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 (Delta N model) and mobility fluctuations (Delta mu 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 V-GS are applied. (C) 1996 American Institute bf Physics.