Optical Properties and Defect Structure of MOVPE InGaN Films

AbstractA series of 100 nm thick InGaN films with In content up to 14% has been grown by MOVPE on SiC substrates. Optical characterization was carried out by means of reflectance spectrometry, photoluminescence and cathodoluminescence. Optical properties of the samples have been correlated with the microstructural properties measured by atomic force microscopy, transmission electron microscopy and X-ray diffraction data. Results indicate a dependence of the optical properties on the In content in the sample, as well as on the residual stress in the films induced by Indium incorporation. Part of the strain is reduced elastically by formation of pinholes which reach the InGaN/GaN interface, where first misfit dislocations are observed to form. Our results show that luminescence is directly correlated with the strain distribution in the layers. Pinholes are observed to act as nonradiative recombination sites for carriers, while strain relaxation around pinholes may enhance luminescence emission. We discuss the influence of strain with respect to In incorporation, the appearance of piezoelectric fields and effects due to strain induced band bending.

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EFFECT OF SUBSTRATE TEMPERATURE ON THE STRUCTURAL AND THE OPTICAL PROPERTIES OF CdTe (100) EPITAXIAL FILMS GROWN ON GaAs (100) SUBSTRATES

Surface Review and Letters ◽

10.1142/s0218625x07010202 ◽

2007 ◽

Vol 14 (04) ◽

pp. 755-759 ◽

Cited By ~ 1

Author(s):

D. U. LEE ◽

J. H. JUNG ◽

T. W. KIM ◽

H. S. LEE ◽

H. L. PARK ◽

...

Keyword(s):

Thin Films ◽

Optical Properties ◽

Substrate Temperature ◽

Misfit Dislocations ◽

X Ray Diffraction ◽

Force Microscopy ◽

Atomic Force ◽

Transmission Electron ◽

Cdte Thin Films ◽

Xrd Patterns

CdTe thin films were grown on GaAs (100) substrates by using molecular beam epitaxy at various temperatures. The results of the X-ray diffraction (XRD) patterns showed that the orientation of the grown CdTe thin films was the (100) orientation. XRD patterns, atomic force microscopy images, high-resolution transmission electron microscopy (HRTEM) images, and photoluminescence spectra showed that the crystallinity of CdTe (100) epilayers grown on GaAs (100) substrates was improved by increasing the substrate temperature. HRTEM images showed that misfit dislocations existed at the CdTe / GaAs heterointerface. These results can help improve understanding of the substrate temperature effect on the structural and the optical properties of CdTe (100)/ GaAs (100) heterostructures.

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Strain Relaxation During Heteroepitaxy on Twist-Bonded Thin Gallium Arsenide Substrates

MRS Proceedings ◽

10.1557/proc-535-45 ◽

1998 ◽

Vol 535 ◽

Author(s):

P. Kopperschmidt ◽

S T. Senz ◽

R. Scholz ◽

G. Kästner ◽

U. Gösele ◽

...

Keyword(s):

Electron Microscopy ◽

Strain Relaxation ◽

Twist Angle ◽

Gaas Layer ◽

X Ray Diffraction ◽

Force Microscopy ◽

Compliant Substrates ◽

Atomic Force ◽

Transmission Electron ◽

Epitaxial Deposition

AbstractWe realized “compliant” substrates in the square centimeter range by twist-wafer bonding of an (100) GaAs handle wafer to another (100) GaAs wafer with a several nm thick epitaxially grown GaAs layer followed by an appropriate back-etch procedure. The twist angle between the two GaAs wafers was chosen between 4 and 15 degrees. The twisted layers were characterized by area scanned X-ray diffraction, optical and electron microscopy and atomic force microscopy. Occasionally we observed regions showing pinholes in the transferred thin twistbonded GaAs layer.After epitaxial deposition of 300 nm InP and InGaAs films with different degrees of mismatch on these substrates, transmission electron microscopy revealed grains which are epitaxially oriented to either the substrate or the twist-bonded layer. The grain boundaries between the twisted and untwisted grains probably collect threading dislocations, thus reducing their density in the areas free of boundaries.

