Intersubband Absorption in Quantum Dash Nanostructures

The band structure and corresponding intersubband absorption coefficient of quantum dash structures are modeled using a self-consistent single-band effective-mass approach and dipole approximation. Size fluctuation of the quantum dash ensemble, described with Gaussian distribution, is included in the model and its effects on the absorption spectrum are analyzed. The profile of the absorption spectrum is suitable for fitting with a sum of Gaussian functions. We find that the quantum dash ensemble has a pronounced and broad absorption spectrum in mid-infrared region, which becomes broader and more asymmetric with increase of the size fluctuation. In addition, for very large size fluctuation, the spectrum becomes flattened in relatively wide wavelength range.