A Simulation Study Of All-silicon Avalanche Photodiode Based On Blacksilicon

Silicon is the most abundant semiconductor element on the earth, because it is easily purified and doped, and the associated fabrication technology has developed for many decades. Owing to its band gap is relatively large(1.1eV), crystal silicon can’t absorb light with longer wavelength effectively. Thus, it is needed to develop a novel silicon photodetector which has higher responsivity and an extended spectral response range. Due to its special surface morphology, black silicon(BS) has a high absorption of visible light and a good absorption of near infrared light, and can be used in photodetectors, solar cells and other optoelectronic devices.This thesis has deeply analysed the working principle of Si-APD and discussed more about the fabrication parameters of the photodetector. The reasons for a high absorption and an extended spectral response of the detectors based on black silicon have also been discussed. Based on the analysis and discussion above, a simulate study on the performance of commercially Si-APD has been completed with a special understanding of the distribution of electric field, after which the simulation has been carried out upon I-V characterization, spectral response, response time, avalanche multiplication factor and so on.Based on the simulation study of commercially Si-APD, we have carried out further simulation study on a novel Si-APD of N+PπP+ structure with black silicon on N+ side. The simulation results show that: 1) when the incident light enters from N+ side, the APD has a higher responsivity than the detector when light enters from P+ side; 2) the obtained parameters of the device are as follows: avalanche breakdown voltage is about-116V; the responsivity is 9A/W(@1.1μm) when M=21.8; the dark current and response time are 10 p A and 10 ns, which are the same as those of commercially photodetectors; 3) the absorption ability of the device increases with the aspect ratio of micro-structure increases, the higher the doping concentration of black silicon layer, the higher the responsivity; 4) avalanche breakdown voltage decreases with the increase of doping concentration in P and π regions, but increases with the increase of thickness of π region. The higher the doping concentration in P and π regions, the higher of avalanche multiplication factor. The near-infrared absorbance of the N+PπP+ type Si-APD with black silicon on its N+ side can be enhanced by increasing the thickness of P and π regions.The present study indicates that while keeping the dark current and response time at a center level, the novel Si-APD based on black silicon can not only increase the quantum efficiency and responsivity obviously, but also extend the spectral response range from the visible to the near-infrared light range.