梯度掺杂纳米晶碳化硅/晶体碳化硅双缓变结的反向软恢复特性

半导体突变结快速恢复二极管(FRD)，反向恢复时因结区电荷难以控制而产生浪涌电流，影响了它在通信、高频电力电子设备中的应用。本项目拟在晶体碳化硅(c-SiC)二侧沉积梯度掺杂纳米晶碳化硅(nc-SiC)多层膜(ML)，构建(p+p-ML)nc-SiC/(n-)c-SiC/(nn+ -ML)nc-SiC双缓变结FRD。根据阳极发射率及少子寿命控制原理，模拟计算反向恢复时间、电流等参数，探究它们与不同结构及原子面SiC材料性质、双缓变结电学特性、低寿命少子控制区的位置及宽带、复合中心浓度及能级的关系。用PECVD在离子注入c-SiC两侧生长掺杂浓度递增的nc-SiC多层膜，形成双缓变结；再制备nc-SiC/nc-Si异质欧姆结与电极连接。表征双缓变结的结构、成份，分析电学性质，查明反向恢复特征，揭示导电机理。改进设计及工艺，实现超快反向软恢复，优化综合性能，为制造功率型电磁兼容器件提供思路。

The fast recovery diode (FRD) with a semiconductor abrupt junction would easily yield surge currents in the reverse recovery operating, which will be limited to apply in the communication equipments, high frequency power electronic systems, and so on..In this project, a kind of double graded junction (DGJ) with progressive doped nano-crystalline silicon carbide (nc-SiC) multi-layers deposited on two sides of a crystalline silicon carbide (SiC) wafer, is proposed to construct a (p+p ML)nc-SiC/(n-)c-SiC/(nn+ ML)nc-SiC FRD of DGJ. According to the controll principles of emitter efficiency and lifetime of minority carrers, via numerical calculating the parameters such as reverse recovery currents and time, etc, the relation between inverse recovery properties and SiC material parameters, electronic characteristics of DGJ, concentrations and locations of defect recombination centers,etc will be clarified. Further, using the plasma enhanced chemical vapor deposition (PECVD) technique, the p type and n type multi-layers of progressive increase doped nc-SiC films will be deposited respectively on both sides of c-SiC implanted by ions to form the (p+p ML)nc-SiC/(n-)c-SiC/(nn+ ML)nc-SiC DGJ. Subsequently, with the same method,the p+ type and n+ type nano-crystalline Si (nc-Si) films will be separately grown on the same type doped nc-SiC films on the wafer to yield ohmic hetero-junctions and to contact the alloy electrodes. The backward recovery properties will be illustrated through structural and component characterization and performance analysis on the DGJ. The ultra-fast reverse soft recovery behavior of the DGJ could be realized while its synthetic performance would be optimized via adjusting the design parameters and improving the techniques of ion implantation and PECVD..This scheme should be useful to design and fabricate the power devices with electromagnetic compatibility.