Investigation of Initial Oxide Growth on GaN Epitaxial Films

Yamada, Takahiro*; Ito, Joyo*; Asahara, Ryohei*; Nozaki, Mikito*; Nakazawa, Satoshi*; Ishida, Masahiro*; Ueda, Tetsuzo*; Yoshigoe, Akitaka ; Hosoi, Takuji*; Shimura, Takayoshi*; Watanabe, Heiji*

Initial oxide growth on GaN epitaxial films by thermal oxidation in dry O ambient was investigated by means of synchrotron radiation X-ray photoemission spectroscopy and atomic force microscopy (AFM). High-resolution SR-PES analysis showed that the intensity ratio of O 1s/N 1s core-level peaks for the sample oxidized at 700 degrees is slightly higher than that for the sample after HCl wet-cleaning, indicating that GaN surface is oxidized. However, the O 1s/N 1s intensity ratio was nearly identical with increasing temperature up to 800 degrees and AFM observation revealed the preferential formation of small grains at the dark pits. On the other hand, the O 1s/N 1s intensity ratio drastically increased with further increasing temperature higher than 800 degrees, indicating significantly enhanced oxide formation on GaN surface.