Conduction and 1/f noise analysis in amorphous silicon thin-film transistors

Conduction and low-frequency noise are analyzed in the channel of hydrogenated amorphous silicon (a-Si:H) thin-film transistors. 1/f noise expressions are proposed starting from a simple conduction model describing drain current in the ohmic range. Carrier fluctuations (ΔN model) and mobility fluctuations (Δμ model) are investigated. For long-channel transistors the conduction is quite similar to crystalline metal–oxide–semiconductor field-effect transistors but involving low mobility values. The 1/f noise behavior is analyzed by mobility fluctuations as predicted by Hooge’s theory. For small channel transistors a crowding effect appears and access series resistances affect the conduction. The excess noise is then mainly controlled by these resistances when large gate voltages VGS are applied.