Correlation of threading screw dislocation density to GaN 2‐DEG mobility

ABSTRACTPorous 6H-SiC and 4H-SiC wafers formed by anodization have been characterized in this study prior to and following the CVD deposition of SiC epitaxial layers, using a combination of synchrotron white beam x-ray topography (SWBXT), SEM, TEM and optical microscopy. Under the high temperatures employed during epitaxial growth, a significant change in pore morphology occurs. While no evidence of reduced screw dislocation density in the epilayers is obtained, a small tilt of the epilayers with respect to the porous substrate observed on x-ray topographs could play a role in limiting penetration of defects from the substrate.

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Study of Edge and Screw Dislocation Density in GaN/Al2O3 Heterostructure

Materials ◽

10.3390/ma12244205 ◽

2019 ◽

Vol 12 (24) ◽

pp. 4205 ◽

Cited By ~ 1

Author(s):

Vladimir Lucian Ene ◽

Doru Dinescu ◽

Iulia Zai ◽

Nikolay Djourelov ◽

Bogdan Stefan Vasile ◽

...

Keyword(s):

High Resolution ◽

Dislocation Density ◽

Screw Dislocation ◽

Diffusion Length ◽

Correlation Lengths ◽

Transmission Electron ◽

Aln Buffer ◽

Gan Film ◽

Defect Densities ◽

Screw Dislocation Density

This study assesses the characteristics (edge and screw dislocation density) of a commercially available GaN/AlN/Al2O3 wafer. The heterostructure was evaluated by means of high-resolution X-ray diffraction (HR-XRD), high-resolution transmission electron microscopy (HR-TEM), and Doppler-Broadening Spectroscopy (DBS). The results were mathematically modeled to extract defect densities and defect correlation lengths in the GaN film. The structure of the GaN film, AlN buffer, Al2O3 substrate and their growth relationships were determined through HR-TEM. DBS studies were used to determine the effective positron diffusion length of the GaN film. Within the epitaxial layers, defined by a [GaN P 63 m c (0 0 0 2) || P 63 m c AlN (0 0 0 2) || (0 0 0 2) R 3 ¯ c Al2O3] relationship, regarding the GaN film, a strong correlation between defect densities, defect correlation lengths, and positron diffusion length was assessed. The defect densities ρ d e = 6.13 × 1010 cm−2, ρ d s = 1.36 × 1010 cm−2, along with the defect correlation lengths Le = 155 nm and Ls = 229 nm found in the 289 nm layer of GaN, account for the effective positron diffusion length Leff~60 nm.

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The Use of AlN Interlayers to Improve GaN Growth on A-Plane Sapphire

MRS Proceedings ◽

10.1557/proc-587-o7.3 ◽

1999 ◽

Vol 587 ◽

Author(s):

D.D. Koleske ◽

M.E. Twigg ◽

A.E. Wickenden ◽

R.L. Henry ◽

R.J. Gorman ◽

...

Keyword(s):

Dislocation Density ◽

Screw Dislocation ◽

Film Growth ◽

Fold Increase ◽

Large Area ◽

Cross Sectional ◽

Acceptor Concentration ◽

Si Doped ◽

Gan Film ◽

Screw Dislocation Density

AbstractThe lack of a suitable, lattice matched substrate for the growth of the group III nitrides typically restricts GaN film growth to substrates such as sapphire or SiC, despite the large lattice and thermal mismatch. With the use of AlN or GaN nucleation layers (NL), GaN films of sufficient quality have been produced for blue LEDs. However, for laser and large-area microwave device applications, the large number of dislocations (> 108 cm−2) limit device performance, and techniques are desired to reduce dislocation density during the growth process. Here, we demonstrate how low temperature AlN interlayers (IL) sandwiched between high temperature (HT) GaN layers can be used to improve the electrical, optical, and structural properties of Si doped GaN films. A nearly two-fold increase in mobility is observed in Si doped GaN grown using 5 AlN IL compared to GaN grown on a single AlN NL. For GaN films grown on multiple AlN IL, cross-sectional transmission electron microscopy images reveal a significant reduction in the screw dislocation density and photoluminescence spectra reveal a reduction in yellow band intensity. An analysis of the electrical data based on a single donor/single acceptor model suggests that the improved electron mobility is the result of a reduced acceptor concentration in the top GaN film. The reduction in the calculated acceptor concentration may be associated with the reduction of the screw dislocation density.

