Dislocation Distribution in Graded Composition IngaAs Layers

1993 ◽  
Vol 325 ◽  
Author(s):  
S.I. Molina ◽  
G. Gutiérrez ◽  
A. Sacedón ◽  
E. Calleja ◽  
R. García
Keyword(s):  
Detection Limit ◽  
Dislocation Density ◽  
Layer Thickness ◽  
Gaas Substrate ◽  
Ingaas Layer ◽  
Constant Composition ◽  
Defect Distribution ◽  
Dislocation Distribution

The defect distribution of a graded composition InGaAs layer grown on GaAs by MBE has been characterized by TEM (XTEM, PVTEM, HREM). The observed configuration does not correspond completely with that theoretically predicted. Dislocation misfit segments are in a quantity much bigger than in constant composition layers. Dislocation density is quite uniform up to a certain layer thickness t1. Few dislocations are observed between this t1 thickness and a larger thickness t2. Dislocation density is below the detection limit of XTEM for thicknesses bigger than t2. Some dislocations are observed to penetrate in the GaAs substrate.Several mechanisms (reactions between 600 dislocations, Hagen-Strunk and modified Frank-Read processes) are proposed to explain the interactions of dislocations in the epilayer and their penetration in the substrate.

Misfit Dislocations at the Critical Thickness for Ingaas/Gaas Strained Layers

1990 ◽  
Vol 202 ◽  
Author(s):  
G. S. Green ◽  
B. K. Tanner ◽  
A. G. Turnbull ◽  
S. J. Barnett ◽  
M. Emeny ◽  
...  
Keyword(s):  
Dislocation Density ◽  
Gaas Substrate ◽  
Critical Thickness ◽  
Thickness Variation ◽  
Misfit Dislocations ◽  
Ingaas Layer ◽  
Double Crystal ◽  
Strained Layers ◽  
Interference Fringes ◽  
Symmetric Reflection

ABSTRACTThe contrast of misfit dislocations in an InGaAs layer, close to the critical thickness and capped with GaAs grown by MBE on a (001) oriented GaAs substrate has been investigated by double axis synchrotron X-radiation topography. The layer thickness variation as a function of position has been measured to a precision of 1A by matching interference fringes observed in the 004 symmetric reflection double crystal rocking curves with simulations. The misfit dislocation density is highly anisotropic, varying from zero to a high value with increasing thickness. The contrast of the dislocations in the 004, 224 and 044 reflections has been examined in detail. All of the long dislocation segments characterized were 60° in character with ½<110> Burgers vectors inclined to the specimen surface. No dislocations were found which did not appear to be of this type. A surprising difference in contrast of the background in the 224 and 224 reflections is discussed.

Anisotropic Lattice Relaxation and its Mechanism of ZnSe Epilayer Grown on (001) GaAs Substrate by Molecular Beam Epitaxy

1995 ◽  
Vol 399 ◽  
Author(s):  
C.S. Kim ◽  
S.K. Noh ◽  
H.J. Lee ◽  
Y.K. Cho ◽  
Y.I. Kim ◽  
...  
Keyword(s):  
Dislocation Density ◽  
Gaas Substrate ◽  
Molecular Beam ◽  
Rotation Angle ◽  
Lattice Relaxation ◽  
High Dislocation Density ◽  
Sinusoidal Oscillation ◽  
Double Crystal ◽  
X Ray ◽  
Anisotropic Lattice

ABSTRACTWe have investigated anisotropic lattice relaxation and its mechanism of ZnSe epitaxial layer grown on (001) GaAs substrate by MBE. Double-crystal X-ray rocking curves for (004), {115} and {404} reflections were measured as a function of the azimuthal rotation angle of the sample. We observed the sinusoidal oscillation of the FWHM of the epilayer peak for (004) reflections due to the asymmetric dislocation density along two orthogonal <110> directions, and the direction of the maximum FWHM corresponding to high dislocation density is along [110]. In addition, the strain along [110] is smaller than that along [1-10], indicating that the layer suffered anisotropic lattice relaxation. The direction of larger relaxation([l-10]) is not consistent with that of high dislocation density([110]). The results suggest that the asymmetry in dislocation density is not responsible for the anisotropic relaxation of the ZnSe epilayer.

