Microwave Operation Of Heterostructure Isolated-Gate FETs

Heterostructure Isolated-Gate Field-Effect Transistors (HIGFETs) have for the first time been operated at microwave frequencies. These enhancement-mode devices are fabricated by a refractory self-aligned gate process using undoped MBE-grown heterostructures employing an AlGaAs gate isolation layer. A planarization process with Au-based overlay metallization is used to reduce the gate resistance. Microwave S-parameter and noise measurements have been made on the devices from I to 15 GHz. At 10 GHz, noise figure values of 2.0 to 2.2 dB with associated gain of 6.8 to 7.0 dB have been measured for nonoptimized 1 /spl mu/m-gate HIGFETs.