Quantum tailoring of optical transitions in InxGa1-x As/AlAs strained quantum wells

The optical properties of n-doped InxGa1-xAs/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 I-->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 mu m range appears feasible while retaining the type I character of the band alignment. These results provide a valid framework for the implementation of InxGa1-xAs/AlAs heterostructures for ultrafast optical communication applications. (C) 1998 American Institute of Physics. [S0003-6951(98)04944-4]