Microstructure and Optical Properties of Nonpolar $m$-Plane GaN Films Grown on $m$-Plane Sapphire by Hydride Vapor Phase Epitaxy

概要

論文の詳細を見る
Thick nonpolar ($10\bar{1}0$) GaN layers were grown on $m$-plane sapphire substrates by hydride vapor phase epitaxy (HVPE) using magnetron sputtered ZnO buffers, while semipolar ($10\bar{1}\bar{3}$) GaN layers were obtained by the conventional two-step growth method using the same substrate. The in-plane anisotropic structural characteristics and stress distribution of the epilayers were revealed by high resolution X-ray diffraction and polarized Raman scattering measurements. Atomic force microscopy (AFM) images revealed that the striated surface morphologies correlated with the basal plane stacking faults for both ($10\bar{1}0$) and ($10\bar{1}\bar{3}$) GaN films. The $m$-plane GaN surface showed many triangular-shaped pits aligning uniformly with the tips pointing to the $c$-axis after etching in boiled KOH, whereas the oblique hillocks appeared on the semipolar epilayers. In addition, the dominant emission at 3.42 eV in $m$-plane GaN films displayed a red shift with respect to that in semipolar epilayers, maybe owing to the different strain states present in the two epitaxial layers.
2008-05-25