Growth of Metamorphic InGaP for Wide-Bandgap Photovoltaic Junction by MBE

2010 ◽  
Vol 1268 ◽  
Author(s):  
John Simon ◽  
Stephanie Tomasulo ◽  
Paul Simmonds ◽  
Manuel J Romero ◽  
Minjoo Larry Lee
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Molecular Beam ◽  
Strain Relaxation ◽  
Wide Bandgap ◽  
Threading Dislocation ◽  
Step Size ◽  
Transmission Electron ◽  
Dislocation Densities ◽  
Substrate Temperatures

AbstractMetamorphic triple-junction solar cells can currently attain efficiencies as high as 41.1%. Using additional junctions could lead to efficiencies above 50%, but require the development of a wide bandgap (2.0-2.2eV) material to act as the top layer. In this work we demonstrate wide bandgap InyGa1-yP grown on GaAsxP1-x via solid source molecular beam epitaxy. Unoptimized tensile GaAsxP1-x buffers grown on GaAs exhibit asymmetric strain relaxation, along with formation of faceted trenches 100-300 nm deep in the [01-1] direction. Smaller grading step size and higher substrate temperatures minimizes the facet trench density and results in symmetric strain relaxation. In comparison, compressively-strained graded GaAsxP1-x buffers on GaP show nearly-complete strain relaxation of the top layers and no evidence of trenches. We subsequently grew InyGa1-yP layers on the GaAsxP1-x buffers. Photoluminescence and transmission electron microscopy measurements show no indication of phase separation or CuPt ordering. Taken in combination with the low threading dislocation densities obtained, MBE-grown InyGa1-yP layers are promising candidates for future use as the top junction of a multi-junction solar cell.

Defect-Engineered Graded GexSi1-x Buffers on Si (001) with Extreme Low Threading Dislocation Density

1995 ◽  
Vol 378 ◽  
Author(s):  
G. Kissinger ◽  
T. Morgenstern ◽  
G. Morgenstern ◽  
H. B. Erzgräber ◽  
H. Richter
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Atomic Force Microscopy ◽  
Dislocation Density ◽  
Threading Dislocation ◽  
Force Microscopy ◽  
Atomic Force ◽  
Transmission Electron ◽  
Dislocation Densities ◽  
Threading Dislocation Density

AbstractStepwise equilibrated graded GexSii-x (x≤0.2) buffers with threading dislocation densities between 102 and 103 cm−2 on the whole area of 4 inch silicon wafers were grown and studied by transmission electron microscopy, defect etching, atomic force microscopy and photoluminescence spectroscopy.

Threading Dislocations in InxGabxAs/GaAs System

1991 ◽  
Vol 240 ◽  
Author(s):  
M. Tamura ◽  
A. Hashimoto ◽  
Y. Nakatsugawa
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Film Thickness ◽  
Cross Section ◽  
Molecular Beam ◽  
Threading Dislocation ◽  
Threading Dislocations ◽  
Edge Type ◽  
Transmission Electron ◽  
Fixed Film

ABSTRACTThreading dislocation morphologies and characters, as well as their generation conditions in InxGa1−xAs films grown by molecular-beam epitaxy on GaAs (001) substrates have been examined, mainly using cross-section al transmission electron microscopy (XTEM) as a function of x and film thickness. The formation of severe threading dislocations is detected in epilayers ofx≧0.2 at a fixed film thickness of 3 μm and with film thicknesses greater than 2μmat x=0.2. Most of the observed threading dislocations are 60°- and pure-edge type dislocations along the <211> and [001] directions, respectively. The former type dislocations are mainly observed in layers of x≧0.2; the latter predominantly exist in layers of X≧O.3.

ZnSe Growth on Lattice-Matched InxGa1-xAs Substrates

1998 ◽  
Vol 05 (03n04) ◽  
pp. 693-700 ◽  
Author(s):  
S. Heun ◽  
R. Lantier ◽  
J. J. Paggel ◽  
L. Sorba ◽  
S. Rubini ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Molecular Beam Epitaxy ◽  
Dislocation Density ◽  
Residual Strain ◽  
Molecular Beam ◽  
Strain Relaxation ◽  
Line Emission ◽  
Transmission Electron ◽  
Lattice Matched

The properties of ZnSe epilayers fabricated by molecular beam epitaxy on lattice-matched In x Ga 1-x As buffers grown on GaAs(001) substrates have been investigated by means of photoluminescence spectroscopy and transmission electron microscopy. For suitable values of x and ternary-layer thickness, the partial character of the strain relaxation within the III–V layer can be compensated for, minimizing the residual strain in the ZnSe overlayer. Large reductions in the dislocation density and Y-line emission as compared to conventional ZnSe/GaAs heterostructures can be reproducibly obtained.

