A Refined Model For Threading Dislocation Filtering In InxGa1−xAs/GaSAs Epitaxial Layers

1996 ◽  
Vol 442 ◽  
Author(s):  
G. Macpherson ◽  
P. J. Goodhew
Keyword(s):  
Large Scale ◽  
Critical Thickness ◽  
Thin Layers ◽  
Threading Dislocation ◽  
Threading Dislocations ◽  
Refined Model ◽  
Force Microscopy ◽  
Atomic Force ◽  
Dislocation Densities ◽  
High Level

AbstractA model is presented for the filtering of threading dislocations in InxGa1−xAs/GaAs epitaxial single layers by accurate control of the layer thickness. The model developed differs from previous models since the InxGa1−xAs growth is restricted to less than ten times the Matthews and Blakeslee critical thickness (hc) where the asymmetry in the [110] and [110] dislocation densities is the greatest. Beyond this thickness it is shown that the removal or annihilation of threading dislocations (TDs) in the epilayer is more than offset by the introduction of new TDs from spiral and Frank-Read type sources. Results from strain sensitive etching with CrO3 aqueous solutions show that the TD density can be reduced by up to a factor of ten below that found in the substrate. Atomic force microscopy shows that these thin layers maintain a high level of surface quality with an absence of striations. Evidence is also shown that this type of defect etching is suitable for revealing large scale dislocation blocking in samples that have been grown significantly beyond 10hc.

Defect-Engineered Graded GexSi1-x Buffers on Si (001) with Extreme Low Threading Dislocation Density

1995 ◽  
Vol 378 ◽  
Author(s):  
G. Kissinger ◽  
T. Morgenstern ◽  
G. Morgenstern ◽  
H. B. Erzgräber ◽  
H. Richter
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Atomic Force Microscopy ◽  
Dislocation Density ◽  
Threading Dislocation ◽  
Force Microscopy ◽  
Atomic Force ◽  
Transmission Electron ◽  
Dislocation Densities ◽  
Threading Dislocation Density

AbstractStepwise equilibrated graded GexSii-x (x≤0.2) buffers with threading dislocation densities between 102 and 103 cm−2 on the whole area of 4 inch silicon wafers were grown and studied by transmission electron microscopy, defect etching, atomic force microscopy and photoluminescence spectroscopy.

SiH4 exposure of GaN surfaces: A useful tool for highlighting dislocations

2005 ◽  
Vol 892 ◽  
Author(s):  
Rachel Oliver ◽  
Menno J. Kappers ◽  
Joy Sumner ◽  
Ranjan Datta ◽  
Colin J. Humphreys
Keyword(s):  
Atomic Force Microscopy ◽  
Vapour Phase ◽  
Threading Dislocation ◽  
Vapour Phase Epitaxy ◽  
Force Microscopy ◽  
Atomic Force ◽  
Dislocation Densities ◽  
Metal Organic ◽  
Organic Vapour

AbstractFast-turnaround, accurate methods for the assessment of threading dislocation densities in GaN are an essential research tool. Here, we present an in-situ surface treatment for use in MOVPE (metal-organic vapour phase epitaxy) growth, in which GaN is exposed to a SiH4 flux at 860 °C in the presence of NH3. Subsequent characterisation by atomic force microscopy shows that the treatment is effective in increasing edge and mixed/screw dislocation pit sizes on both n- and p-type material, and on partially coalesced GaN layers.

High Power 330 nm AlInGaN UV LEDs in the High Injection Regime

2003 ◽  
Vol 798 ◽  
Author(s):  
M. Gherasimova ◽  
J. Su ◽  
G. Cui ◽  
J. Han ◽  
H. Peng ◽  
...  
Keyword(s):  
Light Emitting Diode ◽  
Threading Dislocation ◽  
Light Emitting ◽  
Force Microscopy ◽  
Sapphire Substrates ◽  
Atomic Force ◽  
Transmission Electron ◽  
Dislocation Densities ◽  
Dimensional Growth ◽  
Uv Leds

