Physics of Short-Gate GaAs MESFET's from Hydrostatic Pressure Studies

The use of hydrostatic pressure to study the physics of a GaAs MESFET is reported for the first time. Two aspects of the physics of conventional 1-μm gate structures are focused upon: 1) the possible role played by hot-electron effects in the drain-current saturation and 2) the physical mechanism responsible for excess current. The pressure dependence of the low-field conductance, current-voltage characteristics, and VHF noise properties of the MESFET are examined and compared to those of a Gunn diode. The results show that hot-electron effects are similar in the two devices, thereby providing new evidence that current saturation is associated with Gunn domain formation. The results also suggest that the excess current at large gate voltages is due to electron injection into the substrate under the source side of the gate, rather than to other proposed mechanisms.