Growth of GaN and related materials by gas-source molecular-beam epitaxy using uncracked ammonia gas

Abstract

High-quality GaN and related materials were grown using gas-source molecular-beam epitaxy (GSMBE). The cracking species of an ammonia gas was investigated using a quadruple mass spectrometer. Ammonia gas without cracking was used for the growth and was effectively grown on the substrate surface above 800°C. An undoped GaN layer (1 mm-thick) with a smooth surface was grown on a GaN buffer layer at 850°C. A higher growth rate of GaN was obtained (1.5 μm/h). This is the highest growth rate of the GSMBE using uncracked ammonia gas. The mobility of undoped GaN was 350 cm 2/V s and the carrier concentration was 6×10 16 cm 3 at room temperature. An Al 0.2Ga 0.8N/GaN heterostructure was also grown on a sapphire substrate. The mobility of the AlGaN/GaN heterostructure was 1230 cm 2/V s at room temperature. An Al 0.2Ga 0.8N/GaN hetero field effect transistor (HFET) was fabricated. A good electrical property of HFET with a high breakdown voltage was realized.