ABSTRACTWe report on the growth and testing of the light emitting diode structures incorporating quaternary AlInGaN active region with an emission wavelength of 330 nm. Small area circular devices were fabricated, yielding the output power of 110 μW measured with a bare-chip configuration in a high current injection regime (8 kA/cm2 for a 20 μm diameter device). Structural properties of the constituent epitaxial layers were evaluated by atomic force microscopy and transmission electron microscopy, resulting in the observation of two-dimensional growth morphologies of AlN and AlGaN, and the estimate of threading dislocation densities in the low 109 cm-2 range in the structures grown on sapphire substrates.

scholarly journals The effect of periodic silane burst on the properties of GaN on Si (111) substrates

2004 ◽  
Vol 831 ◽  
Author(s):  
K. Y. Zang ◽  
S. J. Chua ◽  
C. V. Thompson ◽  
L. S. Wang ◽  
S. Tripathy ◽  
...  
Keyword(s):  
Chemical Vapor ◽  
Buffer Layers ◽  
Threading Dislocation ◽  
X Ray Diffraction ◽  
Force Microscopy ◽  
Atomic Force ◽  
Transmission Electron ◽  
Dislocation Densities ◽  
Gan On Si ◽  
Aln Buffer

ABSTRACTThe periodic silane burst technique was employed during metalorganic chemical vapor deposition of epitaxial GaN on AlN buffer layers grown on Si (111). Periodic silicon delta doping during growth of both the AlN and GaN layers led to growth of GaN films with decreased tensile stresses and decreased threading dislocation densities, as well as films with improved quality as indicated by x-ray diffraction, micro-Raman spectroscopy, atomic force microscopy, and transmission electron microscopy. The possible mechanism of the reduction of tensile stress and the dislocation density is discussed in the paper.

scholarly journals Pinholes, Dislocations and Strain Relaxation in InGaN

1998 ◽  
Vol 3 ◽  
Author(s):  
B. Jahnen ◽  
M. Albrecht ◽  
W. Dorsch ◽  
S. Christiansen ◽  
H. P. Strunk ◽  
...  
Keyword(s):  
Critical Thickness ◽  
Strain Relaxation ◽  
Threading Dislocations ◽  
Misfit Dislocations ◽  
Slip Systems ◽  
Force Microscopy ◽  
Atomic Force ◽  
Transmission Electron ◽  
Wurtzite Lattice ◽  
Means Of Transmission

We analyse by means of transmission electron microscopy (TEM) and atomic force microscopy (AFM) the strain relaxation mechanisms in InGaN layers on GaN as dependent on the In content. At the experimentally given thickness of 100 nm, the layers remain coherently strained, up to an In concentration of 14 %. We show that part of the strain is reduced elastically by formation of hexagonally facetted pinholes. First misfit dislocations are observed to form at pinholes that reach the InGaN/GaN interface. We discuss these results in the framework of the Matthews-Blakeslee model for the critical thickness considering the Peierls force for glide of threading dislocations in the different slip systems of the wurtzite lattice.

Crack Nucleation in AlGaN/GaN Heterostructures

2002 ◽  
Vol 743 ◽  
Author(s):  
Peter J. Parbrook ◽  
Malcolm A. Whitehead ◽  
Richard J. Lynch ◽  
Robert T. Murray
Keyword(s):  
Critical Thickness ◽  
Crack Nucleation ◽  
Threading Dislocations ◽  
Strained Layers ◽  
Force Microscopy ◽  
Atomic Force ◽  
Close Proximity ◽  
Stage Process ◽  
Highly Strained ◽  
Crack Array

ABSTRACTThe tensile strain in AlGaN layers on GaN is well established to lead to cracking if a critical thickness is reached, unless measures such as interlayers are applied to prevent their formation. However in devices, such as HFETs such an approach is impractical. Growth of AlGaN-GaN structures was carried out by MOVPE using a standard two stage process for the growth of the GaN on sapphire. The crack structures were examined by optical and atomic force microscopy. Studies on thin AlGaN layers on GaN close to the crack critical thickness show the stress centres from which the cracks propagate are threading dislocations with cracks often initially forming to link together these stress centres if they are in close proximity. These cracks then extend and “lock” into the generally observed 〈2110〉 direction in more highly strained layers. A macroscopically uniform crack array is observed in these thin AlGaN samples.

