REFLECTION HIGH-ENERGY ELECTRON-DIFFRACTION STUDIES OF WURTZITE GAN GROWN BY MOLECULAR-BEAM EPITAXY

We report a comprehensive reflection high-energy electron diffraction study of the surface structure of GaN as a function of substrate tempe rature and III-V ratio for growth using elemental gallium and active n itrogen derived from a rf plasma source. An emission spectroscopy anal ysis of the composition of the;nitrogen plasma showed that the neutral atomic species dominated the growth process. The effect of substrate pretreatment is also discussed. It was found that good quality growth accompanied by a reconstructed surface are only obtainable during grow th under a slightly Ga-rich regime and after pretreatment by nitridati on and the growth of a low temperature buffer layer. Reconstruction mo de diagrams are presented both for layers during growth and also for l ayers which have been cooled after growth. The implications of these p lots are discussed in terms of surface vacancy densities. (C) 1998 Ame rican Vacuum Society.