Advantages and remaining issues of state-of-the-art m-plane free-standing GaN substrates grown by halide vapour phase epitaxy for m-plane InxGa1-xN epitaxial film growth by metalorganic vapour phase epitaxy were described. Because of the low threading dislocation and basal-plane stacking fault densities, improved quantum efficiency and short radiative lifetime were achieved for the near-band-edge emission of 200 to 250nm thick m-plane pseudomorphic InxGa1 − xN (x ≤ 0.14) epilayers. Values of full-width at half-maximum for the X-ray ω-rocking curves remained unchanged as the substrate values being 80 and 60arcsec for the (10•0) diffraction with 〈00•1〉 and <11•0> azimuths, respectively, and 80arcsec for the (10•2) diffraction. As the surface flatness was greatly improved, the In-incorporation efficiency (ηIninc) was lower than the cases for conventional c-plane growth and m-plane growths on defective GaN bases. The former originated from non-identical surface kinetics, and the latter was due to the reduction in the area of inclined and tilted planes. Sub-micrometer-wide zone patterns parallel to the c-axis and 2μm long axis figure-of-eight patterns parallel to the a-axis were clearly visualized in the monochromatic cathodoluminescence intensity images. Because the spatio-time-resolved cathodoluminescence measurement revealed very little spatial variation of low-temperature radiative lifetime, the slight peak energy variation was deemed to originate from non-identical ηIninc for the growing surfaces exhibiting various mis-cut angles. The figure-of-eight patterns were suggested to originate from the anisotropic, severe m-plane tilt mosaic along the a-axis of the GaN substrate, and the zone patterns might originate from the m-plane tilt mosaic along the c-axis. Further reduction in the tilt and twist mosaics was necessary for halide vapour phase epitaxy of free-standing GaN substrates, in order to grow homogeneous InGaN epilayers.

Advantages and Remaining Issues of State-of-the-Art m-Plane Freestanding GaN Substrates Grown by Halide Vapor Phase Epitaxy for m-Plane InGaN Epitaxial Growth. S.F.Chichibu, M.Kagaya, P.Corfdir, J.D.Ganière, B.Deveaud-Plédran, N.Grandjean, S.Kubo, K.Fujito: Semiconductor Science and Technology, 2012, 27[2], 024008