Microwave performance of InP-based HEMTs for low voltage application fabricated by optical lithography

摘要

The low voltage high frequency performance of InP-based HEMTs is examined. All the devices are fabricated by simple optical lithography resulting in gate length /spl ges/0.5 /spl mu/m. The RF results of the structures discussed show that uncompromised small RF performance of InP based FETs can be obtained in the low drain bias range below 2 V. Even for moderate gate lengths of 0.5 /spl mu/m, operation down to Vd=1 V seems feasible. The highest cut-off frequencies extrapolated are f/sub t/=60 GHz and f/sub max/=160 GHz at Vd=1.6 V. This represents an ft*Lg-product of 39 GHz/spl mu/m and a f/sub max//f/sub t/ of 2.6 at the identical gate and drain bias point. This indicates that high power gain is possible at high overshoot velocity. Three different material structures have been analysed. The drift-region analysis indicate that an optimum design is a structure with high open channel current density realised with high carrier concentration.