Time-resolved photoconductivity distribution measurement by a synchronized double-scanning method.

The lifetime and the distribution of photoconductivity generated in laser-illuminated semiconductors are critical to photoconductivity-based applications. We propose a synchronized double-scanning method to measure time-resolved diffusion in the form of an afterglow embedded in the distribution map. The method combines spatial scanning of a coaxial resonator with synchronized laser scanning to map the dynamically excited conductivity on a semiconductor wafer. Thus, the photoconductivity afterglow effects can be mapped and retrieved by images of dynamic photoconductivity distribution. The photoconductivity lifetimes of silicon wafers with different thicknesses and by different lasers were measured and evaluated, which were also validated by the microwave photoconductivity decay (μ-PCD) method. In addition, the behavior of photoconductivity diffusion around a structural defect was exhibited. The method is nondestructive and can be applied in the photoconductivity property diagnostic.