The Influence of the Real Structure on the Deformations in Layer Systems

1992 ◽  
Vol 281 ◽  
Author(s):  
B. Jenichen ◽  
R. Kohler
Keyword(s):  
Thermal Stresses ◽  
Misfit Dislocations ◽  
Bulk Crystals ◽  
Local Curvature ◽  
Double Crystal ◽  
Multilayer Systems ◽  
Misorientation Distribution ◽  
Mosaic Spread ◽  
Inhomogeneous Strain ◽  
Lec Gaas

ABSTRACTThe relaxation of thermal stresses during the Czochralsky growth leads to frozen in deformations in the boules. These deformations lead to a nonintentional inhomogeneous miscut of the wafers. From the X-ray double crystal measurement of frozen in deformations in GaAs bulk crystals a nonintentional miscut of about 10−4 may be estimated. The measurement of the misorientation distribution over a LEC GaAs wafer yielded even higher inhomogeneities which are believed to be due to local curvature of the lcm2 samples. The relaxation of GaAs/AlAs Braggreflectors of 3μm overall thickness depends on the density of threading dislocations i.e. of the type of substrate (LEC or HB). The inhomogeneous strain field of misfit dislocations in InGaAs/GaAs multilayer systems and their inhomogeneous distribution leads to deformations in epitaxial layers limiting the dimensions of coherently scattering domains. The resulting mosaic spread in the epitaxial layer systems has been obtained using triple crystal measurements. The experimentally determined mosaic spread has to be taken into account to simulate the the diffraction pattern more correctly.

Investigation of Multilayer Systems for Optical Bragg Reflectors by X-ray Double Crystal Topography and - DIF-Fractometry

1991 ◽  
Vol 240 ◽  
Author(s):  
B. Jenichen ◽  
R. Köhler ◽  
R. Hey ◽  
M. Höricke
Keyword(s):  
Stress Relaxation ◽  
Threading Dislocations ◽  
Misfit Dislocations ◽  
Bragg Reflectors ◽  
Double Crystal ◽  
Multilayer Systems ◽  
X Ray ◽  
Different Levels

ABSTRACTOptical Bragg reflectors consisting of the binaries AlAs and GaAs were investigated using double crystal topography and diffractometry. In undoped mirror stacks stress relaxation due to the formation of misfit dislocations was observed, which could be prevented by doping the stacks with 1018cm−3 silicon. In topographs taken in the substrate and different satellite reflections an unusual vanishing of the contrast of different segments of the misfit dislocations takes place, that shows these different segments to be located at different levels of the stack. The contrasts of the threading dislocations are quite similar in the substrate and the satellite reflections whereas the misfit dislocations change their contrast markedly.

MOCVD Growth and Characterization of High-Quality ZnSe on GaAs

1994 ◽  
Vol 340 ◽  
Author(s):  
J. C. Chen ◽  
Bing Yang ◽  
F. Semendy ◽  
W. W. Clark ◽  
P. R. Boyd ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Secondary Ion Mass Spectrometry ◽  
Defect Density ◽  
Growth Conditions ◽  
Misfit Dislocations ◽  
High Quality ◽  
Double Crystal ◽  
X Ray ◽  
Mocvd Growth ◽  
Order Of Magnitude

ABSTRACTHigh-quality ZnSe epilayers on GaAs substrates have been grown by MOCVD. Diethylzinc (DEZn) and diethylselenide (DESe) were used as source materials. Growth studies were done at 400°C under different growth conditions in an atmospheric pressure MOCVD reactor. The as-grown ZnSe epilayers were characterized by a wide variety of techniques, such as double crystal x-ray diffraction, low-temperature photoluminescence (PL), transmission electron microscopy (TEM), secondary ion mass spectrometry (SIMS), and scanning electron microscopy (SEM).The results show excellent structural and optical properties of ZnSe. The best material was grown on undoped GaAs at the VI/II ratio near unity. The full-width-at-half-maximum (FWHM) of ZnSe (∼0.2/μm thick) x-ray peak as low as 90 arc seconds was achieved. TEM results also show very low defect density. The density of stacking faults is less than 105/cm2 which is four orders of magnitude less than that of samples grown by conventional MBE [J. Petruzzello et al. J. Appl. Phys. 63, 2299 (1988)] and MOCVD [J.L. Batstone et al. Philos. Mag A, 66, 609, 1992]. The spacing between misfit dislocations is between 5 to 10,μm which is one order of magnitude larger than that of reported sample of comparable thickness.

