Quasibound states induced by AlAs monolayers in InxGa1−xAs/GaAs quantum wells

The optical properties of (In,Ga)As/AlAs/GaAs quantum wells with two monolayer-wide AlAs interface layers sandwiched between (In,Ga)As wells and GaAs barriers were investigated by photoluminescence and photoreflectance spectroscopy. The inclusion of AlAs interface layers caused blue shifts in intersubband transitions associated with the exciton ground state confined in (In,Ga)As wells. Room temperature photoreflectance showed oscillatory features above the GaAs bandgap revealing the existence of numerous quasibound states in both the conduction and valence bands of GaAs. A fairly good agreement is obtained between the experimental results and the calculated intersubband transitions of quasibound states. (C) 1997 Academic Press Limited