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Theoretical modelling of the intraband absorption spectrum in InAs/GaAs quantum dot infrared photodetectors is performed for several typical structures reported in the literature. The calculations are performed within the framework of the two methods: a simple and so far widely used effective mass method with the values of conduction band offset and the effective mass modified to take account of the effects of strain and band mixing on average and the more realistic eight-band k × p method with the strain distribution taken into account via the continuum mechanical model. Both methods give qualitatively the same results; however, the peak positions obtained within the effective mass approach are blue shifted and the absorption cross sections are overestimated, compared to the more accurate k × p approach.

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.