Effects of the annealing temperature on the structural and electronic properties of MBE grown InGaN/GaN quantum wells

A sample consisting of a 2.5nm thick In0.25Ga0.75N quantum well grown by molecular beam epitaxy (MBE) was annealed for 2 hours in a hydride vapour phase epitaxy (HVPE) reactor under an NH3 atmosphere at 880°C, 920°C and 975°C. High-resolution TEM and STEM combined with electron energy-loss spectroscopy (EELS) investigations on the local electronic properties have been carried out to correlate these with the structure evolution during annealing. Image processing techniques such as geometric phase analysis of HR-TEM images reveal significant fluctuations in the indium distribution inside the well on a nanometric scale. An increase of the emission characteristic has been observed for annealing at 920°C.