Fabrication and characteristics of extremely low-noise AlGaAs/InGaAs/GaAs pseudomorphic HEMTs

We developed a 0.15-mu m gate-length AlGaAs/InGaAs/GaAs pseudomorphic HEMT (PHEMT) device with an extremely low noise by optimizing the HEMT structure and the device geometry. The extrinsic transconductance and cutoff frequen cy of the PHEMT device were 666 mS/mm and 125 GHz, respectively. The lowest minimum noise figure, NFmin, of the PHEMT device was observed to be around 80 % of the saturation drain current, I-dss, at 12 GHz and V-ds=2 V. The d evice exhibited a NFmin as low as 0.24 dB with a high associated gain of 14 .5 dB at 12 GHz. This noise figure value is the lowest ever reported for a GaAs-based HEMT device at room temperature. This excellent noise performanc e is thought to result from the reduced parasitic resistance due to the use of a wide-head T-gate and a short gate-to-source distance to the HEMT stru cture which was optimized to suppress short channel effects and to obtain a high transconductance.