纳米晶碳化硅/纳米晶硅基异质结的制备及微波特性

The transit time (TT) devices of SiC and Si operating in microwave detection field hold great promises for military and civilian applications, however, the oscillation frequency of present crystalline homogeneous-junction devices is far lower than the theoretical value. The fabrication and microwave performances of the hetero-junctions based on nanocrystalline-SiC with nanocrystalline-Si (nc-SiC/nc-Si) are investigated in this project. Based on the Drift-Diffusion mechanism, the influence from the hetero-junction interface defects while the quantum effect of nanocrystalline grains will be further taken into account. The Quantum Drift-Diffusion model is employed for simulating the proposed hetero-junctions. The self-adaptive solution will be adopted to solve the above equations and to calculate the parameters of microwave performances such as reactance, the relation between admittance and frequency, the relation between microwave power and frequency et al. of the designed hetero-junctions for guiding the subsequent experiments. Using the technique of plasma enhanced chemical vapor deposition (PECVD), the nc-SiC and nc-Si films are grown, and further to form the varactor hetero-junction of (p)nc-Si/(n)nc-SiC, the tunneling transit time (TUNNETT) one of (p+)nc-SiC/(n+)nc-Si/(n-/n+)Si, and the impact avalanche transit time (IMPATT) one of (p+)nc-SiC/(n)nc-Si/(n-/n+)Si. The microwave performances, the materials' structures and compositions will be measured, the calculated results can be verified by the experimental ones. The relations and laws between the performances of devices and the structures, compositions, fabricated process parameters will be explained, the mechanisms of junction growth and carrier conduction can be clarified. It will bring an optimum scheme for designing the microwave devices with nanomaterials.

SiC、Si渡越时间(TT)器件在微波探测中具有重要的军民用价值，但目前晶体同质结器件的频率远低于理论值。本项目研究纳米晶SiC/纳米晶Si(nc-SiC/nc-Si)基异质结的制备和微波性能。在飘移-扩散机制基础上，还考虑异质结界面缺陷的影响及纳米晶的量子效应，采用量子漂移-扩散模型进行数值仿真异质结；选择自洽方法求解，计算微波性能参数如容抗、导纳-频率、微波功率-频率等。使用PECVD技术生长nc-SiC、nc-Si薄膜，制成(p)nc-Si/(n)nc-SiC变容型、(p+)nc-SiC/(n+)nc-Si/(n-/n+)Si隧穿TT型、(p+)nc-SiC/(n)nc-Si/(n-/n+)Si碰撞雪崩TT型异质结。测试微波性能、材料结构和成份，实验校验计算值；解释微波性能-材料结构及成份-工艺参数之间的关系和规律，以及异质结的生长和导电机理；为利用纳米材料设计微波器件提供优化方案。

SiC基碰撞雪崩渡越时间(IMPATT)二极管等二端半导体微波器件具有输出功率大、体积小、可靠性高、稳定性高等优点，在雷达、通信等领域的应用前景广阔。.本项目围绕SiC基异质结构的设计、制备及特性，按照IMPATT二极管的性能决定于器件结构、材料理化性质的思路，优化SiC基IMPATT二极管的稳态、高频特性，主要开展了如下工作：(1)模拟计算并优化了SiC基异质结(SiC/Si、SiC/GaN、SiC/AlN等)、SiC异构结IMPATT二极管的稳态、高频性能，比较了光照前后SiC/Si异质结侧向型IMPATT二极管性能的变化。(2) 利用PECVD方法制备了非晶SiC/纳米晶Si异质结势垒变容二极管(HBVD)样品，表征了材料的结构，测试分析了样品的电学特性。(3) 受“新冠”疫情等不利影响，不能正常出差测试研制的样品，项目组微调了预定的研究内容，研制了项目需要的耐压微波二极管高精度正反向I-V参数测试仪、二极管半正弦电流浪涌试验仪。.项目研究实现了预定的目标。理论上，采用数值计算方法，比较全面地探究了SiC基异质结、异构结IMPATT二极管的大/小信号性能，探究了隧道效应、波姆势对性能的影响，比较了不同晶型SiC的IMPATT器件性能的差异；解析了SiC/Si异质结侧向型IMPATT二极管的光敏特性，分析了光照前后器件性能的变化情况。这对高频IMPATT二极管的设计具有指导意义。实验方面，利用PECVD方法，制备了非晶SiC/纳米晶Si异质结势垒变容二极管(HBVD)，测试分析结果表明，它的静态、动态截止频率可达到THz范围。研制的仪器拥有完全自主知识产权，符合国家、行业标准要求，试验结果重复性好，值得进一步研发推广。.项目执行期间，已发表相关学术论文10篇，授权专利11项；参与项目的3名硕士生和9名本科生已经顺利毕业，获得学位。