Hydrogen anion and subgap states in amorphous In-Ga-Zn-O thin films for TFT applications
Hydrogen anion and subgap states in amorphous In-Ga-Zn-O thin films for TFT applications
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DOI：
10.1063/1.4985627
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发表时间：
2017-06-05
影响因子：
4
通讯作者：
Hosono, Hideo
中科院分区：
文献类型：
--
作者：
Bang, Joonho;Matsuishi, Satoru;Hosono, Hideo
氢是一种对半导体物理性质具有重要作用的杂质。尽管进行了大量研究，氢在氧化物半导体中的作用仍然是一个未解之谜。这种情况是由于有关杂质氢的化学状态的信息不足而引起的。在这里，我们报告了用于薄膜晶体管（TFT）应用的非晶 In-Ga-Zn-O (a-IGZO) 薄膜中阴离子氢与金属阳离子键合的直接证据，并讨论了氢杂质如何影响 a-IGZO 的电子结构。通过溅射制备的自支撑a-IGZO薄膜的红外吸收光谱表明，氢阴离子作为主要氢物种（浓度类似于10（20）cm（-3））以及以羟基形式存在的氢（类似于10（20）cm（-3））。密度泛函理论计算表明，这些氢阴离子与金属中心之间的键会在价带顶部上方产生亚能隙态，这意味着阴离子氢在 a-IGZO TFT 中常见的负偏压照明应力不稳定性中起着至关重要的作用。由 AIP 出版社出版。
Hydrogen is an impurity species having an important role in the physical properties of semiconductors. Despite numerous studies, the role of hydrogen in oxide semiconductors remains an unsolved puzzle. This situation arises from insufficient information about the chemical state of the impurity hydrogen. Here, we report direct evidence for anionic hydrogens bonding to metal cations in amorphous In-Ga-Zn-O (a-IGZO) thin films for thin-film transistors (TFT) applications and discuss how the hydrogen impurities affect the electronic structure of a-IGZO. Infrared absorption spectra of self-standing a-IGZO thin films prepared by sputtering reveal the presence of hydrogen anions as a main hydrogen species (concentration is similar to 10(20) cm(-3)) along with the hydrogens in the form of the hydroxyl groups (similar to 10(20) cm(-3)). Density functional theory calculations show that bonds between these hydride ions with metal centers give rise to subgap states above the top of the valence band, implying a crucial role of anionic hydrogen in the negative bias illumination stress instability commonly observed in a-IGZO TFTs. Published by AIP Publishing.