Charge carrier inversion in a doped thin film organic semiconductor island

TL;DR

This paper demonstrates the creation of an inversion layer in a doped organic semiconductor island, showing that nanoscale devices can operate in inversion mode, which is crucial for organic transistor technology.

Contribution

It introduces a pulsed bias technique to identify dopant types and demonstrates inversion, depletion, and accumulation regimes in a nanometer-scale organic semiconductor island.

Findings

Inversion, depletion, and accumulation regimes achieved in a 20 nm radius pentacene island.

Pentacene identified as n-doped via the new characterization technique.

Nanoscale organic transistors can operate in inversion mode.

Abstract

Inducing an inversion layer in organic semiconductors is a highly nontrivial, but critical, achievement for producing organic field-effect transistor (OFET) devices, which rely on the generation of inversion, accumulation, and depletion regimes for successful operation. In recent years, a major milestone was reached: an OFET was made to successfully operate in the inversion-mode for the first time. Here, we develop a pulsed bias technique to characterize the dopant type of any organic material system, without prior knowledge or characterization of the material in question. We use this technique on a pentacene/PTCDI heterostructure and thus deduce that pentacene is n-doped by impurities. Additionally, through tip-induced band-bending, we generate inversion, depletion, and accumulation regimes over a 20~nm radius, three monolayer thick n-doped pentacene island. Our findings demonstrate that nanometer-scale lateral extent and thickness are sufficient for an OFET device to operate in the inversion regime.