Self-assembled vertical GaN nanorods grown by molecular-beam epitaxy

Tu, Li‐Wei; Hsiao, Ching‐Lien; W., T.; Lo, Ikai; Hsieh, Kuang-Yeu

doi:10.1063/1.1558216

Cited by 124 publications

(92 citation statements)

References 21 publications

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“…These nanocolumns were independently grown with their c-axis perpendicular to the substrate surface. Until now, many studies on nitride nanoscale columnar structures have been reported, for example, growth of nanocolumns by ECR-MBE [4] and HVPE [5], fabrication of nanocolumns by reactive ion etching [6] and photon-assisted anodic etching [7], growth on (111) Si substrate [8], evaluation of optical properties [9,10], growth of GaN/AlGaN [11,12] and InGaN/GaN [1] quantum wells in the nanocolumns, and so on. In this paper, we describe the optical properties of GaN nanocolumns using room temperature photoluminescence, under low and high (photopump) excitation conditions.…”

Section: Introductionmentioning

confidence: 99%

Stimulated emission from GaN nanocolumns

Kikuchi

Yamano

Tada

et al. 2004

Physica Status Solidi (b)

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Stimulated emission with very low threshold excitation power density was observed for GaN nanocolumns grown on (0001) sapphire substrate by RF-plasma assisted molecular beam epitaxy. The photopump measurements were carried out under 355 nm Nd : YAG laser excitation with the surface emission configuration. The threshold excitation power density was 198 kW/cm 2 at room temperature. The peak wavelength shifted from 370.2 to 370.9 nm when increasing the excitation power from 130 to 440 kW/cm 2 . The peak intensity increased nonlinearly with excitation power. For the lower excitation condition using a 325 nm He -Cd laser, the spontaneous emission peak was observed at 363.2 nm and the intensity was 20~30 times stronger than for a 3.7 µm-thick MOCVD-grown GaN film with a dislocation density of 3~5 × 10 9 cm -2 . With this configuration the peak intensity was increased propotionally with excitation power. These results indicate that GaN nanocolumns have high potential to realize high performance optical devices.

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Section: Introductionmentioning

confidence: 99%

Stimulated emission from GaN nanocolumns

Kikuchi

Yamano

Tada

et al. 2004

Physica Status Solidi (b)

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“…12 As illustrated in Fig. 1, the hexagonal, prismatic-shaped nanorod is generated by cutting from the bulk GaN WZ structure with lattice constants a = 3.23 Å and c = 5.16 Å.…”

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confidence: 99%

“…12 Transmission electron microscopy observations show that as-synthesized GaN nanorods have hexagonal cross sections along the c-axis. 12 As illustrated in Fig.…”

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Surface transformation and inversion domain boundaries in gallium nitride nanorods

