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

Continuous tuning over the entire 8-12 mym 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 later effect is due in part to a decrease in the freecarrier 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.