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Defect physics of CuInSe 2 chalcopyrite semiconductor

Defect physics of CuInSe 2 chalcopyrite semiconductor. S . B. Zhang, Su-Huai Wei, Alex Zunger, H. Katayama-Yoshida, Phys . Rev. B 57 , 9642 ( 1998). Yoshida-lab Hiroki Uede. Defect ( 欠陥 ) Chalcopyrite semiconductor ( カルコパイライト型半導体 ) . Contents. Introduction Calculation method

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Defect physics of CuInSe 2 chalcopyrite semiconductor

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  1. Defectphysics of CuInSe2 chalcopyrite semiconductor S. B. Zhang, Su-Huai Wei, Alex Zunger, H. Katayama-Yoshida, Phys. Rev. B 57, 9642 (1998). Yoshida-lab Hiroki Uede Defect(欠陥) Chalcopyrite semiconductor(カルコパイライト型半導体)

  2. Contents • Introduction • Calculation method • Calculation results • Summary • My work

  3. Application of CuInSe2 and motivation visible light • Photovoltaic solar cell • high absorption coefficient • high efficiency • self-healing • create p- and n-type CuInSe2 crystal p-type conductor at high doping ? • superconducting matter? Photovoltaic solar cell(太陽光発電) Absorption coefficient (吸収係数) Superconducting matter(超伝導物質) 山口真史他 著 『太陽電池の基礎と応用』 丸善株式会社　

  4. What is Chalcopyrite structure? cation1 anion cation cation2 anion Diamond structure Chalcopyrite structure Zinc-blende structure ×2 閃亜鉛鉱型構造

  5. CuInSe2 • Chalcopyrite semiconductor • Experimental energy gap =1.04[eV] (direct gap) • Lattice parameter a=5.786[Å] η=c/a=2.016 c Cu In Se Copper Indium Diselenide for Photovoltaic Applications, edited by T. J. Coutts, L. L. Kazmerski, and S. Wagner (Elsevier, Amsterdam,1986). a

  6. Details • In this study, calculate defect formation energy for the defect α=VCu,VIn, InCu,CuIn and Cui. • Place defect α at the center of a 32-atom supercell. InCu VCu VIn CuIn Cu VCu ,VIn:vacancy of atom Cu, In InCu:antisiteof atom In on site Cu CuIn:antisite of atom Cu on site In Cui :Cu type interstitial Cui In Defect formation energy(欠陥生成エネルギー) Vacancy of atom(原子空孔) Antisite(逆サイト) Interstitial (格子間) Se

  7. Defect formation energyfor a neutral(q=0) defect (1) (2) thermal equilibrium q :charge state :formation energy :total energy of supercell (with the defect α) :total energy ofsupercell (without the defects) ,:numbers of Cu & In atoms ,,:chemical potential of atom ,:total energy of ground-state solid atom Fermi energy electron q defect CuInSe2 crystal thermal equilibrium(熱平衡)

  8. Defect formation energyfor a charge(q≠0) defect (3) (4) (5) thermal equilibrium atom q :charge state :Fermi energy :total energy of N-electrons(defect free) :total energy of the CuInSe2 with holes :total energy of the neutral defect with M-electrons :total energy of a defect with Fermi energy electron q defect CuInSe2 crystal

  9. Limits of Fermi energy and atomic chemical potential • Fermi energy bound between the valence bandmaximum(VBM) and conduction bandminimum(CBM) • Chemical potential Conduction band CBM Energy gap VBM thermal equilibrium valence band(価電子帯)=HOMO conduction band(伝導帯)=LUMO Valence band

  10. Defect transition energy level :defect transition energy level α:kind of defect charge state → q Defect transition energy level(欠陥遷移エネルギー準位)

  11. Computational details • Density Functional theory(DFT) • Local Density Approximation(LDA) by the general potential Linearized Augmented Plane-Wave(LAPW) method • Muffin-tin radius of 2.2 a.u. • the Ceperley-Alder exchange correlation potential as parametrized by Perdew and Zunger • cut-off energy is 10 Ry • equivalent kpoints of the 10 special kpoints in the irreducible zinc-blende Brillouin zone Density Functional theory（密度汎関数法） Local Density Approximation（局所密度近似） Linearized Augmented Plane-wavemethod（線形化補強平面波法） Exchange correlation potential（交換相関ポテンシャル）

  12. Calculation results Defect transition energy level Defect formation energy vs. Fermi energy VCu has a shallow acceptor level Formation energy of VCu is low Formation energy of VCu& InCuare negative

  13. Formation energyof a defect pair α,β:type of defect : A pair with noninteracting constituents : A pair with interacting constituents :the defect pair ordering (6) defect pair(欠陥対)

  14. Calculate results offormation energyof a defect pair A(Cu-rich, In-rich) B(Cu-poor, In-rich) C(Cu-rich, In-poor) Defect pair at B(Cu-poor, In-rich) is lower defect formation energy than other defect pair

  15. Summary • Defect formation energy of Cu vacancies is negative at Cu-poor, In-rich 　　　 →The self-doping ability of p-type • Defect pair is low formation energy at Cu-poor, In-rich 　　　→self-compensation by and Cu-poor, Se-rich is best for p-metal

  16. My work Calculate band structure of CuAlS2, chalcopyrite structure • Calculate chalcopyrite structure as a p-type doped superconductor material • Calculate superconducting critical temperature TC

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