Elastic Stresses in InGaAsP Heterostructures with Alloyed Contact Metallizations

1986 ◽  
Vol 77 ◽  
Author(s):  
V. Swaminathan ◽  
J. Lopata ◽  
J. W. Lee
Keyword(s):  
Active Layer ◽  
Lattice Mismatch ◽  
Compressive Strain ◽  
Control Technique ◽  
Bragg Angle ◽  
Radius Of Curvature ◽  
Elastic Stresses ◽  
Inp Substrate ◽  
Heterostruc Ture ◽  
Order Of Magnitude

ABSTRACTWe have measured the radius of curvature of InGaAsP/InP heterostruc-ture wafers grown by liquid phase epitaxy, after growth and after broad area p-and n-metallizations used in the fabrication of 1.3vm lasers, by the x-ray automatic Bragg angle control technique. The heterostructure consisted of an n-InP buffer layer (0.2μm), an InGaAsP active layer (0.3 – 0.4μm), a p-InP layer (0.7μm) and either a p-InGaAsP or a p-InGaAs cap layer (0.6 – 0.7μm) grown on a 250 μm thick n-Inp substrate. The radius of curvature measured after growth was found to be in good agreement with the value calculated using the lattice mismatch strains. The changes in the radius of curvature after deposition and alloying of a 1000 Å thick AuZnAu p-metallization and after thinning the substrate to 86μu followed by 2900 Å thick alloyed GeAu n-metallization are such that the metal films are under a tensile strain. The value of the strain is calculated to be 8 × 10-3 and 1.6 × 10-3 respectively for the p- and n-metals. The radius of curvature was measured after the final metallization and annealing of 2500 A thick TiPt layer on the p-side. The annealed TiPt layer was found to have a compressive strain of 6 × 10-3. The stress in the active layer remained tensile at all times for both wafers and it was in the range 9 × 10 – 1.4 × 10 dyne cm-2. These values are less than the estimated fracture stress of InGaAsP by an order of magnitude.

Strain Analysis in Thin La1−xCaxMnO3 Films by Grazing Incidence X-ray Scattering

1999 ◽  
Vol 602 ◽  
Author(s):  
M. Petit ◽  
L. J. Martinez-Miranda ◽  
M. Rajeswari ◽  
A. Biswas ◽  
D. J. Kang ◽  
...  
Keyword(s):  
Film Thickness ◽  
Lattice Mismatch ◽  
Compressive Strain ◽  
Strain Analysis ◽  
Grazing Incidence ◽  
Relaxation Processes ◽  
Near Surface ◽  
X Ray ◽  
X Ray Scattering ◽  
Ray Scattering

AbstractWe have performed depth profile analyses of the lattice parameters in epitaxial thin films of La1−xCaxMno3 (LCMO), where x = 0.33 or 0.3, to understand the evolution of strain relaxation processes in these materials. The analyses were done using Grazing Incidence X-ray Scattering (GIXS) on films of different thicnesses on two different substrates, (100) oriented LaAlO3 (LAO), with a lattice mismatch of ∼2% and (110) oriented NGO, with a lattice mismatch of less than 0.1%. Films grown on LAO can exhibit up to three in-plane strained lattice constants, corresponding to a slight orthorhombic distortion of the crystal, as well as near-surface and columnar lattice relaxation. As a function of film thickness, a crossover from a strained film to a mixture of strained and relaxed regions in the film occurs in the range of 700 Å. The structural evolution at this thickness coincides with a change in the resistivity curve near the metalinsulator transition. The in-plane compressive strain has a range of 0.2 – 1.5%, depending on the film thickness for filsm in the range of 400 - 1500 A.

Transferred-Substrate InGaAsP-Based Thermionic Emission Coolers

2000 ◽  
Author(s):  
Christopher J. LaBounty ◽  
Gerry Robinson ◽  
Patrick Abraham ◽  
Ali Shakouri ◽  
John E. Bowers
Keyword(s):  
Thermal Resistance ◽  
Three Dimensional ◽  
Thermionic Emission ◽  
Copper Film ◽  
Cooling Power ◽  
Material System ◽  
Inp Substrate ◽  
Order Of Magnitude ◽  
Thin Copper Film ◽  
Thermally Conducting

