Analysis of threading dislocations in void shape controlled GaN re-grown on hexagonally patterned mask-less GaN

In this article, we analyze the behavior of threading dislocations in GaN layers re-grown on hexagonally patterned mask-less GaN. The growth mode of the material with patterned hexagonal morphology changes with the diameter and the periodicity of the hexagonal patterns. The growth mode directly affects the shape of the voids that are formed in this kind of lateral epitaxy. Transmission electron microscopy has been used to study threading dislocations in GaN layers with voids having different sizes and sidewall angles. The results show that a significant number of threading dislocations near the tapered void's surface undergo a 90° reorientation in their propagation trajectory whereas almost no dislocations bend in the case of smaller voids having more vertical sidewalls. Different types of dislocations in the vicinity of the voids have also been identified using the invisibility g·b criteria. The full width at half maximum values for XRD ω-scan recorded in (002) reflection drop from 256″ to 181″ as the void sidewall inclination changes from 85° to 60°. A similar dropping trend in the full width at half maximum values for asymmetric diffraction reflections has also been observed.

► Study of GaN layers with intentionally created voids/pores of different shapes with TEM.
► Threading dislocations propagation behavior and their type identified.
► 90° dislocation bending observed with inclined sidewall voids.
► XRD analysis of GaN epi-layers shows improved crystalline quality for inclined voids with 90° dislocation bending.