Simulation study on the effect of channel thickness on the characteristics of Ga sub(0.52)In sub(0.48)P/In sub(0.2)Ga sub(0.8)As/Ga sub(0.52)In sub(0.48)P DH-pHEMT

The dc performance of a Ga sub(0.52)In sub(0.48)P/In sub(0.2)Ga sub(0.8)As /Ga sub(0.52)In sub(0.48)P double heterojunction pseudomorphic high electron mobility transistor (DH-pHEMT) grown on GaAs substrate has been simulated using a two-dimensional device simulator, to investigate the dependence of the intrinsic and extrinsic transconductance on the device channel thickness. The electron sheet concentration values for different channel thicknesses have been calculated using an analytical model, and correspond very well to Hall effect measurements of the electron mobility. Simulation results reveal that the optimum channel thickness for maximum intrinsic transconductance is between 80 and 100 angstroms, while there is no significant difference in the maximum extrinsic transconductance for channel thicknesses between 80 and 140 angstroms. This is due to a trade-off between electron sheet concentration and gate-to-channel separation. In addition, narrow channels give larger effective band gap due to energy quantization, which could contribute to an optimum design for Ga sub(0.52)In sub(0.48)P/In sub(0.2)Ga sub(0.8)As/Ga sub(0.52)In sub(0.48)P DH-pHEMTs.