Fluctuation analysis of an organic semiconductor-insulator interface

Area of Science:

• Organic electronics
• Semiconductor physics
• Materials science

Background:

• The space-charge region at organic semiconductor (OS)-insulator interfaces governs device performance.
• Understanding charge carrier dynamics and disorder in OS is critical for advancing organic electronics.

Purpose of the Study:

• To probe the space-charge region of an OS-insulator interface using noise analysis.
• To investigate the relationship between disorder, work function inhomogeneity, and charge carrier fluctuations in OS films.

Main Methods:

• Analysis of spontaneous, thermally driven drain current fluctuations in OS field-effect transistors.
• Characterization of excess drain current noise and its power spectral density.
• Systematic variation of gate voltage and doping levels to examine material properties.

Main Results:

• Excess drain current noise originates from local Fermi level fluctuations due to electron exchange with traps.
• Noise power spectral density exhibits a Lorentzian process, indicating a distribution of time constants attributed to OS film disorder.
• Disorder induces local work function inhomogeneity with a finite correlation length.

Conclusions:

• A model for local work function variations and charge carrier fluctuations in polyaniline films is proposed.
• The findings have significant implications for the design and performance of organic electronic devices.
• Noise measurements provide a powerful tool for characterizing disorder and interfacial properties in organic semiconductors.