Research On Fabrication And Optoelectronic Properties Of Surface Modified Silicon By Ultrafast Laser Pulse

In order to extend the absorption edge of crystalline silicon to the near infrared band to meet the requirement of optical communication, the textured silicon was obtained by irradiation of nanosecond laser pulses. The surface morphology of modified silicon under irradiation with different laser fluence from 0.39J/cm(2) to 24 J/cm(2) was investigated. Then, the optical properties including reflectance, transmittance, and absorptance of silicon samples by nanosecond laser irradiation with different laser fluence were measured. The results show that the absorptance below the bandgap of silicon enhances for all the textured silicon samples and it is up to for near infrared light of 1 300 nm. Next, the thermal stability of infrared absorption for the textured silicon samples was investigated. The thermal annealing process at temperatures of 473 similar to 1 073 K can slightly reduce the absorptance below the bandgap of silicon and the magnitude of reduction only varied within 10%. Moreover, the dependence of reflectance, transmittance, and absorptance of modified silicon on the annealing temperature was studied on. Lastly, the crystal structures of modified silicon were determined by Raman spectroscope. After irradiation of nanosecond laser pulses, the crystalline silicon surface is disordered and amorphous or polycrystalline phases are formed. However, the crystal quality of textured silicon can be improved by post-thermal annealing process.