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Title: Recombination dynamics of excitons in Mg{sub 0.11}Zn{sub 0.89}O alloy films grown using the high-temperature-annealed self-buffer layer by laser-assisted molecular-beam epitaxy

Abstract

Recombination dynamics of excitons in Mg{sub 0.11}Zn{sub 0.89}O epilayers grown by laser-assisted molecular-beam epitaxy on a ScAlMgO{sub 4} substrate were investigated. By using the MgZnO high-temperature-annealed self-buffer layer (HITAB), the value of full width at half maximum of the near-band-edge (NBE) photoluminescence (PL) peak at 3.6 eV was decreased from 133 to 94 meV at 293 K, and the intensity ratio of the NBE emission to the deep emission band centered around 2.2 eV was increased by a factor of 3. Also, the PL lifetime of the NBE peak at 293 K under the excitation density of 1 {mu}J/cm{sup 2} was increased from 49 to 60 ps. These results suggest that HITAB gave rise to improved alloy compositional homogeneity and reduced concentration of point defects.

Authors:
; ; ; ; ; ;  [1];  [2];  [2];  [2];  [3]
  1. Institute of Applied Physics, University of Tsukuba, 1-1-1 Tennodai, Tsukuba 305-8573 (Japan) and NICP, ERATO, Japan Science and Technology (JST) Agency, Kawaguchi 332-0012 (Japan)
  2. (Japan)
  3. (JST) Agency, Kawaguchi 332-0012 (Japan)
Publication Date:
OSTI Identifier:
20960194
Resource Type:
Journal Article
Resource Relation:
Journal Name: Applied Physics Letters; Journal Volume: 90; Journal Issue: 14; Other Information: DOI: 10.1063/1.2719168; (c) 2007 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; ANNEALING; CRYSTAL GROWTH; EV RANGE 01-10; EXCITONS; FILMS; LASER MATERIALS; LASERS; LAYERS; MAGNESIUM ALLOYS; MAGNESIUM COMPOUNDS; MEV RANGE 10-100; MEV RANGE 100-1000; MOLECULAR BEAM EPITAXY; PHOTOLUMINESCENCE; POINT DEFECTS; RECOMBINATION; SEMICONDUCTOR MATERIALS; TEMPERATURE RANGE 0273-0400 K; ZINC ALLOYS; ZINC OXIDES