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Quantitative Analysis of the Recovery Process in Pure Iron Using X-ray Diffraction Line Profile Analysis

Materials ◽

10.3390/ma14040895 ◽

2021 ◽

Vol 14 (4) ◽

pp. 895

Author(s):

Shota Sugiyama ◽

Toshio Ogawa ◽

Lei He ◽

Zhilei Wang ◽

Yoshitaka Adachi

Keyword(s):

Quantitative Analysis ◽

Dislocation Density ◽

Screw Dislocation ◽

Edge Dislocation ◽

Pure Iron ◽

Annealing Temperature ◽

Dislocation Core ◽

Recovery Process ◽

Line Profile Analysis ◽

Screw Dislocation Density

We conducted quantitative analysis of the recovery process during pure iron annealing using the modified Williamson-Hall and Warren-Averbach methods. We prepared four types of specimens with different dislocation substructures. By increasing the annealing temperature, we confirmed a decrease in dislocation density. In particular, screw-dislocation density substantially decreased in the early stage of the recovery process, while edge-dislocation density gradually decreased as annealing temperature increased. Moreover, changes in hardness during the recovery process mainly depended on edge-dislocation density. Increases in annealing temperature weakly affected the dislocation arrangement parameter and crystallite size. Recovery-process modeling demonstrated that the decrease in screw-dislocation density during the recovery process was mainly dominated by glide and/or cross-slip with dislocation core diffusion. In contrast, the decrease in edge-dislocation density during the recovery process was governed by a climbing motion with both dislocation core diffusion and lattice self-diffusion. From the above results, we succeeded in quantitatively distinguishing between edge- and screw-dislocation density during the recovery process, which are difficult to distinguish using transmission electron microscope and electron backscatter diffraction.

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Effect of screw dislocation density on optical properties in n-type wurtzite GaN

Journal of Applied Physics ◽

10.1063/1.2407455 ◽

2007 ◽

Vol 101 (2) ◽

pp. 023516 ◽

Cited By ~ 15

Author(s):

Jeong Ho You ◽

H. T. Johnson

Keyword(s):

Optical Properties ◽

Dislocation Density ◽

Screw Dislocation ◽

Screw Dislocation Density

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Correlation betweenJ c and screw dislocation density in sputtered YBa2Cu3O7-? films

Zeitschrift für Physik B Condensed Matter ◽

10.1007/bf01313823 ◽

1992 ◽

Vol 86 (2) ◽

pp. 177-181 ◽

Cited By ~ 106

Author(s):

J. Mannhart ◽

D. Anselmetti ◽

J. G. Bednorz ◽

A. Catana ◽

Ch. Gerber ◽

...

Keyword(s):

Dislocation Density ◽

Screw Dislocation ◽

Screw Dislocation Density

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Study of Dislocation Densities of Thick GaN Films

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.989-994.387 ◽

2014 ◽

Vol 989-994 ◽

pp. 387-390

Author(s):

Yon Gan Li ◽

Xiang Qian Xiu ◽

Xue Mei Hua ◽

Shi Ying Zhang ◽

Shi Pu Gu ◽

...

Keyword(s):

High Resolution ◽

Dislocation Density ◽

Screw Dislocation ◽

Edge Dislocation ◽

Thick Films ◽

X Ray Diffraction ◽

X Ray ◽

Dislocation Densities ◽

Edge Dislocations

The dislocation density of GaN thick films has been measured by high-resolution X-ray diffraction. The results show that both the edge dislocations and the screw dislocation reduce with increasing the GaN thickness. And the edge dislocations have a larger fraction of the total dislocation densities, and the densities for the edge dislocation with increasing thickness reduce less in contrast with those for the screw dislocation.

