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.

Investigation of GaAs/AlAs multilayer systems for optical Bragg reflectors using x‐ray double crystal techniques

1993 ◽  
Vol 73 (5) ◽  
pp. 2220-2224 ◽  
Author(s):  
B. Jenichen ◽  
R. Hey ◽  
M. Höricke ◽  
R. Köhler
Keyword(s):  
Bragg Reflectors ◽  
Double Crystal ◽  
Multilayer Systems ◽  
X Ray

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.

Misfit dislocations between boron-doped homoepitaxial films and diamond substrates studied by X-ray diffraction topography

2018 ◽  
Vol 51 (6) ◽  
pp. 1684-1690 ◽  
Author(s):  
Marina González-Mañas ◽  
Beatriz Vallejo
Keyword(s):  
Critical Thickness ◽  
Lattice Mismatch ◽  
Lattice Parameter ◽  
Threading Dislocations ◽  
Misfit Dislocations ◽  
Boron Doped Diamond ◽  
X Ray ◽  
Boron Doped ◽  
Slip Planes ◽  
Half Loop

Boron-doped diamond epilayers grown over diamond substrates have a different lattice parameter from the undoped diamond substrate, which introduces a lattice mismatch between substrates and epilayers. This can generate misfit dislocations at the interface when the epilayer reaches a certain critical thickness. For a boron concentration of about 1 × 1020 atoms cm−3, the calculated lattice mismatch is about 1.3 × 10−4 and the critical thickness is of the order of 0.2 µm. In the epilayers studied, grown over high-pressure high-temperature 1b (001) substrates, the lattice mismatch and the epilayer thickness are 1.3 × 10−4, 30 µm and 6.5 × 10−4, 4 µm. The epitaxial strain has been relaxed by the generation of two orthogonal misfit dislocation systems. These are edge dislocations parallel to the [100] and [010] directions with a Burgers vector making an angle of 45° with the (001) interface. Their lengths are 40–60 µm and their lineal densities 200–240 cm−1. They are heterogeneously nucleated, propagated in the form of half-loops along the slip planes (011) and (101), respectively, and related mainly to 〈111〉 threading dislocations emerging from octahedral growth sectors. Another kind of half-loop originates from the substrate growth sector boundaries. Limited X-ray topography has been demonstrated to be a very useful tool to discriminate between substrate and epilayer defects when their lattice mismatch is not sufficient to separate such defects in conventional Lang topography. X-ray section topography has confirmed the presence of [001] dislocations in the epilayers and the misfit half-loops related to threading dislocations propagating from the interface.

Effects of Helium Ion Implantation on the Optical and Crystal Properties of GaAs

1989 ◽  
Vol 147 ◽  
Author(s):  
R. C. Bowman ◽  
P. M. Adams ◽  
J. F. Knudsen ◽  
S. C. Moss ◽  
P. A. Dafesh ◽  
...  
Keyword(s):  
Electron Beam ◽  
Raman Scattering ◽  
X Ray Diffraction ◽  
Phonon Modes ◽  
Double Crystal ◽  
Damage Behavior ◽  
X Ray ◽  
Crystal Properties ◽  
Helium Ion ◽  
Different Levels

AbstractThe damage to GaAs crystals caused by helium ion implants has been monitored by changes in the Raman scattering phonon modes, double-crystal x-ray diffraction rocking curves, photoreflectance (PR), and electron beam electroreflectance (EBER) band edge transitions. As the implanted helium ion dose was increased, the various techniques revealed threshold damage behavior at very different levels. Although PR and EBER were the most sensitive to the defects created at the lowest ion doses, all techniques indicated substantial disorder for implants greater than 1014 ions/cm2.

Spatially Resolved Characterization of Microstructure, Defects and Tilts in GaN Layers Grown on Si(111) Substrates by Maskless Cantilever Epitaxy

2006 ◽  
Vol 934 ◽  
Author(s):  
Rozaliya Barabash ◽  
C. Roder ◽  
G. E. Ice ◽  
S. Einfeldt ◽  
J. D. Budai ◽  
...  
Keyword(s):  
Orientation Imaging Microscopy ◽  
Growth Conditions ◽  
Threading Dislocations ◽  
Misfit Dislocations ◽  
X Ray ◽  
Orientation Imaging ◽  
Spatially Resolved ◽  
Dislocation Arrays ◽  
Tilt Boundaries

ABSTRACTThe spatially resolved distribution of strain, misfit and threading dislocations, and crystallographic orientation in uncoalesced GaN layers grown on Si(111) substrates by maskless cantilever epitaxy was studied by white-beam Laue x-ray microdiffraction, scanning electron microscopy, and orientation imaging microscopy. Tilt boundaries formed at the column/wing interface with the misorientation strongly depending on the growth conditions. A depth-dependent deviatoric strain gradient is found in the GaN. Types and density of misfit dislocations as well as their arrangement within different dislocation arrays was quantified. The results are discussed with respect to the miscut of the Si(111) surface and misfit dislocations formed at the interface.

