Step-flow anisotropy of them-plane GaN (11¯00) grown under nitrogen-rich conditions by plasma-assisted molecular beam epitaxy

Abstract

The homoepitaxial growth of $m$-plane $(1\overline{1}00)$ GaN was investigated by plasma-assisted molecular beam epitaxy under nitrogen-rich conditions. The surface morphologies as a function of sample miscut were studied, providing evidence for a strong growth anisotropy that is a consequence of the anisotropy of Ga adatom diffusion barriers on the $m$-plane surface recently calculated ab initio [Lymperakis and Neugebauer, Phys. Rev. B 79, 241308(R) (2009)]. We found that substrate miscut toward $[000\overline{1}]$ implies a step flow toward $\ensuremath{\langle}11\overline{2}\overline{6}\ensuremath{\rangle}$ while substrate miscut toward $[0001]$ causes formation of atomic steps either perpendicular or parallel to the $[0001]$ direction, under N-rich conditions at 730 ${}^{\ifmmode^\circ\else\textdegree\fi{}}$C. We describe the growth conditions for achieving atomically flat $m$-plane GaN layers with parallel atomic steps.