Heterojunction-engineered carrier transport in elevated-metal metal-oxide thin-film transistors

This study investigates the carrier transport of heterojunction channel in oxide semiconductor thin-film transistor(TFT)using the elevated-metal metal-oxide(EMMO)architecture and indium−zinc oxide(InZnO).The heterojunction band diagram of InZnO bilayer was modified by the cation composition to form the two-dimensional electron gas(2DEG)at the interface quantum well,as verified using a metal−insulator−semiconductor(MIS)device.Although the 2DEG indeed contributes to a higher mobility than the monolayer channel,the competition and cooperation between the gate field and the built-in field strongly affect such mobility-boosting effect,originating from the carrier inelastic collision at the heterojunction interface and the gate field-induced suppression of quantum well.Benefited from the proper energy-band engineering,a high mobility of 84.3 cm2·V^(−1)·s^(−1),a decent threshold voltage(V_(th))of−6.5 V,and a steep subthreshold swing(SS)of 0.29 V/dec were obtained in InZnO-based heterojunction TFT.

Atomic layer deposition for nanoscale oxide semiconductor thin film transistors:review and outlook

Since the first report of amorphous In–Ga–Zn–O based thin film transistors,interest in oxide semiconductors has grown.They offer high mobility,low off-current,low process temperature,and wide flexibility for compositions and processes.Unfortunately,depositing oxide semiconductors using conventional processes like physical vapor deposition leads to problematic issues,especially for high-resolution displays and highly integrated memory devices.Conventional approaches have limited process flexibility and poor conformality on structured surfaces.Atomic layer deposition(ALD)is an advanced technique which can provide conformal,thickness-controlled,and high-quality thin film deposition.Accordingly,studies on ALD based oxide semiconductors have dramatically increased recently.Even so,the relationships between the film properties of ALD-oxide semiconductors and the main variables associated with deposition are still poorly understood,as are many issues related to applications.In this review,to introduce ALD-oxide semiconductors,we provide:(a)a brief summary of the history and importance of ALD-based oxide semiconductors in industry,(b)a discussion of the benefits of ALD for oxide semiconductor deposition(in-situ composition control in vertical distribution/vertical structure engineering/chemical reaction and film properties/insulator and interface engineering),and(c)an explanation of the challenging issues of scaling oxide semiconductors and ALD for industrial applications.This review provides valuable perspectives for researchers who have interest in semiconductor materials and electronic device applications,and the reasons ALD is important to applications of oxide semiconductors.

Review of flexible and transparent thin-film transistors based on zinc oxide and related materials

Flexible and transparent electronics enters into a new era of electronic technologies.Ubiquitous applications involve wearable electronics,biosensors,flexible transparent displays,radio-frequency identifications（RFIDs）,etc.Zinc oxide（ZnO） and relevant materials are the most commonly used inorganic semiconductors in flexible and transparent devices,owing to their high electrical performances,together with low processing temperatures and good optical transparencies.In this paper,we review recent advances in flexible and transparent thin-film transistors（TFTs） based on ZnO and relevant materials.After a brief introduction,the main progress of the preparation of each component（substrate,electrodes,channel and dielectrics） is summarized and discussed.Then,the effect of mechanical bending on electrical performance is highlighted.Finally,we suggest the challenges and opportunities in future investigations.

Low-temperature metal–oxide thin-film transistor technologies for implementing flexible electronic circuits and systems

Here we review two 300℃metal–oxide(MO)thin-film transistor(TFT)technologies for the implementation of flexible electronic circuits and systems.Fluorination-enhanced TFTs for suppressing the variation and shift of turn-on voltage(VON),and dual-gate TFTs for acquiring sensor signals and modulating VON have been deployed to improve the robustness and performance of the systems in which they are deployed.Digital circuit building blocks based on fluorinated TFTs have been designed,fabricated,and characterized,which demonstrate the utility of the proposed low-temperature TFT technologies for implementing flexible electronic systems.The construction and characterization of an analog front-end system for the acquisition of bio-potential signals and an active-matrix sensor array for the acquisition of tactile images have been reported recently.

Performance of La203/InA1N/GaN metal-oxide-semiconductor high electron mobility transistors

We report on the performance of La203/InA1N/GaN metal-oxide-semiconductor high electron mobility transistors （MOSHEMTs） and InA1N/GaN high electron mobility transistors （HEMTs）. The MOSHEMT presents a maximum drain current of 961 mA/mm at Vgs = 4 V and a maximum transconductance of 130 mS/mm compared with 710 mA/mm at Vgs = 1 V and 131 mS/mm for the HEMT device, while the gate leakage current in the reverse direction could be reduced by four orders of magnitude. Compared with the HEMT device of a similar geometry, MOSHEMT presents a large gate voltage swing and negligible current collapse.

