Conductivity of modulation-doped AlGaAs/GaAs/AlGaAsquantum well with an inserted thin AlAs barrier

Abstract

It is shown that the strong enhancement of electronscattering by polar optical phonon absorption with increasingsheet electron concentration ns is responsible for thenegative change of conductivity in theAl0.25Ga0.75As/GaAs/Al0.25Ga0.75As quantumwell (QW). The insertion of a thin AlAs barrier into the QWincreases electron mobility by 1.6 times at ns = 1×1016 m-2 and extends the range of ns at whichthe negative conductivity changes. A modulation-dopedfield-effect transistor based on the high-dopedAl0.25Ga0.75As/GaAs/Al0.25Ga0.75As QW as achannel acquires new specific properties. The transistortransconductance, dependent on applied gate and drain voltages,can change sign, and its value at high doping level can becomparable to that at low doping level, in spite of thegreat decrease of channel electron mobility.