Optimized InP HEMTs for low noise at cryogenic temperatures

Experimental results and Monte Carlo simulations have been analyzed and compared at 300 K and 77 K for 130 nm gate-length InP HEMTs optimized for cryogenic 4-8 GHz low-noise amplifiers. The good agreement observed between simulations and experimental data for DC and small signal equivalent circuit parameters validates the simulation model. Compared to 300 K, an increase of 17% in the simulated mean electron velocity under the gate was observed at low drain current (100 mA/mm) when operating the device at 77 K. In addition, a better electron confinement in the channel was noted. The observations are consistent with an increase of the slope of the transconductance versus gate bias with reduced temperature. The high transconductance at low drain current is crucial for low noise operation of the InP HEMT at low temperature.