Research On Fabrication By Femtosecond Laser Pulse And Properties Of Black Silicon

Black silicon has a special microstructured surface.Then, its surface has near-unity absorptance from the near-ultraviolet(250 nm) to the near-infrared(2500 nm). In recent years, black silicon has already attracted much attention. The application of the new materials in the field of solar cell, photoelectric detection etc. has been studied well currently.We set up an experiment optical system about femtosecond laser etched black silicon.Then,we used this system to fabricate black silicon doped sulfur and selenium. The surface morphology of black silicon was studied under different experimental parameters. We analyzed the influence of the types of the background gas, the power density of the laser and numbers of the laser pulses on the surface morphology of black silicon doped selenium. We mensurated the optical absorptance of black silicon samples fabricated with different conditions. In addition,we studied the effect of the types of the background gas, the Si covered with single layer or double layer films, the power density of the laser and numbers of the laser pulses on the optical properties of black silicon. We analyzed the element composition of the surface elements of black silicon doped selenium by EDS.The factor of black silicon’s near-unity absorptance from 400 nm to 2200 nm was light trapping effect,impurity energy level,defect energy and so on. Next, we fabricated N+/N junction diodes on black silicon doped selenium. We studied the effect of Annealing on this diodes, and the photoelectric responsibility of this diodes can reach up to 0.32A/W.The energy band structure and optical properties of silicon doped S or Se were simulated by the first principle. Two impurity energy were found in the Si band after doping.The conductivity of Si doped S or Se at a certain concentration was explained in theory.