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Influence of Substrate Miscut on the Island Formation Process in In0.2Ga0.8As/GaAs Multilayers

Surface Review and Letters ◽

10.1142/s0218625x03005049 ◽

2003 ◽

Vol 10 (02n03) ◽

pp. 263-270

Author(s):

E. Gartstein ◽

D. Mogilyanski ◽

D. Barlam

Keyword(s):

Strain Relaxation ◽

Relaxation Processes ◽

X Ray Diffraction ◽

Element Analysis ◽

Island Nucleation ◽

Force Microscopy ◽

Atomic Force ◽

Transmission Electron ◽

Initial Substrate ◽

Influence Of Substrate

LPOMVPE-grown In0.2Ga0.8As/GaAs multilayers on GaAs substrates with miscut values of 0°, 0.3° and 2° around the [100] azimuthal direction were investigated by employing X-ray diffraction techniques complemented by atomic force microscopy (AFM) and transmission electron microscopy (TEM). The step-terrace structure evolving on the interfaces upon deposition strongly depends on the initial substrate morphology. The initiation of island nucleation, and both lateral and vertical ordering are related to the interfacial morphological parameters. Finite element analysis (FEA) is performed to elucidate the interplay between structural and strain relaxation processes.

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Strain Relaxation in Heteroepitaxial Si1-xGex Films via Surface Roughening Processes

MRS Proceedings ◽

10.1557/proc-399-407 ◽

1995 ◽

Vol 399 ◽

Cited By ~ 10

Author(s):

Cengiz S. Ozkan ◽

William D. Nix ◽

Huajian Gao

Keyword(s):

Strain Relaxation ◽

Depth Profiling ◽

Surface Roughening ◽

Misfit Dislocations ◽

X Ray Diffraction ◽

X Ray ◽

Force Microscopy ◽

Si Substrates ◽

Transmission Electron ◽

Anisotropic Elastic

ABSTRACTSurface roughening associated with strain relaxation of Si1-xGex films grown epitaxially on (100) Si substrates has been investigated using transmission electron microscopy, atomic force microscopy and x-ray diffraction. Epitaxial films 100 Å in thickness and containing 18% Ge, which are subcritical with respect to the formation of misfit dislocations, show strain relaxation through surface roughening on annealing at 700 °C. Enhanced surface grooves aligned along <100> directions are observed in films annealed at 850 °C. Strain relaxation as measured by x-ray diffraction is significantly greater at the higher temperature. Prolonged anneals at 850 °C also result in islanding. The surface roughening processes have also been studied in subcritical films with 15% Ge at 900 °C. These films also show enhanced grooving aligned along <100> directions. These observations are consistent with an anisotropic elastic analysis which indicates that grooving should occur preferentially along <100> directions. Intermixing effects in these samples have also been investigated through depth profiling using Auger Electron Spectroscopy. In addition to the above subcritical films, other films with 18% and 22% Ge and supercritical thicknesses have also been studied. For these films, surface grooving is observed along <110> directions, which suggests that these grooves are related to the formation of misfit dislocation networks. The role of these surface roughening processes in the nucleation of dislocations has also been explored.

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Pinholes, Dislocations and Strain Relaxation in InGaN

MRS Internet Journal of Nitride Semiconductor Research ◽

10.1557/s1092578300001113 ◽

1998 ◽

Vol 3 ◽

Cited By ~ 65

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.

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Anisotropy of Strain Relaxation in III-V Semiconductor Heterostructures

Defect and Diffusion Forum ◽

10.4028/www.scientific.net/ddf.230-232.93 ◽

2004 ◽

Vol 230-232 ◽

pp. 93-100 ◽

Cited By ~ 1

Author(s):

O. Yastrubchak ◽

T. Wosiński ◽

J.Z. Domagała ◽

E. Łusakowska

Keyword(s):

Lattice Mismatch ◽

Strain Relaxation ◽

Growth Conditions ◽

Threading Dislocation ◽

Misfit Dislocations ◽

Misfit Stress ◽

Force Microscopy ◽

Atomic Force ◽

Transmission Electron ◽

Small Lattice

Partially relaxed III–V heterostructures: GaAs/InGaAs and InP/InAlAs/InGaAs, with a small lattice mismatch, grown using molecular beam epitaxy under compressive or tensile misfit stress at the (001) interface, have been investigated by means of high-resolution X-ray diffractometry, atomic force microscopy and generalized ellipsometry. Additionally, transmission electron microscopy and electron-beam induced current in a scanning electron microscope have been employed to reveal misfit dislocations at the heterostructure interface. Chemical etching was used to determine polarity of the crystals and threading dislocation densities in the epitaxial layers. Our findings are interpreted in terms of the dependent on growth conditions, material’s composition and doping glide velocities of two types of misfit dislocations: α and β, differing in their core structure and lying along two orthogonal 〈110〉 crystallographic directions at the (001) interface.

