Theoretical Limits of the Matching Bandwidth and Output Power of AlScN-Based HEMTs

In this work, the simultaneously achievable matching bandwidth and output power of AlScN-based high electron mobility transistors (HEMTs) are derived and compared to conventional AlGaN, GaAs, and Si devices. Moll’s method is used to extract time delays resulting in carrier velocities close to 1 × 10 7 cm/s for sheet carrier densities ≥ 1.5 × 10 13 cm -2 . Subsequently, theoretical current densities of 2.5-4 A/mm and a maximum transconductance higher than 600 mS/mm are derived for low barrier thicknesses of 5-10 nm and Sc-concentrations of 5%-20%. The matching bandwidth is estimated by the Bode-Fano criterion and connected to the output power of the transistor by the power-bandwidth product, which accounts for both parameters simultaneously. AlScN-based devices are found to exhibit a 4.5-times higher power-bandwidth product compared to conventional AlGaN-based HEMTs, quantifying the enormous, theoretical limits. Experimental data already show an improvement by a factor of 1.45 for AlScN-based devices, even in this early stage of development, which proves their superior properties, when aiming for wideband high-power millimeter-wave (mm-wave) devices.