Oxide-based thin film transistors for flexible electronics

The continuous progress in thin film materials and devices has greatly promoted the development in the field of flexible electronics. As one of the most common thin film devices, thin film transistors（TFTs） are significant building blocks for flexible platforms. Flexible oxide-based TFTs are well compatible with flexible electronic systems due to low process temperature, high carrier mobility, and good uniformity. The present article is a review of the recent progress and major trends in the field of flexible oxide-based thin film transistors. First, an introduction of flexible electronics and flexible oxide-based thin film transistors is given. Next, we introduce oxide semiconductor materials and various flexible oxide-based TFTs classified by substrate materials including polymer plastics, paper sheets, metal foils, and flexible thin glass. Afterwards, applications of flexible oxide-based TFTs including bendable sensors, memories, circuits, and displays are presented. Finally, we give conclusions and a prospect for possible development trends.

Review of recent progresses on flexible oxide semiconductor thin film transistors based on atomic layer deposition processes

The current article is a review of recent progress and major trends in the field of flexible oxide thin film transistors（TFTs）, fabricating with atomic layer deposition（ALD） processes. The ALD process offers accurate controlling of film thickness and composition as well as ability of achieving excellent uniformity over large areas at relatively low temperatures. First, an introduction is provided on what is the definition of ALD, the difference among other vacuum deposition techniques, and the brief key factors of ALD on flexible devices. Second, considering functional layers in flexible oxide TFT, the ALD process on polymer substrates may improve device performances such as mobility and stability, adopting as buffer layers over the polymer substrate, gate insulators, and active layers. Third, this review consists of the evaluation methods of flexible oxide TFTs under various mechanical stress conditions. The bending radius and repetition cycles are mostly considering for conventional flexible devices. It summarizes how the device has been degraded/changed under various stress types（directions）. The last part of this review suggests a potential of each ALD film, including the releasing stress, the optimization of TFT structure, and the enhancement of device performance. Thus, the functional ALD layers in flexible oxide TFTs offer great possibilities regarding anti-mechanical stress films, along with flexible display and information storage application fields.

喷墨打印高迁移率铟锌锡氧化物薄膜晶体管

采用喷墨打印工艺制备了铟锌锡氧化物(indium-zinc-tin-oxide,IZTO)半导体薄膜,并应用于底栅顶接触结构薄膜晶体管(thin-film transistor,TFT).研究了墨水的溶剂成分以及溶质浓度对打印薄膜图案轮廓的影响.结果表明二元溶剂IZTO墨水中乙二醇溶剂可有效平衡溶质向内的马兰戈尼回流与向外的毛细管流,避免了单一溶剂墨水下溶质流动不平衡造成IZTO薄膜的咖啡环状沉积轮廓图案,获得均匀平坦的薄膜图案轮廓和良好接触特性,接触电阻为820Ω,优化后IZTO TFT器件的饱和迁移率达到16.6 cm^(2)/(V·s),阈值电压为0.84 V,开关比高达3.74×10^(9),亚阈值摆幅为0.24 V/dec.通过打印薄膜凝胶化模型解释了IZTO墨水溶剂成分、溶质浓度与最终薄膜形貌的关系.

高温栅偏和电子辐照对SiC MOSFET阈值电压影响研究

为研究栅氧化物在不同老化程度下电子辐照对SiC MOSFET可靠性的影响,结合高温栅偏和电子辐照2种实验对SiC MOSFET电学特性进行分析,讨论栅氧化物受到高温和强电场应力后电子辐照对SiC MOSFET阈值电压的影响。为避免封装材料在高温和电子辐照下对阈值电压产生影响,实验时将被测器件裸露于空气中。实验结果表明,高温正栅偏后器件阈值电压对电子辐照更加敏感,因此提出了电子辐照对SiC MOSFET高温栅偏老化后阈值电压影响的指数关系,且0.2 MeV电子能量辐照300 kGy剂量可将39 V、150℃、2 h高温栅偏后的器件阈值电压恢复至初始值。在Sentaurus TCAD仿真软件中建立SiC MOSFET基础数值模型,设置氧化物内电子浓度和空穴陷阱,模拟高温栅偏和电子辐照对器件阈值电压的影响,讨论阈值电压恢复机制。