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Influence of the Dislocation Density on the Expansion Dynamics of the Crystallographic Slip Zone along Screw Orientations in Aluminum and Copper

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.683.136 ◽

2016 ◽

Vol 683 ◽

pp. 136-141 ◽

Cited By ~ 2

Author(s):

Yulia Petelina ◽

Svetlana Kolupaeva ◽

Konstantin A. Polosukhin ◽

Aleksander Petelin

Keyword(s):

Kinetic Energy ◽

Dislocation Density ◽

Screw Dislocation ◽

Elastic Interaction ◽

Interaction Force ◽

Dislocation Source ◽

Study Results ◽

Crystallographic Slip ◽

Pile Up ◽

Expansion Model

Crystallographic slip is one of key mechanisms determining plastic form change of crystalline solids. Despite a large amount of works done on the subject, crystallographic slip is a very difficult subject to study. Significant progress in the study of the crystallographic slip process is possible only with the use of a set of different methods: experimental methods, methods of mathematical modeling and simulation. The paper presents a modification mathematical expansion model of closed dislocations emitted by one dislocation source with takes into account the elastic interaction force among all dislocations of the forming dislocation pile-up. The model takes into account the Peach-Koehler forces, lattice, impurity, and dislocation friction, linear tension, viscous deceleration, and the intensity of generation of point defects beyond jogs on the dislocation, as well as the elastic interaction force among all dislocations of the forming dislocation pile-up. The analysis of the study results on the expansion dynamics of the dislocation loop along the screw orientation on copper and aluminum with varying of the dislocation density from 3×1011 m−2 to 1012 m−2 is carried out. It is established that the length and the path time of the screw dislocation, as well as the number of dislocations emitted by the dislocation source, essentially depend on the density of dislocations. The dependence of the current radius, velocity, and kinetic energy of the screw dislocation on the path time and the dependence of the current velocity and the kinetic energy of the first screw dislocation emitted by the dislocation source on its current radius are described.

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Suppression of Polytype Transformation with Extremely Low-Dislocation-Density 4H-SiC Crystal in Two-Step Solution Method

Materials Science Forum ◽

10.4028/www.scientific.net/msf.924.60 ◽

2018 ◽

Vol 924 ◽

pp. 60-63 ◽

Cited By ~ 1

Author(s):

Kenta Murayama ◽

Shunta Harada ◽

Fumihiro Fujie ◽

Xin Bo Liu ◽

Ryota Murai ◽

...

Keyword(s):

Dislocation Density ◽

Screw Dislocation ◽

Basal Plane ◽

Solution Method ◽

Threading Dislocations ◽

High Quality ◽

Seed Crystals ◽

Low Dislocation Density ◽

Step Growth ◽

Polytype Transformation

We achieved the growth of extremely-high quality SiC crystal with two-step solution method with specially-designed seed crystals. The two-step growth consists of 1st step growth on Si-face for the reduction of threading dislocations and 2nd step growth on C-face for the reduction of basal plane dislocations and thickening. In this method, we can make the dislocation density extremely low, while the polytype easily changes during growth due to the absence of spiral hillocks originating from threading screw dislocation (TSD). In this study, we prepared specially designed seed crystals for both 1st and 2nd growth steps to provide steps continuously. In the seeds, a few TSDs exist at the upper-side of the step structure. Consequently, we demonstrated the suppression of the polytype transformation during the C-face growth with extremely low-dislocation-density crystal. Accordingly, we successfully obtained extremely low-dislocation density 4H-SiC with TSD, TED and BPD density of 11, 385 and 28 cm-2.

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The Effect of Surface Finish on the Dislocation Density in Sublimation grown SiC Layers

MRS Proceedings ◽

10.1557/proc-640-h1.3 ◽

2000 ◽

Vol 640 ◽

Author(s):

E. K. Sanchez ◽

J. Liu ◽

W. M. Vetter ◽

M. Dudley ◽

R. Bertke ◽

...

Keyword(s):

Silicon Carbide ◽

Dislocation Density ◽

Surface Finish ◽

Etch Rate ◽

Screw Dislocations ◽

Dislocations Density ◽

Edge Dislocations ◽

Screw Dislocation Density ◽

Diamond Paste ◽

Effect Of Surface

ABSTRACTThe effect of the seed surface finish on the dislocation density of sublimation grown silicon carbide was investigated. Growth on seeds that were polished down to 1 μm diamond paste resulted in the nucleation of threading screw dislocations in a density of 106 cm−2 and threading edge dislocations in densities of 107 cm−2. Following the mechanical polish of the seeds with a hydrogen etch or chemo-mechanical polish prior to growth resulted in the screw dislocation density decreasing by four orders of magnitude and the threading edge dislocation density dropping two orders of magnitude. Using the dislocations density and the hydrogen etch rate, the depth of damage in mechanically damaged seeds was determined to be between 400 and 1000 Å.

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