YS/T 679-2008

1.1 This standard applies to the measurement of the minority carrier diffusion length in homogeneous epitaxial layers with known resistivity, deposited on non-intrinsic single-crystal semiconductor material samples or heavily doped substrates of the same conductivity type. It requires that the thickness of the sample or epitaxial layer be greater than four times the diffusion length.
1.2 This standard was developed for the application of single-crystal silicon samples and can be used to measure the effective diffusion length on other semiconductors, such as gallium arsenide (while adjusting the corresponding light illumination wavelength (energy) range and sample preparation process), and to evaluate the effective diffusion length on polycrystalline silicon samples with grain boundaries perpendicular to the surface. This standard can also be used to measure the width of the clean area of silicon wafers.
1.3 The application limits of the sample's resistivity and lifetime have not yet been determined, but measurements have successfully been made on p- and n-type silicon samples with resistivity ranging from 0.1 to 50 Ω·cm and carrier lifetimes as short as 2 ns. The diffusion length measured by this standard is only conducted at room temperature of 22°C ± 0.5°C, and the lifetime and diffusion length are functions of temperature.