Z-scanning Laser Photoreflectance as a Tool for Characterization of Electronic Transport Properties

Abstract

The physical principles motivating the Z-scanning laser photoreflectance technique are discussed. The technique is shown to provide a powerful non-contact means to unambiguously characterize electronic transport properties in semiconductors. The technique does not require modeling of charge transport in the sample or a detailed theoretical model for the sample physics. Rather, the measurement protocol follows directly from the simple relation describing the radial diffusion of carriers injected by a laser source. The use of a probe laser beam permits an analytic parameterization for the Z dependence of the photoreflectance signal which depends soley on the focal parameters and the carrier diffusion length. This allows electronic transport properties to be determined with high precision using a nonlinear least squares fit procedure. The practical use of the technique is illustrated by the characterization of carrier transport properties in semiconducting p-n junctions.