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

Abstract

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¯01} and {11¯00} facets under Ga‐rich condition for selective area growth (SAG) on [ 11¯00 ] lateral direction. In contrast, an equilibrium crystal shape including the larger area of {11¯01} facets and (0001) plateau with smaller {11¯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 H2 carrier gas condition at low temperature. The results under H2 carrier gas are found to be different from those under N2 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.

Atomic‐Scale Investigation of the Lattice‐Asymmetry‐Driven Anisotropic Sublimation in GaN

“…Pyramid consisting of { } planes at the top was predicted as an equilibrium crystal shape using first principles and ab‐initio approach. [ 24 , 33 ] The theoretical prediction that the Ga‐terminated surface has the lowest energy under Ga‐rich conditions, which is also in good agreement with our results. Thus, we believe that the triangular shape is actually a hexagonal pyramid composed of six of planes and one (000 ) plane as a base in the 3D space.…”

Selective-area growth study of GaN micropillars for quasi-vertical Schottky diodes

“…The enhanced LOG of {10-11} facets for micropillars with planar pillar tops (cf section 3.1) indicates that the (0001) top facet will be maintained even for larger growth times. Combined with recent calculations of absolute surface energies during GaN SAG under MOVPE growth conditions [38], our observations suggest the pillar morphology of samples B, C 1 , and H, consisting of {10-11} facets and a (0001) top facet, to largely represent the equilibrium morphology under N-rich conditions and high T SAG . Every pit corresponds to a threading dislocation termination.…”

Roles of growth kinetics on GaN non-planar facets under metalorganic vapor phase epitaxy condition

“…In our previous studies, we have theoretically predicted the equilibrium crystal shapes based on Wulff plot using absolute surface energies for the SAG on nonpolar lateral direction. 24) Although the constructed equilibrium shapes are qualitatively consistent with the experimental results, it is difficult to theoretically predict the aspect ratio which can be compared with experiments. In order to exactly compare the calculated results with experiments, the effect of growth kinetics on GaN non-planar facets should be taken into account.…”

“…This conclusion coincides with the experiment that exhibits a wide area of 0001 ( ) plateau during SAG by MOVPE using N 2 carrier gas, 9) which cannot be achieved from the analysis of equilibrium crystal shape for the SAG. 24) In summary, we have investigated the behavior of Ga adatom on GaN non-planar facets during MOVPE on the basis of ab initio calculations. For non-planar facet consisting of 1100 ( ) and 1101 ( )planes, we have found that the migration from nonplanar facet to planar 1100 ( )and 1101 ( )surfaces hardly occurs regardless of carrier gas.…”