Experimental comparisons in the electrical performance of long and ultrashort gate length GaAs MESFET's

Electrical properties of GaAs single-gate and dual-gate MESFET's with gate lengths of 1.2 µm and 0.2 µm have been compared. By reducing the gate length to 0.2 µm, a very high zero-gate-bias drain current Idssand a large increase in the pinchoff voltage were observed in both single-gate and dual-gate devices, Idssin the shorter gate FET was found to be very close to the full channel current. Only a slight improvement in the maximum intrinsic gmwas noted in the 0.2 µm FET's. The knee voltage for the zero-gate-bias curve was larger in the shorter gate FET. At low current levels, soft pinchoff and soft saturation behaviors were observed in the very short gate FET's. A striking feature of the GaAs MESFET is that its output conductance at large drain voltages does not degrade with shorter gate lengths.