The roles played by island coalescence rate and strain relaxation in the development of anisotropic in-plane strains, striation feature and subsequent degree of polarization in NH3-flow-rate-dependent m-plane GaN were considered. In the high-NH3-flow-rate samples, the results of cathodoluminescence, polarized Raman and in situ optical reflectance measurements revealed that a slower coalescence and unrelieved lattice misfit strain led to larger anisotropic in-plane strains, striated surface and luminescence patterns, and a lower density of basal-plane stacking fault and prismatic stacking fault. In contrast, a lower NH3 flow rate led to more rapid island coalescence and fully relaxed lattice misfit strain such that relaxed in-plane strains, a reduced striation surface, and a higher density of basal-plane and prismatic stacking faults were observed. It was suggested that the anisotropic in-plane strains, striation feature, and basal-plane stacking fault and PSF density were consequences of how rapidly coalescence occurred and the degree of relaxation of lattice misfit strain. In addition, the simulation results of the k•p perturbation approach confirmed a larger anisotropic strain results in a smaller degree of polarization. The research results provided important information for optimized growth of non-polar III-nitrides.

Surface Striation, Anisotropic In-Plane Strain, and Degree of Polarization in Nonpolar m-Plane GaN Grown on SiC. S.W.Feng, C.K.Yang, C.M.Lai, L.W.Tu, Q.Sun, J.Han: Journal of Physics D, 2011, 44[37], 375103