Extraction of virtual-source injection velocity in sub-100 nm III–V HFETs

We have experimentally extracted the virtual-source electron injection velocity, v_x0, of various III-V HFETs at room temperature. This is the carrier velocity that matters for logic applications of these transistors. Sub-100 nm devices with ¿n > 10,000 cm²/V-s exhibit v_x0 in excess of 3 × 10⁷ cm/s even at V_DD = 0.5 V. This is over 2 times that of state-of-the-art Si devices at V_DD > 1. We have verified our extraction methodology for v_x0 by building a simple charge-based semi-empirical model for the I-V characteristics of III-V HFETs. This model yields an excellent description of the entire I-V characteristics of the devices from subthreshold to inversion and from linear to saturation regimes with fitted electron velocities that are very close to those independently obtained through our proposed extraction methodology.