Liquid Phase Epitaxial Growth and Characterization of GaAs on InP Substrates

1994 ◽  
Vol 340 ◽  
Author(s):  
Dong-Keun Kim ◽  
Hyung-Jong Lee ◽  
Byung-Teak Lee
Keyword(s):  
Liquid Phase ◽  
Surface Morphology ◽  
Growth Conditions ◽  
Gaas Layer ◽  
Misfit Dislocations ◽  
Double Crystal ◽  
Transmission Electron ◽  
Grating Region ◽  
Inp Substrates ◽  
Undoped Gaas

ABSTRACTOptimum growth conditions were investigated to obtain high quality heteroepitaxial GaAs layers on InP substrates by liquid phase epitaxy (LPE). Addition of about 0.005wt% of Se to the Ga growth melt effectively suppressed dissolution of the InP substrates into the melt during the initial stage of the growth, resulting in a significantly improved surface morphology. The crystallinity and the surface morphology could be further improved by growing undoped GaAs layers on thin Se-doped buffer GaAs as well as using InP substrates patterned with grating structure. The transmission electron microscopy observation indicated that the misfit dislocations interact with each other at the grating region, resulting in a lower dislocation density in the upper GaAs layer. The (400) double crystal X-ray diffraction peaks of the undoped GaAs showed fullwidth- at-half-maximum of about 380 arcsec, which is comparable with the previously reported values using more sophisticated growth techniques.

scholarly journals Defects In GaAs Bulk Crystals and Multi-Layers Caused by In Diffusion

1993 ◽  
Vol 309 ◽  
Author(s):  
P. Werner ◽  
Z. Liliental-Weber ◽  
W. Swider ◽  
H. Sohn ◽  
WaiFan Yau ◽  
...  
Keyword(s):  
Molecular Beam ◽  
Lattice Strain ◽  
Molecular Beam Epitaxy Growth ◽  
Misfit Dislocations ◽  
Bulk Crystals ◽  
Bulk Gaas ◽  
Transmission Electron ◽  
Show Evidence ◽  
Gaas Buffer Layer ◽  
Rapid Diffusion

AbstractThe objective of this work was to study by transmission electron microscopy the lattice defects in GaAs bulk crystals and heterostructures formed by In diffusion. In such samples hints for the existence of superconductivity have been found. Indium was found to move more than 100 μm into bulk GaAs during lh annealing at 550ºC (such conditions are typical for molecular beam epitaxy growth on GaAs wafers). This rapid diffusion is accompanied by the creation of dislocation networks and metallic In droplets that show evidence for lattice strain. To study the interaction of In with the GaAs lattice, In/GaAs multi-layers were grown by MBE at about 450ºC on a GaAs buffer layer. The interfaces of these structures showed misfit dislocations at islands of InAs besides the presence of lattice strain. Both types of samples showed microwave absorption signals typical for superconductivity. The most likely superconductive phases are small metastable inclusions, probably consisting of amorphous Ga or In.

The Effects of Sapphire Surface Treatments and Nitridation on GaN Nucleation Grown using Hydride Vapor Phase Epitaxy

2003 ◽  
Vol 764 ◽  
Author(s):  
F. Dwikusuma ◽  
T. F. Kuech
Keyword(s):  
Vapor Phase ◽  
Early Stage ◽  
Vapor Phase Epitaxy ◽  
Surface Treatments ◽  
High Density ◽  
Hydride Vapor Phase Epitaxy ◽  
Double Crystal ◽  
Sapphire Surface ◽  
Mosaic Spread ◽  
Island Density

AbstractWe have studied the effects of sapphire surface treatments and nitridation on GaN nucleation grown using the hydride vapor phase epitaxy technique. The surface treatments used were airannealing at 1400°C, etching in pure H2SO4 at 250°C, and etching in a 3:1 mixture of H2SO4:H3PO4 solution at 250°C. A nitridation step was carried out using 20% NH3 in N2 gas mixture at 1100°C. GaN nucleation and the early stage s of growth was investigated by short time growth and quench experiments. Atomic force microscopy and double crystal x-ray diffraction were used to examine the sapphire surface morphology, GaN island density, and GaN island structure. A lower density of GaN islands was grown on the air-annealed sapphire compared to the H2SO4-etched and 3:1 H2SO4:H3PO4-etched sapphire. GaN islands grown on the 3:1 H2SO4:H3PO4-etched sapphire had a broad mosaic spread due to preferential growth on surface pits. Sapphire nitridation resulted in a higher GaN island density with a smaller mosaic spread. A high density and uniform nucleation of GaN islands is critical in producing high quality thick GaN films. The H2SO4-etched sapphire and nitridation resulted in a high density of uniform GaN islands.

