An Investigation Of Si-PIN Four Quadrant Photodetector Based On Black Silicon

In order to study the Si-PIN four quadrant detector based on black silicon materials,the structure of device was optimized.Two kinds of black silicon materials were fabricated by femtosecond laser and MEMS technology.The surface morphology and spectral absorption were studied.The equivalent refractive index and extinction coefficient were calculated.Based on the simulation of two kinds of Si-PIN four-quadrant detectors,the performance parameters such as volt-ampere characteristics,dark current,spectral responsivity,crosstalk and response time were analyzed,compared and discussed,respectively.Finally,based on the manufacturing process of standard Si-PIN four quadrant detector,the Si-PIN four quadrant detector based on black silicon was fabricated.The main results are as follows:(1)The crosstalk of a four-quadrant detector is mainly affected by the diffusion length of carrier,the carrier lifetime,the absorption coefficient of silicon material,the width of dead space,the length of photosensitive surface and the drift carrier velocity,respectively.The width of dead space and the length of sensitive surface are the key factors.The quadrant crosstalk decreases exponentially with the increase of the width of dead space and the length of photosensitive surface.(2)The properties of the black silicon materials fabricated by femtosecond laser are different depending on variable parameters such as power,scanning speed and background atmosphere,respectively.When the laser power is set at 0.2 w and the scanning speed is at 1 mm/s,the surface morphology of black silicon is relatively perfect,and the spectral absorption is more than 95 %.But the morphology of the black silicon prepared in air or in N2 is not so perfect and the density is much lower.The morphology and the distribution of silicon cones prepared in SF6 are better than those prepared in air or in N2,and the near infrared absorption is obviously enhanced.(3)The properties of black silicon material fabricated by MEMS have a great relationship with the surface microstructure.When the scale of the fabricated texture is at nanometer level,the microstructured layer can form a resonant cavity and has an obviously anti-reflect effect on the incident light of 1060 nm.When the size of the microstructure is at micrometer level,the anti-reflect effect on the incident light of the 1060 nm is weakened.Ion-implantation to the MEMS microstructure leads to an increased spectral absorption.(4)Based on the simulation of two kinds of four-quadrant detectors,an ordinary Si-PIN type and a black silicon Si-PIN type,it is found that the introduction of black silicon material can obviously widen the response range and enhance the spectral responsivity.This effect is much more obvious in the near infrared band.However,both the dark current and the quadrant crosstalk of the Si-PIN four-quadrant detector based on black silicon are increased.(5)Based on the black silicon materials fabricated by femtosecond laser etching or MEMS,two kinds of Si-PIN four-quadrant detectors have been putting into industrial fabrication.Up to now,fabrication of black silicon on the N-type layer of the detectors has been completed,and the subsequent steps are still in process.