Structural and morphological studies on wet-etched InAlGaN barrier HEMT structures

Developer-based wet chemical etch of nearly lattice-matched InAlGaN/GaN heterostructures (HEMT-like) has been studied in detail by means of Rutherford backscattering spectroscopy, x-ray diffraction, atomic force microscopy and reciprocal space mapping (RSM). Etch isotropy depended on the rms surface roughness of the as-grown material. The profiles of etched samples varied in crack density, giving rise to island-like structures. We found that a possible reason for the preferential etching can be ascribed to the dislocations present in the quaternary layers originating in the underlying GaN. Moreover, the etched material suffers crystal relaxation as confirmed by RSM.