Local band and defect transitions in InGaN observed by valence electron energy loss spectroscopy

Abstract

The interface of an annealed GaN/InN heterostructure was investigated by valence electron energy loss spectroscopy (VEELS). A monochromated electron beam provides an energy resolution of 180 meV at a beam size of 1 nm in scanning transmission electron microscopy mode. Although simulteanously performed energy dispersive spectra (EDS) scans reveal an 80 nm wide InGaN interdiffusion area, alloying is locally minimal and phase separation is commonly found. Various defect transitions in the range between 1 and less than 0.7 eV were observed together with room temperature band transitions of 1.7 and 3.3 eV 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.