Asymmetric doping induced nonlinear electron mobility in double V-shaped quantum well based FET structure under external electric field

Abstract

The effect of asymmetric doping profile on the electron mobility μ is studied in a Field Effect Transistor (FET) structure based on Al x Ga 1−x As double V-shaped quantum well (D-VQW) in presence of an external electric field F. We introduce asymmetry in the structure by considering different doping concentrations in the side barriers along the substrate and surface. The resultant asymmetric potential is varied as a function of F. Accordingly the energy levels E l and wave functions ξ l within the coupled structure alter. By varying F suitably the resonance of subband states can be realized between the wells. Around the point of resonance, ξ l rearranges significantly. The change in ξ l influences the screened scattering potentials through intersubband effects leading to nonlinear μ. We consider ionized impurity (Imp-) scattering and alloy disorder (Al-) scattering for the D-VQW structure and show that under double subband occupancy, μ has an oscillatory behavior, basically due to Imp-scattering. The oscillatory μ enhances by increasing the well width and central barrier width and also by decreasing the height of the V-shaped well. Our results of nonlinear electron mobility can be employed to tune the transistor performance with gate electric field by adopting an optimized set of structure parameters.