氧化物正电荷影响下半导体空间电势的近似解析解研究

建立了半导体空间电势与界面氧化物正电荷之间联系的解析表达式。从一维情况下精确的泊松方程及其边界条件出发,对N(P)型硅半导体中的泊松方程作积累(耗尽)近似,根据德拜屏蔽效应对边界条件作截断近似,得到了氧化物正电荷影响下两种类型半导体内电势的近似解析解。另外,还进行了精确数值计算,并将它与近似解析解的结果进行比较,结果表明,当氧化物正电荷增加到使P型半导体发生强反型后,近似解不再成立。根据强反型的条件,给出了P型半导体中近似解的适用范围。

Approximate analytical solutions of the electrostatic potential inside semiconductor caused by radiation-induced net positive oxide charge

This paper presents the analytical relation between the electrostatic potential inside the semiconductor and the positive oxide trapped charge at the interface. The expressions for N/P type materials are deduced after the accumulation/depletion approximation to Poisson equation and the truncation approximation to its boundary conditions. The solutions are self-consistent and complete. The exact numerical solutions are also given in this paper. The comparisons between the approximate analytical relations and the numerical solutions show that the analytical relations are good approximations except the case where strong inversion due to net positive oxide charge has occurred on the surface of P type material. Based on the criterion of the occurring of the strong inversion, the requirement for the surface density of positive trapped oxide charge to guarantee the visibility of depletion approximation is given. This work can be helpful in correctly analyzing mechanisms and magnitudes of the damage in the environment involving ionizing radiation in bipolar devices.