Study of initial stages of the GaN growth on sapphire substrates

摘要

The growth of the buffer GaN layer and its influence on the perfection and PL properties of GaN epilayers grown by RP-MOCVD method on (00 centre dot 1) and (10 centre dot 2) sapphire substrate have been studied At different gas flow conditions we found the presence of a "delay time" when GaN deposition did not occur on the sapphire substrate at 500 deg C. The substrate nitridation have a strong affect on the crystallogrphic properties of the partly amorphous buffer. Buffer annealing produces strain relaxation and forming a relatively undefective region. The optimal buffer thickness gives rise to relatively unstrain epilayer as hin as 1 mu m. The initial epigrowth step depends on the Ga-metalorganic flow. The buffer and epilayer thicknesses as a function of substrate position on the graphite susceptor are also presented.