Internal electric field effect on luminescence properties of ZnO/(Mg,Zn)O quantum wells

Makino, T.; Ohtomo, A.; Chia, C. H.; Segawa, Y.; Koinuma, Hideomi; Kawasaki, Masashi

doi:10.1016/j.physe.2003.11.110

Cited by 88 publications

(38 citation statements)

References 15 publications

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“…2͑a͔͒ was much smaller than the reported value ͑50 meV͒ in ZnO / ZnMgO superlattices. 16,17 The small Stokes shift may result from the decreased piezoelectric polarization effect by the fully relaxed strain for the ZnO / ZnMgO nanorod quantum structures in contrast to the two-dimensional ͑2D͒ ZnO / ZnMgO heteroepitaxial multiple layers are strongly supported by the theoretical calculation on the double barrier lnAs/lnP nanorod heterostructures. 18 Based on these experiments, a major investigation of the optical properties of isolated ZnO SQWs was performed by analyzing the polarization-dependent PL spectrum of isolated ZnO SQWs ͑L w = 3.75 nm͒.…”

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confidence: 83%

Near-field measurement of spectral anisotropy and optical absorption of isolated ZnO nanorod single-quantum-well structures

Yatsui

Ohtsu

Yoo

et al. 2005

Applied Physics Letters

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We report low-temperature near-field spectroscopy of isolated ZnO / ZnMgO single-quantum-well structures ͑SQWs͒ on the end of ZnO nanorod to define their potential for nanophotonics. First, absorption spectra of isolated ZnO / ZnMgO nanorod SQWs with the Stokes shift as small as 3 meV and very sharp photoluminescent peaks indicate that the nanorod SQWs are of very high optical quality. Furthermore, we performed polarization spectroscopy of isolated ZnO SQWs, and observed valence-band anisotropy of ZnO SQWs in photoluminescence spectra directly. Since the exciton in a quantum structure is an ideal two-level system with long coherence times, our results provide criteria for designing nanophotonic devices. © 2005 American Institute of Physics. ͓DOI: 10.1063/1.1990247͔ ZnO nanocrystallites are a promising material for realizing nanometer-scale photonic devices, 1 i.e., nanophotonic devices, at room temperature, owing to their large exciton binding energy 2-4 and large oscillator strength. 5 Furthermore, the recent demonstration of semiconductor nanorod quantumwell structures enables us to fabricate nanometer-scale electronic and photonic devices on single nanorods. [6][7][8][9] Recently, ZnO / ZnMgO nanorod heterostructures were fabricated and the quantum confinement effect even from the singlequantum-well structures ͑SQWs͒ was observed. 10 Near-field spectroscopy has made a remarkable contribution to investigations of the optical properties in nanocrystallite, 11 and has resulted in the observation of nanometer-scale optical images, such as the local density of exciton states. 12 However, reports on semiconductor quantum structure are limited to naturally formed quantum dots ͑QDs͒. 12-14 Here we report low-temperature near-field spectroscopy of artificially fabricated ZnO SQWs on the end of a ZnO nanorod.ZnO / ZnMgO SQWs were fabricated on the ends of ZnO stems with a mean diameter of 40 nm and a length of 1 m using catalyst-free metalorganic vapor phase epitxy, in which the ZnO nanorods were grown vertically from a sapphire ͑0001͒ substrate in the c orientation. 10,15 The Mg concentration in the ZnMgO layers averaged 20 at. %. Two samples were prepared for this study: their ZnO well layer thickness L w , were 2.5 and 3.75 nm, while the thicknesses of the ZnMgO bottom and top barrier layers in the SQWs were fixed at 60 and 18 nm, respectively. After growing the ZnO / ZnMgO nanorod SQWs, they were dispersed so that they were laid down on a flat sapphire substrate to isolate them from each other ͓Fig. 1͑a͔͒.The far-field photoluminescence ͑PL͒ spectra were obtained using a He-Cd laser ͑ = 325 nm͒ before dispersion of the ZnO / ZnMgO nanorod SQWs. The emission signal was collected with the acromatic lens ͑f =50 mm͒. To confirm that the optical qualities of individual ZnO / ZnMgO SQWs were sufficiently high, we used a collection-mode near-field optical microscope ͑NOM͒ using a He-Cd laser ͑ = 325 nm͒ for excitation, and a UV fiber probe with an aperture diameter of 30 nm. The excitation source was focused on a nanorod ...

