Electrical Properties of Nanoscale ZnS Thin Film Transistor

Teresa Oh

doi:10.1155/2015/956101

Abstract

To understand the contact mechanism from electrical properties of the ZnS TFTs, ZnS was fabricated on SiOC as a gate insulator on a Si substrate. Ohmic contact without a potential barrier increased the leakage current, but Schottky contact decreased the leakage current because of a Schottky barrier (SB). The ZnS TFTs prepared on SiOC with a Schottky contact improved the stability with respect to the reduction of drain voltages. The structural matching between ZnS and SiOC increased the height of SB such as ZnS annealed at 200°C, which made ZnS become an amorphous structure. ZnS/SiOC films with a low SB increased the capacitance and leakage current. The crystallinity orientation of ZnS localized defect states and the drift current owing to the impurity charge carriers caused the leakage current through low SB near zero voltages. But the increment of diffusion currents in a depletion layer increased the SB and then decreased the leakage current. So the electrical properties of devices were improved by a tunneling effect of diffusion currents.

Highlights

Thin films of wide band gap II–VI compounds, such as CdS, CdSe, and ZnS, have received considerable attention as photoelectronic materials
The thin film transistors with channel materials such as ZnS, IGZO, and AZO were usually showed as the unipolar transfer characteristics [3–8], but it was reported that ZnO thin film transistor that used SiOC as a gate insulator had bidirectional ambipolar properties
The depletion layer, which is related to a height of Schottky barrier (SB), is an important factor to define Schottky and

Summary

Introduction

Thin films of wide band gap II–VI compounds, such as CdS, CdSe, and ZnS, have received considerable attention as photoelectronic materials. Its advantages include large energy band gap, nontoxic environmental materials, and superior optical properties that make ZnS suitable for nanoscale devices [1, 2]. The root cause can be attributed to poor electrostatics between the gate and the channel. The thin film transistors with channel materials such as ZnS, IGZO, and AZO were usually showed as the unipolar transfer characteristics [3–8], but it was reported that ZnO thin film transistor that used SiOC as a gate insulator had bidirectional ambipolar properties. SiOC became low dielectric constant with lowering the polarity, which helps to have good chemical and physical properties for high electrical quality [9–15]. Some factors which include the interactions between ZnO and SiOC phases and the strong adsorption to the substrate at the ZnO/SiOC surface are responsible for the improvement of performance [16–18]

Methods

Results

Conclusion