In_xGa_1-xAs quantum-well high-electron-mobility transistors with a record combination of fT and fmax: From the mobility relevant to ballistic transport regimes

We report \text{In}{x}\text{Ga}{1-x}\text{As} quantum-well (QW) high-electron mobility transistors (HEMTs) with an outstanding combination of DC and high-frequency characteristics. In particular, we explored the impact of the indium mole fraction in the \text{In}.\text{Ga}{1-x}\text{As} QW channel from the viewpoint of epi-layer structures, and the comprehensive rm{L}{rm{g}} scaling behavior from the mobility relevant regime to the ballistic regime from 10 \mu rm{m} to sub-30 nm. To fully understand both DC and high-frequency characteristics of those devices, we physically modeled experimental figures of merit (FOMs), such as DC maximum transconductance and DIBL, only with physical and geometrical parameters of apparent mobility (\mu{app}), saturation velocity (v{sat}) and aspect ratio (\gamma). Then, we correlated those experimental DC FOMs to high-frequency FOMs, such as cutoff frequency (f{T}) and maximum oscillation frequency (f{max}). Not only was our physical approach presented in this work capable of explaining all the DC and high-frequency characteristics, but the fabricated composite-\text{In}{0.8}\text{Ga}{0.2} As HEMT with rm{L}{rm{g}}=30 nm also represented the best balance of rm{f}{rm{T}} and rm{f}{\max} in any transistor technology.