Thermal stability of Al1−xInxN (0 0 0 1) throughout the compositional range as investigated during in situ thermal annealing in a scanning transmission electron microscope

Abstract

The thermal stability of Al1−xInxN (0⩽x⩽1) layers was investigated by scanning transmission electron microscopy (STEM) imaging, electron diffraction, and monochromated valence electron energy loss spectroscopy during in situ annealing from 750 to 950°C. The results show two distinct decomposition paths for the layers richest in In (Al0.28In0.72N and Al0.41In0.59N) that independently lead to transformation of the layers into an In-deficient, nanocrystalline and a porous structure. The In-richest layer (Al0.28In0.72N) decomposes at 750°C, where the decomposition process is initiated by In forming at grain boundaries and is characterized by an activation energy of 0.62eV. The loss of In from the Al0.41In0.59N layer was initiated at 800°C through continuous desorption. No In clusters were observed during this decomposition process, which is characterized by an activation energy of 1.95eV. Finally, layers richest in Al (Al0.82In0.18N and Al0.71In0.29N) were found to resist thermal annealing, although the initial stages of decomposition were observed for the Al0.71In0.29N layer.