Understanding x-ray diffraction of nonpolar gallium nitride films

Moram, M. A.; Johnston, Carol F.; Hollander, J. L.; Kappers, M. J.; Humphreys, C. J.

doi:10.1063/1.3129307

Cited by 136 publications

(167 citation statements)

References 16 publications

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“…Basal plane stacking faults ͑BPSFs͒ are among the most abundant defects in nonpolar nitride films, in particular the intrinsic I 1 -type BPSFs. 15,17,18,33 However, the two accessible on-axis reflections for a-plane InN, i.e., ͑1120͒ and ͑2240͒, are unaffected by the BPSF. 18,27 Therefore, the respective Williamson-Hall plots would give LCLs that are greatly overestimated.…”

Section: A Assessment Of Film Structure By Xrdmentioning

confidence: 99%

“…15,17,18,33 However, the two accessible on-axis reflections for a-plane InN, i.e., ͑1120͒ and ͑2240͒, are unaffected by the BPSF. 18,27 Therefore, the respective Williamson-Hall plots would give LCLs that are greatly overestimated. Nevertheless, these LCLs could be instructive for the distribution of defects different from BPSFs or other structural characteristics.…”

Section: A Assessment Of Film Structure By Xrdmentioning

confidence: 99%

“…27 We note that the observed surface morphology differs from the typical striated surface morphology ͑with striations along the ͓0001͔ direction͒ of a-plane GaN films, often decorated with surface pits. 3,13,18,19,33 The m-plane InN film exhibits a periodic trenchlike surface structure and a surface roughness of 6.9 nm. This trenchlike surface morphology most likely replicates the surface morphology of the substrate, as previously shown for m-plane GaN films grown on LiAlO 2 .…”

Section: Methodsmentioning

confidence: 99%

“…18,27 Therefore, LCLs sensitive to the BPSF density, could be derived from the Williamson-Hall plot analysis of the ͑hh00͒ reflections ͑h=1,2͒. The BPSF density can be then estimated on the assumption that BPSF are the main factor determining the limited LCLs.…”

Section: A Assessment Of Film Structure By Xrdmentioning

confidence: 99%

“…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. 17,18 Surface roughness was also shown to affect the RC broadening 18 observed anisotropy. 19 Reports on the structural anisotropy of semipolar GaN just begun to emerge and the on-axis RC of semipolar ͑1122͒ GaN films have been recently found to also exhibit anisotropic behavior.…”

Section: Introductionmentioning

confidence: 99%

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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: A Assessment Of Film Structure By Xrdmentioning

confidence: 99%

Section: A Assessment Of Film Structure By Xrdmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: A Assessment Of Film Structure By Xrdmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Structural anisotropy of nonpolar and semipolar InN epitaxial layers

Darakchieva

Xie

Franco

et al. 2010

Journal of Applied Physics

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Structural properties of bulk GaN substrates: Impact of structural anisotropy on non‐polar and semi‐polar crystals

Serafińczuk

Kucharski

Zając

et al. 2015

Crystal Research and Technology

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In this paper we show the structural parameters and structural anisotropy of the bulk GaN substrates of various crystallographic orientations (00.1), (10.0), (11.0) and (20.1) obtained by ammonothermal method. The structural parameters were investigated using high resolution X‐Ray Diffraction. Perfect crystalline structure manifests in very narrow peaks in X‐ray rocking curves. The full width at half maximum (FWHM) values of 16 and 18 arcsec for the symmetrical and asymmetrical peaks, respectively, have been observed. In addition, we observed structural anisotropy in the non‐polar and semi‐polar crystals, depending on the orientation of the sample relative to the X‐ray beam. It is conducted that this anisotropy is a intrinsic property of non‐polar and semi‐polar GaN substrates.

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An X‐ray diffraction technique for analyzing basal‐plane stacking faults in GaN

Paduano

Weyburne

Drehman

2010

Physica Status Solidi (a)

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An X-ray diffraction (XRD) technique for analyzing basalplane stacking faults (BSFs) is introduced and tested on GaN. The analysis considers the coexistence of multiple X-ray broadening terms including tilt, twist, limited coherence length, and inhomogeneous strain. By measuring and fitting a series of symmetric and asymmetric reflections planes, we deduce the lattice tilt, twist, lateral coherence length, and inhomogeneous strain contributions, which allow us to determine the existence of any additional broadening in m-plane GaN. We found that in fact certain v-scans do have excess broadening and that their lattice plane dependence is similar to the functional dependence of BSFs derived for powder . Applying such functional dependence allows us to estimate the BSF densities (I 1 -and I 2 -type). The typical stacking fault density was estimated to be 1 Â 10 6 /cm in m-plane GaN grown on m-plane sapphire by MOCVD, while the relative densities of I 1 -and I 2 -type are sample dependent. In contrast to the m-plane GaN, stacking faults in GaN on c-plane sapphire do not contribute significantly to Bragg peak broadening and are below the detection limit.

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Understanding x-ray diffraction of nonpolar gallium nitride films

Cited by 136 publications

References 16 publications

Structural anisotropy of nonpolar and semipolar InN epitaxial layers

Structural anisotropy of nonpolar and semipolar InN epitaxial layers

Structural properties of bulk GaN substrates: Impact of structural anisotropy on non‐polar and semi‐polar crystals

An X‐ray diffraction technique for analyzing basal‐plane stacking faults in GaN

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