Intersubband transitions in partially interdiffused GaAs/AlGaAs multiple quantum-well structures

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Abstract
Continuous tuning over the entire 8–12 μm wavelength range is demonstrated for the intersubband absorption resonance in n‐doped GaAs/AlxGa1−xAs multiple quantum‐well structures following partial interdiffusion of the well and barrier layers via rapid thermal annealing. The data indicate that redshifting of the intersubband absorption resonance arises both from interdiffusion‐induced modification of the confining potential and from a decrease in the depolarization shift. The latter effect is due in part to a decrease in the free‐carrier concentration within the Si‐doped quantum wells following rapid thermal annealing. Significant diffusion of the localized Si dopant is also observed over the range of annealing temperatures investigated here. Calculated values of the Al‐Ga interdiffusion coefficient, as a function of anneal temperature, indicate that Si diffusion through the heterointerfaces contributes substantially to layer intermixing.