• Title/Summary/Keyword: superlattice

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The Structural Investigation for the Enhancement of Electrical Conductivity in Ga-doped ZnO Targets

  • Yun, Sang-Won;Seo, Jong-Hyeon;Seong, Tae-Yeon;An, Jae-Pyeong;Gwon, -Hun;Lee, Geon-Bae
    • Proceedings of the Materials Research Society of Korea Conference
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    • 2011.05a
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    • pp.243.2-243.2
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    • 2011

  • ZnO materials with a wide band gap of approximately 3.3 eV has been used in transparent conducting oxides (TCO) due to exhibitinga high optical transmission, but its low conductivity acts as role of a limitation for conducting applications. Recently, Ga or Al-doped ZnO (GZO, AZO) becomes transparent conducting materials because of high optical transmission and excellent conductivity. However, the fundamental mechanism underlying the improvement of electrical conductivity of the GZO is still the subject of debate. In this study, we have fully investigated the reasons of high conductivity through the characterization of plane defects, crystal orientation, doping contents, crystal structure in Zn1-xGaxO (x=0, 3, 5.1, 5.6, 6.6 wt%). We manufactured Zn1-xGaxO by sintering ZnO and Ga2O3 powers, having a theoretical density of 99.9% and homogeneous Ga-dopant distribution in ZnO grains. The GZO containing 5.6 wt% Ga represents the highest electrical conductivity of $7.5{\times}10^{-4}{\Omega}{\cdot}m$. In particular, many twins and superlattices were induced by doping Ga in ZnO, revealed by X-ray diffraction measurements and TEM (transmission electron microscopy) observations. Twins developed in conventional ZnO crystal are generally formed at (110) and (112) planes, but we have observed the twins at (113) plane only, which is the first report in ZnO material. Interestingly, the superlattice structure was not observed at the grains in which twins are developed and the opposite case was true. This structural change in the GZO resulted in the difference of electrical conductivity. Enhancement of the conductivity was closely related to the extent of Ga ordering in the GZO lattice. Maximum conductivity was obtained at the GZO with a superlattice structure formed ideal ordering of Ga atoms.

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First-principles Study on the Magnetism and Electronic Structure of (CrAs)3(MnAs)3(110) Superlattice ((CrAs)3(MnAs)3(110) 초격자의 전자구조와 자성에 대한 제일원리 연구)

  • Lee, J.I.;Hong, S.C.
    • Journal of the Korean Magnetics Society
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    • v.16 no.2
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    • pp.111-114
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    • 2006

  • We investigated the magnetism and electronic structures for the layered structures consisting of (110) layers of zinc-blende CrAs and MnAs. We calculated the electronic structures for $(CrAs)_3(MnAs)_3(110)$ superlattice consisted of alternating three layers of CrAs(110) and MnAs(110) by the full-potential linearized augmented plane wave (FLAPW) method. The calculated magnetic moment of Cr in interface layer ($3.07\;\mu_B$) was slightly larger than that of Cr atom in center layer ($3.06\;\mu_B$), while that of interface Mn atom ($3.74\;\mu_B$) was slightly smaller than the value of Mn atom in center layer ($3.76\;\mu_B$). The electronic structure and half-metallicity in this superlattice were discussed using the calculated density of states.

  • https://doi.org/10.4283/JKMS.2006.16.2.111 인용 PDF KSCI

Optical Properties of Plasmons in a GaAs/AlxGa1-xAs Multiple Quantum Well Under Electric and Magnetic Fields (전기장과 자기장하의 GaAs/AlxGa1-xAs 다중 양자 우물 내 플라즈몬의 광학적 속성)

  • Ahn, Hyung Soo;Lee, Sang Chil;Kim, Suck Whan
    • New Physics: Sae Mulli
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    • v.68 no.11
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    • pp.1183-1191
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    • 2018

  • The plasmon behaviors in a superlattice of $GaAs/Al_xGa_{1-x}As$ multiple quantum wells with a half-parabolic confining potential due to different dielectric interfaces are studied under magnetic and electric fields perpendicular and parallel to the superlattice axis by using a previously published theoretical framework. From the density-density correlation functions by considering the intrasubband and the inter-subband transitions under the random phase approximation, we calculate the dispersion energies of the surface and the bulk states as functions of the composition of the multiple quantum well structure and of the magnetic field strength and the average electric field strength over the quantum well. The Raman intensities for various magnetic field strengths and average electric field strengths over the quantum well are also obtained as a function of the energy of the incoming light for these states.

  • https://doi.org/10.3938/NPSM.68.1183 인용 KSCI