First-principles theoretical study on band of strained wurtzite Nb-doped ZnO

Abstract

The strain effects of the Zn_1−xMg _xO substrate on the bands structure of wurtzite Nb-doped ZnO bulk materials have been investigated using first-principles calculations based on density functional theory. Firstly, the band gap increases gradually with increasing Nb contents in unstrained Nb-doped ZnO, which is consistent with the experimental results. Secondly, the band gap decreases with increasing substrate stress in Nb-doped ZnO/Zn_1−xMg _xO. Splitting energies between HHB (Heavy Hole Band) and LHB (Light Hole Band), HHB and CSB (Crystal Splitting Band) in Zn_0.9167Nb_0.0833O/Zn_1−xMg _xO almost remain unchanged with increasing substrate stress, while decrease slightly in Zn_0.875Nb_0.125O/Zn_1−xMg _xO. In addition, detailed analysis of the strain effects on the effective masses of electron and hole in Nb-doped ZnO/Zn_1−xMg _xO is also given.

Keywords

strain / band gap / Splitting energies / effective mass

References

[1] Stölzel M, Kupper J, Brandt M, et al. Electronic and Optical Properties of ZnO/(Mg,Zn)O Quantum Wells with and without a Distinct Quantum-confined Stark Effect[J]. J. Appl. Phys., 2012, 111(6): 063 701

[2] Rakshit B, Mahadevan P. Indirect to Direct Band Gap Transition under Uniaxial Strain in Layered ZnO[J]. J. Appl. Phys., 2013, 102(14): 143 116

[3] Juday R, Silva E M, Huang J Y, et al. Strain-related Optical Properties of ZnO Crystals due to Nano Indentation on Various Surface Orientations[J]. J. Appl. Phys., 2013, 113(18): 183 511

[4] Qiao L P, Chai C C, Jin Z, et al. Strain Effects on Valence Bands of Wurtzite ZnO[J]. Sci. China Phys., Mech. Astrono., 2013, 56(9): 1 684-1 688.

[5] Liu W Z, Xu H Y, Zhang L X, et al. Localized Surface Plasmonenhanced Ultraviolet Electroluminescence from n-ZnO/i-ZnO/p-GaN Heterojunction Light-emitting Diodes via Optimizing the Tthickness of MgO Spacer Layer[J]. J. Appl. Phys., 2012, 101(14): 142 101

[6] Shao J Z, Dong W W, Li D, et al. Metal-semiconductor Transition in Nb-doped ZnO Thin Films Prepared by Pulsed Laser Deposition[J]. Thin Solid Films, 2010, 518(18): 5 288-5 291.

[7] Orlin A, Konstantin L, Doriana D M. Optical and Electrical Properties of ZnO Thin Films Doped with Al, V and Nb[J]. Phys. Status Solidi, 2013, 10(4): 709-712.

[8] Cao F, Wang Y D, Liu D L, et al. Preparation and Characterization of Transparent Conductive Nb-Doped ZnO Films by Radio-Frequency Sputtering. Chin[J]. Phys. Lett., 2009, 26(3): 034 210

[9] Lin J M, Zhang Y Z, Ye Z Z, et al. Nb-doped ZnO Transparent Conducting Films Fabricated by Pulsed laser Deposition[J]. Applied Surface Science, 2009, 255(13): 6 460-6 463.

[10] Changh K, Dong H S, Suk-Ho C. Strongly-enhanced Near-band-edge Photoluminescence of Nb-implanted ZnO Flms[J]. Journal of Crystal Growth, 2011, 326(1): 42-44.

[11] Gokulakrishnan V, Parthiban S, Jeganathan, et al. Structural, Optical, and Electrical Properties of Nb-Doped ZnO Thin Films Prepared by Spray Pyrolysis Method[J]. Journal of Electronic Materials, 2011, 40(12): 2 382-2 387.

[12] Xu J W, Wang H, Jiang M H, et al. Properties of Nb-doped ZnO Transparent Conductive Thin Films Deposited by RF Magnetron Sputtering using a High Quality Ceramic Target[J]. Bulletin of Materials Science, 2010, 33(2): 119-122.

[13] Bai L N, Lian J S, Jiang Q. Optical and Electronic Properties of Wurtzite Structure Zn_1−xMg_xO Alloys[J]. Chin. Phys. Lett., 2011, 28(11): 117 101-117 104.

[14] Fan X F, Sun H D, Shen Z X, et al. A First-principle Analysis an the Phase Stabilities, Chemical Bonds and Band Gaps of Wurtzite Structure A_xZn_1−x Alloys (A=Ca, Cd, Mg)[J]. Journal of Physics: Condensed Matter., 2008, 20(23): 235 221

[15] Lin H X, Jing S, Yu L C, et al. Optical and Structural Properties of ZnO/ZnMgO Composite Thin Films Prepared by Sol-gel Technique[J]. Journal of Alloys and Compounds, 2013, 548: 155-160.

[16] Sua S C, Ling C C, Lu Y M, et al. The Optical Properties of High Quality ZnO/ZnMgO Quantum Wells on Si(111) Substrates[J]. Solid State Communications, 2012, 152(4): 311-313.

[17] Su S C, Lv Y M. Ultraviolet Electroluminescence of ZnMgO/n-ZnO/ZnMgO/p-GaN Heterojunction Light Emitting Diode[J]. Chinese Journal of Luminescence, 2011, 32(8): 821-823.

[18] Hao L, Guo J F, Song Z L, et al. A ZnO/ZnMgO Multiple-Quantum-Well Ultraviolet Random Laser Diode[J]. Ieee Electron Device Letters, 2011, 32(1): 54-56.

[19] Li Y F, Yao B, Lu Y M, et al. Biaxial Stress-dependent Optical Band Gap, Crystalline, and Electronic Structure in Wurtzite ZnO: Experimental and ab initio Study[J]. J. Appl. Phys., 2008, 104(8): 083 516

[20] Liu X C, Ji Y J, Zhao J Q, et al. First-principles Study on Electronic Structure of In-doped Wurtzite ZnO[J]. Acta Physica Sinica, 2010, 59(7): 4 925-4 929.

[21] Anisimov V I, Aryasetiawan A I Lichtenstein. First-principles Calculations of the Electronic Structure and Spectra of Strongly Correlated Systems: the LDA+U Method[J]. J. Phys: Condens. Matter., 1997, 9(4): 767-808.

[22] E Burstein. Anomalous Optical Limit in InSb[J]. Phys. Rev., 1954, 93: 632-636.

[23] Miloslavskii V K, Pogrebniak P S. The Burstein-Moss Effect in Polycrystalline ZnO Films[J]. Physica Status Solidi, 1972, 51(2): 99-102.

[24] Wolff P A. Theory of the Band Structure of Very Degenerate Semicoductors[J]. Phys. Rev., 1962, 126: 405-408.