The Investigation of Thin Protecting Layers on Roughened Galvanized Steel Surfaces Produced by Different Coating Methods

2008 ◽  
Vol 589 ◽  
pp. 433-438 ◽  
Author(s):  
Péter Németh ◽  
Ágnes Csanády ◽  
Katalin Papp ◽  
Anna C. Pintér ◽  
László Szabó ◽  
...  
Keyword(s):  
Thickness Distribution ◽  
Thin Layers ◽  
Galvanized Steel ◽  
Photoemission Spectroscopy ◽  
Force Microscopy ◽  
Atomic Force ◽  
Coating Methods ◽  
Chemical States ◽  
Steel Surfaces ◽  
Thickness Variations

Protective, chromate substitute thin layers on roughened galvanized surfaces produced at OCAS (Arcelor, Belgium) were characterized and compared using Scanning Electron Microscopy (SEM+EDS), Atomic Force Microscopy (AFM), Nanoindentation and X-ray Photoemission Spectroscopy (XPS). EDX maps, line scans and point analyses obtained at various places of the surfaces have shown differences between the CVD and silane nanolayers in the matter of thickness distribution and composition. At cross-section specimens the thickness of the layers could be shown. The hardness differences caused by layer thickness variations are hard to follow by nanoindentation as the penetration depth of the indenter is much larger than the thickness of the coatings. XPS measurements can distinguish between the chemical states of silicon in CVD and silane coatings.

Characterization of High Quality, Large-Scale Growth of Monolayer WS2 Domains via Chemical Vapor Deposition Technique

2021 ◽  
Author(s):  
Somayeh Asgary ◽  
Amir Hoshang Ramezani ◽  
Zhaleh Ebrahimi Nejad
Keyword(s):  
Large Scale ◽  
Average Length ◽  
Chemical Vapor ◽  
Growth Time ◽  
High Quality ◽  
Force Microscopy ◽  
Atomic Force ◽  
Regular Triangle ◽  
Vapor Deposition Technique

Abstract WS2 flakes have been grown successfully on SiO2 substrate via chemical vapor (CVD) deposition method by reduction and sulfurization of WO3 using Ar/ H2 gas and sulfur evaporated from solid sulfur powder. The prepared samples were characterized by optical microscopy (OM), atomic force microscopy (AFM), scanning electron microscopy (SEM), Raman spectra and photoluminescence (PL). Large domain WS2 monolayers are obtained by extending the growth time. The perfect triangular single-crystalline WS2 flakes with an average length of more than 35 µm were achieved. The sharp PL peak (∼1.98 eV) and two distinct Raman peaks (E2g and A1g) with a ∼ 71.5 cm-1 peak split indicating that relatively high quality WS2 crystals with a regular triangle shape can be synthesized. Higher growth time shows larger triangular-shaped of WS2.

scholarly journals Large-scale analysis of high-speed atomic force microscopy data sets using adaptive image processing

2012 ◽  
Vol 3 ◽  
pp. 747-758 ◽  
Author(s):  
Blake W Erickson ◽  
Séverine Coquoz ◽  
Jonathan D Adams ◽  
Daniel J Burns ◽  
Georg E Fantner
Keyword(s):  
High Speed ◽  
Large Scale ◽  
Data Sets ◽  
Force Microscopy ◽  
Topographic Features ◽  
Atomic Force ◽  
Large Scale Analysis ◽  
Adaptive Image Processing ◽  
True Representation ◽  
Microscopy Data

Modern high-speed atomic force microscopes generate significant quantities of data in a short amount of time. Each image in the sequence has to be processed quickly and accurately in order to obtain a true representation of the sample and its changes over time. This paper presents an automated, adaptive algorithm for the required processing of AFM images. The algorithm adaptively corrects for both common one-dimensional distortions as well as the most common two-dimensional distortions. This method uses an iterative thresholded processing algorithm for rapid and accurate separation of background and surface topography. This separation prevents artificial bias from topographic features and ensures the best possible coherence between the different images in a sequence. This method is equally applicable to all channels of AFM data, and can process images in seconds.

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