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Effect of the Degree of the Gate‐Dielectric Surface Roughness on the Performance of Bottom‐Gate Organic Thin‐Film Transistors
Author(s) -
Geiger Michael,
Acharya Rachana,
Reutter Eric,
Ferschke Thomas,
Zschieschang Ute,
Weis Jürgen,
Pflaum Jens,
Klauk Hagen,
Weitz Ralf Thomas
Publication year - 2020
Publication title -
advanced materials interfaces
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.671
H-Index - 65
ISSN - 2196-7350
DOI - 10.1002/admi.201902145
Subject(s) - materials science , gate dielectric , thin film transistor , dielectric , surface roughness , gate oxide , optoelectronics , transistor , surface finish , substrate (aquarium) , monolayer , high κ dielectric , layer (electronics) , nanotechnology , composite material , electrical engineering , voltage , engineering , oceanography , geology
In organic thin‐film transistors (TFTs) fabricated in the inverted (bottom‐gate) device structure, the surface roughness of the gate dielectric onto which the organic‐semiconductor layer is deposited is expected to have a significant effect on the TFT characteristics. To quantitatively evaluate this effect, a method to tune the surface roughness of a gate dielectric consisting of a thin layer of aluminum oxide and an alkylphosphonic acid self‐assembled monolayer over a wide range by controlling a single process parameter, namely the substrate temperature during the deposition of the aluminum gate electrodes, is developed. All other process parameters remain constant in the experiments, so that any differences observed in the TFT performance can be confidently ascribed to effects related to the difference in the gate‐dielectric surface roughness. It is found that an increase in surface roughness leads to a significant decrease in the effective charge‐carrier mobility and an increase in the subthreshold swing. It is shown that a larger gate‐dielectric surface roughness leads to a larger density of grain boundaries in the semiconductor layer, which in turn produces a larger density of localized trap states in the semiconductor.