Low-frequency (1/f) noise in nanocrystal field-effect transistors

Area of Science:

• Materials Science
• Condensed Matter Physics
• Nanotechnology

Background:

• Low-frequency noise is a critical parameter for electronic device performance.
• Understanding noise origins in nanocrystal field-effect transistors (NCFETs) is essential for their technological application.
• Surface states and sub-band gap states significantly impact charge transport and noise characteristics in NCFETs.

Purpose of the Study:

• To investigate the origins and magnitude of low-frequency noise in high-mobility NCFETs.
• To elucidate the role of sub-band gap states, particularly those at nanocrystal surfaces, in 1/f noise.
• To demonstrate noise reduction strategies through device engineering and surface passivation.

Main Methods:

• Fabrication and characterization of high-mobility CdSe nanocrystal field-effect transistors.
• Analysis of 1/f noise in linear, saturation, and subthreshold regimes.
• Device geometry engineering and nanocrystal surface passivation techniques.

Main Results:

• Identified 1/f noise as the dominant low-frequency noise type in NCFETs.
• Demonstrated that sub-band gap states, especially surface states, significantly influence 1/f noise.
• Observed that in linear and saturation regimes, noise follows Hooge's model (mobility fluctuations).
• In the subthreshold regime, noise transitions to carrier number fluctuations (McWhorter's model) due to trap states.
• Achieved a Hooge parameter of 3 × 10⁻² for CdSe NCFETs, comparable to other thin-film devices.

Conclusions:

• Noise in NCFETs originates from mobility and carrier number fluctuations, influenced by sub-band gap and surface states.
• Device engineering and surface passivation are effective in controlling and reducing noise.
• CdSe NCFETs exhibit promising low-noise characteristics for integrated circuitry applications.