Origination and Properties of Dislocations in Thin Film Nitrides

Epitaxial group-III nitride films, although in single crystalline form, contain still a large number of threading dislocations. These set limits to performance and lifetime of devices, notably to high power structures like lasers. The strategy in material development was and will be (at least until lattice-matched substrates become available) to reduce the dislocation densities. The present contribution elaborates on possible dislocation origination mechanisms that determine the population of dislocations in the epitaxial layers. These mechanisms can be controlled to a certain degree by proper deposition procedures. The achieved dislocation populations then determine the processes that can reduce the dislocation densities during growth of the epitaxial layers. The mutual annihilation of threading dislocations is rather efficient although affected by the glide properties of the growing epitaxial crystal and the thermal stresses during the cooling down after growth.

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Raman scattering characterization of group III-nitride epitaxial layers including cubic phase

Journal of Crystal Growth ◽

10.1016/s0022-0248(98)00320-0 ◽

1998 ◽

Vol 189-190 ◽

pp. 435-438 ◽

Cited By ~ 16

Author(s):

Hiroshi Harima ◽

Toshiaki Inoue ◽

Shin-ichi Nakashima ◽

Hajime Okumura ◽

Yuuki Ishida ◽

...

Keyword(s):

Raman Scattering ◽

Cubic Phase ◽

Epitaxial Layers ◽

Group Iii ◽

Group Iii Nitride

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Modelling of III-Nitride Epitaxial Layers Grown on Silicon Substrates with Low Dislocation-Densities

MRS Advances ◽

10.1557/adv.2019.49 ◽

2019 ◽

Vol 4 (13) ◽

pp. 755-760 ◽

Cited By ~ 2

Author(s):

Khaled H. Khafagy ◽

Tarek M. Hatem ◽

Salah M. Bedair

Keyword(s):

Thermal Stresses ◽

Life Time ◽

Epitaxial Layers ◽

Silicon Substrates ◽

Thermal Expansion Coefficients ◽

Dislocation Densities ◽

Large Lattice ◽

Expansion Coefficients ◽

And Performance ◽

Mesh Convergence

ABSTRACTLarge lattice and thermal expansion coefficients mismatches between III-Nitride (III N) epitaxial layers and their substrates inevitably generate defects on the interfaces. Such defects as dislocations affect the reliability, life time, and performance of photovoltaic (PV) devices. High dislocation densities in epitaxial layer generate higher v-shaped pits densities on the layer top surface that also directly affect the device performance. Therefore, using an approach such as the embedded void approach (EVA) for defects reduction in the epitaxial layers is essential. EVA relies on the generation of high densities of embedded microvoids (∼108/cm2), with ellipsoidal shapes. These tremendous number of microvoids are etched near the interface between the III N thin-film and its substrate where the dislocation densities present with higher values.This article used a 3-D constitutive model that accounts the crystal plasticity formulas and specialized finite element (FE) formulas to model the EVA in multi-junction PV and therefore to study the effect of the embedded void approach on the defects reduction. Mesh convergence and 2-D analytical solution validation is conducted with accounting thermal stresses. Several aspect and volume ratios of the embedded microvoids are used to optimize the microvoid dimensions.

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Band-gap-related energies of threading dislocations and quantum wells in group-III nitride films as derived from electron energy loss spectroscopy

Physical Review B ◽

10.1103/physrevb.66.035302 ◽

2002 ◽

Vol 66 (3) ◽

Cited By ~ 30

Author(s):

A. Gutiérrez-Sosa ◽

U. Bangert ◽

A. J. Harvey ◽

C. J. Fall ◽

R. Jones ◽

...

