Growth mode and surface reconstruction of GaN(000(1)over-bar) thin films on 6H-SiC(000(1)over-bar)

Two-dimensional growth of GaN thin films on an atomically flat C-face 6H-Si C(000 (1) over bar) surface prepared by ultra, high vacuum Si-etching is ob served when using an AIN buffer layer in N plasma-assisted molecular beam e pitaxy. Scanning tunneling microscopy and reflection high energy electron d iffraction observations reveal a series of Ga-stabilized reconstructions wh ich are consistent with those reported for an N-polar GaN(000 (1) over bar) film. The result, including the effect observed previously for GaN thin fi lm on Si-terminated 6H-SiC(0001), agrees with the polarity assignment of he teroepitaxial wurtzite GaN films on polar 6H-SiC substrates, i.e., GaN film grown on SiC(000 (1) over bar) is < 000<(1)over bar> > oriented (N-face) w hile that on SiC(0001) is < 0001 > oriented (Ga-face).