We performed two-dimensional Monte Carlo (MC) simulations of 200-nm-gate InP-based In0.52Al0.48As/In0.75Ga 0.25As pseudomorphic high electron mobility transistors (HEMTs) at 300 and 16 K to clarify the effect of temperature on electron transport. On decreasing the temperature, the calculated maximum transconductance gm increases from 1110mS/mm at 300 K to 1400mS/mm at 16 K. On the other hand, the calculated cutoff frequency fT increases from 168 GHz at 300 K to 223 GHz at 16 K. The electron velocity overshoot under the gate is enhanced by reducing the temperature. The resulting average electron velocity under the gate increases from 3:60 × 107 cm/s at 300 K to 5:26 × 107 cm/s at 16 K. The average velocity of the electrons and electron occupancy in each valley were calculated to clarify the trend of the electron velocity with temperature. We found that the intervalley phonon scattering as well as the intravalley scattering plays a very important role in determining the average electron velocity at 300 K. The contribution of the intervalley scattering to the average electron velocity is almost of the same degree as that of the intravalley scattering at 300 K.
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