Tem Investigations of CdTe/GaAs(001) Interfaces

1993 ◽  
Vol 319 ◽  
Author(s):  
J.E. Angelo ◽  
W.W. Gerberich ◽  
G. Bratina ◽  
L. Sorba ◽  
A. Franciosi ◽  
...  
Keyword(s):  
Molecular Beam Epitaxy ◽  
Defect Structure ◽  
Molecular Beam ◽  
Misfit Strain ◽  
Growth Direction ◽  
Film Structure ◽  
Buffer Layers ◽  
Ex Situ ◽  
Cross Sectional ◽  
Transmission Electron

AbstractIn this study, cross-sectional transmission electron microscopy (XTEM) was used to investigate the defect structure at the interface between CdTe(001) and GaAs(001) as well as CdTe(1 11) and GaAs(001). The heterostructures were fabricated by molecular beam epitaxy on GaAs(001) buffer layers grown in-situ by molecular beam epitaxy. The defect structure at the as-deposited CdTe(001)/GaAs(001) interface consists of both dislocations and planar faults. The planar faults are both microtwins and stacking faults. It is found that annealing of the film ex-situ causes a restructuring of the CdTe near the interface, with the microtwins being completely removed upon annealing to 450°C for 100 hours. The CdTe(111)/GaAs(001) thin film structure consists of a large number of microtwins parallel to the growth direction. This twinned structure is shown to be related to the relaxation of a residual misfit strain normal to the twin direction. Possible mechanisms for the relaxation are discussed.

TEM Investigations of CdTe/GaAs(001) Interfaces

1992 ◽  
Vol 281 ◽  
Author(s):  
J. E. Angelo ◽  
W. W. Gerberich ◽  
G. Bratina ◽  
L. Sorba ◽  
A. Franciosi
Keyword(s):  
Molecular Beam Epitaxy ◽  
Defect Structure ◽  
Molecular Beam ◽  
Interfacial Structure ◽  
Buffer Layers ◽  
Gaas Surface ◽  
Ex Situ ◽  
Etch Pits ◽  
Oriented Growth ◽  
Cross Sectional

ABSTRACTIn this study, cross-sectional transmission electron microscopy (XTEM) was used to investigate the defect structure which occurs at the interface between CdTe(001) and GaAs(001). The heterostructures were fabricated by molecular beam epitaxy on chemically etched and thermally deoxidized GaAs(001) substrates as well as GaAs(001) buffer layers grown in-situ by molecular beam epitaxy. This allowed for investigation of the GaAs surface preparation on the subsequent interfacial structure. The as-etched substrate led to a microscopically rough interface with the CdTe depositing in etch pits on the GaAs surface, while growth on the buffer layer led to a macroscopically flat interface. Further, growth was accomplished on different Te-induced surface reconstructions ((6×1) vs (2×1)) in an effort to understand the role of the precursor surface treatment on the subsequent interfacial structure. In this case growth on the (6×1) reconstruction led to the introduction of (111)-oriented inclusions at the interface, while the (2×1) reconstruction led to pure (001)-oriented growth. A mechanism for the formation of planar defects at the CdTe/GaAs(001) interface is described which is based on local misorientations of the CdTe and GaAs. Finally, preliminary results of ex-situ annealing experiments on the interfacial defect structure will be discussed.

Real-Time Monitoring by Spectroscopic Ellipsometry and Desorption Mass Spectroscopy During Molecular Beam Epitaxy of AlGaAs/GaAs at High Substrate Temperatures

1999 ◽  
Vol 569 ◽  
Author(s):  
W. T. Taferner ◽  
K. Mahalingam ◽  
D. L. Dorsey ◽  
K. G. Eyink
Keyword(s):  
Molecular Beam Epitaxy ◽  
Mass Spectroscopy ◽  
Spectroscopic Ellipsometry ◽  
Molecular Beam ◽  
Elevated Temperatures ◽  
Gaas Layer ◽  
Ex Situ ◽  
Cross Sectional ◽  
Transmission Electron ◽  
Substrate Temperatures

ABSTRACTA series of AlGaAs/GaAs depositions were monitored in-situ by spectroscopic ellipsometry and desorption mass spectroscopy, under various substrate temperatures (890 K - 990 K) where non-unity sticking conditions occur. An upper bound on the temperature where AlGaAs/GaAs heterostructures may be grown was determined. Ex-situ cross-sectional transmission electron microscopy verified that the AlGaAs/GaAs layer thicknesses grown by molecular beam epitaxy were accurately determined by spectroscopic ellipsometry at these elevated temperatures. The substrate temperature dependence on Ga desorption rates was consistent with Monte Carlo simulation where desorption from both physisorbed and chemisorbed states were included.

