Superior High Transistor's Effective Mobility of 325 cm²/V-s by 5 nm Quasi-Two-Dimensional SnON nFET

This work reports the first nanocrystalline SnON (7.6% nitrogen content) nanosheet n-type Field-Effect Transistor (nFET) with the transistor's effective mobility (µ_eff) as high as 357 and 325 cm²/V-s at electron density (Q_e) of 5 × 10¹² cm^-2 and an ultra-thin body thickness (T_body) of 7 nm and 5 nm, respectively. At the same T_body and Q_e, these µ_eff values are significantly higher than those of single-crystalline Si, InGaAs, thin-body Si-on-Insulator (SOI), two-dimensional (2D) MoS₂ and WS₂. The new discovery of a slower µ_eff decay rate at high Q_e than that of the SiO₂/bulk-Si universal curve was found, owing to a one order of magnitude lower effective field (E_eff) by more than 10 times higher dielectric constant (κ) in the channel material, which keeps the electron wave-function away from the gate-oxide/semiconductor interface and lowers the gate-oxide surface scattering. In addition, the high µ_eff is also due to the overlapped large radius s-orbitals, low 0.29 m_o effective mass (m_e*) and low polar optical phonon scattering. SnON nFETs with record-breaking µ_eff and quasi-2D thickness enable a potential monolithic three-dimensional (3D) integrated circuit (IC) and embedded memory for 3D biological brain-mimicking structures.