Citation Formats

Kubota, Masashi, Onuma, Takeyoshi, Tsukazaki, Atsushi, Ohtomo, Akira, Kawasaki, Masashi, Sota, Takayuki, Chichibu, Shigefusa F., Institute for Materials Research, Tohoku University, Aoba, Sendai 980-8577, Department of Electrical Engineering and Bioscience, Waseda University, 3-4-1 Ohkubo, Shinjuku 169-8555, Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, Sendai 980-8577, and Institute of Applied Physics and 21st Century COE Office, University of Tsukuba, 1-1-1 Tennodai, Tsukuba 305-8573, Japan and Nakamura Inhomogeneous Crystal Project, ERATO, Japan Science and Technology. Recombination dynamics of excitons in Mg{sub 0.11}Zn{sub 0.89}O alloy films grown using the high-temperature-annealed self-buffer layer by laser-assisted molecular-beam epitaxy. United States: N. p., 2007. Web. doi:10.1063/1.2719168.
Kubota, Masashi, Onuma, Takeyoshi, Tsukazaki, Atsushi, Ohtomo, Akira, Kawasaki, Masashi, Sota, Takayuki, Chichibu, Shigefusa F., Institute for Materials Research, Tohoku University, Aoba, Sendai 980-8577, Department of Electrical Engineering and Bioscience, Waseda University, 3-4-1 Ohkubo, Shinjuku 169-8555, Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, Sendai 980-8577, & Institute of Applied Physics and 21st Century COE Office, University of Tsukuba, 1-1-1 Tennodai, Tsukuba 305-8573, Japan and Nakamura Inhomogeneous Crystal Project, ERATO, Japan Science and Technology. Recombination dynamics of excitons in Mg{sub 0.11}Zn{sub 0.89}O alloy films grown using the high-temperature-annealed self-buffer layer by laser-assisted molecular-beam epitaxy. United States. doi:10.1063/1.2719168.
Kubota, Masashi, Onuma, Takeyoshi, Tsukazaki, Atsushi, Ohtomo, Akira, Kawasaki, Masashi, Sota, Takayuki, Chichibu, Shigefusa F., Institute for Materials Research, Tohoku University, Aoba, Sendai 980-8577, Department of Electrical Engineering and Bioscience, Waseda University, 3-4-1 Ohkubo, Shinjuku 169-8555, Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, Sendai 980-8577, and Institute of Applied Physics and 21st Century COE Office, University of Tsukuba, 1-1-1 Tennodai, Tsukuba 305-8573, Japan and Nakamura Inhomogeneous Crystal Project, ERATO, Japan Science and Technology. Mon . "Recombination dynamics of excitons in Mg{sub 0.11}Zn{sub 0.89}O alloy films grown using the high-temperature-annealed self-buffer layer by laser-assisted molecular-beam epitaxy". United States. doi:10.1063/1.2719168.
@article{osti_20960194,
title = {Recombination dynamics of excitons in Mg{sub 0.11}Zn{sub 0.89}O alloy films grown using the high-temperature-annealed self-buffer layer by laser-assisted molecular-beam epitaxy},
author = {Kubota, Masashi and Onuma, Takeyoshi and Tsukazaki, Atsushi and Ohtomo, Akira and Kawasaki, Masashi and Sota, Takayuki and Chichibu, Shigefusa F. and Institute for Materials Research, Tohoku University, Aoba, Sendai 980-8577 and Department of Electrical Engineering and Bioscience, Waseda University, 3-4-1 Ohkubo, Shinjuku 169-8555 and Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, Sendai 980-8577 and Institute of Applied Physics and 21st Century COE Office, University of Tsukuba, 1-1-1 Tennodai, Tsukuba 305-8573, Japan and Nakamura Inhomogeneous Crystal Project, ERATO, Japan Science and Technology},
abstractNote = {Recombination dynamics of excitons in Mg{sub 0.11}Zn{sub 0.89}O epilayers grown by laser-assisted molecular-beam epitaxy on a ScAlMgO{sub 4} substrate were investigated. By using the MgZnO high-temperature-annealed self-buffer layer (HITAB), the value of full width at half maximum of the near-band-edge (NBE) photoluminescence (PL) peak at 3.6 eV was decreased from 133 to 94 meV at 293 K, and the intensity ratio of the NBE emission to the deep emission band centered around 2.2 eV was increased by a factor of 3. Also, the PL lifetime of the NBE peak at 293 K under the excitation density of 1 {mu}J/cm{sup 2} was increased from 49 to 60 ps. These results suggest that HITAB gave rise to improved alloy compositional homogeneity and reduced concentration of point defects.},
doi = {10.1063/1.2719168},
journal = {Applied Physics Letters},
number = 14,
volume = 90,
place = {United States},
year = {Mon Apr 02 00:00:00 EDT 2007},
month = {Mon Apr 02 00:00:00 EDT 2007}
}