The Critical Thickness of Layers Subject to Anisotropic Misfit.

1991 ◽  
Vol 239 ◽  
Author(s):  
Richard Beanland
Keyword(s):  
Dislocation Density ◽  
Layer Thickness ◽  
Critical Thickness ◽  
Theoretical Calculations ◽  
Critical Layer ◽  
Epitaxial Layers ◽  
Misfit Dislocations ◽  
Critical Layer Thickness ◽  
New Formulation

ABSTRACTIt is well known that it becomes energetically favourable for misfit dislocations to be introduced into strained epitaxial layers above a certain ‘critical’ layer thickness, hc. To date, theoretical calculations of hc have only been made for cases of isotropie misfit - i.e. cases where the misfit is the same for every direction in the interface. Using a new formulation of the Frank-Bilby equation and the concept of coherency dislocations, it is now possible to treat cases of anisotropie misfit, such as silicon on sapphire (SOS). The method used to obtain the critical thickness is described, and values of hc and equilibrium dislocation density are given for various materials systems.

Experiments and analysis of the two-step growth of InGaAs on GaAs substrate

CrystEngComm ◽  
2015 ◽  
Vol 17 (30) ◽  
pp. 5808-5813 ◽  
Author(s):  
Jinping Li ◽  
Guoqing Miao ◽  
Zhiwei Zhang ◽  
Yugang Zeng
Keyword(s):  
Dislocation Density ◽  
Epitaxial Layer ◽  
Gaas Substrate ◽  
Density Reduction ◽  
Step Growth

In this highlight, a mechanism has been proposed to explain the dislocation density reduction in the epitaxial layer by a LT-buffer.

scholarly journals Theoretical description of the ligand function for ionoselective electrodes reversible to metal anion complexes. 1. Lower detection limit and its determining factors

2020 ◽  
pp. 17-28
Author(s):  
Vladimir V. Egorov ◽  
Andrei V. Semenov ◽  
Andrei D. Novakovskii ◽  
Yauhen B. Akayeu
Keyword(s):  
Detection Limit ◽  
Layer Thickness ◽  
Diffusion Layer ◽  
Theoretical Description ◽  
Diffusion Layer Thickness ◽  
Thiocyanate Ion ◽  
Lower Detection Limit ◽  
Diffusion Parameters ◽  
Lower Detection ◽  
And Diffusion

Within the framework of the steady-state diffusion model, the theoretical description for the thiocyanate ion lower detection limit (LDL) by the tetrathiocyanatozincate selective electrode, has been presented. The main assumptions of this model are constancy of the ion exchanger concentration along the membrane, traditionally used in various phaseboundary potential diffusion models, and linear profiles of components’ concentrations in diffusion layers. Simple quantitative expressions have been obtained, connecting thiocyanate ion concentration in the solution surface layer (responsible for LDL value) with phase boundary extraction equilibria constants, stability constants for zinc thiocyanate complexes, and diffusion parameters in the membrane and solution phases. Calculated LDL values are in good agreement with experimental data provided in the literature. It has been shown that LDL can be reduced substantially by controlling such easily regulated diffusion parameters as diffusion layer thickness in the membrane phase, which is a function of time, and diffusion layer thickness of the sample solution, which is governed by stirring regime.

