Influence of Reflectance on Determination of Free Carrier Absorption of Silicon Wafer

Abstract

A revised modulated free carrier absorption (MFCA) theory is proposed, in which photomodulated thermal reflectance (PMTR) is subtracted from the transmitted signals of semiconductors. With this theory, one simultaneously extracts the carrier transport properties, such as the carrier lifetime, carrier diffusion coefficient, and the front surface recombination velocity, of silicon wafers. Proof-of-concept experiments were performed on a single crystal p-type, 100 cut silicon having $8\,\Omega {\cdot }\hbox {cm}$ to $12\,\Omega {\cdot }\hbox {cm}$ resistivity. MFCA and transmitted data (composed of MFCA and PMTR) are fitted to an MFCA theoretical model. Fitted results showed that the accuracies of fitted transport properties can be greatly improved by the MFCA technique if the PMTR component is subtracted from the transmitted signal.