Equilibrium Morphologies of Faceted GaN under the Metalorganic Vapor-Phase Epitaxy Condition: Wulff Construction Using Absolute Surface Energies

An equilibrium Wulff construction using absolute surface energies for various orientations is conducted to elucidate the morphology change of GaN under the metalorganic vapor-phase epitaxy (MOVPE) condition. The calculated equilibrium shapes suggest that the morphology mainly consists of {11 over bar 01} and {11 over bar 00} facets under Ga-rich condition for selective area growth (SAG) on [ 11 over bar 00 ] lateral direction. In contrast, an equilibrium crystal shape including the larger area of {11 over bar 01} facets and (0001) plateau with smaller {11 over bar 00} facets emerges under N-rich condition. Furthermore, by incorporating growth conditions such as growth temperature and carrier gas, it is found that the (0001) plateau hardly emerges under H-2 carrier gas condition at low temperature. The results under H-2 carrier gas are found to be different from those under N-2 carrier gas where the (0001) plateau slightly emerges at low temperature. The calculated results manifest that our approach can provide the determination of equilibrium shape of semiconductor materials during epitaxial growth.