Reduction of V-pit and threading dislocation density in InGaN/GaN heterostructuresgrown on cracked AlGaN templates

Abstract

The high density of threading dislocations, often leading to the formation of invertedhexagonal pits in InGaN/GaN heterostructures on sapphire substrates, lowersthe radiative efficiency of light emitting devices. In this study, a cracked AlGaNtemplate has been implemented as a strain-relaxed layer for subsequent growth ofInGaN/GaN heterostructures. The detailed electron microscopy and surface topographicanalyses show that such a template has led to a reduction of threading dislocationdensity especially for screw dislocations and V-pits in the overgrown InGaN/GaNlayers. The relaxed regrowth of such heterostructures also leads to an improvedcrystalline quality and a higher In incorporation in InGaN. The improvement inthe optical and structural quality of these InGaN/GaN layers is investigated bymeans of photoluminescence spectroscopy and transmission electron microscopy.