that the stacking faults exist predominantly on {1 1 1} A planes. The inclusion of h-GaN was estimated by comparing the integrated XRD intensities for h-GaN {1 0 1 1} and c-GaN(0 0 2) planes. It was found that the inclusion of h-GaN phase drastically decreased with increasing growth temperature above 680°C to reach about 4 × 10^-3 (or below) at temperatures of 710-740°C.