Abstract Most optoelectronic devices are based on III-V semiconductors such as the InP/InGaAsP material system. Solid state refrigerators based on the same material system can be monolithically integrated with optoelectronics. Thermionic emission cooling in InGaAsP-based heterostructures has been shown experimentally to provide cooling power densities of several 100 W/cm2. Cooling by several degrees across thin films on the order of a micron thick has been demonstrated. Thermionic emission of hot electrons over heterobarriers allows for enhanced cooling power beyond what is possible from the bulk thermoelectric properties. The thermal resistance of the InP substrate between the hot side of the thin film cooler and the heat sink is found to be a limitation in cooler performance. Several possibilities are examined for replacing the InP substrate with a higher thermally conducting one such as silicon, copper, or even diamond, and a process for substrate transfer to a thin copper film has been developed. Three-dimensional simulations predict an order of magnitude improvement in the thermal resistance of the substrate. Experimental results of packaged InGaAsP coolers with copper substrates will be discussed.

scholarly journals Electron Density and Its Relation with Electronic and Optical Properties in 2D Mo/W Dichalcogenides

Nanomaterials ◽  
2020 ◽  
Vol 10 (11) ◽  
pp. 2221
Author(s):  
Pingping Jiang ◽  
Marie-Christine Record ◽  
Pascal Boulet
Keyword(s):  
Optical Properties ◽  
Lattice Mismatch ◽  
Compressive Strain ◽  
Interatomic Interaction ◽  
Structure Property ◽  
Electronic And Optical Properties ◽  
Cubic Equation ◽  
Structure Property Relationships ◽  
Stacking Order ◽  
Structures And Properties

Two-dimensional MX2 (M = Mo, W; X = S, Se, Te) homo- and heterostructures have attracted extensive attention in electronics and optoelectronics due to their unique structures and properties. In this work, the layer-dependent electronic and optical properties have been studied by varying layer thickness and stacking order. Based on the quantum theory of atoms in molecules, topological analyses on interatomic interactions of layered MX2 and WX2/MoX2, including bond degree (BD), bond length (BL), and bond angle (BA), have been detailed to probe structure-property relationships. Results show that M-X and X-X bonds are strengthened and weakened in layered MX2 compared to the counterparts in bulks. X-X and M-Se/Te are weakened at compressive strain while strengthened at tensile strain and are more responsive to the former than the latter. Discordant BD variation of individual parts of WX2/MoX2 accounts for exclusively distributed electrons and holes, yielding type-II band offsets. X-X BL correlates positively to binding energy (Eb), while X-X BA correlates negatively to lattice mismatch (lm). The resulting interlayer distance limitation evidences constraint-free lattice of vdW structure. Finally, the connection between microscopic interatomic interaction and macroscopic electromagnetic behavior has been quantified firstly by a cubic equation relating to weighted BD summation and static dielectric constant.

Lattice-Mismatch Strain and Confinement in Nanoscale Si/SiO2 Structures Fabricated Using Thermal Oxidation

MRS Advances ◽  
2019 ◽  
Vol 4 (5-6) ◽  
pp. 351-357 ◽  
Author(s):  
Erin I. Vaughan ◽  
Clay S. Mayberry ◽  
Danhong Huang ◽  
Ashwani K. Sharma
Keyword(s):  
Band Structure ◽  
Effective Mass ◽  
Thermal Oxidation ◽  
Lattice Mismatch ◽  
Hole Transport ◽  
Bandgap Energy ◽  
Transient Time ◽  
Mismatch Strain ◽  
Carrier Effective Mass ◽  
Order Of Magnitude

ABSTRACTThe behavior of electron and hole transport in semiconductor materials is influenced by lattice-mismatch at the interface. It is well known that carrier scattering in a confined region is dramatically reduced. In this work, we studied the effects of coupling both the strain and confinement simultaneously. We report on the fabrication and characterization of nanoscale planar, wall-like, and wire-like Si/SiO2 structures. As the Si nanostructure dimensions were scaled down to the quantum regime by thermal oxidation of the Si, changes to the band structure and carrier effective mass were observed by both optical and electrical techniques. Transient-time response measurements were performed to examine the carrier generation and recombination behavior as a function of scaling. Signal rise times decreased for both carrier types by an order of magnitude as Si dimensions were reduced from 200 to 10 nm, meaning that the carrier velocity is increasing with smaller scale structures. This result is indicative of decreased Si bandgap energy and carrier effective mass. Photoluminescence measurements taken at 50K showed changes in the PL response peak energies, which illustrates changes in the band structure, as the Si/SiO2 dimensions are scaled.

