Structural asymmetry induced nonmonotonic electron mobility in pseudomorphic double quantum well high electron mobility transistor structure

摘要

Non-monotonic mobility mu of electrons is obtained in a pseudomorphic GaAs/InxGa1-xAs high electron mobility transistor having double quantum well structure with asymmetric doping concentrations in the outer barriers. A dip in mu occurs close to the resonance of subband states because of the quantum mechanical transfer of the wave functions between the wells. Near resonance, the asymmetry in subband wave functions and anticrossing of energy levels as a function of doping concentration influence the intra- and intersubband scattering rate matrix elements. Near resonance, the subband wave functions spread asymmetrically and the energy levels exhibit anticrossing as a function of doping concentration thereby influencing the intra and intersubband scattering rate matrix elements. The dip in mu, which amplifies with raise in the asymmetry of the width of wells, is basically due to the subband mobilities limited by the interface roughness scattering. We also show that an appropriate selection of the structure parameters leads to a hump in mobility dominated by the intersubband effects on the screened ionized impurity scattering potential under double subband occupancy. The nonlinearity in mu can be utilized to study the characteristics improvement of devices such as high electron mobility transistors.