Variable threshold AlGaAs/InGaAs heterostructure field-effect transistors with paired gates fabricated using the wafer-bonding technique

We investigated a novel field-effect transistor (HFET) structure with paire d gates (PGs), where one gate is above and the other below the channel, in order to realize an HFET that accepts two gate input signals. Using the waf er-bonding technique, we succeeded in fabricating AlGaAs/InGaAs PG-HFETs on a 3-inch-diameter wafer. The static characteristics of the fabricated HFET indicate that the drain current (I-D) is controlled by the paired gates, p roviding maximum transconductance of 240 mS/mm. Since the drain current can he controlled by each gate voltage independently, the PG-HFET functions as a variable threshold HFET. It has also been confirmed from the drain-curre nt transfer characteristics in subthreshold region that the channel potenti al is controlled much better by PGs with a subthreshold parameter N-G of 1. 4 (corresponding to subthreshold gate swing S of 84 mV/decade).