Improved GaN grown on Si(111) substrate using ammonia flow modulation on SiN _x mask layer by MOCVD

In this paper, 1 μm n-GaN was grown by using varied and fixed ammonia flow (NH₃) on SiN _x mask layer on Si(111) substrate using metal organic chemical vapor deposition (MOCVD). In-situ optical reflectivity traces of GaN growth show that the three- to two-dimensional process has been prolonged by using varied ammonia flow on SiN _x mask layer method compared with that grown by fixing ammonia flow. Structural and optical properties were characterized by high-resolution X-ray diffraction and photoluminescence, and compared with the sample grown by fixing ammonia flow, GaN grown using the varied ammonia flow on SiNx mask layer showed better structure and optical quality. It was assumed that the low NH₃ flow in the initial growth stage considerably increased the GaN island density on the nano-porous SiN _x layer by enhancing vertical growth. Lateral growth was significantly favored by high NH₃ flow in the subsequent step. As a result, the improved crystal and optical quality was achieved utilizing NH₃ flow modulation for GaN buffer growth on Si(111) substrate.