Noise performance at cryogenic temperatures at AlGaAs/InGaAs HEMT's with 0.15- mu m T-shaped WSi/sub x/ gates

T-shaped 0.15- mu m WSi/sub x/ gate HEMTs have been fabricated on AlGaAs/InGaAs MBE wafers. Their S-parameters, output noise spectral density P/sub no/, and noise temperatures T/sub e/ at cryogenic temperatures, were measured. The current gain cutoff frequency f/sub T/ increases from 61 GHz at 295 K to 87 GHz at 90 K. P/sub no/ and T/sub e/ measurements indicate that the hot-electron effect is noticeable at low temperatures at high drain current. At 30 GHz, the noise temperature is 19+or-3 K with an associated gain of 10.4 dB at the physical temperature of 20 K. The results demonstrate the great potential of AlGaAs/InGaAs HEMTs for low-temperature applications.>