InGaAs Inversion Layer Mobility and Interface Trap Density From Gated Hall Measurements

In this letter, we use gated Hall method for direct measurement of free carrier density and electron mobility in inversion InGaAs MOSFET channels. At room temperature, the highest Hall mobility of 1800 cm²/Vs is observed at electron density in the channel ≈ 1 × 10¹² cm^-2. A comparison with mobility values estimated from transistor characteristics reveals a significant underestimation of mobility, which arises from overestimation of channel density obtained from C - V measurements. Temperature dependence of the electron mobility provides the evidence that remote Coulomb scattering dominates at electron density < 3 × 10¹¹ cm^-2. Contrary to the capacitance-based methods commonly used for extraction of interface trap density, a gated Hall method can separate the contributions of fast-trapped charges and free carriers in the channel to the total charge of a MOS capacitor. This allows for reliable estimation of trap density at the III-V/high-k interface including border traps. The results illustrate that even high-quality interfaces providing high-mobility transport suffer from fast border traps above the conduction band. In contrast with Si where the effect of border traps is negligible, in low density-of-state InGaAs channel material as much as half of the channel electrons can be trapped and excluded from transport, increasing switching energy and dissipated power.