基于n型柔性半导体的有机晶体管及其电子-离子双响应特性

为了研究n型有机混合离子电子导体电子-离子双响应特性及分子量对载流子迁移率的影响,采用具有平面刚性的梯形分子链结构的高分子量聚苯并二咪唑苯并菲绕啉二酮制备高性能有机电化学晶体管,并对晶体管紫外可见吸收光谱和晶体管器件电气性能进行表征。结果表明,利用高分子量聚苯并二咪唑苯并菲绕啉二酮制备的n型有机电化学晶体管表现出极高的响应速度(0.034 s)、高载流子迁移率(4.72×10^(-3) cm^(2)/(V·s)),以及在水系电解液中优异的稳定性(稳定运行超过120次脉冲循环)。

Effect of active layer deposition temperature on the performance of sputtered amorphous In–Ga–Zn–O thin film transistors

The effect of active layer deposition temperature on the electrical performance of amorphous InGaZnO （a-IGZO） thin film transistors （TFTs） is investigated. With increasing annealing temperature, TFT performance is firstly improved and then degraded generally. Here TFTs with best performance defined as ＂optimized-annealed＂ are selected to study the effect of active layer deposition temperature. The field effect mobility reaches maximum at deposition temperature of 150℃ while the room-temperature fabricated device shows the best subthreshold swing and off-current. From Hall measurement results, the carrier concentration is much higher for intentional heated a-IGZO films, which may account for the high off-current in the corresponding TFT devices. XPS characterization results also reveal that deposition temperature affects the atomic ratio and Ols spectra apparently. Importantly, the variation of field effect mobility of a-IGZO TFTs with deposition temperature does not coincide with the tendencies in Hall mobility of a-IGZO thin films, Based on the further analysis of the experimental results on a-IGZO thin films and the corresponding TFT devices, the trap states at front channel interface rather than IGZO bulk layer properties may be mainly responsible for the variations of field effect mobility and subthreshold swing with IGZO deposition temperature.

高迁移率金属氧化物半导体薄膜晶体管的研究进展

基于金属氧化物半导体(MOS)的薄膜晶体管(TFT)由于较高的场效应迁移率(μFE)、极低的关断漏电流和大面积电性均匀等特点,已成为助推平板显示或柔性显示产业发展的一项关键技术。经过30余年的研究,非晶铟镓锌氧化物(a-IGZO)率先替代非晶硅(a-Si)在TFT中得到推广应用。然而,为了同时满足显示产业对更高生产效益、更佳显示性能(如高分辨率、高刷新率等)和更低功耗等多元升级要求,需要迁移率更高的MOS TFTs技术。本文从固体物理学的角度,系统综述了MOS TFTs通过多元MOS材料实现高迁移率特性的研究进展,并讨论了迁移率与器件稳定性之间的关系。最后,总结展望了MOS TFTs的现状和发展趋势。

Theory and Practice of“Striping”for Improved ON/OFF Ratio in Carbon Nanonet Thin Film Transistors

A new technique to reduce the influence of metallic carbon nanotubes(CNTs)relevant for large-scale integrated circuits based on CNT-nanonet transistorsis proposed and verified.Historically,electrical and chemical filtering of the metallic CNTs have been used to improve the ON/OFF ratio of CNT-nanonet transistors;however,the corresponding degradation in ON-current has made these techniques somewhat unsatisfactory.Here,we abandon the classical approaches in favor of a new approach based on relocation of asymmetric percolation threshold of CNT-nanonet transistors by a technique called“striping”;this allows fabrication of transistors with ON/OFF ratio>1000 and ON-current degradation no more than a factor of 2.We offer first principle numerical models,experimental confirmation,and renormalization arguments to provide a broad theoretical and experimental foundation of the proposed method.

纳米氧化锌粒子薄膜的场效应载流子迁移率特性的研究

将纳米氧化锌粒子制备纳米膜,研究其场效应性能与载流子迁移性能。通过在有机溶剂介质中热分解油酸锌配合物,合成出尺寸均匀的六方相氧化锌纳米晶粒子。以沉积了铝钛氧化物层与铟锡氧化物层的玻璃为载体,通过旋涂工艺将纳米氧化锌粒子涂覆于其表面,制备出场效应薄膜晶体管。通过工艺优化,制成的半导体纳米氧化锌薄膜晶体管具有优异的可控结构及致密分布的氧化锌纳米晶体,表现出优异的场效应性能与载流子迁移性能。这种直接由氧化锌纳米晶制备的薄膜晶体管具有非毒性、好的透明性以及优越而稳定的场效应半导体器件性能。该技术可高效,便利且低成本大批量地制备氧化锌薄膜晶体管,便于后续在电子等领域的应用。

