Mechanism of Ambipolar Field-Effect Carrier Injections in One-Dimensional Mott Insulators

TL;DR

This study investigates how ambipolar carrier injections occur in one-dimensional Mott insulators used in field-effect transistors, revealing that correlation effects and barrier balancing enable ambipolar conduction despite work function differences.

Contribution

The paper introduces a combined Hubbard and tight-binding model with scalar and vector potentials to explain ambipolar injection mechanisms in 1D Mott insulators.

Findings

Ambipolar injection occurs even with large work function differences.

Correlation effects balance Schottky barrier effects to enable ambipolar conduction.

Collective transport weakens correlation effects under higher Schottky barriers.

Abstract

To clarify the mechanism of recently reported, ambipolar carrier injections into quasi-one-dimensional Mott insulators on which field-effect transistors are fabricated, we employ the one-dimensional Hubbard model attached to a tight-binding model for source and drain electrodes. To take account of the formation of Schottky barriers, we add scalar and vector potentials, which satisfy the Poisson equation with boundary values depending on the drain voltage, the gate bias, and the work-function difference. The current-voltage characteristics are obtained by solving the time-dependent Schr\"odinger equation in the unrestricted Hartree-Fock approximation. Its validity is discussed with the help of the Lanczos method applied to small systems. We find generally ambipolar carrier injections in Mott insulators even if the work function of the crystal is quite different from that of the electrodes. They result from balancing the correlation effect with the barrier effect. For the gate-bias polarity with higher Schottky barriers, the correlation effect is weakened accordingly, owing to collective transport in the one-dimensional correlated electron systems.