Bias dependence of f/sub T/ and f/sub max/ in an In/sub 0.52/Al/sub 0.48/As/n/sup +/-In/sub 0.53/Ga/sub 0.47/As MISFET

Detailed microwave characterization of a recently fabricated In/sub 0.52/Al/sub 0.48/As/n/sup +/-In/sub 0.53/Ga/sub 0.47/As MISFET reveals that high values of current-gain cutoff frequency (f/sub T/) and unilateral-gain cutoff frequency (f/sub max/) are obtained for a broad range of gate bias voltage values. A significant peak in f/sub T/ and f/sub max/ has also been observed at high gate-source bias values. The peak coincides with the onset of electron accumulation at the heterointerface and is attributed to reduced ionized impurity scattering coupled with reduced drain conductance. This result suggests an improved device structure that optimizes operation in the accumulation regime.>