金属氧化物薄膜晶体管及其在新型显示中的应用

为适应高分辨率、大尺寸的液晶(LCD)和有源有机发光二极管(AMOLED)等新型显示技术发展的需要,开发了一种新型的基于金属氧化物有源半导体材料的薄膜晶体管(MOTFT)驱动面板.文中阐述了MOTFT的材料、器件结构、制作工艺以及应用,并对影响MOTFT性能的因素进行了讨论.研发团队开发的MOTFT的迁移率最高可达21.6cm2/(V.s),阈值电压为1.63V,开关比为109,亚阈值摆幅为0.216 V/decade.基于该MOTFT驱动面板,在国内率先实现了5英寸彩色AMOLED显示屏.该MOTFT驱动面板具有迁移率高、制作工艺简单、成本较低以及容易实现大面积等优势,在LCD和AMOLED等新型显示领域具有广泛的应用前景.

柔性衬底氧化物半导体透明导电膜的研究进展

回顾和评述了柔性衬底氧化物透明导电膜 (包括锡掺杂的三氧化二铟ITO薄膜、铝掺杂的氧化锌AZO薄膜等 )的研究进展情况。报道了在柔性衬底上制备的ITO膜、ZnO膜的光电性质对衬底种类、制备工艺以及制备参数的依赖关系 。

离子辅助沉积掺铝氧化锌透明导电膜的研究

报道了采用离子辅助电子枪蒸发技术制备优质氧化锌透明导电膜的工艺和结果 ,分析了源掺杂 ,镀膜气氛 ,衬底温度等参数与膜的电导率及透光特性的关系 ,作出了电阻率低达 2× 1 0 - 3Ω· cm,厚为 40 0 nm的膜的方块电阻为 1× 1 0 3Ω/□ ,可见光透过率大于 80 %的优质透明导电膜。实验表明氧离子辅助蒸发可增加氧化锌分子的能量 ,提高其迁移率 ,显著提高薄膜的致密程度 ;氧离子能使分解的锌原子充分氧化 ;离子轰击可平滑薄膜表面。总之 。

高性能金属铟镓锌氧化物TFT的研究

在2.5 G试验线上研究了金属氧化物IGZO薄膜晶体管(TFT)的性能,获得良好的IGZO TFT性能,迁移率为10.65cm2/V·s,阈值电压Vth为-1.5 V,开态电流为1.58×10-4 A,关态电流为3.0×10-12,开关比为5.27×107,亚阈值摆幅为0.44V/Dev,验证了TFT的均一性和重复性。此外还研究了可见光照和电压偏应力对IGZO TFT性能的影响,可见光照不会促使IGZO TFT Vth的漂移,进行2 h的负偏电压应力测试,IGZO TFT的Vth几乎没有漂移。使用上述IGZO TFT基板成功地制作了中国大陆第一款Oxide-LCD样机(18.5英寸),展现出良好的效果。

驱动电子墨水电子纸的柔性TFT背板制造技术

基于电子墨水技术的电子纸是目前最有竞争力的类纸媒显示器。实现电子墨水电子纸的柔性是这项显示技术的关键之一。文章分析了当前电子墨水电子纸的主要研究方向,详细介绍了基于金属柔性基板的TFT制造技术、基于固定塑料基板的以激光释放塑基电子工艺(EPLaR)为代表的TFT制造技术、以激光退火表面释放技术(SUFTLA)为代表的TFT转移技术以及有机薄膜晶体管(OTFT)技术等4项柔性TFT背板的主要实现方法。对比了它们的材料选取,工艺特点和器件性能,分析了各项柔性TFT背板工艺的优缺点,提出了改进方向。

透明非晶态氧化物半导体薄膜晶体管的研究进展

透明非晶态氧化物半导体薄膜晶体管(TAOS-TFT)以其诸多优势受到研究人员的青睐,最近几年发展迅速。文章以传统薄膜晶体管做对照,详细介绍了TAOS-TFT的原理、结构和性能,总结出TAOS-TFT相对于Si基TFT具有制备温度低、均一性好、迁移率高、对可见光全透明和阈值电压低等5方面的优势,指出了TAOS-TFT在进一步实用化过程中所面临的几个重要问题,其中最为重要的是需要尽快建立自身的集约化物理模型。