Structural properties of GaAs/InGaAs/GaAs (001) and InGaAs/GaAs (001) heterostructures and correlation with electronic properties

1990 ◽  
Vol 48 (4) ◽  
pp. 602-603
Author(s):  
J.M. Bonar ◽  
R. Hull ◽  
R. Malik ◽  
R. Ryan ◽  
J.F. Walker
Keyword(s):  
Band Gap ◽  
Electronic Properties ◽  
Gaas Substrate ◽  
Critical Thickness ◽  
Lattice Mismatch ◽  
Band Offset ◽  
Misfit Dislocations ◽  
Gaas Substrates ◽  
Gaas Structure ◽  
Low X

In this study we have examined a series of strained heteropeitaxial GaAs/InGaAs/GaAs and InGaAs/GaAs structures, both on (001) GaAs substrates. These heterostructures are potentially very interesting from a device standpoint because of improved band gap properties (InAs has a much smaller band gap than GaAs so there is a large band offset at the InGaAs/GaAs interface), and because of the much higher mobility of InAs. However, there is a 7.2% lattice mismatch between InAs and GaAs, so an InxGa1-xAs layer in a GaAs structure with even relatively low x will have a large amount of strain, and misfit dislocations are expected to form above some critical thickness. We attempt here to correlate the effect of misfit dislocations on the electronic properties of this material.The samples we examined consisted of 200Å InxGa1-xAs layered in a hetero-junction bipolar transistor (HBT) structure (InxGa1-xAs on top of a (001) GaAs buffer, followed by more GaAs, then a layer of AlGaAs and a GaAs cap), and a series consisting of a 200Å layer of InxGa1-xAs on a (001) GaAs substrate.

Equilibrium Analysis of Lattice-Mismatched Nanowire Heterostructures

2002 ◽  
Vol 737 ◽  
Author(s):  
E. Ertekin ◽  
P.A. Greaney ◽  
T. D. Sands ◽  
D. C. Chrzan
Keyword(s):  
Simple Model ◽  
Misfit Dislocation ◽  
Critical Thickness ◽  
Lattice Mismatch ◽  
Equilibrium Analysis ◽  
Misfit Dislocations ◽  
Model Based ◽  
Large Lattice ◽  
Large Lattice Mismatch

ABSTRACTThe quality of lattice-mismatched semiconductor heterojunctions is often limited by the presence of misfit dislocations. Nanowire geometries offer the promise of creating highly mismatched, yet dislocation free heterojunctions. A simple model, based upon the critical thickness model of Matthews and Blakeslee for misfit dislocation formation in planar heterostructures, illustrates that there exists a critical nanowire radius for which a coherent heterostructured nanowire system is unstable with respect to the formation of misfit dislocations. The model indicates that within the nanowire geometry, it should be possible to create perfect heterojunctions with large lattice-mismatch.

CRITICAL THICKNESS FOR Nb NANOFILM ON SAPPHIRE SUBSTRATE: AN EXAMPLE TOWARD UNDERSTANDING EVOLUTION OF COHERENT NANOSTRUCTURES

2011 ◽  
Vol 10 (01n02) ◽  
pp. 351-354 ◽  
Author(s):  
ARUN KUMAR ◽  
ANANDH SUBRAMANIAM
Keyword(s):  
Stress State ◽  
Edge Dislocation ◽  
Sapphire Substrate ◽  
Critical Thickness ◽  
Lattice Mismatch ◽  
Energy Criterion ◽  
Misfit Dislocations ◽  
Combined Simulation ◽  
Triangular Network ◽  
Theoretical Analyses

On growth beyond critical thickness, interfacial misfit dislocations partially relax the misfit strains in epitaxially grown nanofilms. In this study the stress state and growth of nanofilms are simulated using Finite Element Method (FEM) by imposing stress-free strains, corresponding to the lattice mismatch between Nb nanofilm and Sapphire substrate. On growth of the Nb nanofilm, a triangular network of edge misfit dislocations nucleates at the (0001) Al 2 O 3∥(111) Nb interface. Using a combined simulation of a coherently strained nanofilm and an edge dislocation, the critical thickness for the nucleation of an edge dislocation is determined using an equilibrium energy criterion. Theoretical analyses in literature use only the component of the Burgers vector parallel to the interface, which is an erroneous description of the stress state and energetics of the system. In this investigation the full interfacial edge dislocation is simulated using standard commercially available software and comparisons are made with results available in literature to bring out the utility of the methodology.

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.