Stresses in Multilayered Thin Films

MRS Bulletin ◽  
1999 ◽  
Vol 24 (2) ◽  
pp. 34-38 ◽  
Author(s):  
Robert C. Cammarata ◽  
John C. Bilello ◽  
A. Lindsay Greer ◽  
Karl Sieradzki ◽  
Steven M. Yalisove
Keyword(s):  
Thin Films ◽  
Angular Displacement ◽  
Incident Beam ◽  
Two Dimensions ◽  
Bragg Angle ◽  
Radius Of Curvature ◽  
Wave Source ◽  
Contour Maps ◽  
Film Substrate ◽  
Image Position

Almost all thin films deposited on a substrate are in a state of stress. Fifty years ago pioneering work concerning the measurement of thin-film stresses was conducted by Brenner and Senderoff. They electroplated a metal film onto a thin metal substrate strip fixed at one end and measured the deflection of the free end of the substrate with a micrometer. Using a beam-bending analysis, they were able to calculate a residual stress from the measured deflection of the bimetallic film-substrate system. A variety of other, more sensitive methods of measuring the curvature of the surface of a film-substrate system have since been developed using, for example, capacitance measurements and interferometry techniques.When a monochromatic x-ray beam is incident onto a curved single crystal, the diffraction condition is satisfied only for regions of the crystal where the inclination angle with respect to the incident beam exactly matches the Bragg angle. When a parallel beam plane-wave source is used, the diffracted beam from a particular set of (hkl) planes gives rise to a single narrow-contour band. If the crystal is rocked by an angle ω, the contour band will move by a certain distance D. The radius of curvature R of the crystal lattice planes is given bywhere θ is the Bragg angle. Equal rocking angles produce equivalent D values for uniform curvature, or varied D values for nonuniform curvature. Using this procedure, detailed contour maps of the angular displacement field of the crystal can be mapped in two dimensions.

Experimental determination of the instrumental transparency function of texture goniometers

2000 ◽  
Vol 33 (4) ◽  
pp. 1162-1174 ◽  
Author(s):  
K. Moras ◽  
A. H. Fischer ◽  
H. Klein ◽  
H. J. Bunge
Keyword(s):  
Pole Figure ◽  
Silicon Crystal ◽  
Window Size ◽  
Geometrical Model ◽  
Bragg Angle ◽  
Rocking Curve ◽  
Order Of Magnitude ◽  
Simple Geometrical Model ◽  
Position Sensitive Detectors

The instrumental transparency functions of five commercially available texture goniometers were measured experimentally with six monocrystalline samples cut in different orientations from a large highly perfect silicon crystal with a rocking curve of less than 0.01°. Transparency functions were measured in steps of 0.02 to 0.2° in the pole-figure angles α, β. The window size Δα depends on the Bragg angle θ in the form 1/sinθ; the window size Δω is constant for each goniometer. The dominant instrumental parameter determining the long axis Δα of the pole-figure window is the axial width of the detector entrance slit. This parameter is smallest for area detectors (smaller by more than an order of magnitude compared with conventional scintillation detectors as well as one-dimensional position-sensitive detectors). The main features of the pole-figure window and their dependence on the instrumental parameters can be deduced fairly well from a simple geometrical model. The particular shapes of the transparency functions of the studied goniometers are markedly different. Particularly, they are not very well represented by Gauss functions. The two-dimensional transparency function can be fairly well characterized by its α and β profiles. The normalized profiles are virtually independent of the goniometer angles 2θ and α. The increasing size of the pole-figure window with decreasing θ puts a lower limit on the Bragg angle below which pole-figure measurement ceases to be meaningful.

Cracks Emanating From an Erosion in a Pressurized Autofrettaged Thick-Walled Cylinder—Part II: Erosion Depth and Ellipticity Effects

1998 ◽  
Vol 120 (4) ◽  
pp. 354-358 ◽  
Author(s):  
M. Perl ◽  
C. Levy ◽  
H. Fang
Keyword(s):  
Stress Intensity Factor ◽  
Stress Intensity ◽  
Radius Of Curvature ◽  
Mode I ◽  
Constant Depth ◽  
Erosion Depth ◽  
Short Cracks ◽  
Order Of Magnitude ◽  
Two Parameters ◽  
Walled Cylinder

In Part I of this paper, the effects of constant depth erosion on the mode I stress intensity factor (SIF) were determined for a crack emanating from the erosion deepest point in a pressurized, autofrettaged, thick-walled cylinder. The erosion geometries investigated included semi-circular erosions and several arc erosions of various radii of curvature. Due to the trends found in that portion of the study, erosion depth and ellipticity are believed to have equally important impact on the SIFs. The present paper delves further into these two parameters using the following configurations: (a) semi-circular erosions of relative depths of 1–10 percent of the cylinder’s wall thickness, W; and (b) semi-elliptical erosions with ellipticities of d/h = 0.3 – 2.0. Deep cracks are found to be practically unaffected by the erosion, similar to the results presented in Part I of the paper. The effective SIF for relatively short cracks is found to be dramatically enhanced by the stress concentration factor (SCF), which encompasses the depth of the erosion as well as its radius of curvature at the tip. As a result of the increased effective SIF, a significant decrease in the vessel’s fatigue life of up to an order of magnitude may occur.

