Extraction of Channel Electron Effective Mobility in InGaAs/Al $_{\bf 2}$ O $_{\bf 3}$ n-FinFETs

A compact set of equations based on the multiple subbands quasi-ballistic transport theory is developed, and is used to investigate the channel electron effective mobility in recently reported In_0.53Ga_0.47As/Al₂O₃ tri-gate n-FinFET. The extracted electron effective mobility μn is around 370 cm²/V·s at low V_g - V_th bias at room temperature and decreases with increasing V_g, and increases with increasing temperature (240-332K). It is very different from the case of Si n-MOSFETs, where the electron mobility decreases with increasing temperature. The low channel effective mobility and the ab-normal temperature dependence of μ_n are ascribed to the high acceptor interface trap and border trap energy densities in the conduction band energy of InGaAs. The ballistic channel resistance R_Ball at low Vds is calculated and compared with the measured channel resistance R_CH. The low transmission coefficient T = R_Ball/R_CH ≈ 0.06 to 0.05 indicates that there is a large room to improve the InGaAs/Al₂O₃ n-FinFET performance.