High Frequency Properties Of InA1As/InGaAs High Electron Mobility Transistors At 77 K

We report the first high frequency measurements at 77 K of an InAlAs/InGaAs high electron mobility transistor. At 296 K, the current gain is 18 dB at 10 GHz and the current gain cutoff frequency is 80 GHz. At 77 K, the current gain increases to 22 dB at 10 GHz but the cutoff frequency drops to 36 GHz. The lower cutoff frequency at 77 K is associated with a steep current gain rolloff which is measured to be 12 dB/octave compared with 6 dBloctave at 296 K. This result can be modeled by excess device capacitance at 77 K.