Modeling and simulation of doped channel heterostructure FETs and integrated circuits

The authors describe a model used for the design of doped channel pseudormorphic AlGaAs/InGaAs/GaAs quantum-well HIGFETs and for the simulation of digital integrated circuits based on these devices. The model is based on the self-consistent quantum mechanical calculation of subbands and electron density in InGaAs quantum wells, obtained by solving a one-dimensional effective mass Schrodinger equation. Such a calculation shows that the potential barrier between the quasi-Fermi level in the channel and the bottom of the conduction band in the barrier layer is considerably larger for the doped-channel structure. This lowers the thermionic emission gate current of the doped channel device compared to the undoped channel structure, as confirmed by experimental data. The authors measured peak transconductance g_m = 471 mS/mm and peak I_dsat = 660 mA/mm in 0.6-μm-gate doped-channel services. These results demonstrate the advantages of the DCHFET over the standard MODFET structure and their potential for high speed IC applications.