A Comprehensive Benchmarking Method for the Net Combination of Mobility Enhancement and Density-of-States Bottleneck

In this letter, we propose a comprehensive benchmarking method to simultaneously address mobility enhancement and density-of-states bottleneck in advanced field-effect-transistors (FETs) with novel high-mobility (high-μ) channel materials, where we focused on conventional covalent bonding semiconductors with pure and partially ionic character. This method relies only on the measured extrinsic transconductance of a long-channel FET in the saturation regime together with the source resistance, yielding the product of the effective mobility ( μ
_eff
) and effective gate capacitance ( C
_{g_eff}
). We tested this method in In
_x
Ga
_1-x
As quantum-well high-electron-mobility transistors (HEMTs) with various indium mole fractions, such as 0.53, 0.7, 0.8 and 1, as well as in Si n-FETs. We found that the In
_x
Ga
_1-x
As HEMTs with μ
_eff
over 10,000 cm
²
/V·s at 300 K provided more than 20 times greater μ
_eff
×C
_{g_eff}
than Si n-FETs. More specifically, the product initially improved as x increased, then showed a peak value of 10,300 μF·V
^-1
·s
^-1
at x of around 0.8, and degraded slightly beyond that composition. To verify the validness of the proposed method, we separately measured and analyzed C
_{g_eff}
and μ
_eff
using the split-CV technique, showing excellent agreement with the ones from the proposed method.