Extended defect structure of a-plane GaN produced by sidewall lateral epitaxial overgrowth

This paper demonstrates the use of Sidewall Lateral Epitaxial Overgrowth (S-LEO) on a-plane GaN thick films on r-plane sapphire by hydride vapor phase epitaxy (HVPE). Comprehensive study of the extended defect microstructure of the a-plane GaN films was carried out using cross-sectional and plan-view transmission electron microscopy (TEM). A very low density of primary threading dislocations and a heterogeneous microstructure can be found in the GaN films. In the window region and N-face wing region, the extended defects included type I1 and type I2 basal stacking faults (BSFs), as well as prismatic stacking faults (PSFs) on a-planes. The density of type I1 BSFs was in the order of ∼2×105 cm−1, type I2 BSFs in the order of ∼104 cm−1, and corresponding localized partial dislocation density less than 1.5×109 cm−2. PSFs on a-planes were connected to two neighboring type I1 BSFs with an estimated density of 3×102 cm−1 in the plan-view images. In the Ga-face overgrowth regions, the density of BSFs was lower than 104 cm−1. However, inversion domains bounded by (1 1̄ 0 2), (1 1̄ 0 2̄), and (1 1̄ 0 0) planes were found in the Ga-face wing regions. The nature of inversion domain boundaries (IDB) on m-planes can be explained by the Auserman-Gehamn model using high-angle annular dark-field TEM images.

► Extended defect structure of novel lateral overgrowth technique for nonpolar GaN including quantification of the density of different types of basal plane stacking faults.
► Observation of prismatic stacking faults in GaN and determination of the nature of the prismatic stacking fault.
► Observation of inversion domains and determination of the atomic structure of the inversion domain boundary.