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

摘要

It is shown that the strong enhancement of electron scattering by polar optical phonon absorption with increasing sheet electron concentration n_s is responsible for the negative change of conductivity in the Al_(0.25)Ga_(0.75)As/GaAs/Al_(0.25)Ga_(0.75)As quantum well (QW). The insertion of a thin AlAs barrier into the QW increases electron mobility by 1.6 times at n_s=1X10~(16) m~(-2) and extends the range of n_s at which the negative conductivity changes. A modulation-doped field-effect transistor based on the high-doped Al_(0.25)Ga_(0.75)As/GaAs/Al_(0.25)Ga_(0.75)As QW as a channel acquires new specific properties. The transistor transconductance, dependent on applied gate and drain voltages, can change sign, and its value at high doping level can be comparable to that at low doping level, in spite of the great decrease of channel electron mobility.