Low-temperature microwave characteristics of pseudomorphic In/sub x/Ga/sub 1-x/As/In/sub 0.52/Al/sub 0.48/As modulation-doped field-effect transistors

Low-temperature microwave measurements of both lattice-matched and pseudomorphic In/sub x/Ga/sub 1-x/As/In/sub 0.48/As (x=0.53, 0.60, and 0.70) channel MODFETs on InP substrates were carried out in a cryogenic measurement system. The measurements were done in the temperature range of 77 to 300 K and in the frequency range of 0.5 to 11.0 GHz at different bias conditions. The cutoff frequency (f/sub T/) for the In/sub x/Ga/sub 1-x/As/In/sub 0.52/Al/sub 0.48/As MODFETs improved from 22 to 29 GHz, 29 to 38 GHz, and 39 to 51 GHz, for x=0.53, 0.60, and 0.70, respectively, as the temperature was lowered from 300 to 77 K, which is approximately a 31% increase at each composition. No degradations were observed in device performance. These results indicate an excellent potential of the pseudomorphic devices at low temperatures.<
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