Formation of A-Type Dislocations in Gan Adjacent to InGaN Epilayer at Lateral Free Surfaces of InGaN/GaN Heterostructures

Abstract

In this work we show that elastic relaxation of lateral free surfaces of InGaN epilayer may induce plastic deformation of adjacent GaN resulted in introduction of a -type dislocations beyond InGaN/GaN interface. The a -type dislocations are observed in cross-section TEM studies in GaN layers either below or above InGaN/GaN interface. Cathodoluminescence imaging of bulk samples shows the formation of a -type dislocations limited to the areas close to the lateral edges of the sample. The finite element simulations of the residual stress distribution at the lateral edge of structures containing InGaN layers, show the maximum of compressive σ zz stress in some distance from the InGaN/GaN interface, which could be a driving force for formation of the observed a -type dislocations. The presence of such defects at free edges of devices based on InGaN layers may have a significant negative impact on the device performance. It may especially affect the mirrors of laser diodes, leading to their faster degradation.