A Monte Carlo analysis of new nanoscale ballistic field effect transistors (BFETs) for millimetre-wave applications

This paper presents a new nanometre-gate ballistic field effect transistor (BFET) suitable for millimetre-wave applications. The BFET features an inverse modulation-doped channel with a specially designed source contact, enabling maximum use of electron velocity overshoot for the gate length Lg smaller than 100 nm. By performing a self-consistent 2D Monte Carlo simulation that dealt with both intrinsic and extrinsic device regions on an equal footing, we found for the first time that electron preheating in the source contact region enhances Γ-L intervalley transitions, significantly decreasing the average electron velocity in the intrinsic region. Based on the numerical results, the general criteria of the source contact structure are clarified to realise BFETs. Excellent BFET scaling properties are demonstrated in comparison with those of HEMTs. The average electron velocity of 20-nm-gate AlGaAs/GaAs BFETs was estimated to be 2.5 times larger than those reported for HEMTs fabricated on GaAs substrates