Thermal vibrations and bonding in GaAs: an extended-face crystal study

Stevenson, Andrew W.

doi:10.1107/s0108767393013947

Cited by 34 publications

(18 citation statements)

References 28 publications

(38 reference statements)

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“…This is explained by the constructive overlap of bonding orbitals and the charge transfer between nearest neighbours. As shown recently (Pietsch & Hansen, 1996), only a few of the charge density maps calculated from different data sets of X-ray structure amplitudes IFhl published until now (Levalois & Allais, 1986;Saravanan et aL, 1992;Stevenson, 1994) are in qualitative agreement with this theoretical prediction.…”

Section: Introductionmentioning

confidence: 73%

Comparison of Experimental and Theoretical Structure Amplitudes and Valence Charge Densities of GaAs

Stahn¹,

Möhle²,

Pietsch³

1998

Acta Crystallogr Sect B

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The current best sets of X-ray structure amplitudes for GaAs, gallium arsenide, are completed by highly precise data recorded at 0.50 < sin 0/~. < 1.35 ,~-1. For the strong reflections the required accuracy of AF/F < 1% was realized by the use of PendellOsung measurements at k = 0.30 A, recording the integral intensities as a function of the effective thickness from "-500 lam thick GaAs wafers. Additionally, several weak reflections were determined from their integral intensities within the kinematic limit at wavelengths ~. = 0.3, 0.56 and 0.71 ,~. From these data individual Debye-Waller factors for gallium and arsenic were determined using the model of independent spherical atoms [BGa = 0.666 (4) and BAs = 0.566 (4)A2]. The extended set of experimental structure factors now available is compared with those obtained by ab initio solid-state Hartree-Fock (HF) and density functional (DF) calculations. Therefore, the theoretical data were adapted to room temperature using the experimentally evaluated Debye-Waller factors and the model mentioned above. The valence and difference charge densities obtained from experimental and theoretical data show the expected charge accumulation between nearest neighbours slightly shifted towards the arsenic site. The disagreement remaining between the experimental and theoretical data, on the one hand, and between those of both ab initio methods, on the other hand, are of the same order of magnitude.

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Section: Introductionmentioning

confidence: 73%

Comparison of Experimental and Theoretical Structure Amplitudes and Valence Charge Densities of GaAs

Stahn¹,

Möhle²,

Pietsch³

1998

Acta Crystallogr Sect B

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“…Short discussions concerning the phase problem when using the Gram-Charlier expansion were published some years ago (Nelmes & Tun, 1987, 1988Hansen, 1988): the former authors showed that skewness can be detected by using a limited Gram-Charlier expansion, but that this is not the case for the Edgeworth expansion, whereas Hansen drew attention to the fact that the result is not unique. In a recent study of GaAs (Stevenson, 1994), there is also some discussion about poorly determined parameters (here third-order anharmonicity), which is explained by high correlations between these parameters.…”

Section: Introductionmentioning

confidence: 99%

The Phase Problem in the Analysis of X-ray Diffraction Data in Terms of Electron-Density Distributions

Haouzi¹,

Hansen²,

Hénaff³

et al. 1996

Acta Crystallogr A Found Crystallogr

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The refinement of electron-density distributions for noncentrosymmetric crystals from X-ray diffraction data may lead to a very good fit between model and data but to totally meaningless electron densities. This is to a large extent because varying certain parameters, or combination of parameters, in the model mainly leads to a change in the phases of the structure factors. A formal analysis of why this happens, when using multipole models, is given as well as specific examples using real data: the contributions of odd-order multipoles, which are invariant under crystal-class symmetry operations, are poorly determined. The importance of applying constraints on the models is stressed. The conclusions of this analysis can be carried over to refinements of anharmonic atomic vibrations.

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“…There is no significant change in bond length between crystalline and amorphous samples, both of which agree with c-GaAs reference values. 25 The uncertainty in the bond length was approximately 60.009 Å . Compared with a crystalline coordination of four, the EXAFS analysis reveals a coordination of $2.8 for the amorphous samples.…”

Section: A the As Atom Environmentmentioning

confidence: 99%

Local structure of amorphous GaN1−xAsx semiconductor alloys across the composition range

Levander

Новиков

et al. 2013

Journal of Applied Physics

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Typically only dilute (up to ∼10%) highly mismatched alloys can be grown due to the large differences in atomic size and electronegativity of the host and the alloying elements. We have overcome the miscibility gap of the GaN1−xAsx system using low temperature molecular beam epitaxy. In the intermediate composition range (0.10 < x < 0.75), the resulting alloys are amorphous. To gain a better understanding of the amorphous structure, the local environment of the As and Ga atoms was investigated using extended x-ray absorption fine structure (EXAFS). The EXAFS analysis shows a high concentration of dangling bonds compared to the crystalline binary endpoint compounds of the alloy system. The disorder parameter was larger for amorphous films compared to crystalline references, but comparable with other amorphous semiconductors. By examining the Ga local environment, the dangling bond density and disorder associated with As-related and N-related bonds could be decoupled. The N-related bonds had a lower dangling bond density and lower disorder.

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Thermal vibrations and bonding in GaAs: an extended-face crystal study

Cited by 34 publications

References 28 publications

Comparison of Experimental and Theoretical Structure Amplitudes and Valence Charge Densities of GaAs

Comparison of Experimental and Theoretical Structure Amplitudes and Valence Charge Densities of GaAs

The Phase Problem in the Analysis of X-ray Diffraction Data in Terms of Electron-Density Distributions

Local structure of amorphous GaN1−xAsx semiconductor alloys across the composition range

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