Numerical Simulation Of GaAs MESFET´s With Heavily Compensated Substrates

This paper describes numerical simulations of GaAs MESFETs on a semi-insulating substrate in which impurity compensation by deep traps is included. It is shown that higher acceptor density in the substrate results in lower device current due to the formation of space charge layer at the channel-substrate Interface. It is also shown that drain currents increase continuously, because electrons are injected to fill the traps in the substrate and the current path through the substrate is formed. This substrate current becomes remarkable for shorter gate-length MESFET´s on a substrate with lower impurity densities. It is suggested that to minimize short-channel effects in GaAs MESFET´s, impurity densities in the semi-insulating substrate must be high.