Electronic Structure And Thermoelectric Properties Study On Nitride Multicomponent Alloys

Thermoelectric materials have become the focus of current researches because they can convert thermal energy into electrical energy.Bi₂Te₃ is a currently widely used thermoelectric material.It can not be used in some areas because it can only work in low temperature environment and it is toxic.GaN is a new kind of wide bandgap thermoelectric material.It has become a promising thermoelectric material because of its good thermal stability,non-toxic,non-polluting,high Seebeck coefficient and conductivity.In this paper,the alloying method is used to improve the thermoelectric properties of the nitride materials.The Al and In elements are used as the alloying elements.The electronic structure and thermoelectric properties of GaN and its alloys are calculated by the first-principles theory and Boltzmann's theory.The first-principles calculation is based on the density functional theory.The band structures,state densities,Seebeck coefficients,conductivities,power factors and ZT values of the GaN and its alloys depend on the carrier concentration and alloy composition are calculated.The calculation results show that the Seebeck coefficients of AlGaN alloys are not much different from those of GaN.They are both decrease with the increase of carrier concentration.However,the Seebeck coefficients of InGaN alloys firstly increase and then decrease with the increase of the carrier concentration due to the influence of the bipolar conduction.At 1100 K,the ZT values of P-type AlGaN alloys increased by 61%-97%compared with GaN,and the ZT values of N-type AlGaN alloys increased by 98%-108%.The ZT values of P-type InGaN alloys increased by 89%-99%compared with GaN,and the ZT values of N-type InGaN alloys increased by 159%-197%.The results show that the alloying method is significantly improved the thermoelectric properties of the nitride materials compared with GaN.The P-type ZT values of the same alloy materials are all higher than the N-type ZT values of those materials.Those results mean the P-type nitride materials are more suitable for the thermoelectric applications.The ZT values of the nitride materials increase with the increase of temperature and the ZT values reach the maximum at 1100 K,which shows that the nitride materials can work stably at high temperature.