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

Abstract

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-μm-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 1260cm2∕Vs for a sheet carrier density of 1.24×1013cm−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 (10μA∕mm at VDS=20V).