Keyword(s):

Energy Loss ◽

Quantum Wells ◽

Band Gap ◽

Electron Energy ◽

Electron Energy Loss Spectroscopy ◽

Threading Dislocations ◽

Group Iii ◽

Group Iii Nitride ◽

Electron Energy Loss

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Defect Reduction in Mocvd Grown Si/GaAs

MRS Proceedings ◽

10.1557/proc-116-141 ◽

1988 ◽

Vol 116 ◽

Cited By ~ 16

Author(s):

M.M. Al-Jassim ◽

Takashi Nishioka ◽

Yoshio Itoh ◽

Akio Yamamoto ◽

Masafumi Yamaguchi

Keyword(s):

Layer Thickness ◽

Threading Dislocations ◽

Defect Reduction ◽

Closed Loops ◽

Si Substrates ◽

Dislocation Densities ◽

Low Pressure Mocvd ◽

Strained Layer Superlattices ◽

Lattice Matched

AbstractThe effectiveness of thermal annealing and strained layer superlattices (SLS's) in defect reduction in Si/GaAs structures was studied. The GaAs layers were grown on (100) Si substrates by low pressure MOCVD. They were evaluated by TEM, HREM, EBIC and PL. As-grown layers contained dislocation densities in the 108-109 cm−2 range, depending on the layer thickness. Post-growth and in situ annealing were performed on a wide variety of these structures. TEM examination showed that in situ annealing was more effective as it resulted in confining a large portion of the threading dislocations to the interface region. Furthermore, the interaction of threading dislocations to form closed loops was evident. Additionally, the effect of GaAs/GaInAs and GaInAs/GaAsP SLS's on dislocation bending was investigated. The former SLS, although not lattice matched to GaAs, proved more effective.

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Strong and robust polarization anisotropy of site- and size-controlled single InGaN/GaN quantum wires

Scientific Reports ◽

10.1038/s41598-020-71590-x ◽

2020 ◽

Vol 10 (1) ◽

Author(s):

Hwan-Seop Yeo ◽

Kwanjae Lee ◽

Young Chul Sim ◽

Seoung-Hwan Park ◽

Yong-Hoon Cho

Keyword(s):

Quantum Wire ◽

Quantum Wires ◽

Geometrical Shape ◽

Optical Polarization ◽

Polarization Anisotropy ◽

Single Quantum ◽

Group Iii ◽

Highly Efficient ◽

Group Iii Nitride ◽

Size Controlled

Abstract Optical polarization is an indispensable component in photonic applications, the orthogonality of which extends the degree of freedom of information, and strongly polarized and highly efficient small-size emitters are essential for compact polarization-based devices. We propose a group III-nitride quantum wire for a highly-efficient, strongly-polarized emitter, the polarization anisotropy of which stems solely from its one-dimensionality. We fabricated a site-selective and size-controlled single quantum wire using the geometrical shape of a three-dimensional structure under a self-limited growth mechanism. We present a strong and robust optical polarization anisotropy at room temperature emerging from a group III-nitride single quantum wire. Based on polarization-resolved spectroscopy and strain-included 6-band k·p calculations, the strong anisotropy is mainly attributed to the anisotropic strain distribution caused by the one-dimensionality, and its robustness to temperature is associated with an asymmetric quantum confinement effect.

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The effect of variable properties and rotation in a visco-thermoelastic orthotropic annular cylinder under the Moore–Gibson–Thompson heat conduction model

Proceedings of the Institution of Mechanical Engineers Part L Journal of Materials Design and Applications ◽

10.1177/1464420720985899 ◽

2021 ◽

pp. 146442072098589

Author(s):

Ahmed E Aboueregal ◽

Hamid M Sedighi

Keyword(s):

Thermal Conductivity ◽

Thermal Stresses ◽

Thermal Conductivity Coefficient ◽

Variable Properties ◽

Transformation Technique ◽

Present Contribution ◽

Conduction Model ◽

Thermoelastic Model ◽

Shock Heating ◽

Physical Fields

The present contribution aims to address a problem of thermoviscoelasticity for the analysis of the transition temperature and thermal stresses in an infinitely circular annular cylinder. The inner surface is traction-free and subjected to thermal shock heating, while the outer surface is thermally insulated and free of traction. In this work, in contrast to the various problems in which the thermal conductivity coefficient is considered to be fixed, this parameter is assumed to be variable depending on the temperature change. The problem is studied by presenting a new generalized thermoelastic model of thermal conductivity described by the Moore–Gibson–Thompson equation. The new model can be constructed by incorporating the relaxation time thermal model with the Green–Naghdi type III model. The Laplace transformation technique is used to obtain the exact expressions for the radial displacement, temperature and the distributions of thermal stresses. The effects of angular velocity, viscous parameter, and variance in thermal properties are also displayed to explain the comparisons of the physical fields.

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