On using photoconductivity decay to determine Si free carrier recombination lifetime: possibilities and challenges

7th Global Conference on Materials Science and Engineering

工业技术（总论）;材料科学

Anfimov, I.M.^1 ; Anfimov, M.V.^1 ; Egorov, D.S.^1 ; Kobeleva, S.P.^1 ; Pushkov, K.V.^1 ; Schemerov, I.V.^1 ; Yurchuk, S.Yu.^1

National University of Science and Technology MISiS, Moscow

119049, Russia^1

关键词: Continuity equations;    Free carrier recombination;    Lifetime measurements;    Measurement equipment;    Numerical calculation;    Photoconductivity decay;    Surface recombination velocities;    Surface recombinations;   

Others  :  https://iopscience.iop.org/article/10.1088/1757-899X/474/1/012011/pdf
DOI  :  10.1088/1757-899X/474/1/012011

来源: IOP

【 摘 要 】

Free carrier recombination lifetime (τ) in Si single crystals is a parameter, that characterizes the quality of the material. The primary procedure for τ measurement in ingots is photoconductivity decay (PCD) analyses, including contactless μ-PCD and eddy current methods. One of the main problem in this methods is a surface recombination influence on the PCD curve. It is usually assumed that in ingots the influence of surface recombination can be neglected. Well-known dependence of effective lifetime (τeff ) on τ, surface recombination velocity (S) and sample thickness (d) describes the maximum value of a lifetime. Based on the numerical calculations of the one dimensional continuity equation we have shown that if the sample thickness exceed 5LD , the maximum lifetime cannot be achieved before PCD signal decline to 5% of maximum, so the question arises what is the interval of the decay curve where the experimental value of the τeff has to be determined. We used the range from 45-5% of the maximum PCD signal following the recommended SEMI MF 1575 standard (τSEMI ). The dependencies of τSEMI on τ, d and S were calculated for different versions of PCD measurements and measurement equipment. The recommended thickness for lifetime measurements of non-passivated samples is in the range (1-5)LD . The hardware capabilities of contactless methods are compared.