Impact of intrinsic parameter fluctuations on the performance of HEMTs studied with a 3D parallel drift-diffusion simulator

Intrinsic parameter fluctuations in state-of-the-art high electron mobility transistors (HEMTs) are studied using a 3D parallel drift-diffusion device simulator. Two sources of intrinsic parameter fluctuations have been considered: the random discrete dopants in the δ-doped layer and the variations in the material composition of the channel. The effect of those two sources is investigated in a 120 nm gate length pseudomorphic HEMT with an In0.2Ga0.8As channel and in a 50 nm gate length InP HEMT with an In0.7Ga0.3As channel. We have found that the random discrete dopants in the δ-doping layer are the major factor introducing the variations in the drive current and the device performance. In the devices studied, the variations in the drive current decrease as a function of the gate voltage. Furthermore, at a fixed gate voltage, the variations decrease with the drain voltage in the 50 nm InP HEMT while in the 120 nm PHEMT the variations increase with the drain voltage.