Research On The Fabrication And Properties Of Silicon Doped With Chalcogen

The high reflectivity of crystal silicon greatly reduces the responsivity of silicon based detector.Meanwhile,the energy gap of silicon restricts its expanding application in near-infrared wavelengths.The appearance of chalcogen-doped silicon has improved the problem,which has the characteristics of wide spectrum and high absorption.Therefore,black silicon has a broad application prospect in the fields of photoelectric detection and solar cells.In this paper,S-doped,Se-doped and?S,Se?co-doped silicon are fabricated by femtosecond laser irradiation.In this paper,the preparation process of doped silicon is described in detail,including the preparation of the solid film,the fabrication of microstructural silicon by femtosecond laser and the preparation of the electrode,etc.In order to realize the fabrication of?S,Se?co-doped silicon,this paper combines two kinds of doping methods,which are gas environment and solid film.The femtosecond laser etching system was built to control the parameters such as spot diameter,energy density and repetition frequency.The influence of femtosecond laser repetition frequency on the doped silicon was also investigated.Then,the annealing process was analyzed,and obtained the annealing atmosphere,annealing time and annealing temperature of S-doped,Se-doped and?S,Se?co-doped silicon.The surface morphology,absorption spectrum,Hall effect and photoelectric sensitivity of black silicon were measured,and the optical and electrical properties of S-doped,Se-doped and?S,Se?co-doped silicon were systematically studied.The surface morphology of black silicon shows that the surface of S-doped silicon and?S,Se?co-doped silicon have pointed cones structure,and the surface of Se-doped silicon has columnar structure.This was related to different gas environment,the pointed cones were caused by the etching effect of fluoride ion in SF₆.The absorption spectrum of black silicon shows that the absorption of doped silicon can reach more than 90%both in visible and near-infrared wavelengths.After annealing,the near-infrared absorption decreased differently and the reduction was mainly due to the diffusion of impurities.Because the diffusion coefficient of Se is less than S,the decrease of absorption of Se-doped silicon is smaller,and the co-doped silicon is between them.The Hall effect of black silicon shows that the sheet carrier density of the doped silicon has increased after annealing,which was related to the repair of lattice defects.The interval doping has become the substitutional doping,which made the carrier concentration increased.The extent of the increase was related to the diffusion coefficient and the diffusion length of the doped elements.The photoelectric response has calculated by the I-V characteristic curve of the doped silicon.The high temperature annealing has improved the contact between the electrode and the surface of the material,and eliminated the complex center of the deep level,thus greatly improvd the responsivity of the black silicon.At 1064nm,the responsivity of the?S,Se?co-doped silicon achieves 1.60 A/W at-12 V reverse bias,which is higher than that of S or Se doped silicon.