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mentioning

confidence: 83%

Near-field measurement of spectral anisotropy and optical absorption of isolated ZnO nanorod single-quantum-well structures

Yatsui

Ohtsu

Yoo

et al. 2005

Applied Physics Letters

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“…ZnO possess unique figures of merit, such as low thin-film growth temperatures (100-750°C) [10], and radiation hardness [11], which are crucial for practical optoelectronic devices. Despite the challenges of reliable p-type doping in ZnO, there have been reports on fabrication of photodetectors [12], quantum wells [13], and superlattices [14] based on ZnO. As was predicted [15], the observation of roomtemperature UV lasing from the ordered, nano-sized ZnO crystals provides an important step for the development of practical blue-UV laser.…”

Section: Introductionmentioning

confidence: 94%

Ultra violet sensors based on nanostructured ZnO spheres in network of nanowires: a novel approach

Hullavarad

Karulkar

et al. 2007

Nanoscale Res Lett

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The ZnO nanostructures consisting of micro spheres in a network of nano wires were synthesized by direct vapor phase method. X-ray Photoelectron Spectroscopy measurements were carried out to understand the chemical nature of the sample. ZnO nanostructures exhibited band edge luminescence at 383 nm. The nanostructure based ZnO thin films were used to fabricate UV sensors. The photoresponse measurements were carried out and the responsivity was measured to be 50 mA W−1. The rise and decay time measurements were also measured.

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“…Actually, for surface acoustic wave devices, A-plane ZnO has better property than C-plane ZnO [4]. Furthermore, in the development of ZnO-based UV light emitters with ZnO/ZnMgO quantum wells (QWs), one may meet the problem of quantum confined Stark effect due to piezoelectric polarizations in strained QWs [5], which decreases the quantum efficiency of light emission from the QWs. In fact, GaN-based light emitters with InGaN/GaN QWs are now facing to this problem, hence nonpolar such as A-plane or M-plane films are suggested and investigated [6,7].…”

Section: Introductionmentioning

confidence: 99%

Epitaxial growth of nonpolar ZnO by MOVPE

Moriyama

Fujita

2006

Phys. Status Solidi (c)

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Epitaxial growth characteristics of nonpolar (M-and A-plane) ZnO on M-and R-plane sapphire substrates were investigated. The growth of ZnO along the c-axis direction, which aligns parallel to [2-1-10] and [01-11] directions of M-and R-plane sapphire, is achieved under lower growth temperature and/or VI/II ratio, and this growth direction is preferable for smooth lateral growth. Increasing the growth time, the surface becomes rough on M-plane, while is significantly improved on R-plane sapphire. The growth behaviour on R-plane sapphire can be attributed to the small lattice mismatching along the ZnO c-axis direction and enhanced lateral growth characteristics. From photoluminescence measurements, the appearance of peak at 3.383 eV, which is at higher energy compared to well-known impurity-and/or defect-related peaks, at 10 K suggests the residual strain in ZnO films.

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Internal electric field effect on luminescence properties of ZnO/(Mg,Zn)O quantum wells

Cited by 88 publications

References 15 publications

Near-field measurement of spectral anisotropy and optical absorption of isolated ZnO nanorod single-quantum-well structures

Near-field measurement of spectral anisotropy and optical absorption of isolated ZnO nanorod single-quantum-well structures

Ultra violet sensors based on nanostructured ZnO spheres in network of nanowires: a novel approach

Epitaxial growth of nonpolar ZnO by MOVPE

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