Defects and Electrical Properties of Crystalline Silicon at Different Metallurgical Route

2013 ◽  
Vol 420 ◽  
pp. 134-138
Author(s):  
Hui Xian Lai ◽  
Liu Qing Huang ◽  
Ming Fang ◽  
Cheng Hao Lu ◽  
Juan Chen ◽  
...  
Keyword(s):  
Electrical Properties ◽  
Dislocation Density ◽  
Crystalline Silicon ◽  
Acid Leaching ◽  
Refining Slag ◽  
Dislocation Distribution ◽  
Vacuum Refining ◽  
Slag Treatment ◽  
Individual Grains ◽  
Dislocation Formation

To investigate the effects of the metallurgical route on the defects in mc-Si, various metallurgical routes were conducted. Dislocation formation and the resistivity of the mc-Si were also studied. The results showed that high inhomogeneity in dislocation distribution within individual grains and paralleled tacking faults could be observed when the ingot was grown by using the feedstock prepared by adopting the sequence of slag treatment, acid leaching and vacuum refining. Different grains have various dislocation density, which was showed in ingot grown by utilizing the feedstock prepared by adopting the sequence of vacuum refining, slag treatment and acid leaching, tacking faults could also be seen, as well as some dislocation clusters. The resistivity of this two ingots was detected at various height by using the a 4-point probe silicon tester, it was expected that the resistivity of these two ingots has the same tendency of the change, and the value of the resistivity of the ingot obtained using the previous technology was relatively higher than that of the ingot obtained using the latter technology.

Analysis of Inhomogeneous Dislocation Distribution in Multicrystalline Si

2013 ◽  
Vol 205-206 ◽  
pp. 77-82
Author(s):  
Jun Chen ◽  
Ronit R. Prakash ◽  
Jian Yong Li ◽  
Karolin Jiptner ◽  
Yoshiji Miyamura ◽  
...  
Keyword(s):  
Solar Cells ◽  
Grain Boundary ◽  
Grain Boundaries ◽  
Crystal Orientation ◽  
Photovoltaic Performance ◽  
Defect Distribution ◽  
Dislocation Distribution ◽  
Boundary Character ◽  
Geometrical Effect ◽  
Crystallographic Defects

Grain boundaries and dislocations are major crystallographic defects in multicrystalline Si materials for solar cells. Heavily dislocated grains are detrimental to the photovoltaic performance. This paper attempts to clarify the origin of inhomogeneous defect distribution in multicrystalline Si. The impacts of crystal orientation and grain boundary were investigated. The crystal orientation gives an important geometrical effect in the possibility of initiating slip in a grain when subjected to stress. The presence of grain boundary can also affect dislocation distribution depending on boundary character.

High Resolution X-ray Diffraction Analysis of GaN-Based Heterostructures Grown by OMVPE

1996 ◽  
Vol 449 ◽  
Author(s):  
M.S. Goorsky ◽  
A.Y. Polyakov ◽  
M. Skowronski ◽  
M. Shin ◽  
D.W. Greve
Keyword(s):  
High Resolution ◽  
Dislocation Density ◽  
Layer Thickness ◽  
Vapor Phase ◽  
Edge Dislocation ◽  
Initial Level ◽  
X Ray Diffraction ◽  
X Ray ◽  
Crystal Perfection ◽  
Misorientation Angles

ABSTRACTWe demonstrate the use of triple axis diffraction measurements, including Φ scans (in which the sample is rotated about an axis perpendicular to its surface) to assess the crystal perfection of wurtzite GaN layers on sapphire grown using different pre-nitridation growth treatments by or-ganometallic vapor phase epitaxy. The Φ scans determine the in-plane misorientation angles between the crystallites and hence provide information on the edge dislocation density. Using glancing incidence (1014) and (1015) reflections, we determined that the misorientation among the GaN crystallites decreases with increasing layer thickness and that the pre-nitridation conditions control the initial level of misorientation. Triple axis ω and ω-2θ scans around the (0002) reflection did not show a systematic trend with increasing layer thickness. However, layers grown without a pre-nitridation step tended to exhibit higher values of both mosaic spread and strain. The appropriate asymmetric reflections for GaN-based Φ scan measurements are determined using structure factor calculations, which are presented here.

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