Improved GaN grown on Si(111) substrate using ammonia flow modulation on SiNx mask layer by MOCVD
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In this paper, 1 μm n-GaN was grown by using varied and fixed ammonia flow (NH3) on SiNx 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 SiNx 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 SiNx 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.
KeywordsGaN epilayer MOCVD NH3 modulation
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