基于外延单晶金刚石的同位素电池能量转换单元的设计、制作及性能

Diamond is an ideal material for beta-voltaic nuclear battery due to its outstanding properties such as large band-gap width, high radiation hardness and carrier mobility. At present, the energy conversion unit (transducer) for the beta-voltaic nuclear battery based on Si, 4H-SiC and GaN are facing some problems such as low energy conversion efficiency or radiation damage-induced performance degradation. In this project, Schottky barrier diodes with different junction parameters will be designed and fabricated based on boron-doped P-type homo-epitaxial mono-crystalline diamond and can be employed as transducers for beta-voltaic nuclear batteries. Under the radiation of radioisotope, the electrical output performances of as-fabricated diamond-based transducers will be carefully investigated. This project will focus on theoretical design and performance simulation as well as actual fabrication of the diamond-based Schottky barrier diodes. Moreover, the electrical performances of as-fabricated Schottky barrier diodes can be measured. The aim of this project is to understand the intrinsic relationship between the structural characteristics of homo-epitaxial mono-crystalline diamond, the junction parameters of Schottky barrier diodes and the electrical output performances of these diamond transducers, which would provide theoretical basis and practical supports for the further development of isotopic betavoltaic batteries having high performance and actual applications.

金刚石具有大的带隙宽度、高的辐射硬度、高的载流子迁移率等特性，是一种制作辐射伏特效应同位素电池的理想材料。针对现有的辐射伏特效应同位素电池能量转换单元（如基于单晶硅、4H-SiC和GaN）的低能量转换效率或辐照损伤所致的性能衰减等问题，本项目拟以掺硼P型同质外延单晶金刚石为研究对象，设计并研制具有不同结型参数的金刚石肖特基势垒二极管；并以其作为辐射伏特效应同位素电池的能量转换单元，详细研究在同位素源辐照下的电学输出性能；重点开展基于金刚石同质外延层的肖特基势垒二极管能量转换单元的理论设计和性能模拟，并以此为基础和指导，实现该能量转换单元的实际制作和性能检测；深入理解金刚石同质外延层的结构特性、肖特基势垒二极管的结型参数及能量转换单元的电学输出性能之间的内在关联，从而为进一步研制高性能的具有实际意义的辐射伏特效应同位素电池提供理论依据和技术支撑。

本项目旨在探索平面型肖特基叉指状二极管作为同位素电池能量转换单元的理论可行性。在本项目的研究中，首先，我们采用基于蒙特卡罗数值计算方法的 Geant4 软件，对基于外延单晶金刚石的肖特基二极管结构的同位素电池能量转换单元的能量沉积、器件性能等进行模拟计算分析，所得结果为实际器件的设计制作提供理论依据和指导；其次以乙硼烷作为掺硼源，采用微波等离子体化学气相沉积技术制备了掺硼p型单晶金刚石薄膜，详细研究了B/C比和沉积温度等因素对所制备的掺硼P型单晶金刚石薄膜的表面形貌、晶体质量和电学性能的影响。在此基础上，我们利用光刻和金属掩模工艺，在一系列不同掺杂浓度的掺硼金刚石上通过真空蒸发和磁控溅射技术制作了平面型叉指状肖特基电极和欧姆电极，研究了不同掺杂水平对肖特基器件性能的影响；还制备了不同电极间距的肖特基结，研究电极间距对器件性能的影响。从而为进一步研制高性能的具有实际意义的辐射伏特效应同位素电池提供理论依据和技术支撑。