Microstructure of heteroepitaxial GaN revealed by x-ray diffraction

Chierchia, Rosa; Böttcher, T.; Heinke, H.; Einfeldt, S.; Figge, S.; Hommel, D.

doi:10.1063/1.1571217

Cited by 359 publications

(273 citation statements)

References 19 publications

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“…Change in the growth rate or V/III ratio did not affect the o FWHM. In XRD measurements of symmetrical reflections, the o-2y and o scans represent the degree of distribution of the lattice constant perpendicular to the surface and the tilt of crystalline planes, respectively [14]. These observations suggest that the films consist of domains with hexagonal single-phase crystal structure that are tilted in respect to each other.…”

Section: Resultsmentioning

confidence: 87%

Growth of InN by vertical flow MOVPE

Suihkonen

Sormunen

Rangel-Kuoppa

et al. 2006

Journal of Crystal Growth

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InN films were grown by metal-organic vapour phase epitaxy (MOVPE). The growth was performed in a MOVPE apparatus with a vertical reactor geometry optimized for the growth of GaN. The reactor geometry is found to cause enhanced cracking of NH 3 , and the growth rate is limited by the amount of reactive indium in the temperature range of 550-650 1C. The grown films are characterized comprehensively. Experimental results indicate that the InN films, grown on sapphire substrates, contain metallic indium and the film surface consist of hexagonal islands. Growth temperature has a strong effect on the surface island size, optical quality and electrical properties of the InN layer. The desorption of nitrogen is assumed to cause the formation of metallic indium above 550 1C. r

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Section: Resultsmentioning

confidence: 87%

Growth of InN by vertical flow MOVPE

Suihkonen

Sormunen

Rangel-Kuoppa

et al. 2006

Journal of Crystal Growth

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“…Continuous films are achievable if GaN nuclei can be preferentially formed first along the periodic step edges and GaN nuclei then advance laterally to coalesce. We performed the growth of GaN on epitaxial graphene by using metalorganic chemical vapour deposition (MOCVD) with following conditions: the conventional two-step growth used for GaN epitaxy on sapphire or SiC (nucleation at 580°C/growth at 1,150°C) 15,20,21 , one-step growth at 1,100°C and modified two-step growth (nucleation at 1,100°C/growth at 1,250°C). Figures 2b-d show plan-view scanning electron microscopy (SEM) images of GaN films grown on graphene by the above three conditions, respectively.…”

Section: Resultsmentioning

confidence: 99%

Principle of direct van der Waals epitaxy of single-crystalline films on epitaxial graphene

Kim¹,

Bayram²,

Park³

et al. 2014

Nat Commun

350

299

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There are numerous studies on the growth of planar films on sp 2 -bonded two-dimensional (2D) layered materials. However, it has been challenging to grow single-crystalline films on 2D materials due to the extremely low surface energy. Recently, buffer-assisted growth of crystalline films on 2D layered materials has been introduced, but the crystalline quality is not comparable with the films grown on sp 3 -bonded three-dimensional materials. Here we demonstrate direct van der Waals epitaxy of high-quality single-crystalline GaN films on epitaxial graphene with low defectivity and surface roughness comparable with that grown on conventional SiC or sapphire substrates. The GaN film is released and transferred onto arbitrary substrates. The post-released graphene/SiC substrate is reused for multiple growth and transfer cycles of GaN films. We demonstrate fully functional blue light-emitting diodes (LEDs) by growing LED stacks on reused graphene/SiC substrates followed by transfer onto plastic tapes.

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“…This method is usually utilized to obtain the mosaic properties of III-nitrides. 17,18 Extracted from the slope and y intersection of these plots, the tilt and the lateral correlation length are obtained as 0.39°͑0.48°͒ and 317 nm͑29 nm͒ parallel to ͑perpendicular to͒ the c axis, which shows obviously anisotropic mosaic block dimensions. The features of m-plane GaN are also approved from the symmetric ͑1100͒ RSMs at azimuth 0°and 90°, as shown in Figs.…”

mentioning

confidence: 99%

Anisotropic crystallographic properties, strain, and their effects on band structure of m-plane GaN on LiAlO2(100)

Liu

Zhang

Xie

et al. 2008

Applied Physics Letters

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The m-plane GaN films grown on LiAlO 2 ͑100͒ by metal-organic chemical vapor deposition exhibit anisotropic crystallographic properties. The Williamson-Hall plots point out they are due to the different tilts and lateral correlation lengths of mosaic blocks parallel and perpendicular to GaN͓0001͔ in the growth plane. The symmetric and asymmetric reciprocal space maps reveal the strain of m-plane GaN to be biaxial in-plane compress xx = −0.79% and zz = −0.14% with an out-of-plane dilatation yy = 0.38%. This anisotropic strain further separates the energy levels of top valence band at ⌫ point. The energy splitting as 37 meV as well as in-plane polarization anisotropy for transitions are found by the polarized photoluminescence spectra at room temperature. © 2008 American Institute of Physics. ͓DOI: 10.1063/1.2951618͔The wurtzite structure of III-nitrides leads to electrostatic fields along the ͓0001͔ direction due to spontaneous and piezoelectric polarization, when the film is grown on c-oriented substrates. 1 These built-in electric fields along the ͓0001͔ direction separate the electron and hole wave functions in a quantum well ͑QW͒ thereby reducing the recombination probability of electron-hole pairs. Consequently, it results in reduction of quantum efficiency of light-emitting diodes. 2 A way to overcome this deficiency is to grow GaNbased QWs along nonpolar orientations, for example, m plane 3,4 or a plane. 5,6 It has been shown that the electric field can be avoided in such nitride QWs. When ͓1100͔ or ͓1120͔ becomes the growth direction, the c axis of GaN lattice lies down in the growth plane. As a consequence, the C 6v hexagonal symmetry of the c growth plane is reduced to C 2v symmetry of the m growth plane. Firstly, it would show the anisotropic crystallographic characteristics. 7,8 Secondly, the nonpolar GaN films experience strong anisotropic deformation due to different in-plane lattice mismatches and thermalexpansion coefficients between GaN and underlying substrates. In the case of c-plane GaN films, isotropic strain in the c-plane preserves C 6v symmetry in the x-y plane so that no significant in-plane physical anisotropy occurs. The situation is quite different for nonpolar GaN films. Anisotropic in-plane strain components further lift the symmetry in the growth plane, which significantly modify the top three valence band ͑VB͒ states at ⌫ point. 9,10 Both the energy splitting and polarization selection of the transitions between conduction band ͑CB͒ and VB have been observed by absorption, reflectance, and photoreflectance spectroscopy. 11,12 Recently, transmission anisotropy spectroscopy has been utilized to obtain the energy splitting and polarization information of m-plane GaN films. 13 Although the in-plane strain components are important for the modifications in band structure of nonpolar GaN, it is still difficult to experimentally determine the full state of strain. In the case of m plane, GaN films are grown along GaN ͓1100͔ direction. The growth plane is the x-z plane, and the growth direc...

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Microstructure of heteroepitaxial GaN revealed by x-ray diffraction

Cited by 359 publications

References 19 publications

Growth of InN by vertical flow MOVPE

Growth of InN by vertical flow MOVPE

Principle of direct van der Waals epitaxy of single-crystalline films on epitaxial graphene

Anisotropic crystallographic properties, strain, and their effects on band structure of m-plane GaN on LiAlO2(100)

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