Study On The Detection Wavelength Expanding Of Silicon-Based Near-Infrared Photodetectors

Silicon-based germanium photodetectors are the most widely used photodetectors in silicon-based optoelectronic integrated circuits.However,due to the band gap limitation of germanium,it is increasingly difficult to meet the rapidly developing biological,virtual reality and other fields for detection of different wavelengths.,The expansion of the detection range has become one of the focuses of research.This article focuses on the design and optimization of silicon-based near-infrared photodetectors.The thesis mainly completed the following research work:Different components of tin are doped into germanium to adjust the band gap of the germanium-tin alloy to achieve the purpose of extending the detection range.At present,the waveguide-type germanium-tin detector has not been reported.In this paper,the waveguide-type germanium tin photodetector is simulated,and the light propagation and optical field distribution are analyzed using the finite difference time domain method(FDTD),and the germanium tin composition,device size,coupling structure,especially the evanescent The influence of wave coupling structure,evanescent wave coupling without germanium buffer layer and butt coupling structure on the optical and electrical properties of the device was studied.The simulation results show that in the evanescent wave coupling structure,only 2.5%tin can increase the absorption of U-band light by pure germanium from 16%to 88.7%.As the tin composition increases,the absorption rate is further Promote.In the simulation of the germanium tin photodetector with the germanium buffer layer removed,the absorption is much better than that with the buffer layer,and only 10 ?m can achieve 90%absorption.The germanium-tin photodetector with the docking coupling structure has better coupling efficiency,adopts lateral doping,and avoids the contact between the metal and the absorption region and causes the light loss.However,it is still necessary to explore how to further reduce the width of the intrinsic region.small.In addition,the thesis also uses multi-physics simulation to establish a silicon nitride film-induced strain model of germanium waveguides,analyzes the introduction of strain in two-dimensional and three-dimensional structures,and conducts preliminary explorations on the way that tensile strain germanium extends the detection wavelength.Finally,a reasonable structure setting was selected for the width of 2.5-3 ?m,silicon nitride thickness of 200-400 nm,germanium thickness of 200 nm,and device length of 5-10 ?m,which can achieve a strain of 0.35%in the center and 0.39%in the upper layer.Introduce.The paper calculates the corresponding variable germanium band gap,absorption coefficient and extinction coefficient.Through optical simulation,the total light absorption at room temperature and low temperature is obtained.At room temperature,the total absorption of the best result is 84.6%,which is very good.the result of.It can still reach more than 80%absorption at low temperature.In the actual material growth,the thesis used the low temperature method and the low temperature-high temperature method for epitaxial growth.The results show that the low temperature-high temperature method can prepare high-quality germanium materials with a smooth surface and introduce 0.17%of the initial strain.Provide support for subsequent tape-out work.