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.

Preparation of 30×30 mm2 Free-Standing GaN Wafer by Mechanical Liftoff and Optical Properties in The Backside of The Free GaN by Cathodoluminescence

2000 ◽  
Vol 639 ◽  
Author(s):  
Hwa-Mok Kim ◽  
Jae-Eung Oh ◽  
Tae-Won Kang
Keyword(s):  
Optical Properties ◽  
Beam Energy ◽  
Film Growth ◽  
Hydride Vapor Phase Epitaxy ◽  
Threading Dislocations ◽  
Electron Beam Energy ◽  
X Ray Diffraction ◽  
Free Standing ◽  
Double Crystal ◽  
X Ray

ABSTRACTIn this study, free-standing GaN was produced from 350- to 400-μm-thick GaN films grown on sapphire by using hydride vapor phase epitaxy. The thick films were separated from the substrate by using the mechanical polishing method with a diamond slurry. After liftoff, the bow is slight or absent in the resulting free-standing GaN. Double-crystal X-ray diffraction, hall measurements, and cathodoluminescence were used for characterizing the free-standing GaN wafer. To investigate spatially the backside of the free-standing GaN substrate, we controlled the electron beam energy from 5 keV to 30 keV. As the beam energy increased, dark regions, i.e., nonradiative regions, become smaller than bright regions. We think this means that nonradiative centers, i.e., threading dislocations, merge during film growth.

Index of Refraction Anisotropy in InGaAs/InP Heterostructures Measured by Ellipsometry

1989 ◽  
Vol 160 ◽  
Author(s):  
Brian R. Bennett ◽  
Jesús A. Del Alamo
Keyword(s):  
Optical Properties ◽  
Molecular Beam Epitaxy ◽  
Molecular Beam ◽  
Index Of Refraction ◽  
Misfit Dislocations ◽  
X Ray Diffraction ◽  
Double Crystal ◽  
X Ray ◽  
Asymmetric Pattern ◽  
Optical Effects

AbstractWe applied ellipsometry to characterize layers of InxGa1-xAs grown by molecular beam epitaxy on (001) InP. Samples with mismatched layers exhibit significant anisotropy in the index of refraction. We explain these observations by the presence of misfit dislocations which form in an asymmetric pattern. This results in asymmetric strain and, via piezo-optical effects, an anisotropy in the optical properties. This effect makes ellipsometry a more sensitive technique than double-crystal x-ray diffraction for detecting misfit dislocations in these heterostructures.

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.

Thermal and Lattice Misfit Stress Relaxation in Growing AlN Crystal with Simultaneous Evaporation of SiC Substrate

2017 ◽  
Vol 897 ◽  
pp. 711-714 ◽  
Author(s):  
Tatiana S. Argunova ◽  
Mikhail Yu. Gutkin ◽  
Kirill D. Shcherbachev ◽  
Sergey S. Nagalyuk ◽  
Olga P. Kazarova ◽  
...  
Keyword(s):  
Stress Relaxation ◽  
Phase Contrast ◽  
Lattice Misfit ◽  
Phase Contrast Imaging ◽  
Threading Dislocations ◽  
X Ray Diffraction ◽  
Contrast Imaging ◽  
Misfit Stress ◽  
Edge Type ◽  
X Ray

AlN single crystals were prevented from cracking by simultaneous growth and evaporation of SiC substrates. The freestanding crystals (<1 mm thick) were proved continuous by synchrotron phase contrast imaging and used as a model system to investigate the type of dislocation structure near AlN/SiC interface by x-ray diffraction techniques. We have found that, unlike the situation in GaN films, where predominantly edge-type threading dislocations cross the layer along its normal, the dislocations configure to form mosaic structure. We suggest a theoretical model that describes the misfit stress relaxation in growing AlN crystal.

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