Structural evolution of GaN during initial stage MOCVD growth

Abstract

The structural evolution of GaN films during the initial growth process of metalorganic chemical vapor deposition (MOCVD) - low temperature nucleation layer growth, annealing, and high temperature epitaxial growth - was investigated in a synchrotron x-ray scattering experiment. The nucleation layer grown at 560°C that was predominantly cubic GaN consisted of tensile-strained aligned domains and relaxed misaligned domains. The hexagonal GaN, transformed from the cubic GaN during annealing to 1100 °C, showed disordered stacking. The atomic layer spacing decreased as the fraction of the hexagonal domains increased. Subsequent growth of epitaxial GaN at 1100 °C resulted in the formation of ordered hexagonal GaN domains with rather broad mosaicity.

Thermodynamic model of low temperature metalorganic chemical vapor deposition of GaN

“…6,7,13,19 Therefore, TMG and NH 3 will be considered in the developed model. Thermal pyrolysis of TMG is an irreversible reaction and, therefore, the initial state of the Ga precursor in the gaseous phase can be represented as the Ga atoms.…”

“…One of these peculiarities is the formation of the thermodynamically stable wurtzite and metastable zinc-blende modifications of GaN in the same growth process. [5][6][7] Simultaneous formation of the stable and metastable crystal modifications demonstrates the nonequilibrium character of LT-MOCVD of GaN.…”