Transport and resistance noise spectroscopy of Bi₂S₃ nanobeam transistors

Semiconducting chalcogenides have attracted interest due to the interesting properties they display, especially in low dimensional structures. Bi₂S₃ nanostructures exhibit valuable physical properties such as high bulk mobility, small bandgap, and low thermal conductivity and serve as good candidates for electrical and thermoelectric applications. Bi₂S₃, like many other sulfide compounds, is prone to sulfur vacancies which generate midgap states in the band structure thereby altering the electrical and optical properties. The electrical transport and resistance noise behavior of Bi₂S₃ nanobeam field effect transistors are investigated over a wide range of frequency, temperature, and gate voltage. As the gate voltage is swept from the OFF state to the ON state of the transistor, the noise magnitude shows orders of magnitude raise indicating that the Fermi level passes through a high density of unoccupied states. The results will be discussed to understand the presence of midgap states and trapping/de-trapping of charge carriers in these states as the charge carrier density is modulated.