Plasma-assisted MBE of GaN and AlGaN on 6H SiC(0001)

The growth of undoped and doped GaN and AlGaN films on off-axis 6H SiC substrates was investigated using plasma-assisted molecular beam epitaxy (MBE). Smooth and crack-free GaN and AlGaN films were obtained; the best results occurred at the highest growth temperature studied (800 C) and with a 40 to 50 nm AlN buffer layer grown at the same temperature. Carrier concentrations of up to n = 4 {times} 10{sup 20} cm{sup {minus}3} were accomplished with silicon, with a 40 to 50% activation rate as determined by secondary ion mass spectrometry (SIMS). Unintentionally doped Al{sub x}Ga{sub 1{minus}x}N (x {approx} 0.1) was n-type with a carrier concentration of 7 {times} 10{sup 18} cm{sup {minus}3}. N-type AlGaN (x {approx} 0.1)/p-type 6H SiC (0001) heterostructures showed excellent junction characteristics with leakage currents of less than 0.1 nA at 5 V reverse bias at room temperature and 0.5 nA at 200 C operating temperature.