Anisotropic structural characteristics of (112̄0) GaN templates and coalesced epitaxial lateral overgrown films deposited on (101̄2) sapphire

Wang, Hongmei; Chen, Chang; Gong, Zheng; Zhang, Jianping; Gaevski, Mikhail; Су, Минг; Yang, Jinwei

doi:10.1063/1.1644054

Cited by 165 publications

(122 citation statements)

References 11 publications

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“…Indeed, the full widths at half maximum ͑FWHMs͒ of the on-axis ͑1120͒ rocking curves ͑RCs͒ of a-plane GaN films were reported to have either an "M" or a "W" shape dependence on the azimuth angle with minimum FWHM parallel to the GaN ͓0001͔ or ͓1100͔ directions. [13][14][15][16] Similar azimuth dependence of the on-axis ͑1100͒ RC FWHM has also been reported for m-plane GaN films. 17 The anisotropic behavior of the RC FWHM in nonpolar GaN films was attributed to the combined or sole effect of anisotropic distribution of dislocations, 14,15 tilt, 15 wafer bending, 16 and stacking faults.…”

Section: Introductionsupporting

confidence: 77%

Structural anisotropy of nonpolar and semipolar InN epitaxial layers

Darakchieva

Xie

Franco

et al. 2010

Journal of Applied Physics

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We present a detailed study of the structural characteristics of molecular beam epitaxy grown nonpolar InN films with a-and m-plane surface orientations on r-plane sapphire and ͑100͒ ␥-LiAlO 2 , respectively, and semipolar ͑1011͒ InN grown on r-plane sapphire. The on-axis rocking curve ͑RC͒ widths were found to exhibit anisotropic dependence on the azimuth angle with minima at InN ͓0001͔ for the a-plane films, and maxima at InN ͓0001͔ for the m-plane and semipolar films. The different contributions to the RC broadening are analyzed and discussed. The finite size of the crystallites and extended defects are suggested to be the dominant factors determining the RC anisotropy in a-plane InN, while surface roughness and curvature could not play a major role. Furthermore, strategy to reduce the anisotropy and magnitude of the tilt and minimize defect densities in a-plane InN films is suggested. In contrast to the nonpolar films, the semipolar InN was found to contain two domains nucleating on zinc-blende InN͑111͒A and InN͑111͒B faces. These two wurtzite domains develop with different growth rates, which was suggested to be a consequence of their different polarity. Both, a-and m-plane InN films have basal stacking fault densities similar or even lower compared to nonpolar InN grown on free-standing GaN substrates, indicating good prospects of heteroepitaxy on foreign substrates for the growth of InN-based devices.

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Section: Introductionsupporting

confidence: 77%

Structural anisotropy of nonpolar and semipolar InN epitaxial layers

Darakchieva

Xie

Franco

et al. 2010

Journal of Applied Physics

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“…The density of extended defects in nonpolar GaN ͑including threading dislocations and stacking faults 5 ͒ is much higher than that in c-plane epilayers and exhibits an anisotropic nature. [6][7][8] Furthermore, the surface of nonpolar GaN layers frequently shows striation morphology with a substantial surface undulation perpendicular to the striation direction. 6,9 In contrast to the rich literature of c-plane GaN, very little has been reported regarding the heteroepitaxy of nonpolar GaN.…”

Section: Microstructural Evolution In M-plane Gan Growth On M-plane Sicmentioning

confidence: 99%

“…[6][7][8] Furthermore, the surface of nonpolar GaN layers frequently shows striation morphology with a substantial surface undulation perpendicular to the striation direction. 6,9 In contrast to the rich literature of c-plane GaN, very little has been reported regarding the heteroepitaxy of nonpolar GaN. 7 In this paper, we report an investigation of the nucleation and coalescence of m-plane GaN grown on m-plane 4H-SiC substrates.…”

Section: Microstructural Evolution In M-plane Gan Growth On M-plane Sicmentioning

confidence: 99%

Microstructural evolution in m-plane GaN growth on m-plane SiC

Sun

Kwon

Ren

et al. 2008

Applied Physics Letters

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“…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.…”

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...

show abstract

Anisotropic structural characteristics of (112̄0) GaN templates and coalesced epitaxial lateral overgrown films deposited on (101̄2) sapphire

Cited by 165 publications

References 11 publications

Structural anisotropy of nonpolar and semipolar InN epitaxial layers

Structural anisotropy of nonpolar and semipolar InN epitaxial layers

Microstructural evolution in m-plane GaN growth on m-plane SiC

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

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