The Research Of Four Quadrant Photodetector

Four quadrant photodetector has the ability of position resolution and is the core device in spatial position resolution and tracking,which is widely used in civil and military fields.In this paper,we fabricated the high-performance four-quadrant photodetectors and achieved fine spot position resolution based on the n-p-n structure.This method provides a technical solution to solve the contradiction between the spot positioning accuracy and the captured spot.Studying the radiation damage mechanism of silicon photodetectors,which is order to propose reinforcement scheme for improving the radiation resistance of the device.The details of this research are as follows:1.The working principle of the four-quadrant photodetector is that the photocurrent relevant to the received spot area.The spot position is obtained by processing current data from the four quadrants.In order to improve the ability to capture the spot in space the photosensitive area needs to be increased.However,it will result positioning failure when the spot area is smaller than photosensitive area of one quadrant.First,we designed and fabricated Si four quadrant photodetector.Then a method of position programmable based on n-p-n structure was proposed,which realized accurate location in one single quadrant with a diameter of 2 mm light spot.2.The domestic materials and technologies adopt gettering process,which effectively reduces the dark current by one order of magnitude.The diameter of the photosensitive surface of fourquadrant photodetector is 11.3 mm which dark current is about 11 nA at 180 V and the dark current density is 3.63×10-8 A/cm2.The peak response is 920 nm @0.58 A/W.The corresponding quantum efficiency reaches 78.2%.3.The causes of radiation damage of silicon photodetector are simulated and studied.Experiments were carried out preliminarily to verifying radiation damage mechanism.Finally,three kinds of irradiation hardening schemes are proposed,including reducing the thickness of oxide layer,increasing doping concentration and leading out noise current by electrode.