Microsecond Pulse I\u2013V Approach to Understanding Defects in High Mobility Bi-layer Oxide Semiconductor Transistor

Hyunsuk Woo,Sanghun Jeon

doi:10.1038/s41598-017-06613-1

Abstract

The carrier transport and device instability of amorphous oxide semiconductor devices are influenced by defects that are exponentially distributed in energy, because of amorphous phase channels and front/back interfaces with a large number of sub-gap states. Thus, understanding defects and charge trapping in oxide semiconductor transistors is required for being core device element in reliable production lines. In this paper, we present the transient charging effect, the charge trapping mechanism, and the dynamic charge transport of high-mobility bilayer oxide semiconductor transistors. To this end, we exploited microsecond ramps, pulse ID–VG, transient current, and discharge current analysis methods. The mobility enhancement rate of single HfInZnO (HIZO) and bilayer HfInZnO-InZnO (HIZO-IZO) were 173.8 and 28.8%, respectively, in the charge-trapping-free environment. Transient charge trapping can be classified to temperature insensitive fast charging and thermally activated slow charging with two different trap energies. Insignificant fast transient charging of a bilayer-oxide high-mobility thin film transistor(TFT) can be explained by the low density of sub-gap states in the oxide semiconductor. Understanding defects and transient charging in the oxide semiconductor helps to determine the origin of device instability of oxide TFTs, and finally, to solve this problem.

Highlights

In our work, we aim to understand defects and investigate both their impact on device performance and the transient charge trapping characteristics of dual active-layer TFTs with HfInZnO (HIZO) front channels and InZnO (IZO) back channels using pulse I–V measurements, and provide an accurate method for determining www.nature.com/scientificreports/
For all of the electrode, Mo electrode was deposited by radio frequency (RF) sputtering using O2/Ar gas and subsequently growing a gate insulator of SiO2 by the plasma-enhanced chemical vapor deposition (PECVD)
For single-layer HIZO and bilayer HIZO-IZO TFTs, the extracted N0 values are on the order of 8.4 × 1013 and 2.2 × 1012 cm−2, respectively

Summary

Introduction

We aim to understand defects and investigate both their impact on device performance and the transient charge trapping characteristics of dual active-layer TFTs with HfInZnO (HIZO) front channels and InZnO (IZO) back channels using pulse I–V measurements, and provide an accurate method for determining www.nature.com/scientificreports/. Mobility in an environment with minimal charge trapping[42,43,44,45,46] To this end, we employed microsecond fast ramp I–V (μs-FIV), pulse I–V (PIV), the transient current method, and discharge current analysis (DCA). We discuss the model of charging phenomena of single-layer HIZO and bilayer HIZO-IZO oxide TFTs using the transient current measurement method with varying temperature[36, 51, 52]. The various pulsed I–V techniques described in this paper are expected to help accurately extract the sub-gap density of states and the transistor parameters, and improve understanding of the impact of charging on oxide TFTs

Objectives

Methods

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Conclusion