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Structural and Optical Properties of InAsSbBi Grown by Molecular Beam Epitaxy on Offcut GaSb Substrates

Photonics ◽

10.3390/photonics8060215 ◽

2021 ◽

Vol 8 (6) ◽

pp. 215

Author(s):

Rajeev R. Kosireddy ◽

Stephen T. Schaefer ◽

Marko S. Milosavljevic ◽

Shane R. Johnson

Keyword(s):

Molecular Beam Epitaxy ◽

Molecular Beam ◽

Optical Quality ◽

X Ray Diffraction ◽

Interface Quality ◽

Force Microscopy ◽

Atomic Force ◽

Transmission Electron ◽

Lateral Variations

Three InAsSbBi samples are grown by molecular beam epitaxy at 400 °C on GaSb substrates with three different offcuts: (100) on-axis, (100) offcut 1° toward [011], and (100) offcut 4° toward [011]. The samples are investigated using X-ray diffraction, Nomarski optical microscopy, atomic force microscopy, transmission electron microscopy, and photoluminescence spectroscopy. The InAsSbBi layers are 210 nm thick, coherently strained, and show no observable defects. The substrate offcut is not observed to influence the structural and interface quality of the samples. Each sample exhibits small lateral variations in the Bi mole fraction, with the largest variation observed in the on-axis growth. Bismuth rich surface droplet features are observed on all samples. The surface droplets are isotropic on the on-axis sample and elongated along the [011¯] step edges on the 1° and 4° offcut samples. No significant change in optical quality with offcut angle is observed.

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Stress Relaxation in Uniquely Oriented SiGe/Si Epitaxial Layers

MRS Proceedings ◽

10.1557/proc-594-163 ◽

1999 ◽

Vol 594 ◽

Author(s):

M. E. Ware ◽

R. J. Nemanich

Keyword(s):

Stress Relaxation ◽

Surface Morphology ◽

Strain Relaxation ◽

Epitaxial Layers ◽

Misfit Dislocations ◽

Strained Layers ◽

Force Microscopy ◽

Si Substrates ◽

Atomic Force ◽

Deposited Films

AbstractThis study explores stress relaxation of epitaxial SiGe layers grown on Si substrates with unique orientations. The crystallographic orientations of the Si substrates used were off-axis from the (001) plane towards the (111) plane by angles, θ = 0, 10, and 22 degrees. We have grown 100nm thick Si(1−x) Ge(x) epitaxial layers with x=0.3 on the Si substrates to examine the relaxation process. The as-deposited films are metastable to the formation of strain relaxing misfit dislocations, and thermal annealing is used to obtain highly relaxed films for comparison. Raman spectroscopy has been used to measure the strain relaxation, and atomic force microscopy has been used to explore the development of surface morphology. The Raman scattering indicated that the strain in the as-deposited films is dependent on the substrate orientation with strained layers grown on Si with 0 and 22 degree orientations while highly relaxed films were grown on the 10 degree substrate. The surface morphology also differed for the substrate orientations. The 10 degree surface is relatively smooth with hut shaped structures oriented at predicted angles relative to the step edges.

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Epitaxial BaTiO3 Thin Films on Different Substrates for Optical Waveguide Applications

MRS Proceedings ◽

10.1557/proc-597-145 ◽

1999 ◽

Vol 597 ◽

Cited By ~ 5

Author(s):

M. Siegert ◽

Judit G. Lisoni ◽

C. H. Lei ◽

A. Eckau ◽

W. Zander ◽

...

Keyword(s):

Thin Films ◽

Optical Waveguides ◽

Rutherford Backscattering Spectrometry ◽

Optical Data ◽

X Ray Diffraction ◽

X Ray ◽

Force Microscopy ◽

Ion Channeling ◽

Atomic Force ◽

Transmission Electron

AbstractIn the process of developing thin film electro-optical waveguides we investigated the influence of different substrates on the optical and structural properties of epitaxial BaTiO3 thin films. These films are grown by on-axis pulsed laser deposition (PLD) on MgO(100), MgAl2O4(100), SrTiO3(100) and MgO buffered A12O3(1102) substrates. The waveguide losses and the refractive indices were measured with a prism coupling setup. The optical data are correlated to the results of Rutherford backscattering spectrometry/ion channeling (RBS/C). X-ray diffraction (XRD), atomic force microscopy (AFM) and transmission electron microscopy (TEM). BaTiO3 films on MgO(100) substrates show planar waveguide losses of 3 dB/cm and ridge waveguide losses of 5 dB/cm at a wavelength of 633 nm.

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