Metalorganic Molecular Beam Epitaxy of Magnesium Oxide on Silicon

2000 ◽  
Vol 619 ◽  
Author(s):  
F. Niu ◽  
B.H. Hoerman ◽  
B.W. Wessels
Keyword(s):  
Thin Films ◽  
Molecular Beam Epitaxy ◽  
Molecular Beam ◽  
Amorphous Layer ◽  
Film Structure ◽  
Gate Insulator ◽  
Oxide Semiconductor ◽  
Epitaxial Relationship ◽  
Transmission Electron ◽  
Metalorganic Molecular Beam Epitaxy

ABSTRACTEpitaxial cubic MgO thin films were deposited on single crystal Si (001) substrates by metalorganic molecular beam epitaxy (MOMBE) using the solid precursor magnesium acetylacetonate as the source and an RF excited oxygen plasma as the oxidant. The growth process involved initial formation of an epitaxial β-SiC interlayer followed by direct deposition of a MgO overlayer. The film structure was characterized by X-ray diffraction as well as conventional and high-resolution transmission electron microscopy. Both the MgO overlayer and β-SiC interlayer had an epitaxial relationship such that MgO (001) (or SiC (001)) // Si (001) and MgO [110] (or SiC [110])// Si [110]. No evidence of an amorphous layer was observed at either the MgO/SiC or SiC/Si interface. Dielectric properties of the epitaxial MgO thin films on Si (001) were evaluated from capacitance-voltage (C-V) characteristic of metal-oxide-semiconductor (MOS) structures. The C-V measurements indicated an interface trap density at midgap as low as 1011 to 1012 cm−2 eV−1 and fixed oxide charge of the order of 1011/ cm2, respectively. These results indicate that epitaxial MgO deposited by MOMBE has potential as a gate insulator.

A Study of the Defect Structure in GaAS1−xPx/GaAs AS x<0.25

1993 ◽  
Vol 317 ◽  
Author(s):  
G. Aragon ◽  
M.J. De Castro ◽  
S.I. Molina ◽  
Y. Gonzalez ◽  
L. Gonzalez ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Molecular Beam Epitaxy ◽  
Defect Structure ◽  
Gaas Substrate ◽  
Molecular Beam ◽  
Atomic Layer ◽  
Multiple Cracks ◽  
Transmission Electron ◽  
Phosphorous Content

ABSTRACTThe defect structure of GaAsP layer grown by Atomic Layer Molecular Beam Epitaxy on (001) GaAs substrate has been studied by Transmission Electron Microscopy. The phosphorous content and the epilayer thickness have been changed below 25% and 1μm respectively. Three kinds of defect structure have been found: a) α-δ fringes at the interface for coherent epilayer, b) Misfit dislocation for thin epilayers and c) Multiple cracks normal to the interface and parallel to one <110> direction for thick epilayers.

Interrelation between Strain Relaxation and InxAl1-xAs Compositional Graded Step Buffer Layers on GaAs Substrate Grown by Molecular Beam Epitaxy

2007 ◽  
Vol 124-126 ◽  
pp. 127-130
Author(s):  
Sook Hyun Hwang ◽  
Yu Mi Park ◽  
Hoon Ha Jeon ◽  
Kyung Seok Noh ◽  
Jae Kyu Kim ◽  
...  
Keyword(s):  
Molecular Beam Epitaxy ◽  
Gaas Substrate ◽  
Molecular Beam ◽  
Strain Relaxation ◽  
Buffer Layers ◽  
X Ray Diffraction ◽  
Compositional Gradient ◽  
Transmission Electron ◽  
Two Samples ◽  
Compositional Gradients

We have grown delta-doped In0.5Ga0.5As /In0.5Al0.5As heterostructures on GaAs substrate applying with InxAl1-xAs compositional graded-step buffers, called metamorphic structures, grown by molecular beam epitaxy. Three types of buffer layers with different compositional gradients and thicknesses have designed to investigate the influence of the strain relaxation process. We characterized the samples by using transmission electron microscopy, triple-axis X-ray diffraction and Hall measurement. Two samples with different compositional gradient show almost same results in electrical properties. On the other hand, it is found that samples with different step thicknesses had shown the large differences in epilayer tilt and mosaic spread in the step-graded buffers. These results indicate that there exists an interrelation between the strain-relaxed buffer and 2DEG transport properties.

Ge Nanocrystals Grown on Si(111) by Molecular Beam Epitaxy with and without CaF2 Buffer Layers

1994 ◽  
Vol 358 ◽  
Author(s):  
Peter W. Deelman ◽  
Thomas Thundat ◽  
Leo J. Schowalter
Keyword(s):  
Molecular Beam Epitaxy ◽  
Substrate Temperature ◽  
Molecular Beam ◽  
Buffer Layers ◽  
Ex Situ ◽  
Rheed Pattern ◽  
Island Growth ◽  
Clustering Behavior ◽  
Ge Nanocrystals

ABSTRACTThe Stranski-Krastanov growth mode of Ge thin films on Si and the clustering behavior of Ge on calcium fluoride have been exploited to grow self-assembled nanocrystals by molecular beam epitaxy. The growth of the samples was monitored in situ with RHEED, and they were analyzed ex situ with AFM and RBS. For each system (Ge/Si and Ge/CaF2/Si), the dependence of Ge islanding on substrate temperature and on substrate misorientation was studied. When grown on Si(111) at temperatures between 500°C and 700°C, Ge clusters nucleated at step edges on vicinal wafers and nucleated homogeneously on on-axis wafers. Above 600°C, no transition to a spotty RHEED pattern, which would be expected for island growth, was observed for the vicinal samples. Ge grown at 500°C on on-axis Si(111) formed islands with a relatively narrow size distribution, typically 160nm in diameter and 10nm to 20nm in height. When grown on a CaF2 buffer layer, Ge islands nucleated homogeneously at a substrate temperature of 750°C, resulting in randomly distributed, oblate crystallites approximately 100nm to 200nm in diameter. At 650°C and 700°C, although we still observed many randomly distributed, small crystallites, most islands nucleated at step bunches and had a length scale of over 500nm.

