Strain Relaxation at Low Misfits: Dislocation Injection vs. Surface Roughening

1995 ◽  
Vol 399 ◽  
Author(s):  
D.D. Perovic ◽  
B. Bahierathan ◽  
D.C. Houghton ◽  
H. Lafontaine ◽  
J.-M. Baribeau
Keyword(s):  
Misfit Dislocation ◽  
Strain Relaxation ◽  
Relaxation Mechanism ◽  
Theoretical Description ◽  
Dislocation Nucleation ◽  
Surface Roughening ◽  
X Ray Diffraction ◽  
Dislocation Generation ◽  
Force Microscopy ◽  
Atomic Force

ABSTRACTTwo competing strain relaxation mechanisms, namely misfit dislocation generation and surface roughening, have been extensively studied using the GexSi1-x/Si (x< 0.5) system as an example. A predictive model has been developed which accurately describes the nature of misfit dislocation nucleation and growth under non-equilibrium conditions. Using optical and electron microscopy, coupled with a refined theoretical description of dislocation nucleation, it is shown that strain relieving dislocations are readily generated at low misfits with a characteristic activation energy barrier regardless of the growth technique employed (i.e. MBE, RTCVD and UHVCVD). Secondly we have studied the alternative elastic strain relaxation mechanism involving surface undulation; x-ray diffraction, electron and atomic force microscopy have been used to characterize GexSi1-x/Si (x<0.5) structures grown by UHVCVD and MBE at relatively higher temperatures. A theoretical model has been used to model the critical thickness for surface wave generation. The conditions governing the interplay between dislocation formation and surface buckling are described in terms of a "morphological instability diagram".

Development of Cross-Hatch Morphology During Growth of Lattice Mismatched Layers

2001 ◽  
Vol 673 ◽  
Author(s):  
A. Maxwell Andrews ◽  
J.S. Speck ◽  
A.E. Romanov ◽  
M. Bobeth ◽  
W. Pompe
Keyword(s):  
Misfit Dislocation ◽  
Film Growth ◽  
Strain Relaxation ◽  
Dislocation Generation ◽  
Force Microscopy ◽  
Step Flow ◽  
Atomic Force ◽  
Subsequent Step ◽  
Step Flow Growth ◽  
Lateral Scale

ABSTRACTAn approach is developed for understanding the cross-hatch morphology in lattice mismatched heteroepitaxial film growth. It is demonstrated that both strain relaxation associated with misfit dislocation formation and subsequent step elimination (e.g. by step-flow growth) are responsible for the appearance of nanoscopic surface height undulations (0.1-10 nm) on a mesoscopic (∼100 nm) lateral scale. The results of Monte Carlo simulations for dislocation- assisted strain relaxation and subsequent film growth predict the development of cross-hatch patterns with a characteristic surface undulation magnitude ∼50 Å in an approximately 70% strain relaxed In0.25Ga0.75As layers. The model is supported by atomic force microscopy (AFM) observations of cross-hatch morphology in the same composition samples grown well beyond the critical thickness for misfit dislocation generation.

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

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.

Optical absorbance enhancement by electrochemical surface roughening of CuInS2 thin films

2009 ◽  
Vol 24 (10) ◽  
pp. 3044-3049 ◽  
Author(s):  
Romain Cayzac ◽  
Florence Boulc'h ◽  
Virginie Hornebecq ◽  
Thierry Djenizian ◽  
Marc Bendahan ◽  
...  
Keyword(s):  
Thin Films ◽  
Electrochemical Etching ◽  
Surface Roughening ◽  
X Ray Diffraction ◽  
Optical Absorbance ◽  
Force Microscopy ◽  
Atomic Force ◽  
Copper Indium ◽  
Cuins2 Thin Films ◽  
Copper Indium Disulphide

This work presents a simple electrochemical etching method to increase the surface roughness of copper indium disulphide (CIS) thin films using low concentration of hydrochloric acid. Film morphologies were investigated using scanning electron microscopy and atomic force microscopy. The structure of films was investigated using x-ray diffraction. A comparative study of optical properties of as-deposited and roughened CIS thin films by transmittance and reflectance experiments show a strong enhancement of absorbance for wavelengths between 600 and 900 nm.

