n,p柱宽度对超结SiGe功率二极管电学特性的影响

结合SiGe材料的优异性能与超结结构在功率器件方面的优势,提出了一种超结SiGe功率二极管.该器件有两个重要特点:一是由轻掺杂的p型柱和n型柱相互交替形成超结结构,取代传统功率二极管的n^-基区;二是阳极p⁺区采用很薄的应变SiGe材料.该二极管可以克服常规Si p⁺n^-n⁺功率二极管存在的一些缺陷,如阻断电压增大的同时,正向导通压降随之增大,反向恢复时间也变长.利用二维器件模拟软件MEDICI仿真 关键词： 超结 锗硅二极管 n p柱宽度 电学特性

Effects of p and n pillar widths on electrical characteristics of super junction SiGe power diodes

By combining merits of both SJ structure and SiGe material, a novel super junction (SJ) SiGe power diode is presented. The two important characteristics of SJ SiGe diode are its columnar structure of alternating p/n pillars substituting n^- base region of conventional Si p⁺n^-n⁺ diode and its far thinner strained SiGe p⁺ layer, which can overcome the drawbacks of conventional Si power switching diodes, such as when the reverse blocking voltage is higher, the forward voltage drop is larger and the reverse recovery time becomes longer. For the SJ SiGe diode with 20% Ge content, the following conclusions can be obtained compared with comparable conventional Si power diodes: the breakdown voltages increase by 1.6 times, the forward voltage drop is reduced by 60 mV (at a current density of 10 A/cm²) and the softness factor S increases by 2 times. Though the reverse recovery time is shortened slightly, the peak reverse current density decreases by 17% and the soft recovery characteristics is improved notedly. The key parameters of the p and n pillar widths have imporant effects on the forward conduction characteristic, reverse blocking characteristic and reverse recovery characteristic of SJ SiGe power diode. The smaller the pillar width becomes, the higher the breakdown voltage is and the lower the reverse leakage current is, whereas the forward voltage drop increases slightly. The pillar width has no obviously monotonic effect on the reverse recovery characteristic. If the width is too small, the soft reverse recovery characteristic is degenerated. To optimize the parameter of pillar width, we can obtain excellent SJ SiGe diode with fast recovery speed, high breakdown voltage and low forward drop at the same time.