p型CuAlO2薄膜光电性能协同调控及发光晶体管器件应用

In this project, delafossite CuAlO2 film, a stable p-type wide bandgap semiconductor, is selected as the research topic. It aims at the key basic scientific problems to be solved in CuAlO2 film, including hard-to-form crystallinity, labile phase transition, deep valence band maximum, strong localized and anisotropic valence orbitals, and so on. Herein we propose to fabricate highly-crystallized, phase-pure rhombohedral CuAlO2 films by magnetron sputtering and using a single-step approach (without annealing) through in situ high temperature heating during growth. The crystallization mechanism and phase transition behavior of the Cu-Al-O film will be revealed. Multipurpose strategies will be adopted to tune the opto-electrical properties of the CuAlO2 films via the synergistic effects of energy band offset/bowing (Cu-O/CuAlO2 alloying), band edge modification (incorporation of Cu2+ 3d9 orbitals) and impurities doping (substituting S for O). The statuses/concentrations of the impurities in the CuAlO2 films and the rule affecting the opto-electrical properties will be explored in detail. Thin film light-emitting transistors based on p-CuAlO2/n-ZnO heterojunctions will be developted. The ambipolar field-effect modulation functionality and the capability of light emission (blue-violet) will be realized synchronously. Moreover, the relationship between the microstructure-properties of the channel materials and the functionality of the device will be elucidated. The successful implementation of this project will generate data with significant guidance in the development of p-type wide bandgap semiconductors and transparent optoelectronic devices.

本项目选取具有稳定p型半导体特性的宽带隙铜铁矿相CuAlO2薄膜材料为研究对象，针对CuAlO2薄膜结晶困难、易发生相变，价带顶能级深，价带电子结构局域化且存在强各向异性特性等关键基础科学问题，提出采用磁控溅射技术，基底原位高温加热"一步法"（无需退火）制备高度结晶纯相菱形六面体结构CuAlO2薄膜，揭示Cu-Al-O系薄膜的晶化机理及相变演化规律；综合运用能带补偿（Cu-O/CuAlO2合金化）/带边修饰（引入Cu2+ 3d9轨道），杂质掺杂（S替代O）手段协同调控CuAlO2薄膜的光电性能，研究杂质在CuAlO2薄膜中的存在形态、含量及对光电性能的影响规律；研制p-CuAlO2/n-ZnO异质结薄膜发光晶体管器件，同时实现双极场效应调制和蓝-紫光可调发光功能，阐明材料微观结构和性能与器件功能的内在关联和规律。本项目的实施将对发展宽带隙p型半导体材料和透明光电子器件具有重要的指导意义。

以国家自然科学基金项目-“p型CuAlO2薄膜光电性能协同调控及发光晶体管器件应用”（51202224）为研究内容为指导，面对“透明”电子、光电子器件对宽带隙p 型半导体材料的重大战略需求，项目选取具有稳定p 型半导体特性的宽带隙铜铁矿相CuAlO2 薄膜材料为研究对象，针对CuAlO2薄膜结晶困难、易发生相变，价带顶能级深，价带电子结构局域化且存在强各向异性特性等关键基础科学问题，重点研究了Cu-Al-O 系薄膜的晶化机理及相变演化规律，运用薄膜合金化和杂质掺杂手段对CuAlO2的能级结构进行了改造，构建了p-CuAlO2/n-InGaZnO异质结薄膜发光晶体管器件，实现了双极场效应调制功能。研究工作取得如下主要成果：.1. 采用磁控溅射技术原位加热“一步法”制备了高度结晶、均匀致密的纯铜铁矿相菱形六面体结构CuAlO2 薄膜，在国际上首次给出了高分辨电子显微镜和衍射分析证据，阐明了衬底加热温度是影响Cu-Al-O薄膜结晶度和相组成的首要关键参数。.2. 综合运用能带补偿（Cu-O/CuAlO2 合金化）、带边修饰（引入Cu2+ 3d9 轨道），S掺杂手段协同调控了CuAlO2 薄膜光学及半导体输运特性，研究了杂质在CuAlO2 薄膜中的存在形式、含量及对薄膜光电性能影响的规律和机制，研究发现通过同时引入Cu-O杂化体和替代型S原子，Cu2+ 3d9轨道将伴随进入CuAlO2价带轨道，S替代晶格中的O可以削弱O 2p轨道的局域化效应，因此通过“能带补偿/带边修饰”协同过程将CuAlO2带边结构进行了最大有效的改善。CuAlO2薄膜的电阻率实现了6-7个量级的调控（10^4 Ωcm vs. 10-3 Ωcm）；同时，得到了空穴迁移率高达40cm2/Vs的p型CuAlO2薄膜，开创性地实现了p型场效应调制功能。.3. 构建了p-CuAlO2/n-InGaZnO异质结薄膜发光晶体管器件，实现了双极场效应开关功能。.本项目的实施对发展宽带隙p 型半导体材料，能带结构改造、半导体输运特性操控和新型光电子器件构建具有重要的指导意义。