Observation of a two-dimensional electron gas in the AlGaN/GaN on SiC substrates

GaN/Al0.08Ga0.92N heterostructure has been grown on(0001) 6H-SiC substrates using low pressure metalorganic chemical vapor deposition(LP-MOCVD). Triethylgallium (TEGa), trimethylaluminum(TMA) and ammonia(NH3) were used as the Ga, Al and N sources, respectively. The carrier gas is hydrogen(H-2)and the growth pressure is kept at 76 torr. Five pairs of GaN/Al0.08Ga0.92N(100 Angstrom/100 Angstrom)were used as buffer layer, then follow by an 1.3 mu m GaN film. The 500 Angstrom AlGaN bulk structure was grown on the GaN and Finally an 100 Angstrom GaN cap layer to prevent the oxidation of AlGaN layer. The full width half maxima(FWHM) of x-ray peak is 115 are second for the thick layer of GaN (1.3 mu m), this value is smaller than we reported for the GaN on sapphire substrate (It was about 300 are second). The Hall mobility and sheet carrier concentration are 887 cm(2)/Vs, 1.0 x 10(16)cm(-2) at 300K and 4661 cm(-2)/Vs, 7.2 x 10(12)cm(-2) at 77K. This high electron mobility is an indication of a two-dimensional electron gas(2DEG) formed at the GaN/AlGaN interface.