Possible contribution of the Gibbs−Thomson effect to filling nanopipes in GaN homoepitaxial layers

Abstract

Reported suppression of the transformation of screw dislocations into nanopipes in GaN homoepitaxial layers by increasing total pressure (P total) during metalorganic vapor-phase epitaxy was assumed to be a phenomenon of nanopipe formation followed by its refill. We thermodynamically calculated equilibrium vapor pressure of Ga (P Ga) by considering the Gibbs−Thomson effect. Even with an assumption of a small surface free energy of 1.4 J m−2, the difference between the calculated P Ga’s in the vicinity of a wafer surface and in a nanopipe rapidly increased at P total > 750 hPa, explaining the increased vapor-phase diffusing flux of Ga into a nanopipe.