Self-assembled GaN quantum dots in GaN/Al _xGa _1-xN structures grown by PAMBE

High-resolution scanning electron microscopy (HRSEM), cathodoluminescence (CL) and electron beam induced current (EBIC) techniques were used to investigate the structural, optical and electrical properties of GaN/Al _xGa _1-xN structures with self-assembled quantum dots (QDs) grown by molecular beam epitaxy (MBE), The results of the spatially resolved investigations show that GaN QD assemblies divided laterally by a 2D GaN layer can be formed on Al _0.4Ga _0.6N surface. The size and the density of QD assemblies are significantly affected by the surface polarity and the thickness of the GaN epilayer. The CL spectra of the QDs show blue-shifted GaN near-band-gap emission, and the shift is stronger for the Ga-face GaN epilayers. The EBIC measurements indicate reduced non-radiative charge-carrier recombination in the QD regions.