A two-stage epitaxial lateral overgrowth method was used to obtain uniformly coalesced (11▪0) a-plane GaN using metal organic chemical vapour deposition by employing a relatively lower growth temperature in the first stage, followed by conditions which led to enhanced lateral growth in the second. Using a two-stage epitaxial lateral overgrowth method, the average Ga-polar to N-polar wing growth rate ratio was reduced from between 4 and 6 to between 1.5 and 2. This consequently reduced the height difference between the 2 approaching wings at the coalescence front that resulted from the wing tilt (0.44° for Ga wings and 0.37° for N wings, measured by X-ray diffraction), thereby making their coalescence much easier. Transmission electron microscopy showed that the threading dislocation density in the wing areas was 1.0 x 108/cm2. This was more than 2 orders of magnitude lower than that in the window areas (4.2 x 1010/cm2). However, a high density of basal stacking faults (1.2 x 104/cm) was still present in the wing areas; as compared with c-plane GaN, where they were rarely observed away from the substrate. Atomic force microscopy and photoluminescence measurements of the coalesced epitaxial lateral overgrowth a-plane GaN sample also revealed an improved material quality.

Defect Reduction in (11▪0) a-Plane GaN by Two-Stage Epitaxial Lateral Overgrowth. X.Ni, Ü.Özgür, Y.Fu, N.Biyikli, J.Xie, A.A.Baski, H.Morkoç, Z.Liliental-Weber: Applied Physics Letters, 2006, 89[26], 262105 (3pp)