Interaction of the dual effects triggered by AlN interlayers in thick GaN grown on 3C-SiC/Si substrates

In this work, the stress distribution of a thick GaN layer, which was realized with multiple AlN interlayers (ILs) on a 3C-SiC/Si (111) substrate, was mapped by low-temperature cathodoluminescence spectroscopy. A relaxation of compressive stress was distinguished in the top GaN layers above the AlN ILs by the inhomogeneous luminescent property. Through cross-sectional transmission electron microscopy, misfit dislocations (MDs) transformed from threading dislocations were observed. Analysis confirmed that the transformation process of dislocations should account for a part of compressive stress relaxation. As a result, a trade-off between compressive stress induction and dislocation transformation effects, both of which were induced by the AlN ILs, was proposed. In this model, the mean length of MDs in the GaN/AlN multi-layer structure was evaluated as L = 84 nm.