GaAs/AlGaAs HEMT structures with multiquantum well channels

The DC performance of 1 mu m gate length HEMTs with three parallel conducting GaAs quantum wells is presented. By variation of the gate voltage the three channels can be switched on successively, leading to three separate peaks in the device transconductance. By optimising the depth of the gate recess the authors fabricated transistors which exhibit good output characteristics and extremely high maximum drain currents of up to 1100 mA/mm.