Modeling and simulation of polycrystalline ZnO thin-film transistors
Modeling and simulation of polycrystalline ZnO thin-film transistors
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DOI：
10.1063/1.1628834
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发表时间：
2003-12-15
影响因子：
3.2
通讯作者：
Kawasaki, M
中科院分区：
文献类型：
--
作者：
Hossain, FM;Nishii, J;Kawasaki, M
由透明沟道半导体（如ZnO）制成的薄膜晶体管（TFT）具有重要的技术意义，因为它们对可见光不敏感使得器件结构简单。事实上，已经有几种ZnO TFT实现1-10 cm 2/V s的相当好的场效应迁移率的证明，但是ZnO TFT的总体性能并不令人满意，这可能是由于存在致密的晶界。我们模拟了ZnO TFT中的晶界，并通过使用二维器件模拟器对ZnO TFT进行了模拟，以确定晶界对器件性能的影响。通过考虑TFT沟道中间的单个晶界开始多晶ZnO TFT建模，用位于晶界中的高斯缺陷分布来制定。在晶界处形成了双肖特基势垒，并分析了其势垒高度与缺陷密度和栅偏压的关系。模拟扩展到具有许多晶界的TFT，以定量分析沿沟道沿着发展的电势分布。多晶ZnO TFT和多晶Si TFT之间的主要区别之一是多晶ZnO TFT中的小得多的纳米尺度晶粒在其传输特性的亚阈值或关态区域处诱导双肖特基势垒的强烈重叠，该双肖特基势垒在微晶中具有较高的激活能并且在晶界中具有较低的势垒。通过模拟，我们能够估计总的陷阱态的密度定位在晶界的多晶ZnO TFT通过确定在设备中的表观迁移率和晶粒尺寸。(C)2003年，美国物理学会。
Thin-film transistors (TFTs) made of transparent channel semiconductors such as ZnO are of great technological importance because their insensitivity to visible light makes device structures simple. In fact, there have been several demonstrations of ZnO TFTs achieving reasonably good field effect mobilities of 1-10 cm2/V s, but the overall performance of ZnO TFTs has not been satisfactory, probably due to the presence of dense grain boundaries. We modeled grain boundaries in ZnO TFTs and performed simulation of a ZnO TFT by using a two-dimensional device simulator in order to determine the grain boundary effects on device performance. Polycrystalline ZnO TFT modeling was started by considering a single grain boundary in the middle of the TFT channel, formulated with a Gaussian defect distribution localized in the grain boundary. A double Schottky barrier was formed in the grain boundary, and its barrier height was analyzed as a function of defect density and gate bias. The simulation was extended to TFTs with many grain boundaries to quantitatively analyze the potential profiles that developed along the channel. One of the main differences between a polycrystalline ZnO TFT and a polycrystalline Si TFT is that the much smaller nanoscaled grains in a polycrystalline ZnO TFT induces a strong overlap of the double Schottky barriers with a higher activation energy in the crystallite and a lower barrier potential in the grain boundary at subthreshold or off-state region of its transfer characteristics. Through the simulation, we were able to estimate the density of total trap states localized in the grain boundaries for polycrystalline ZnO TFT by determining the apparent mobility and grain size in the device. (C) 2003 American Institute of Physics.