GROWTH MODE AND SURFACE RECONSTRUCTION OF GaN(000\bar1) THIN FILMS ON 6H-SiC(000\bar1)

Two-dimensional growth of GaN thin films on an atomically flat C-face 6H-SiC(000\bar1) surface prepared by ultra-high vacuum Si-etching is observed when using an AlN buffer layer in N plasma-assisted molecular beam epitaxy. Scanning tunneling microscopy and reflection high energy electron diffraction observations reveal a series of Ga-stabilized reconstructions which are consistent with those reported for an N-polar GaN(000\bar1) film. The result, including the effect observed previously for GaN thin film on Si-terminated 6H-SiC(0001), agrees with the polarity assignment of heteroepitaxial wurtzite GaN films on polar 6H-SiC substrates, i.e., GaN film grown on SiC(000\bar1) is \langle000\bar1\rangle oriented (N-face) while that on SiC(0001) is \langle0001\rangle oriented (Ga-face).