Research On Optoelectronic Performance Of Topological Insulator Schottky Junctions

Topological insulator is a new type of material what is extremely popular today.These materials are isolated inside and the surface is conductive metallic state.Under the spin-orbit coupling interaction,the spin and momentum of the surface electronic states are locked and protected by time inversion symmetry.The size of the bulk energy gap of the topological insulator is an important index.When the energy gap is small,intrinsic doping during the preparation process will cause carriers to be generated in the body,affecting the measurement and application of the surface metal state.Bismuth selenide?Bi₂Se₃?is a typical representative of large-gap topological insulators,and its size is approximately0.3 eV.Recent studies have shown that there are some novel phenomena that occur in topological insulators.For example,in the prophecy of Majorana fermionics,magnetic monopole,and it has great application value in the future spintronics,quantum computing and other fields.This paper will first introduce the research background of topological insulators,including its discovery history and research progress.Next,the preparation process of high-quality Bi₂Se₃ thin films was introduced,including the exploration of the substrate temperature and the ratio of elemental beam current,and the quality of the obtained thin film was analyzed to obtain the optimum experimental parameters relative to the laboratory equipment.Next,we used a variety of substrates,including Al₂O₃,Si,InP,and Ge.By comparison,we found that using the molecular beam epitaxy method to grow high quality Bi₂Se₃ thin films on various substrates.Temperature,beam ratio and other conditions are basically the same.Bi₂Se₃ thin films were prepared on the semiconductor germanium using the surface metal properties of topological insulator Bi₂Se₃.Schottky junctions were formed between germanium and selenide germanium.The Schottky junctions were operated according to the principle of Schottky junction photoresponse.The mechanism was analyzed and discussed in depth;then,the electrical transport and the photoresponse tests at different wavelengths were performed on the Schottky junctions,and the effects of the germanium substrate on the electrical transport and the photoresponse of Bi₂Se₃ thin films were investigated.The photoresponse of Bi₂Se₃ was found to be the largest in the infrared region,slightly smaller in the visible region,and almost unresponsive to violet light.Through the cooling treatment of the sample,the response of the heterojunction in the temperature range of 180-300 K was investigated.The infrared light with a wavelength of 980 nm always maintains a stable response,and the lower the temperature,the better the light response characteristics of the sample.