Study On Photoelectric Properties Of The Device Based On Bi₂Se₃ Topological Insulator Thin Film

Bi2Se3 is a topological insulator,in which bulk states are insulating and surface states are metallic. Due to spin-orbit coupling effects, spin and momentum are locked and protected by time-reversal symmetry. Therefore, topological insulator shows potential applications in spintronics, optoelectronics, and quantum computation.Firstly, this dissertation introduces the general situation of topological insulators,including the concepts and the previous studies of topological insulators.Secondly, the processes of the preparation of Bi2Se3 thin films with high quality have been explored. As keeping the beam ratio of source material and growth time invariable, the optimizing growth temperatures are determined by testing and analysis of thin films. Also, retaining the growth temperature unchanged, the best beam ratio of the Bi and Se is obtained. We find that the conditions, such as the substrate temperature and the ratio of the beam of the materials, are almost the same for Bi2Se3 thin films grown on different substrates by molecular beam epitaxy.Thirdly, In this dissertation, it is considered that the interface between the Bi2Se3 and the silicon is schottky contact because of the metallic surface of Bi2Se3. On the other hand,the bulk states of the Bi2Se3 are semiconducting. Therefore,the contact is also PN junction. We test and analyze electrical transport and optical response of heterostructure of Bi2Se3 with the Si substrate. Under the illumination of the laser with the wavelength of 980 nm, the intrinsic heterojunction produce photovoltaic effects,which make the optical response of Bi2Se3 large.Lastly, the further analysis of the working principle for the schottky junction of Bi2Se3 and Si are made. We test the photoelectric properties under the different temperatures and the lights with different wavelengths. For different wavelength, we find it's response under the infrared light of 980nm is the largest when the same temperature and the same optical power are employed. However, the response to visible light is relatively small. It is also found that the response to the wavelength of 980nm is stable in the temperature range of 290K-180K.