Optimization of synthesis of the solid solution, Pb(Zr1–xTix)O3 on a single substrate using a high-throughput modified molecular-beam epitaxy technique

2009 ◽  
Vol 24 (1) ◽  
pp. 164-172 ◽  
Author(s):  
P.S. Anderson ◽  
S. Guerin ◽  
B.E. Hayden ◽  
Y. Han ◽  
M. Pasha ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Molecular Beam Epitaxy ◽  
High Throughput ◽  
Molecular Beam ◽  
Ex Situ ◽  
X Ray Diffraction ◽  
Single Substrate ◽  
Transmission Electron ◽  
Substrate Temperatures

Synthesis of Pb(Zr1–xTix)O3 (PZT) on a single substrate using a high-throughput molecular-beam epitaxy technique was demonstrated. In situ synthesis of crystalline PZT at elevated substrate temperatures could not be achieved, as reevaporation of Pb (PbO) occurred and the partial pressure of O2 was insufficient to prevent formation of a PbPtx phase during deposition. Instead, ex situ postdeposition annealing was performed on PZT deposited at room temperature. Dense single phase PZT was prepared with a compositional range of 0.1 > x > 0.9, for film thicknesses up to 800 nm. Transmission electron microscopy revealed the grain size increased from 50 nm to ∼0.5 μm with increasing Zr-concentration and became more columnar. Raman, x-ray diffraction, and scanning electron microscopy/energy dispersive spectroscopy results revealed a morphotropic phase boundary between rhombohedral and tetragonal phases occurred at x ∼0.4 rather than at x = 0.47 in bulk ceramics. This was attributed to clamping arising from mismatch in thermal expansion between the film and substrate.

Growth and characterization of GaAs on Si substrates grown by molecular-beam epitaxy

1987 ◽  
Vol 65 (8) ◽  
pp. 897-903
Author(s):  
P. Mandeville ◽  
A. J. SpringThorpe ◽  
C. J. Miner ◽  
R. A. Bruce ◽  
J. F. Currie ◽  
...  
Keyword(s):  
Molecular Beam Epitaxy ◽  
Molecular Beam ◽  
Defect Density ◽  
Growth Parameters ◽  
Current Gain ◽  
Hall Resistance ◽  
Cross Sectional ◽  
Si Substrates ◽  
Transmission Electron ◽  
Dimensional Electron Gas

Single-crystal GaAs layers have been grown by molecular beam epitaxy (MBE) on (100) Si substrates. Surface morphology, defect density, and optical and electrical properties have been studied as a function of the growth parameters. The characterization techniques included photoluminescence, Hall effect, cross-sectional transmission electron microscopy, and X-ray diffraction. GaAs metal semiconductor field-effect transitors on Si exhibited transconductances of 128 mS∙mm−1 and current-gain cutoff frequencies as high as 19 GHz. Special heterostructures showed Shubnikov–de Haas oscillations at low temperature and plateaux in the Hall resistance, which confirmed the presence of two-dimensional electron gas in the heterostructure.

Study on Barium Strontium Titanate Thin Films Integrated on Si Substrates by Laser Molecular Beam Epitaxy

2009 ◽  
Vol 79-82 ◽  
pp. 823-826
Author(s):  
X.Y. Zhou ◽  
Yun Zhou ◽  
G.Y. Wang ◽  
Y. Wang ◽  
Helen Lai Wah Chan ◽  
...  
Keyword(s):  
Molecular Beam Epitaxy ◽  
Molecular Beam ◽  
Lattice Structure ◽  
Bias Field ◽  
Sio2 Layer ◽  
X Ray Diffraction ◽  
Cross Sectional ◽  
Laser Molecular Beam Epitaxy ◽  
Si Substrates ◽  
Transmission Electron

(Ba,Sr)TiO3 thin film has been deposited on Si (001) wafer with the SiO2 layer as the block layer through laser molecular-beam epitaxy using an ultra thin Sr layer as template. X-ray diffraction measurements and the cross-sectional observations under transmission electron microscope indicated that BST was well crystallized. This deposition of Sr layer is considered to remove the thin SiO2 layer to produce a layer, which is crystallized and has a lattice structure matching with that of perovskite BST. The maximum in-plane dielectric tunability is calculated to be 50% at 1 GHz under a moderate DC bias field of 13.3 V/µm. This BST/Si structure is believed to be a promising candidate in the development of ferroelectric BST-based microwave devices.

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