Highly Conductive and Transparent AZO Films Fabricated by PLD as Source/Drain Electrodes for TFTs.

Hongke Zhang,Yuxi Deng,Xiaochen Zhang,Xiaoqing Li,Honglong Ning,Hong Tao,Rihui Yao,Junbiao Peng,Xubing Lu,Zhiqiang Fang

doi:10.3390/ma11122480

Hongke Zhang, Yuxi Deng + Show 8 more

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https://doi.org/10.3390/ma11122480

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Abstract

Aluminum-doped ZnO (AZO) has huge prospects in the field of conductive electrodes, due to its low price, high transparency, and pro-environment. However, enhancing the conductivity of AZO and realizing ohmic contact between the semiconductor and AZO source/drain (S/D) electrodes without thermal annealing remains a challenge. Here, an approach called pulsed laser deposition (PLD) is reported to improve the comprehensive quality of AZO films due to the high energy of the laser and non-existence of the ion damage. The 80-nm-thick AZO S/D electrodes show remarkable optical properties (transparency: 90.43%, optical band gap: 3.42 eV), good electrical properties (resistivity: 16 × 10−4 Ω·cm, hall mobility: 3.47 cm2/V·s, carrier concentration: 9.77 × 1020 cm−3), and superior surface roughness (Rq = 1.15 nm with scanning area of 5 × 5 μm2). More significantly, their corresponding thin film transistor (TFT) with low contact resistance (RSD = 0.3 MΩ) exhibits excellent performance with a saturation mobility (µsat) of 8.59 cm2/V·s, an Ion/Ioff ratio of 4.13 × 106, a subthreshold swing (SS) of 0.435 V/decade, as well as good stability under PBS/NBS. Furthermore, the average transparency of the unpatterned multi-films composing this transparent TFT can reach 78.5%. The fabrication of this TFT can be suitably transferred to transparent arrays or flexible substrates, which is in line with the trend of display development.

Highlights

Over the last decades, flexible and transparent electronics have attracted widespread attention.Numerous important studies on transparent materials and their application to devices have been published, especially towards the fabrication of transparent thin film transistor (TFT) [1,2,3,4,5]
Aluminum-doped ZnO (AZO) electrodes fabricated by pulsed laser deposition (PLD) at room temperature exhibit superior resistivity, transparency, optical band gap, and surface roughness
Electrodes are used to produce transparent TFTs without thermal annealing and their corresponding devices exhibit a μsat of 8.59 cm2 /V·s, an subthreshold swing (SS) of 0.435 V/decade, an Ion /Ioff ratio of 4.13 × 106, a high transmittance of 78.5%, and excellent stability under positive gate-bias stress (PBS)/negative gate-bias stress (NBS)

Summary

Introduction

Flexible and transparent electronics have attracted widespread attention. A large number of investigators have attempted to fabricate high-quality AZO films at room temperature by various measures [18,19,20,21]. Among these ways, PLD is a relatively good method for manufacturing high-quality. AZO electrodes fabricated by PLD at room temperature exhibit superior resistivity, transparency, optical band gap, and surface roughness. The optimum AZO (PLD-AZO) S/D electrodes are used to produce transparent TFTs without thermal annealing and their corresponding devices exhibit a μsat of 8.59 cm2 /V·s, an SS of 0.435 V/decade, an Ion /Ioff ratio of 4.13 × 106 , a high transmittance of 78.5%, and excellent stability under PBS/NBS. The contact resistance of TFTs is as low as 0.3 MΩ, resulting in better output characteristics

Experimental

Results and Discussion

Conclusions