Effect of low-temperature GaN buffer layer on the crystalline quality of subsequent GaN layers grown by MOVPE

Abstract

We have investigated the correlation between the formation of single-crystal GaN islands in low-temperature (LT)-GaN buffer layer and the crystalline quality of subsequently grown high-temperature (HT)-GaN layer. X-ray diffraction (XRD) analysis showed that the LT-GaN layer was partially crystallized even without an annealing process. The annealing process transformed the nanometer-sized LT-GaN grains into the larger-sized islands whose size and density could be controlled by changing the growth temperature of LT-GaN layer. Atomic force microscopy (AFM) and XRD analyses indicated that the crystalline quality of HT-GaN layer depended strongly on the size and density of the islands in the LT-GaN layer. The full-width at half-maximum (FWHM) values of XRD rocking curves of GaN(0 0 0 2) and ( 1 0 1 ¯ 2 ) reflections were 198 and 232 arcsec, respectively, when the LT-GaN layer was grown at 475 °C.