Screw dislocations on pyramidal planes induced by Vickers indentation in HVPE GaN

Abstract

The dislocation structure around the Vickers indentation on a hydride vapor-phase epitaxy GaN wafer was observed by multi-photon photoluminescence imaging and cross-sectional scanning transmission electron microscopy. Straight dislocation lines parallel to the six equivalent directions, i.e. a rosette pattern, were observed in the subsurface. Below the rosette pattern, a flower-like pattern similar to dislocation loops expanded in the six equivalent directions. Under the flower-like pattern, an inverted triangular dark area composed of dislocations on pyramidal planes was observed. This structure did not vary with load (20–980 mN) or crack formation. The inverted triangular dark area contained screw dislocations with a slip system and an estimated density of 2 × 109 cm−2. The penetration depth of the screw dislocation on the pyramidal plane was found to be proportional to the length of the diagonal indentation line.