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Carrier transport in amorphous silicon-based thin-film transistors studied by spin-dependent transport

1996; American Physical Society; Volume: 54; Issue: 11 Linguagem: Inglês

10.1103/physrevb.54.7957

1095-3795

Genshiro Kawachi, Carlos F. O. Graeff, Martin S. Brandt, M. Stutzmann,

Semiconductor materials and devices

Carrier transport processes in hydrogenated amorphous silicon-based thin-film transistors (a-Si:H TFT's) are investigated by spin-dependent transport (SDT). Spin-dependent photoconductivity (SDPC) signals arising from less than ${10}^{6}$ spins in a small transistor are detected with an adequate signal-to-noise ratio. SDPC measurements reveal two different limiting steps for the light-induced leakage current in TFT's depending on the gate voltage: bulk recombination in undoped a-Si:H and recombination near the source junction. Also, the leakage current mechanism under high source-drain fields is identified by SDT measurements in the dark as electron hopping via defect states located at the interface between undoped a-Si:H and the passivation silicon nitride layer. Both silicon dangling bonds and nitrogen dangling bonds seem to be involved in the electron hopping process. At temperatures below 100 K, spin-dependent hopping of electrons in conduction-band tail states is observed. The change of the dominant transport path from extended state conduction to variable range hopping conduction with decreasing temperature is confirmed by SDT measurements. \textcopyright{} 1996 The American Physical Society.