Browsing by Author "Xu, Lei"

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Enhanced Reliability of In-Ga-ZnO Thin-Film Transistors Through Design of Dual Passivation Layers
(2018-07-01)
Abliz, Ablat
;
Wan, Da
;
Chen, Jui-Yuan
;
Xu, Lei
;
He, Jiawei
This paper investigates the effects of different passivation layers (PVLs) on the electrical performance and reliability of amorphous indium gallium zinc oxide (a-In-Ga-ZnO) thin film transistors (TFTs). By rational design, the fabricated a-InGaZnO TFT with hafnium oxide and aluminum oxide (HfO2/Al2O3) dual PVLs exhibits a field-effect mobility of 13.5 cm(2)/Vs, low sub threshold swing of 0.32 V/decade, and especially, small threshold voltage shifts of 0.5 (-0.6) V and 1.1 (-1.2) V under positive (negative) gate bias, and light illumination stress at the relative humidity of 40%. Furthermore, the a-In-Ga-ZnO TFTs with HfO2/Al2O3 dual PVLs maintain reasonable mobility and electrical performance even exposure to ambient condition for up to four months. This enhanced stability is attributed to the presence of high-quality HfO2/Al2O3 dual PVLs, which not only could suppress the photodesorption, reduce the total trap density and subgap photoexcitation behavior, but also protect the channel from environmental effects. Thus, the rational-designed HfO2/Al2O3 dual PVLs passivated a-In-Ga-ZnO TFTs with superior reliability represent a great step toward the achievement of long-term reliable zinc oxide-based oxide TFTs.
Rational Design of ZnO:H/ZnO Bilayer Structure for High Performance Thin-Film Transistors
(2016-03-30)
Abliz, Ablat
;
Huang, Chun-Wei
;
Wang, Jingli
;
Xu, Lei
;
Liao, Lei
The intriguing properties of zinc oxide-based semiconductors are being extensively studied as they are attractive alternatives to current silicon-based semiconductors for applications in transparent and flexible electronics. Although they have promising properties, significant improvements on performance and electrical reliability of ZnO-based thin film transistors (TFTs) should be achieved before they can be applied widely in practical applications. This work demonstrates a rational and elegant design of TFT, composed of poly crystalline ZnO:H/ZnO bilayer structure without using other metal elements for doping. The field-effect mobility and gate bias stability of the bilayer structured devices have been improved. In this device structure, the hydrogenated ultrathin ZnO:H active layer (similar to 3 nm) could provide suitable carrier concentration and decrease the interface trap density, while thick pure-ZnO layer could control channel conductance. Based on this novel structure, a high field-effect mobility of 42.6 cm(2) V-1 s(-1), a high on/off current ratio of 108 and a small subthreshold swing of 0.13 V dec(-1) have been achieved. Additionally, the bias stress stability of the bilayer structured devices is enhanced compared to the simple single channel layer ZnO device. These results suggest that the bilayer ZnO:H/ZnO TFTs have a great potential for low-cost thin-film electronics.
The different roles of contact materials between oxidation interlayer and doping effect for high performance ZnO thin film transistors
(2015-02-02)
Xu, Lei
;
Huang, Chun-Wei
;
Abliz, Ablat
;
Hua, Yang
;
Liao, Lei
To improve the performance of ZnO thin film transistors (TFTs) by using appropriate metal contacts, the different roles of contact materials between oxidation interlayer and doping effect are investigated. With careful characterization, an oxidation interlayer has been verified at the interface between ZnO film and Al or Ti contact, which is suggested to be responsible for contact resistance and thermal reliability. On the other hand, it is observed that the doping effect is the main reason for the Sn or Cu contact characteristics. The superior contact using Sn is due to an oxidation-free interface, donor doping effect, and a low barrier height. By using a metal contact with a high Gibbs free energy, the metal layer would hardly consume oxygen from channel layer during sputtering and easily form no oxidation interlayer. Thus, choosing a metal contact is important when fabricating high-performance metal-oxide TFTs for flat-panel displays. (C) 2015 AIP Publishing LLC.