Growth of crack-free, carbon-doped GaN and AlGaN/GaN high electron mobility transistor structures on Si (111) substrates by ammonia molecular beam epitaxy

The growth of C-doped GaN epilayers on p-Si (111) substrates by ammonia molecular beam epitaxy is reported. Highly insulating and crack-free 1.5-mu m-thick C-doped GaN layers have been prepared using ionized methane as the dopant source. Using such a template, AlGaN/GaN two-dimensional electron gas structures with a mobility of 1260 cm(2)/V s for a sheet carrier density of 1.24x10(13) cm(-2) have been achieved at room temperature. Fabricated devices demonstrated an excellent pinch-off characteristic as revealed by an on-to-off ratio higher than four orders of magnitudes and by very low leakage current (10 mu A/mm at V-DS=20 V). (c) 2006 American Institute of Physics.