Carrier lifetime measurement of silicon carbide for photoconductive switch applications using an IR probe laser

A system for measuring the recombination lifetime of high purity, semi-insulating (HPSI) 4H-SiC through transient free carrier absorption (FCA) for optimization of SiC photoconductive semiconductor switches (PCSS) is presented. The system measures the transient absorption of a continuous, low-power (<;5mW) 1550 nm infrared probe laser. Free carriers were generated with both above and below bandgap illumination from the harmonics of a Nd: YAG laser (532 nm, 355 nm, and 266 nm-10ns FWHM), and the carrier lifetime was numerically calculated from the absorption transient. High spatial resolution (~10 um) was attained through the use of a high-precision, three-axis stage. The carrier lifetime measurements of various regions of several SiC PCSSs over varying levels of photo-excitation are presented.