热原子层沉积钛掺杂氧化镓薄膜的光学性能  

Optical Properties of Titanium-doped Gallium Oxide Thin Films by Thermal Atomic Layer Deposition

作　　者：李存钰 朱香平[1,2] 赵卫 李继超[1,2] 胡景鹏 LI Cunyu;ZHU Xiangping;ZHAO Wei;LI Jichao;HU Jingpeng(State Key Laboratory of Transient Optics and Photonics,Xi′an Institute of Optics and Precision Mechanics,Chinese Academy of Sciences,Xi′an 710119,China;University of Chinese Academy of Sciences,Beijing 100049,China;Xi′an Zhongke Atomic Precision Manufacturing Technology Co.,Ltd.,Xi′an 710110,China)

机构地区：[1]中国科学院西安光学精密机械研究所瞬态光学与光子技术国家重点实验室,西安710119 [2]中国科学院大学,北京100049 [3]西安中科原子精密制造科技有限公司,西安710110

出　　处：《光子学报》2023年第6期118-127,共10页Acta Photonica Sinica

基　　金：国家自然科学基金国家重大科研仪器研制项目(No.52127817);中国科学院重大科研仪器设备研制项目(No.ZDKYYQ20220007);中国科学院重点部署项目(No.ZDRW‒XH‒2021‒6);中国科学院科研仪器设备研制项目,陕西省“两链”融合重点专项(No.2021LLRH‒03)。

摘　　要：在250℃的低温下,以三甲基镓、四(二甲氨基)钛为前躯体源,O_(3)为反应气体,采用热原子层沉积制备了Ti掺杂Ga_(2)O_(3)(TGO)薄膜。Ga_(2)O_(3)和TiO_(2)的生长速率分别为0.037 nm/cycle和0.08 nm/cycle,TGO薄膜厚度低于理论计算值。X射线光电子能谱仪测试结果表明膜中Ti浓度随Ga_(2)O_(3)/TiO_(2)循环比减少而增加,O 1s、Ga 2p和Ti 2p的峰位置向较低的结合能移动,这是因为Ti原子取代了Ga原子的某些位点引起了结合能降低,表明Ti元素成功掺杂到Ga_(2)O_(3)薄膜中。TiO_(2)和Ga_(2)O_(3)的芯能级光谱分析表明薄膜中存有Ti^(4+)和Ga^(3+)离子。TGO薄膜的O 1s芯能级光谱中Ga-O键随着Ti-O键含量增加而下降,表明TGO薄膜中形成Ga_(2)O_(3)-TiO_(2)复合材料。掠入射X射线衍射图中没有出现衍射峰,表明沉积的Ga_(2)O_(3)和TGO薄膜为非晶态。原子力显微镜观察到薄膜表面平整光滑,均方根粗糙度为0.377 nm,这得益于原子层沉积逐层生长的优势。TGO薄膜在可见光区表现出较高的透明度,对紫外光强烈吸收。随着Ti掺杂浓度的增加,TGO薄膜的折射率由于化学变化从1.75增加到1.99,紫外光区消光系数增大引起透过率减小,吸收边缘出现了红移,光学带隙从4.9 eV减小到4.3 eV。分光光度法和X射线光电子能谱法测定薄膜光学带隙所得的结果一致。Gallium oxide(Ga_(2)O_(3))is a wide bandgap(4.8 eV)semiconductor oxide with the advantages of high transparency and excellent chemical and thermal stability.Therefore,Ga_(2)O_(3) thin film has a wide range of applications in metal oxide field effect transistors,photodetectors and so on.However,the large bandgap of Ga_(2)O_(3) is unfavorable to the conductivity,which limits the application of Ga_(2)O_(3) film in optoelectronic devices.The optical and electrical properties of Ga_(2)O_(3) can be significantly improved by elemental doping,thereby enhancing device performance.The lattice deformation of Ti-doped Ga_(2)O_(3)(TGO)is small due to the close matching of the Shannon ion radii(0.0605 nm,0.042 nm)of Ti^(4+)in octahedral and tetrahedral coordination with Ga^(3+)(0.062 nm,0.047 nm).The reported plasma-enhanced atomic layer deposition at 120℃for the preparation of TGO films requires four precursors:triethyl gallium,oxygen plasma,titanium tetraisopropoxide(TTIP)and H2O.Using H2O as an oxidizer requires long purging times after water vapor exposure and brings in hydroxyl(-OH)impurities at deposition temperatures below 150℃.Compared with H2O,O_(3) has stronger oxidability and higher volatility and does not introduce impurities.In order to avoid the problems caused by using H2O as precursor.TiO_(2),Ga_(2)O_(3) and TGO films are prepared by thermal atomic layer deposition using Trimethylgallium(TMG)and Tetrakis-dimethyl-amido Titanium(TDMAT)as precursor sources and O_(3) as reaction gas at 250℃.The Ti-doped Ga_(2)O_(3) concentration is adjusted by designing the Ga_(2)O_(3)/TiO_(2) cycle ratio.TGO thin films form sandwich structure through different cycles(9,6 and 3)of Ga_(2)O_(3) and 1 cycle of TiO_(2).The growth rates of Ga_(2)O_(3) and TiO_(2) measured by spectroscopic ellipsometry are 0.037 nm/cycle and 0.08 nm/cycle,respectively.The growth rate of TGO film is lower than the theoretical calculated value due to the delayed growth of Ga_(2)O_(3) nucleation caused by the decrease of surface reactive site density

关 键 词：氧化镓薄膜 Ti掺杂Ga_(2)O_(3)薄膜 热原子层沉积 折射率 光学带隙 

分 类 号：O484.1[理学—固体物理] O472.3[理学—物理]