Outstanding High Field-Effect Mobility of 299 cm² V⁻¹ s⁻¹ by Nitrogen-Doped SnO₂ Nanosheet Thin-Film Transistor

Record high field-effect mobility (µ_FE) thin film transistors (TFTs) based on 5 and 7 nm thickness SnON channel layer is reported. The SnON TFT device with 7.6% nitrogen content achieves a record high µ_FE of 299 cm² V⁻¹ s⁻¹ at 7 nm thickness and 277 cm² V⁻¹ s⁻¹ at 5 nm thickness, compared to SnO₂ with µ_FE of 211 cm² V⁻¹ s⁻¹. At the same 5 nm quasi-2D channel thickness, this µ_FE of nanocrystalline SnON transistor is comparable to single crystalline Si and InGaAs metal oxide semiconductor field-effect transistor (MOSFET) and also higher than the phonon-scattering-limited 2D MoS₂ FET. From the principle of quantum-mechanical calculation, the high µ_FE of nanosheet SnON TFT is due to lower effective mass of electrons, 0.29 m₀ in the conduction band in contrast to 0.41 m₀ of SnO₂. SnON can reduce the defect trap densities by introducing non-oxide anions where the valence band can be controlled to remove or passivate the oxygen vacancy levels by substitutional alloying with nitrogen anions to circumvent instability, increase on-current (I_ON) and improve the µ_FE. It is highly expected that the high performance quasi-2D nanosheet SnON TFTs will be utilized in embedded DRAM and monolithic 3D integrated circuits (ICs).