4H-SiC p-n结基于精确碰撞电离模型的雪崩倍增因子研究

Study on Avalanche Multiplication Factor of 4H-SiC p-n Junction Based on Accurate Impact Ionization Model

雪崩倍增效应是4H-SiC雪崩光电二极管、功率半导体器件等器件的关键机理。作为其中最重要的物理参数,雪崩倍增因子(M)的精确解析表达式目前未见报道。文章提出4H-SiC p-n结M的精确计算方法及其解析表达式。基于更准确的碰撞电离模型,通过MATLAB对4H-SiC单边突变结(p^(+)-n)电子和空穴的碰撞电离积分(I)进行精确的数值计算,给出击穿电压(BV)随掺杂浓度的经验表达式,进一步提出电离积分随外加电压及掺杂浓度的拟合表达式。此外,对外加电压接近BV的情形进行细致的相对误差分析,表明电子电离积分受电场影响显著。对于雪崩光电二极管及功率器件较宽的BV范围,所提出的拟合表达式在外加反向偏压大于0.65BV时具有较高的精确度(相对误差小于5%)。

The avalanche multiplication effect is the key mechanism of 4H-SiC avalanche photodiodes and power semiconductor devices.As the most important physical parameter,the accurate analytical expression of avalanche multiplication factor(M)has not been reported.In this article,an analytical empirical formula of multiplication factor for 4H-SiC p-n junction was presented based on accurate theoretical methodology.Utilizing the accurate impact ionization model,the impact ionization integrals(I)of electron and hole for a 4H-SiC abrupt diode were calculated by MATLAB.The simulations were carried out by MEDICI to verify the theoretical results.Breakdown voltage(BV)as a function of doping concentration was established.Ulteriorly,the multiplication factor as a function of doping concentration and reversely-biased voltage was derived in an empirical form.The research on the relative error analysis on I indicates that a tiny relative error of the electric field could lead to a large relative error of I.For a wide range of BV,the empirical formula could achieve a high accuracy for V_(R) larger than O.65BV with relativeerrorless than 5%.