IMPROVED MODFET PERFORMANCE THROUGH GATE CURRENT CONTROL.

Using an improved physical theory of the gate current in MODFETs the authors were able to decrease the gate current in the devices. By using an AlAs spacer layer, the turn-on voltage of the devices (i. e. , the voltage at which the gate current density reaches 5 mu A/ mu m**2 was increased to 1. 2 V. This improvement increased the noise margin in an inverter with a fanout of one to greater than 500 mV at room temperature, and greater than 300 mV at 170 degree C. The lower gate current allowed the extrinsic transconductance (G//m) to peak at a higher gate voltage, which resulted in a higher peak G//m. The average G//m for a 1- mu m FET over a 3-in. wafer reached 286 mS/mm. Here, the model for the gate current in MODFET devices and data from MODFETs fabricated with AlAs spacer layers are presented.