Research On Silicon And Silicon Photoelectric Detector Irradiated By Femtosecond Laser

Silicon is widely used in manufacturing integrated circuit and photoelectric detectors. In recent years, size of silicon devices has been decreasing. At the present time, their size has arrived at nanometer scale, and it approximately takes several picoseconds, or even shorter time, for free carriers to transport during such small distances. Therefore, research of carrier dynamics in silicon on shorter and shorter time scale is urgently developed. Processes on such short time scale are difficultly measured by traditional electronic method, so ultrafast spectroscopy method is the only choice of carrying out such experiments. Additionally, application of photoelectric detectors is severely influenced by laser. In the past experiments, people focus on the effect of photoelectric detectors irradiated by continuous laser or pulsed laser with pulse width more than nanosecond. Study of effect of photoelectric detectors irradiated by femtosecond pulsed laser should be profoundly carried out.In this paper, ultrafast time-resolved carrier density of single- crystal silicon and effect of silicon photoelectric detectors irradiated by femtosecond pulsed laser has been studied. Firstly, testing system of femtosecond pump-probe reflectivity based on pump-probe technique has beenestablished. Time resolution of the system reaches 60 femtosecond, which assures that ultrafast variation of reflectivity of silicon can be effectively measured. With the relation between carrier density and reflectivity based on Drude model, time-resolved carrier density can be worked out through the experimental result of variation of reflectivity. Secondly, mathematical model of time-resolved carrier density has been established on the base of semiconductor rate equation theory. We have calculated the mathematical model and compared the result of numerical calculation and experimental data. It proves out that they are approximately identical. At last, we get the damage threshold of silicon CCD and silicon photodbde irradiated by femtosecond pulsed laser.