Dependence on Gate Length of Electrical Properties of Self-aligned AlGaAs/GaAs HEMTs Studied by Monte Carlo Technique

Various electrical properties of self-aligned AlGaAs/GaAs heterostructure field¿effect transistors (HEMTs) have been studied by self-consistent ensemble Monte Carlo simulations for gatelengths between 0.1 and 1.0 ¿m, and for different depths of ohmic contacts. The maximum transconductance is found to be only weakly dependent on gate length and contact depth. The output drain conductance and the threshold voltage show pronounced short-channel effects for gate lengths at or below 0.2 ¿m and shallow contacts. With deeper contacts, the short¿channel effects appear at longer gate lengths. The switching times vary with gate length from 1.0 ps at 0.1 ¿m to 5.0 ps at 1.0 ¿m. The observed effects are discussed in terms of simple models.