Fabrication Of Micro/nano Structured Silicon And Its Application In Photoelectrical Detector

Silicon content in the earth is very huge and the difficulty of silicon purification is not high, so semiconductor devices based on silicon material have become the mainstream of modern electronic and/or optoelectronic devices. After a long time of development,the semiconductor manufacturing industry has entered into a rather mature stage. With the in-depth study of semiconductor materials, the defects inside silicon hinders its further applications. Light detection and solar energy application have much higher requirements in light absorption at near-infrared and visible wavelength. Monocrystalline silicon has a large band gap width, so can not absorb light at these wavelengths efficiently. Although other semiconductor materials can solve this problem in a certain degree, but the high cost of those materials restricts their applications. With the unremitting efforts, scientists have found a new kind of material called microstructured silicon, which is represented as "black silicon". The surface of different microstructured silicon materials have many similar structural characteristics, i.e., they all have uniform microscopic structures in their surface. These structures can improve the light absorbing capacity of silicon at visible light band and/or at near infrared band.In this theses, the preparation of porous silicon by light catalytic electrochemical corrosion was studied, and the surface microstructure of porous silicon was obtained at micron scale. The surface morphology has been characterized by SEM. This paper has put forward an innovative idea of fabricating nano-porous silicon, and studied the catalytic particle adhesion process of catalytic metal etching, and finally, the so called nano-porous silicon material has been made successfully, by using the combine of light catalytic electrochemical method with metal catalytic chemical etching one. According to our previous research on microstructured silicon, this paper prepared the electrodes for nano-porous silicon and tried to fabricate a Si-based PIN photoelectric detector with microstructured silicon on its surfaces. Results have shown that, the idea of combining light catalytic electrochemical with metal catalytic chemical etching can be used to fabricate nano-porous silicon. Based on the microstructured silicon, a new PIN unit which has high responsivity at near infrared wave band was successfully made, and presented its important significance to improve the performance of silicon-based PIN detector. The main research results are as follows:1) Porous silicon made from photocatalytic electrochemical corrosion technology has large and uniform microstructure in surface at micron scale. Its light absorption rate is significantly enhanced in the 300 nm ~ 1100 nm wavelength range.2) The use of "silver mirror reaction" to obtain uniform distribution of catalytic silver particles, can not only prepare nanoscale silicon microstructures by one-step, but also be combined with the metal-catalyzed electrochemical etching process, to fabricate "nano-porous silicon" material. The microstructured materials have significant light absorption characteristics in the visible and near-infrared absorption rate of more than 85%.3) It is shown that on the surface of microstructured silicon, a good electrical contact between electrode and silicon can be obtained by chemical plating, and a new Si-PIN photo-detecting device based on these microstructured silicon materials presents better response characteristics in near-infrared band.