An Investigation Of Si-PIN Photodetector Based On Black Silicon

Black silicon is a new type of material etched on the surface of crystalline silicon. It can reduce the reflection of incident light obviously, and has an effect of near-infrared inhancement, and so has a broad application in the field of photodetectors and solar cells. On one side, thanks to the microstructured surface, the black silicon can control, manage and absorb the incident light effectively, thus reduce the reflectance of crystalline silicon obviously. On the other side, when sulfur(S) or tellurium(Te) element is implanted onto the surface of silicon substrates, a new impurity level is introduced into the bandgap of silicon, making the band structure of silicon changed, and so an absorption enhancement of near-infrared incident light could be obtained.In this thesis, we combine MEMS, metal-assist chemical etching and ion-implantation technologies to fabricate an evenly distributed and periodically arranged microstructured black silicon array on the surface of crystalline silicon, and then measure the light reflectance and absorption of the microstructured black silicon samples. Our experimental results show that the black silicon surface material has excellent light absorption in the visible and near-infrared wavelength. Based on the well etched black silicon, we choose Si-PIN photodetector as the application object, and then introduce an etched array to the lower surface(N layer) of the detector with some S or Te element through ion implantation. The processing is followed by a silicon wafer level, and two kinds of PIN detector structures are taken, one of which is the detector with front illuminated surface and the other is the detector with back illuminated surface. After several steps, a new kind of Si-PIN photodetector based on black silicon is successfully completed, and some main parameters such as spectral response, responsivity, response time and dark current are measured. The main results are as follows:(1) The microstructured black silicon array made by MEMS, metal-assist chemical etching and ion implantation has an obvious light absorption enhancement in the visible and near-infrared spectrum.(2) The spectral response range of the front-illuminated Si-PIN photodetector based on black silicon is from 400 to 1100 nm, and the peak responsivity of the photodetector reaches to 0.71 A/W(@1000 nm, 12 V). It is noted that the responsivity of the detector reaches to 0.45 A/W at 1060 nm.(3) The spectral response range of the back-illuminated Si-PIN photodetector based on black silicon is from 400 to 1100 nm, and the peak responsivity of the photodetector reaches to 0.68 A/W(@1030 nm, 12 V). It is noted that the responsivity of the detector reaches to 0.48 A/W at 1060 nm.(4) The response time of both front-illuminated and back-illuminated Si-PIN photodetector based on black silicon is less than 10 ns, and the dark current of the detectors is less than 10 nA.(5) The novel Si-PIN photodetectors based on black silicon are capable of being operated normally from-25 to 60 oC.