GaN基半导体材料热电性质的第一性原理计算与究-电路与系统专业毕业论文.docx

河北科技大学硕士学位论文 II 万方数据 AbstractAbstract Abstract Abstract Thermoelectric materials are new functional materials which call directly convert thermal energy into electrical energy,or vice versa．GaN—based semiconductor materials have very broad applications in thermoelectric materials due to the characteristics of large band gap，high thermal conductivity,high Seebeck coefficient and temperature resistance． The properties of TE materials are usually characterized by the dimensionless figure of merit ZT．Good TE materials require large power factor$20 and low thermal conductivity K．The electronic properties of GaN are calculated by the first principle calculation method witll the basic approximation theory and density functional theory．The semi-classical Boltzmann theory is used to calculate the TE properties of N-type and P—type GaN semiconductors．Seebeck coefficient，electrical conductivity,power factors and ZT curve are obtained from the calculations．The results show that the Seebeck coefficient decrease wi也the increasing of N-type and P-type semiconductor carrier concentration，and when the carrier concentration is constant，the Seebeck coefficient increase、析t11 the increasing of the temperature．The electrical conductivity increase、Ⅳitll the increasing of N··type and P-·type semiconductor carrier concentration；and when the carrier concentration is constant，the electrical conductivity decrease with the increasing of the temperature．The power factor of N—type and P-type semiconductor increases first and then decreases wi廿l the increasing of cartier concentration．The N-type semiconductor power factor achieve maximum value—．1 750 I．tW／mKz at the temperature of 300K and the cartier concentration of 1017cm3．The P-type semiconductor power factor achieve maximum value-3500pW／mK2 at the temperature of 1200K and the carrier concentration of 1020cm-3．The thermal conductivity is chosen to be a constant(K=5．85x104／T)due to the little change． Wim the increase of carrier concentra