Xiao

Wang

et al. 2009

Applied Physics Letters

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Phase transformation and subdomain structure in ͓0001͔-oriented gallium nitride ͑GaN͒ nanorods of different sizes are studied using molecular dynamics simulations. The analysis concerns the structure of GaN nanorods at 300 K without external loading. Calculations show that a transformation from wurtzite to a tetragonal structure occurs along ͕0110͖ lateral surfaces, leading to the formation of a six-sided columnar inversion domain boundary ͑IDB͒ in the ͓0001͔ direction of the nanorods. This structural configuration is similar to the IDB structure observed experimentally in GaN epitaxial layers. The transformation is significantly dependent on the size of the nanorods. © 2009 American Institute of Physics. ͓doi:10.1063/1.3268467͔With a wide band gap, gallium nitride ͑GaN͒ promises superior performances for blue light-emitting diodes, 1 highpower sources, and optical data storage devices.2 Recent advances in the synthesis of one-dimensional nanostructures have brought forth possibilities for GaN to be used in more applications.3 Structural transformations and defects are subjects of active experimental and theoretical research for GaN, 4 because they lead to significant changes in physical and chemical properties and, therefore, affect applications. These transformations and defects can be caused by external or internal factors. For epitaxially grown GaN layers, because of the lack of a lattice and thermally matching substrate, they always contain large numbers of defects.5 Highresolution x-ray diffraction studies of GaN layers have indicated that both carrier mobility and the intensity of photoluminescence are strongly related to defects.6 It was also observed that a phase transformation from wurtzite ͑WZ͒ to rock-salt structure can be induced by high pressure in GaN. 7 However for GaN nanostructures, surface stresses due to high surface-to-volume ratios are another factor that may lead to structural transitions. Experimental observations and atomistic simulations show that structural reorientation can occur in metal ͑copper, silver, and gold͒ nanowires due to high surface-stresses. 8,9 This reorientation causes some of the face-centered-cubic metal nanowires to exhibit a shape memory and pseudoelasticity which are not possessed by corresponding bulk materials. 9 The microscopic details of structural transformations in nanostructures are, however, difficult to investigate through direct experimental observations. Atomistic simulations can play an important role in this regard. Recently, molecular dynamics ͑MD͒ simulations are carried out to analyze the atomistic structures of singlecrystal GaN nanotubes and the buckling behavior of GaN nanowires.10 Yet, the effect of surface-stresses on the structural transformation in GaN nanorods is still poorly understood and merit careful inspection. Here, MD simulations are carried out to investigate the surface transformation and defect formation in GaN nanorods. The analyses concern the equilibrium structure of GaN nanorods with lateral dimensions between 22.6-67.4 Å ...

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“…[1][2][3][4][5][6][7] In the past two decades, reports on GaN films grown by chemical vapor deposition ͑CVD͒ or molecular beam epitaxy ͑MBE͒ have dominated thanks to the relative ease of achieving electronic-grade epitaxial films. 3,4,6 A few groups have demonstrated band edge photoluminescence ͑PL͒ in GaN films, grown by radio-frequency and direct-current ͑DC͒ magnetron sputter epitaxy ͑MSE͒.…”

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confidence: 99%

Electronic-grade GaN(0001)/Al2O3(0001) grown by reactive DC-magnetron sputter epitaxy using a liquid Ga target

Junaid

Hsiao

Pališaitis

et al. 2011

Applied Physics Letters

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Electronic-grade GaN (0001) epilayers have been grown directly on Al2O3 (0001) substrates by reactive DC-magnetron sputter epitaxy (MSE) from a liquid Ga sputtering target in an Ar/N2 atmosphere. The as-grown GaN epitaxial film exhibit low threading dislocation density on the order of ≤ 1010 cm-2 obtained by transmission electron microscopy and modified Williamson-Hall plot. X-ray rocking curve shows narrow fullwidth at half maximum (FWHM) of 1054 arcsec of the 0002 reflection. A sharp 4 K photoluminescence peak at 3.474 eV with a FWHM of 6.3 meV is attributed to intrinsic GaN band edge emission. The high structural and optical qualities indicate that MSEgrown GaN epilayers can be used for fabricating high-performance devices without the need of any buffer layer.On the day of the defence date the status of this article was: Manuscript.Original Publication:Muhammad Junaid, Ching-Lien Hsiao, Justinas Palisaitis, Jens Jensen, Per Persson, Lars Hultman and Jens Birch, Electronic-grade GaN(0001)/Al2O3(0001) grown by reactive DC-magnetron sputter epitaxy using a liquid Ga target, 2011, Applied Physics Letters, (98), 14, 141915.http://dx.doi.org/10.1063/1.3576912Copyright: American Institute of Physicshttp://www.aip.org

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Self-assembled vertical GaN nanorods grown by molecular-beam epitaxy

Cited by 124 publications

References 21 publications

Stimulated emission from GaN nanocolumns

Stimulated emission from GaN nanocolumns

Surface transformation and inversion domain boundaries in gallium nitride nanorods

Electronic-grade GaN(0001)/Al2O3(0001) grown by reactive DC-magnetron sputter epitaxy using a liquid Ga target

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