  • Zn{sub 1-x}Mg{sub x}O thin films with a Mg content x between 0 and 0.42 grown by plasma-assisted molecular beam epitaxy on c-plane sapphire substrates were investigated by electron spin resonance at 5 K. Above band gap illumination induces a persistent resonance signal, which is attributed to free conduction band electrons. The g-factors of the Zn{sub 1-x}Mg{sub x}O epitaxial layers and their anisotropy were determined experimentally and an increase from g{sub ||}=1.957 for x=0 to g{sub ||}=1.970 for x=0.42 was found, accompanied by a decrease in anisotropy. A comparison with g-factors of the Al{sub x}Ga{sub 1-x}N system is also given.
  • Zn{sub 1-x}Mg{sub x}O epitaxial films with Mg concentrations 0{<=}x{<=}0.3 were grown by plasma-assisted molecular beam epitaxy on a-plane sapphire substrates. Precise determination of the Mg concentration x was performed by elastic recoil detection analysis. The bandgap energy was extracted from absorption measurements with high accuracy taking electron-hole interaction and exciton-phonon complexes into account. From these results a linear relationship between bandgap energy and Mg concentration is established for x{<=}0.3. Due to alloy disorder, the increase of the photoluminescence emission energy with Mg concentration is less pronounced. An analysis of the lattice parameters reveals that the epitaxial films grow biaxially strainedmore » on a-plane sapphire.« less
  • Nonradiative photoluminescence (PL) lifetime ({tau}{sub nr}) and point defect density in the (0001) ZnO epilayer grown on (111) Si substrates by laser-assisted molecular-beam epitaxy (L-MBE) using a (0001) ZnS epitaxial buffer layer were compared with those in the ZnO films on (111) and (001) Si substrates prepared by direct transformation of ZnS epilayers on Si by thermal oxidation [Yoo et al., Appl. Phys. Lett. 78, 616 (2001)]. Both the ZnO films exhibited excitonic reflectance anomalies and corresponding PL peaks at low temperature, and the density or size of vacancy-type point defects (Zn vacancies), which were measured by the monoenergetic positronmore » annihilation measurement, in the L-MBE epilayer was lower than that in the films prepared by the oxidation transformation. The ZnO epilayer grown on a (0001) ZnS epitaxial buffer on (111) Si exhibited longer {tau}{sub nr} of 105 ps at room temperature.« less
  • Growth of a natural buffer layer has been observed for DyBa{sub 2}Cu{sub 3}O{sub 7{minus}{ital x}} films grown on Si substrates. The best DyBa{sub 2}Cu{sub 3}O{sub 7{minus}{ital x}} film, grown by molecular beam epitaxy with ozone as a source of activated oxygen, was 2300-A thick, highly {ital c}-axis oriented, and had a resistive-transition onset at 90 K and zero resistance by 70 K. The natural buffer layer, which grew at the interface of the DyBa{sub 2}Cu{sub 3}O{sub 7{minus}{ital x}} film and the Si substrate, consisted of Si, Ba, and O. Transmission electron microscopy on this film revealed a 150-A amorphous layer,more » whereas Auger electron spectroscopy depth profiling showed 400 A of chemical interdiffusion.« less
  • Deep level defects in n-type unintentionally doped a-plane Mg{sub x}Zn{sub 1-x}O, grown by molecular beam epitaxy on r-plane sapphire were fully characterized using deep level optical spectroscopy (DLOS) and related methods. Four compositions of Mg{sub x}Zn{sub 1-x}O were examined with x = 0.31, 0.44, 0.52, and 0.56 together with a control ZnO sample. DLOS measurements revealed the presence of five deep levels in each Mg-containing sample, having energy levels of E{sub c} - 1.4 eV, 2.1 eV, 2.6 V, and E{sub v} + 0.3 eV and 0.6 eV. For all Mg compositions, the activation energies of the first three statesmore » were constant with respect to the conduction band edge, whereas the latter two revealed constant activation energies with respect to the valence band edge. In contrast to the ternary materials, only three levels, at E{sub c} - 2.1 eV, E{sub v} + 0.3 eV, and 0.6 eV, were observed for the ZnO control sample in this systematically grown series of samples. Substantially higher concentrations of the deep levels at E{sub v} + 0.3 eV and E{sub c} - 2.1 eV were observed in ZnO compared to the Mg alloyed samples. Moreover, there is a general invariance of trap concentration of the E{sub v} + 0.3 eV and 0.6 eV levels on Mg content, while at least and order of magnitude dependency of the E{sub c} - 1.4 eV and E{sub c} - 2.6 eV levels in Mg alloyed samples.« less