Influence of a Strained AlGaN Overlayer on the GaN Matrix near AlGaN/GaN Heterointerfaces

Abstract

Unusual splitting of the GaN peaks in the X-ray diffraction (XRD) and the photoluminescence (PL) spectra has been observed in strained AlGaN/GaN heterostructures. As the Al mole fraction increases, a single GaN peak splits into three peaks in both the XRD and the PL spectra, and the GaN PL peak due to the donor-bound exciton moves to higher energy in parallel with a pair of extrinsic peaks. The splittings of the peak and the blue shifts may possibly be associated with different crystalline domains in the GaN matrix layer, those domain being separated by the strong tensile stress in the AlGaN overlayer. This implies that the crystallinity of the GaN matrix near the AlGaN/GaN heterointerface can be influenced by strained the AlGaN overlayer.