Surface-growth-mode-induced strain effects on the metal–insulator transition in epitaxial vanadium dioxide thin films

RSC Advances ◽  
2015 ◽  
Vol 5 (98) ◽  
pp. 80122-80128 ◽  
Author(s):  
Mengmeng Yang ◽  
Yuanjun Yang ◽  
Bin Hong ◽  
Liangxin Wang ◽  
Zhenlin Luo ◽  
...  
Keyword(s):  
Vanadium Dioxide ◽  
Lattice Mismatch ◽  
Compressive Strain ◽  
Epitaxial Films ◽  
Surface Growth ◽  
Growth Mode ◽  
Metal Insulator ◽  
Mismatch Strain ◽  
Lattice Mismatch Strain ◽  
Vanadium Dioxide Thin Films

The surface growth mode can induce the anomalous compressive strain in thicker VO2/Al2O3 epitaxial films, which can't be explained by conventional epitaxial lattice-mismatch. Strain may be an effective tool for manipulating MIT of the VO2 films.

EFFECT OF EPITAXIAL STRAIN ON THE STRUCTURAL AND FERROELECTRIC PROPERTIES OF Bi2FeCrO6 THIN FILMS

2010 ◽  
Vol 03 (01) ◽  
pp. 83-88 ◽  
Author(s):  
R. NECHACHE ◽  
C. HARNAGEA ◽  
A. RUEDIGER ◽  
F. ROSEI ◽  
A. PIGNOLET
Keyword(s):  
Thin Films ◽  
Piezoelectric Coefficient ◽  
Lattice Mismatch ◽  
Strain Relaxation ◽  
Ferroelectric Properties ◽  
Compressive Strain ◽  
Epitaxial Strain ◽  
Lattice Cell ◽  
Monoclinic Distortion ◽  
Similar Crystal Structure

Bi 2 FeCrO 6 thin films were epitaxially grown by pulsed laser deposition on (100)-oriented LaAlO 3, ( LaAlO 3)0.3( Sr 2 LaTaO 6)0.7 and SrTiO 3 single crystalline substrates with and without epitaxial CaRuO 3 buffered layer. The in-plane compressive strain induces monoclinic distortion of the Bi 2 FeCrO 6 lattice cell. The strain originates from lattice mismatch between CaRuO 3 and single crystal substrates. The similar crystal structure of the substrate and the layer lead to coherent epitaxial growth of the heterostructures and avoid strain relaxation in particular for BFCO films deposited on LaAlO 3 substrates. The ferroelectric character is demonstrated for all grown BFCO films. The residual in-plane strain weakly affects the effective piezoelectric coefficient of BFCO layers.

scholarly journals An analysis of compressive strain in adjacent temperature-gradient and equi-temperature layers in a natural snow cover

1980 ◽  
Vol 26 (94) ◽  
pp. 283-289 ◽  
Author(s):  
Richard L. Armstrong
Keyword(s):  
Strain Rate ◽  
Snow Cover ◽  
Compressive Strain ◽  
Coarse Grained ◽  
Adjacent Layer ◽  
Dominant Type ◽  
Fine Grained ◽  
Order Of Magnitude ◽  
Alpine Research ◽  
Natural Snow

AbstractCompressive strain-rates in discrete layers of a sub-alpine snow cover are analyzed. Individual layers are identified according to density and the dominant type of metamorphism which contributed to their formation. Data were collected during four winter seasons at the Institute of Arctic and Alpine Research (INSTAAR) snow-study site (3 400 m), Red Mountain Pass, south-western Colorado, U.S.A. At average densities of less than 250 kg m₋3the influence of metamorphism on strain-rate is not apparent. However, at densities greater than 250 kg m₋3, two separate relationships emerge for strain as a function of crystal type and density. While two adjacent layers may exhibit comparable densities, a layer of sintered, fine grained (ET) snow indicates a strain-rate approximately one order of magnitude greater than an adjacent layer of cohesionless, coarse-grained (TG) snow.

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