Nucleation mechanism of misfit dislocations in multi-quantum wells

1990 ◽  
Vol 48 (4) ◽  
pp. 598-599
Author(s):  
J. Zou ◽  
D.J.H. Cockayne ◽  
A. Sikorski ◽  
B.F. Usher
Keyword(s):  
Quantum Wells ◽  
Cross Section ◽  
Molecular Beam ◽  
Critical Thickness ◽  
Nucleation Mechanism ◽  
Misfit Dislocations ◽  
Plan View ◽  
Gaas Substrates ◽  
Bottom Interface ◽  
Almost All

A series of plan-view and cross-section samples of multi-quantum wells (MQWs) consisting of 32nm GaAs and 10.5nm In0.15Ga0.85As grown by molecular beam epitaxy on GaAs substrates were examined by TEM. Tne number of periods (n) of the MQWs were 3, 6, 12, 24, and 48. The results showed that for n smaller than or equal to 12 periods, almost all misfit dislocations (MDs) were found near the epitaxial surface (see figure 1) which is far away from the interface between the MQWs and the substrate; but for n equal to or larger than 24 periods, most MDs were observed at the bottom interface between the MQWs and the substrate (shown in figure 2).To explain these observations, a new nucleation mechanism for the MDs has been derived from energy considerations, based on the theory of the critical thickness of the half circular dislocation loop (HCDL) in a single epitaxial layer and the strain contribution in the MQWs.

Electron microscopy of GaAs grown on Si- and Ge-based substrates

1991 ◽  
Vol 49 ◽  
pp. 854-855
Author(s):  
D.P. Malta ◽  
J.B. Posthill ◽  
M.L. Timmons ◽  
P.R. Sharps ◽  
R. Venkatasubramanian ◽  
...  
Keyword(s):  
Critical Thickness ◽  
Lattice Mismatch ◽  
Low Cost ◽  
Antiphase Domain ◽  
Threading Dislocation ◽  
Misfit Dislocations ◽  
Thermally Induced ◽  
Induced Stress ◽  
Dislocation Reduction ◽  
Domain Boundaries

A GaAs-on-Si technology is desirable to take advantage of the mobility and direct bandgap of GaAs in combination with the crystalline quality, low cost and established technology of Si. Differences in lattice constant (4.1%), thermal expansion coefficient (a factor of ~ 3), and bonding polarity between the two materials can lead to problems such as: threading dislocation formation, thermally induced stress and delamination, and antiphase domain boundaries (APBs), respectively. The lattice mismatch is responsible for the formation of (necessary) misfit dislocations which can concurrently create threading dislocations with typical densities in the range of 106 - 108cm-2. This density of electrically active defects in a device region is highly undesirable.A proposed scheme for lattice mismatch accommodation and potential threading dislocation reduction has previously been reported in which each layer of a SixGe1-x multilayer structure (MLS) is grown beyond the critical thickness with a progressively higher Ge composition than the previous layer.

scholarly journals InAs/GaSb Superlattice Based Mid-Infrared Interband Cascade Photodetectors Grown on Both Native GaSb and Lattice-Mismatched GaAs Substrates

Proceedings ◽  
2019 ◽  
Vol 27 (1) ◽  
pp. 38
Author(s):  
Hackiewicz ◽  
Kopytko ◽  
Rutkowski ◽  
Martyniuk ◽  
Ciura
Keyword(s):  
Gaas Substrate ◽  
Room Temperature ◽  
Device Performance ◽  
Misfit Dislocations ◽  
Type Ii ◽  
Electrical And Optical Properties ◽  
Mid Infrared ◽  
Type Ii Superlattice ◽  
Gaas Substrates ◽  
Optical Immersion

Electrical and optical properties of interband cascade infrared photodetectors with InAs/GaSb type-II superlattice absorbers are investigated in this work. We compare the detection parameters of detectors grown on the native GaSb substrate and lattice-mismatched GaAs substrate and seek solutions to enhance device performance, specifically with using an optical immersion. The detectors grown on GaAs have better detection parameters at room temperature, but at lower temperatures the misfit dislocations become more important and detectors grown on GaSb become better.

Organometallic Vapor Phase Epitaxial Growth of ZnGeAs2 and (ZnGeAs2)xGe1−x on GaAs

1988 ◽  
Vol 144 ◽  
Author(s):  
G. S. Solomon ◽  
J. B. Posthill ◽  
M. L. Timmons
Keyword(s):  
Single Crystal ◽  
Band Gap ◽  
Lattice Constant ◽  
Vapor Phase ◽  
Gaas Substrate ◽  
Lattice Mismatch ◽  
Chalcopyrite Structure ◽  
Zinc Blende ◽  
Indirect Band Gap ◽  
Zinc Blende Structure

