Electron mobility in ultra-thin InGaAs channels: Impact of surface orientation and different gate oxide materials

Electron mobility is investigated in sub-20 nm-thick InGaAs channels, sandwiched between different gate oxides (SiO2, Al2O3, HfO2) and InP as substrate, using physics-based numerical modeling. Effects of body thickness downscaling to 2 nm, different gate oxides, and surface orientation [(1 0 0) and (1 1 1)] are examined by including all electron valleys and all relevant scattering mechanisms. We report that ultra-thin (1 1 1) Al2O3-InGaAs-InP devices offer greater electron mobility than (1 0 0) devices even in the extremely-thin channels. Furthermore, ultra-thin (1 0 0) InGaAs devices outperform SOI in terms of electron mobility for body thicknesses above ∼4 nm, while (1 1 1) InGaAs channels are superior to SOI for all body thickness values above ∼3 nm. The study of different gate oxides indicates that HfO2 is the optimum gate dielectric regardless of device orientation, offering a mobility improvement of up to 124% for (1 1 1) and 149% for (1 0 0) surface orientation, when compared to the initial Al2O3-InGaAs-InP structure. The (1 1 1) orientation offers improvement over (1 0 0) device irrespective of the body thickness and gate oxide material, with the highest difference reported for SiO2, followed by Al2O3 and HfO2.