Determination of minority-carrier diffusion length by integral properties of electron-beam-induced current profiles

The diffusion length of minority carriers in n-type floating-zone Si samples is obtained with the electron-beam-induced current technique in planar configuration. The charge collection current data as a function of the beam-junction distance are analyzed on the basis of the]] moment method" developed by Donolato [C. Donolato, Solid-State Electron. 28, 1143 (1985)], which is based on the calculation of the variance of the derivative of the current profile. With respect to other methods reported in literature, this has the advantage that it requires no assumptions on the surface recombination velocity and thus provides a diffusion length value free from its influence. The data are also analyzed with the asymptotic method, which requires conventional assumptions on the surface recombination velocity. The comparison between the results has allowed us to test the capabilities of the above-mentioned method. Particular attention is paid to the injection level and its influence on bulk and surface properties.