Optical Properties and Defect Structure of MOVPE InGaN Films

1999 ◽  
Vol 588 ◽  
Author(s):  
A. Cremades ◽  
M. Albrecht ◽  
J. M. Ulloa ◽  
J. Piqueras ◽  
H. P. Strunk ◽  
...  
Keyword(s):  
Optical Properties ◽  
Strain Relaxation ◽  
Misfit Dislocations ◽  
Nonradiative Recombination ◽  
X Ray Diffraction ◽  
Band Bending ◽  
Force Microscopy ◽  
Atomic Force ◽  
Transmission Electron ◽  
Piezoelectric Fields

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.

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

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.

Surface Morphology of InxGa1-xAs/GaAs Relaxed Layers Characterized by Atomic Force Microscopy

1994 ◽  
Vol 340 ◽  
Author(s):  
G. Padeletti ◽  
G. M. Ingo ◽  
P. Imperatori
Keyword(s):  
Surface Roughness ◽  
Atomic Force Microscopy ◽  
Strain Relaxation ◽  
Grazing Incidence ◽  
Dislocation Network ◽  
X Ray Diffraction ◽  
X Ray ◽  
Force Microscopy ◽  
Atomic Force ◽  
Combined Use

ABSTRACTGa0.65In0.35As layers of a varying nominal epilayer thickness (10 – 1000 nm) have been grown by the MBE technique on GaAs (100) substrates and characterized by the combined use of atomic force microscopy (AFM) and grazing incidence X-ray diffraction (GIXD). The surface roughness and morphology have been investigated. The GIXD and AFM results show that the thinnest films are characterized by an asymmetric strain relaxation along the two <110> directions with no surface crosshatched pattern but with a misfit dislocation network. AFM images on the thickest films show also well-oriented protrusions along the [110] direction, which increase in size and become more elongated as the nominal film thickness increases.

Misfit Dislocation Nucleation and Interactions at GexSi1-x/Si Interfaces

1989 ◽  
Vol 160 ◽  
Author(s):  
D.D. Perovic ◽  
G.C. Weatherly ◽  
D.C. Houghton
Keyword(s):  
Misfit Dislocation ◽  
Dominant Role ◽  
Strain Relaxation ◽  
Dislocation Nucleation ◽  
Interfacial Dislocation ◽  
Dislocation Generation ◽  
Transmission Electron ◽  
Metastable Structures ◽  
Nucleation Mechanisms ◽  
Generation Mechanisms

AbstractIn the study of elastic strain relaxation in semiconductor heterostructures, a number of misfit dislocation generation mechanisms have been suggested to account for the high interfacial dislocation density observed in these almost defect-free crystals. Several MBE-grown GexSi1-x/Si heterostructures, both in the as-grown and annealed condition have been studied using transmission electron microscopy. The results indicate that some of the popular theories of dislocation generation are less important or not applicable based on both theoretical and experimental considerations. Specifically, it will be shown that: (i) heterogeneous sources play a dominant role in the nucleation mechanisms, (ii) the strain relaxation behaviour during MBE growth may be different from that observed in metastable structures annealed after growth and (iii) the Hagen-S trunk multiplication mechanism is inoperative under most conditions in this system.

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

1995 ◽  
Vol 399 ◽  
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.

Sb surfactant-mediated epitaxy of Ge on Si(113) studied by AFM, SEM and GIXRD

2005 ◽  
Vol 901 ◽  
Author(s):  
Torben Clausen ◽  
Jan-Ingo Flege ◽  
Thomas Schmidt ◽  
Jens Falta
Keyword(s):  
Strain State ◽  
Strain Relaxation ◽  
Three Dimensional ◽  
Grazing Incidence ◽  
Interface Roughness ◽  
X Ray Diffraction ◽  
X Ray ◽  
Force Microscopy ◽  
Atomic Force ◽  
Scanning Electron

AbstractWe have investigated the Sb surfactant-mediated growth of Ge on Si(113) over the temperature range from 500°C to 700°C. The surface morphology, film thickness, interface roughness and strain state of the films have been determined by the use of scanning electron microscopy, atomic force microscopy and grazing incidence x-ray diffraction. After growth at temperatures between 500°C and 600°C smooth Ge films have been observed, which show a partial strain relaxation. However, increasing the temperature to 700°C, a rough surface with a high density of three-dimensional islands has been found.

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