Study On The Fabrication And The Near-Infrared Photodetection Properties Of Au/Textured Si Schottky Junction

Owing to the outstanding advantages such as low cost,great mechanical property,compatibility with CMOS technology and etc,Silicon,the most widely utilized semiconductor material so far,is served as a prominent platform to accomplish microsystems where photonic and microelectronic are monolithically integrated on a chip.For conventional silicon-based photodetectors,it is usually impossible to take advantage of the photovoltaic?PV?effect driven by valence-to-conduction band transition of carriers to operate in the near infrared?NIR?regime?>1100 nm?due to relatively huge energy bandgap?1.12eV?of Si.Thus,the CMOS-compatible NIR Si-based photodetectors have attracted largish research attention.Comparatively,a very promising approach is the internal photoemission effect?IPE?which exploits photon-assisted transmission of hot electrons across a Schottky junction at the Au/Si interface,indicating that the response range of the IPE photodetector is decided by the relatively low Schottky barrier height?0.7eV?at the Au/Si interface instead of the forbidden band of Si.Unfortunately,the low absorption due to high reflectivity of the metal layer in NIR regime results in a poor responsivity of the photon-excited IPE photodetection.The appearance of plasmonics provides a feasible method to solve this problem.Researchers have proposed the surface plasmon?SP?metal mirco-or nano-structures to realize the localized field enhancement,which can improve the absorption of IPE devices in NIR regime.In addition,plasmon-induced hot electrons have a higher excitation efficiency and energy compared with photon-excited hot electrons.However,in most cases,very expensive precision lithography techniques are in need and it is not practical for the large scale and low cost manufacturing.In this thesis,the Au Nano thin-films/micro-pyramid textured Si-based Schottky IPE NIR photodetectors are designed and fabricated on wet chemical etching and film deposition method.In addition,the NIR responsivity has been increased through taking both optical and electrical perspectives into consideration,which provides theoretical guidance and experimental proof for the development of new low-cost and lithography-free NIR Si-based photodetectors.The main works in this thesis are listed as follows:?1?Pyramid textured Si substrates have been prepared massively by low-cost chemical etching monocrystalline silicon.The influence of technological parameters on texturized Si preparation has been studied in detail,including etching time,reaction temperature and additive.The ideal compact and well-proportioned pyramidal texturized structure of about 3?m has been obtained in 2%wt NaOH,2%wt Na₂SiO₃and 8vol%IPA aqueous solution at 80?with 35 minutes.?2?Schottky junction has been proved to be formed at the interface of Au/Texturized Si.Fitting calculation based on forward current and voltage data in dark state shows that the texturized Si still keeps good Schottky contact with Au:Schottky junction barrier height ?_ns=0.687eV,ideal factor n=1.51.?3?NIR photodetection at 1310nm has been realized by utilizing Au/texturized Si Schottky junction.Under the optimization of texturized structure and the distribution of hot electrons?illumination direction?,the responsivity of the Au/texturized photodetector operating at 1200nm back-side illumination mode with 0 bias voltage has exhibited up to 10-times increase compared with the control sample with a flat Au/Si surface.Finally,the classic three-step model of IPE has been verified both experimentally and theoretically.