Quantum tailoring of optical transitions in InxGa1−xAs/AlAs strained quantum wells

The optical properties of n-doped ${\mathrm{In}}_x{\mathrm{Ga}}_{\text{1−x}}\mathrm{As/AlAs}$ pseudomorphic quantum wells grown on GaAs(001) are investigated as a function of layer thickness and indium concentration. The nature of interband and intersubband transitions is clarified using an improved tight-binding model and a combination of low-temperature photoluminescence spectroscopy and intersubband absorption studies. A type $\mathrm{I\to type}$ II crossover is found to occur in very narrow wells. Moreover, for appropriate quantum-well parameters, tailoring of the intersubband transition wavelength down to the 1.2 μm range appears feasible while retaining the type I character of the band alignment. These results provide a valid framework for the implementation of ${\mathrm{In}}_x{\mathrm{Ga}}_{\text{1−x}}\mathrm{As/AlAs}$ heterostructures for ultrafast optical communication applications.