TEM investigation of defect reduction and etch pit formation in GaN

Abstract

ABSTRACTGaN samples of this study were chemically wet etched to gain easier access to the dislocation sturcture. The scanning electron microscopy and transmission electron microscopy investigations revealed four different types of etch pits. After brief etching, several dislocations with screw component showed large etch pits, which may be correlated with the core of the screw dislocation. By means of SiNx micromasking the dislocation density could be reduced by more than one order of magnitude. The reduction of threading dislocations in the SiNx region in GaN grown on 〈0001〉 sapphire is due to bending of the threading dislocations into the {0001} plane, such that they form dislocation loops if they meet dislocations with opposite Burgers vectors. Accordingly, the achievable reduction of the dislocation density is limited by the probability that these dislocations interact. Edge dislocations bend more easily on account of their low line tension. This results in a preferential bending and reduction of dislocations with edge character.