Low ballistic mobility in submicron HEMTs

Ballistic effects in short channel high electron mobility transistors (HEMTs) greatly reduce the field effect mobility compared to that in long gate structures. This reduction is related to a finite electron acceleration time in the channel under the device gate. As an example, the field effect mobility at room temperature in 0.15-μm gate AlGaAs/GaAs HEMTs cannot exceed 3000 cm²/V-s. These predictions are consistent with the values of the field effect mobility extracted from the measured AlGaAs/GaAs HEMT current-voltage characteristics.