ABSTRACTEpitaxial single crystal (001) chalcopyrite-structure ZnGeAs2 and single crystal (100) zinc blende-structure (ZnGeAs2)xGe1−x alloys have been grown by organometallic vapor phase epitaxy on (100) GaAs. Selected area electron diffraction was used to determine the crystal structure for several Zn:Ge molar flow ratios. Bulk chemical composition was determined by electron microprobe and correlated to crystal lattice constants obtained from x-ray diffraction. Due to the lattice mismatch between chalcopyrite-structure ZnGeAs2 and the GaAs substrate, the epitaxy is elastically strained, compressing the a-lattice constant and elongating the c-lattice constant. Optical absorption and transmission spectroscopy indicate the zinc-blende-structure material has an indirect band gap of approximately 0.6 eV, whereas the chalcopyrite ZnGeAs2 has a direct band gap of 1.15 eV. Secondary ion mass spectroscopy reveals significant Zn diffusion into the GaAs substrate if the Zn:Ge molar flow ratio exceeds the ratio required for stoichiometric chalcopyrite-structure crystal growth.

Electronic structure and total energy of diamond/BeO interfaces

1992 ◽  
Vol 7 (3) ◽  
pp. 696-705 ◽  
Author(s):  
Walter R.L. Lambrecht ◽  
Benjamin Segall
Keyword(s):  
Electronic Structure ◽  
Total Energy ◽  
Band Gap ◽  
Lattice Mismatch ◽  
Interface Energy ◽  
Adhesion Energy ◽  
Misfit Dislocations ◽  
Densities Of States ◽  
Representative Model ◽  
Experimental Values

Electronic structure calculations are used to study the bonding at diamond/BeO interfaces. The {110} interface between zinc blende BeO and diamond is used as a representative model for general reconstructed interfaces characterized by an equal amount of Be–C and O–C bonds. The interface energy is calculated to be 2 J/m2 and combined with the estimated free surface energies to obtain an estimate of the adhesion energy. It is found to be close to the adhesion of BeO to itself, but somewhat lower than that of diamond to itself. The effects of the 7% lattice mismatch on the total energy and the band structure for a biaxially strained pseudomorphic diamond film are investigated. The effect of misfit dislocations, expected to occur for thicker films, on the adhesion energy is estimated to be lower than 10%. The bulk properties, such as equilibrium lattice constant, bulk modulus, cohesive energy, and band gap of BeO are shown to be in good agreement with experimental values and previous calculations. The valence-band offset is calculated to be 3.9 eV and found to take up most of the large band gap discontinuity. The nature of the bonding is discussed in terms of the local densities of states near the interface. The interface localized features are identified in terms of Be–C and O–C bonding and antibonding states.

A Molecular Dynamics Study of InGaAs Layers on GaAs Substrates

1994 ◽  
Vol 340 ◽  
Author(s):  
G J Moran ◽  
I Morrison ◽  
C C Matthai
Keyword(s):  
Molecular Dynamics ◽  
Molecular Dynamics Simulations ◽  
Elasticity Theory ◽  
Critical Thickness ◽  
Strain Relaxation ◽  
Thin Layers ◽  
Misfit Dislocations ◽  
Strain Relief ◽  
Gaas Substrates ◽  
Dynamics Simulations

ABSTRACTWe have performed molecular dynamics simulations of thin layers of InGaAs on GaAs substrates for different In concentrations to determine the critical thickness before strain relaxation occurs. We have considered both dislocation formation and islanding as possible mechanisms for strain relief. The results for the critical thickness for strain relief by misfit dislocations is slightly lower than that found using elasticity theory. For high In concentrations, facetted islands are found to be stable and are energetically favoured.

Selective Oxidation and Etching of Reacted Pt Films on Gaas

1990 ◽  
Vol 181 ◽  
Author(s):  
Eliezer Weiss ◽  
Robert C. Keller ◽  
Margaret L. Kniffin ◽  
C.R. Helms
Keyword(s):  
Water Vapor ◽  
Auger Electron Spectroscopy ◽  
Selective Oxidation ◽  
Electron Spectroscopy ◽  
Gaas Substrate ◽  
Gallium Oxide ◽  
Auger Electron ◽  
Gaas Substrates ◽  
Gaas Structure ◽  
Pt Films

ABSTRACTThe oxidation of prereacted Pt films on (100)-oriented n-GaAs substrates was studied in the temperature range between 550 and 750°C using Auger electron spectroscopy and Xe+ ion profiling. The GaPt/PtAs2/GaAs structure formed during annealing in hydrogen was oxidized using a mixture of water vapor and hydrogen. The GaPt phase can be oxidized completely, whereas the inner PtAs2 and GaAs interfaces are left unoxidized. The oxidation of the platinum-gallium phase is self limited by the diffusion of the Ga through the gallium oxide overlayer. The oxide can be etched off to leave a structure consisting only of platinum-arsenide on the GaAs substrate.

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