Transport and quantum lifetimes of electrons in modulation doped Al0.3Ga0.7As/In0.15Ga0.85As double quantum well structure

Abstract

The enhancement of transport and quantum lifetimes of electrons in barrier delta-doped Al0.3Ga0.7As/In0.15Ga0.85As pseudomorphic Double-Quantum-Well structure is analysed as a function of applied electric field and well width. We consider screened ionised-impurity, interface-roughness, and alloy-disorder scattering potentials and show that the quantum lifetime is dominated by ionised-impurity scattering while the transport lifetime is decided by most of the scattering mechanisms. In the absence of electric field, there is double subband occupancy, and therefore, the transport as well as quantum lifetimes are influenced by the intersubband effects. Application of electric field perpendicular to the interface of the quantum well structure enhances the transport lifetime whereas reduces quantum lifetime non-monotonically resulting in a rapid enhancement of their ratio through ionised impurity scattering. Further, as the well width increases, the effect of ionised-impurity scattering decreases leading to the enhancement of both the transport and quantum lifetimes as well as their ratio. In fact, for well width of 150 Å, an improvement in the ratio of transport and quantum lifetimes can be achieved from 9.8 to 90 by increasing the electric field from 0 to 7.6 kV/cm.