Growth and Characterization of InAsxP1−x/InP Strained Multiple Quantum Wells by Gas Source Molecular Beam Expitaxy

1996 ◽  
Vol 450 ◽  
Author(s):  
H. C. Kuo ◽  
S. Thomas ◽  
A. P. Curtis ◽  
G. E. Stillman ◽  
C. H. Lin ◽  
...  
Keyword(s):  
Quantum Wells ◽  
Molecular Beam ◽  
Interband Transition ◽  
Multiple Quantum Wells ◽  
Multiple Quantum ◽  
Misfit Dislocations ◽  
Double Crystal ◽  
Cross Sectional ◽  
Transition Energies ◽  
Gas Source

AbstractInAsxPi.x/InP (10 period 50/100Å with x=0.25–0.79) pseudomorphically strained multiple quantum wells (SMQWs) were grown by gas source molecular beam expitaxy (GSMBE) at 470°C and characterized by cross-sectional transmission electron microscope (XTEM), double crystal x-ray diffraction (DCXRD), and optical spectroscopy. The structural analysis demonstrates that excellent control of the sharp interface and limited As-P interdiffusion can be achieved by GSMBE growth. XTEM images of these SMQWs display no misfit dislocations, and DCXRD scans reveal high order superlattice satellite peaks. Photoluminescence (PL) and transmission measurements were performed for all SMQWs to evaluate crystal quality. Only slight degradation in luminescence was observed as the As composition increased. Based on the three-band Kane model which includes the lattice strain, the transition energies of SMQWs were calculated using the conduction-band offset (Qc=δEc/δEg) as an adjustable parameter. The best fit of measured and calculated interband transition energies suggests that Qc is independent of As composition and is 0.70±0.05. Finally, a growth kinetics model based on the Langmuir equation was derived to realize the As/P incorporation ratio in the InAsP materials. Theoretical results show good agreement with experimental data.

Raman and X-ray diffraction study of relaxation in Si–Si1–xGex strained-layer superlattices

1989 ◽  
Vol 67 (4) ◽  
pp. 351-357 ◽  
Author(s):  
D. J. Lockwood ◽  
J.-M. Baribeau ◽  
P. Y. Timbrell
Keyword(s):  
Sharp Decrease ◽  
Growth Direction ◽  
Longitudinal Optical ◽  
Acoustic Mode ◽  
Progressive Relaxation ◽  
Misfit Dislocations ◽  
X Ray Diffraction ◽  
Double Crystal ◽  
Raman Scattering Spectroscopy ◽  
X Ray

We report a study of the relaxation of Si–Si1–xGex strained single layers and superlattices by Raman scattering spectroscopy, double crystal X-ray diffraction, and transmission and scanning electron microscopy. Samples of various dimensions and compositions were produced by molecular beam epitaxy at a growth temperature of 500 ± 30 °C. The thermal stability of the various specimens was investigated by annealing experiments at temperatures between 600 and 900 °C. Considerable deterioration of the crystal quality and progressive relaxation were observed in some of the samples. Relaxation occurred through formation of misfit dislocations at the first Si–Si1–xGex interface and these caused threading dislocations to form within the epilayer. The degradation of the superlattice interfaces on annealing is correlated with a sharp decrease in the acoustic mode Raman intensities. Strain values perpendicular to the growth direction as a function of annealing temperature are obtained from a kinematical simulation of the X-ray rocking curves. These results are compared with the frequency shifts of the longitudinal optical phonons in the Raman spectra. The results obtained for the critical layer thicknesses versus x are consistent with the excess stress model of Tsao and co-workers.

Two-Dimensional Grain Growth Simulation by Local Curvature Multi-Vertex Model

2012 ◽  
Vol 715-716 ◽  
pp. 551-556 ◽  
Author(s):  
Teruyuki Tamaki ◽  
Kenichi Murakami ◽  
Hotaka Homma ◽  
Kohsaku Ushioda
Keyword(s):  
Grain Boundary ◽  
Boundary Energy ◽  
Two Dimensional ◽  
Vertex Model ◽  
Triple Junctions ◽  
Local Curvature ◽  
Misorientation Distribution ◽  
Grain Boundary Character ◽  
Random Microstructure ◽  
Physical Principles

A local curvature multi-vertex model was developed. This model is the straightforward two-dimensional topological network model based on the physical principles which are the curvatures of grain boundaries and the grain boundary tensions at triple junctions. The model was applied to the artificial random microstructure under some conditions of grain boundary characters. The misorientation distribution was changed very little under constant grain boundary energy and mobility, but it was change much under grain boundary character dependent on misorientation. Therefore, in order to discuss actual textures, it is important to take grain boundary characters into account.

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