Study On Energy Band Structure And Conductivity Of Ge_1-xSn_x Array/Si Matrix Thermoelectric Composite Semiconductor

Thermoelectric materials have the advantages of simple structure,small size and long life,and are known as the most promising materials in the 21st century.In recent years,the exploration of a new generation of thermoelectric materials with excellent thermoelectric properties has been a research hotspot.In view of the low cost and wide applicability of Si semiconductors,the realization of thermoelectric applications of Si semiconductors is an important direction of current research and development of thermoelectric materials.The ZT value is an important index for evaluating the performance of thermoelectric materials,and the larger the ZT value,the more excellent the thermoelectric properties of the material.The magnitude of the ZT value is related to the coefficient of the thermoelectric material,the Seebeck coefficient S,the electrical conductivityσ,and the thermal conductivityκ.According to the literature,the insertion of nano-arrays into the matrix material to form a composite semiconductor can effectively improve the Seebeck coefficient of the material,reduce the thermal conductivity,and improve the thermoelectric properties of the material.However,there are few reports on the influence of the method of inserting nano-array into the matrix material on the conductivity of the material.In view of this,this paper will study the method of doping or stress application on the composite semiconductor formed by Si semiconductor as the matrix.The effect of semiconductor conductivity.Based on the deformation potential theory and the perturbation theory,the Ge array/Si matrix composite semiconductor conduction band and valence band energy band structure model are established,and the change of the composite semiconductor band structure under stress is calculated.On the basis of the energy band structure,the Ge array/Si matrix composite semiconductor electric transport model is established,and the electric transport process is calculated based on the non-equilibrium Green’s function theory and the envelope function method.The relationship between the conductivity and the internal impurity doping concentration of the Ge array/Si matrix composite semiconductor,the applied biaxial stress,and the Ge array pitch were analyzed and obtained.The results of the thesis show that the internal electric field potential of the composite semiconductor exhibits a periodic distribution,and the electrical conductivity changes significantly with the doping concentration and stress.As the doping concentration increases,the conductivity increases rapidly,and the effect of stress on conductivity is relatively small,but overall it also shows a positive correlation.After comparison,it is found that the maximum conductivity value can be obtained when the doping concentration is 10¹99 cm-3under 1.5 Gpa stress.At the same time,we studied the electron transport process inside the composite semiconductor under different topologies.By changing the spacing between the Ge arrays to observe the change of conductivity,it is found that the conductivity shows a strong dependence on the size of the embedded Ge.When the Ge array has a pitch of 12 nm,its conductivity peaks.At the same time,considering that the direct bandgap modified Ge has higher carrier mobility than Ge,it is beneficial to improve the electrical transport capacity.Therefore,the alloying and stress are introduced,and the Ge_1-xSn_x array/Si matrix composite semiconductor band structure and conductivity are calculated based on the same theory.The results show that higher conductivity can be obtained under the combination of Sn composition x=0.03,stress T=1 Gpa and Sn composition x=0.04,stress T=1.5 Gpa.In this paper,the research on the conductivity of composite semiconductor materials has obtained practical conclusions,which can provide meaningful reference for the research and development of Group IV thermoelectric materials.