Characterization of the surface irregularities of cubic GaN using micro-Raman spectroscopy

The surface irregularities of molecular-beam-epitaxy-grown cubic GaN on GaA s substrates were characterized by micro-Raman spectroscopy. Some surface i rregularities are found to be the result of the mixed phases of cubic (zinc -blende) and hexagonal (wurtzite) GaN, while others originate from the allo ying of GaN with the GaAs substrate. The polarization scattering of the sur face irregularities suggests that misoriented wurtzite GaN clusters sit on or are imbedded in the cubic GaN layer. It is revealed that the crystalline defects created during the growth of cubic GaN induce a growth of hexagona l GaN and, therefore, the surface irregularities consist of a phase mixture of cubic and hexagonal GaN polytypes. (C) 2001 American Institute of Physi cs.