Modulation Doping for Threshold Voltage Control in Organic Field-Effect Transistors

Ilia Lashkov*, Kevin Krechan, Katrin Ortstein, Felix Talnack, Shu Jen Wang, Stefan C. B. Mannsfeld, Hans Kleemann, Karl Leo

*Corresponding author for this work

Research output: Contribution to journalJournal articlepeer-review

12 Citations (Scopus)

Abstract

Organic electronics is the technology enabling truly flexible electronic devices. However, despite continuous improvements in the charge-carrier mobility, devices used for digital circuits based on organic field-effect transistors (OFETs) have still not achieved a commercial breakthrough. A substantial hurdle to the realization of effective digital circuitry is the proper control of the threshold voltage Vth. Previous approaches include doping or self-assembled monolayers to provide the threshold voltage control. However, while self-assembled monolayers-modified OFETs often do not show the level of reproducibility which is required in digital circuit engineering, direct doping of the channel material results in a poor on/off ratio leading to unfavorable power dissipation. Furthermore, direct doping of the channel material in organic semiconductors could cause the formation of trap states impeding the charge-carrier transport. Employing the concept of modulation-doped field-effect transistors (MODFETs), which is well established in inorganic electronics, the semiconductor–dopant interaction is significantly reduced, thereby solving the above-described problems. Here, we present the concept of an organic semiconductor MODFET which is composed of an organic–organic heterostructure between a highly doped wide-energy-gap material and an undoped narrow-energy-gap material. The effectiveness of charge transfer across the interface is controlled by the doping concentration and thickness of an undoped buffer layer. A complete picture of the energy landscape of this heterostructure is drawn using impedance spectroscopy and ultraviolet photoelectron spectroscopy. Furthermore, we analyze the effect of the dopant density on the charge-carrier transport properties. The incorporation of these heterostructures into OFETs enables a precise adjustment of the threshold voltage by using the modulation doping concept.

Original languageEnglish
Pages (from-to)8664-8671
Number of pages8
JournalACS Applied Materials and Interfaces
Volume13
Issue number7
DOIs
Publication statusPublished - 24 Feb 2021

User-Defined Keywords

  • modulation doping
  • threshold voltage control
  • organic field-effect transistors
  • charge transport
  • in situ conductivity
  • organic heterostructureShow

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