Research On Photoelectric Properties Of Modified Ge Materials

With the development of the integrated circuit industry,the development of high-performance Si-based optoelectronic integrated circuits is particularly important for solving the bottleneck problem of integrated circuit development.The direct band and indirect bandgap energy level difference of germanium?Ge?is only 0.138 eV.It can be converted into a direct bandgap or quasi-direct bandgap semiconductor material by applying certain modification conditions.This helps to improve its carrier recombination efficiency and carrier mobility,so that it can further develop high-performance modified Ge optical devices and electrical devices.At the same time,the Ge material preparation process is compatible with the Si process and can be applied to Si-based optoelectronic integration.Therefore,the direct band gap modified Ge material is of great significance for the realization of Si-based monolithic optoelectronic integration and has received extensive attention from scholars at home and abroad.In this paper,we first use the KP perturbation theory to study the conduction band and valence band E-k relationship of modified Ge materials,and establish a physical model of the modified Ge materials with different energy levels with modification conditions.It is found through calculation that Ge can be changed to direct band gap semiconductor material by applying 2.46 GPa stress under tensile stress conditions.In the case of a GeSn alloy,Ge can be changed to a direct band gap semiconductor material by incorporating 8%of the Sn component.At the same time,the changes of the physical parameters such as the effective mass of the carrier,the effective mass of the density of state,the state density and the density of state of the modified Ge materials with the modification conditions were also studied.Secondly,the variation of optical properties of modified Ge materials with modification conditions was studied.On the one hand,a conduction band electron concentration distribution model of modified Ge material is established according to the modified Ge material energy band structure model,and an unbalanced carrier lifetime model and a modified Ge material internal quantum efficiency model are established at the same time.Studies have found that the internal quantum efficiency of Ge materials can be improved by applying tensile stress and GeSn alloying methods.The highest internal quantum efficiency that can be obtained under direct band gap conditions is 86.4%and 83.6%,respectively.When doping with low tensile stress and low Sn components,the doping concentration must not be higher than 10¹⁹cm^-3,otherwise the quantum efficiency of Ge material decreases.On the other hand,the absorption coefficient and refractive index model of the modified Ge material were established,and the change law of the absorption coefficient and refractive index of modified Ge material with modification conditions was analyzed.In the end,this paper studies the carrier mobility characteristics of modified Ge materials.Firstly,the carrier scattering mechanism was studied,and the relevant scattering model was established.Based on the establishment of the carrier scattering model,the carrier mobility of the modified Ge material?conductance band electrons and valence band hole mobility?was further studied.It was found that,on the one hand,the electron mobility of the strained Ge conduction band decreases with the increase of stress in the indirect band gap,while in the case of the direct band gap,it increases first and then decreases with the increase of the stress.For valence hole mobility,increase first and then decrease as stress increases.On the other hand,the conduction band electron mobility of GeSn alloy increases with the increase of Sn composition,while the valence band mobility decreases with the increase of Sn composition.In this paper,theoretical analysis of the energy band structure and optical and electrical properties of modified Ge materials can be used to prepare high-performance modified Ge material optoelectronic devices,and to achieve important reference for Si-based monolithic optoelectronic integration.