Preparation and Performance Study of Supersaturated Sulfur-Doped Silicon Materials

Keywords: Super-saturated doping; Positron annihilation technique; Pulsed laser; Infrared-enhanced absorption. This paper reports the preparation of super-saturated sulfur-doped silicon materials by means of pulsed-laser gas-phase doping and ion implantation. The doped samples were annealed using both conventional thermal furnaces and excimer lasers. The effects of pulsed-laser fluence, wavelength, scanning rate, ion-implantation conditions, and annealing processes on the surface morphology, optical absorption, carrier concentration, and mobility of the samples were investigated. Scanning electron microscopy, Raman spectroscopy, and positron annihilation techniques were employed to characterize the surface morphology, crystal structure, and microstructural features such as defects in the samples. The experimental results indicate:

　　Keywords: Supersaturated doping; Positron annihilation technique; Pulsed laser; Infrared-enhanced absorption

　　In this study, supersaturated sulfur-doped silicon materials were prepared by means of pulsed laser vapor-phase doping and ion implantation. The doped samples were annealed using both conventional thermal furnaces and excimer lasers. The effects of pulsed laser fluence, wavelength, scanning rate, ion implantation conditions, and annealing processes on the surface morphology, optical absorption coefficient, carrier concentration, and mobility of the samples were investigated. The surface morphology, crystal structure, and microstructural features such as defects were characterized using scanning electron microscopy, Raman spectroscopy, and positron annihilation techniques. The experimental results indicate that the surface morphology of the samples enhances their absorption in the visible light range, primarily because visible light undergoes multiple reflections at the sample surface, leading to highly efficient absorption. Compared with annealing in a conventional thermal furnace, the samples annealed by pulsed laser exhibit a smaller reduction in optical absorption in the infrared wavelength range. This is attributed to the precipitation of some sulfur impurities from the doped samples after annealing in a conventional furnace, highlighting the significant role of supersaturated sulfur impurities in silicon in enhancing infrared absorption. Doppler broadening spectra reveal that the optoelectronic properties of the system are closely related to the microstructural factors, including the annealing process, surface morphology, and defect characteristics. On this basis, detectors with low bias voltage and high gain at room temperature were fabricated using the prepared materials, and their gain mechanisms and infrared response characteristics were preliminarily explored.

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