In situ pendeoepitaxy of GaN using heteroepitaxial AlGaN/GaN cracks

Pendeoepitaxy on patterned templates has been proven to be efficient for reducing threading dislocation densities in GaN thin films. In this letter, we report on in situ crack-assisted pendeoepitaxy of GaN using spontaneously formed cracks in AlGaN/GaN heterostructures. Our approach involves the growth of an AlGaN/GaN template followed by in situ thermal etching and deposition of an amorphous silicon nitride mask in a low pressure metal organic chemical vapor deposition system. Microwirelike GaN seeds are then formed along the crack lines during the initial stage of GaN overgrowth, which act as nucleation stripes for epitaxial lateral overgrowth. Transmission electron microscopy revealed that the lateral overgrowth of the wirelike GaN seeds effectively bends threading dislocations toward 〈11̄00〉 directions on the amorphous silicon nitride mask. The threading dislocation density by this method has been reduced from 2 × 10⁹ cm^-2 in control samples to 2 × 108 cm^-2 in some parts and 5 × 10⁷ cm^-2 in other parts of the GaN layer as determined by plan-view transmission electron microscopy which is very encouraging.