The interface of an annealed GaN/InN heterostructure was investigated by valence electron energy loss spectroscopy. A monochromated electron beam provided an energy resolution of 180meV at a beam size of 1nm in scanning transmission electron microscopy mode. Although simultaneously performed energy dispersive spectra scans revealed an 80nm-wide InGaN interdiffusion area, alloying was locally minimal and phase separation was commonly found. Various defect transitions in the range between 1 and less than 0.7eV were observed together with room temperature band transitions of 1.7 and 3.3eV for InN and GaN, respectively. An enhanced concentration of vacancies accumulated at the interface may explain the pronounced interdiffusion and some of the observed defect transitions.

Local Band and Defect Transitions in InGaN Observed by Valence Electron Energy Loss Spectroscopy. P.Specht, X.Xu, R.Armitage, E.R.Weber, R.Erni, C.Kisielowski: Physica B, 2006, 376-377, 552-5