Incorporation of Excess Arsenic in GaAs and AlGaAs Epilayers Grown at Low Substrate Temperatures by Molecular Beam Epitaxy

1991 ◽  
Vol 241 ◽  
Author(s):  
M. R. Melloch ◽  
N. Otsuka ◽  
K. Mahalingam ◽  
A. C. Warrew ◽  
J. M. Woodall ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Activation Energy ◽  
Transmission Electron Microscopy ◽  
Molecular Beam Epitaxy ◽  
Molecular Beam ◽  
Volume Fraction ◽  
Transmission Electron ◽  
Si Doped ◽  
Substrate Temperatures ◽  
Inverse Substrate

ABSTRACTExcess arsenic can be incorporated in GaAs and AIGaAs epilayers by growing at low substrate temperatures (LT-GaAs and LT-AIGaAs) by molecular beam epitaxy (MBE). Upon annealing these epilayers, the excess As precipitates forming GaAs:As and AIGaAs:As. Using transmission electron microscopy (TEM), we have measured the densities and sizes of the As precipitates and thereby determined the amount of excess As incorporated in these epilayers. The volume fraction of excess As as a function of inverse substrate growth temperature follows an Arrhenius-type behavior with an activation energy of 0.87 eV. The sizes of the As precipitates increase and the densities decrease with increase anneal temperatures; for Si-doped GaAs:As this results in n-type material when the densities become small enough that the depletion regions around the As precipitates no longer overlap. Also investigated is the formation of As precipitates at GaAs/AIGaAs heterojunctions and superlattices, and our attempts to tailor the As precipitate distribution.

Investigation of Phosphorus In-Diffusion and Strain in GaAsP/GaAs Using High-Resolution Transmission Electron Microscopy

2020 ◽  
Vol 62 ◽  
pp. 1-7
Author(s):  
Wonjae Chang
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
High Resolution ◽  
Molecular Beam ◽  
Growth Direction ◽  
Gaas Layer ◽  
Strained Layers ◽  
Atomic Arrangement ◽  
Transmission Electron ◽  
Substrate Temperatures

We report our experiments based on the interfaces of a 5-period superlattice, containing GaAsP(3Å)/GaAs (190Å) heterostructures grown by molecular beam epitaxy (MBE). The atomic arrangement at the interfaces of GaAsP/GaAs is investigated using high resolution transmission electron microscopy (HRTEM). Our results indicate that the superlattice was grown coherently with strained layers. We propose that the atomic arrangement at the interface is GaP, assuming that phosphorus incorporation occurs primarily via substitution due to desorption of arsenic at the surface for substrate temperatures above 500°C. The incorporation of phosphorus has been investigated using fast Fourier transform (FFT) patterns and shows a form of strain distribution near the heterointerface. The FFT patterns of the superlattice reveal that strain distributes mostly near the interface and gradually decreases along the direction of growth. Phosphorus diffused into a GaAs layer changes the lattice constant in the growth direction, which reduces strain in the superlattice.

Vertical self-organization of Ge1−xMnx nanocolumn multilayers grown on Ge(001) substrates

2016 ◽  
Vol 30 (20) ◽  
pp. 1650269 ◽  
Author(s):  
Thi Giang Le ◽  
Minh Tuan Dau
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
High Resolution ◽  
Molecular Beam Epitaxy ◽  
Elastic Constant ◽  
Structural Properties ◽  
Molecular Beam ◽  
Self Organization ◽  
Transmission Electron ◽  
2D Model

High-resolution transmission electron microscopy (HR-TEM) has been used to investigate the structural properties of GeMn/Ge nanocolumns multilayer samples grown on Ge(001) substrates by means of molecular beam epitaxy (MBE) system. Four bilayers with the spacer thickness in the range between 6 nm and 15 nm and 10 periods of bilayers of Ge[Formula: see text]Mn[Formula: see text]/Ge nanocolumn are presented. A simplified 2D model based on the theory of elastic constant interactions has been used to provide reasonable explanations to the vertical self-organization of GeMn nanocolumns in multilayers.

Investigation of Defect Formation in 4H-SiC(0001) and (000-1) Epitaxy

2008 ◽  
Vol 600-603 ◽  
pp. 267-272 ◽  
Author(s):  
Hidekazu Tsuchida ◽  
Isaho Kamata ◽  
Masahiro Nagano
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Defect Formation ◽  
Grazing Incidence ◽  
Microscopic Structure ◽  
Threading Dislocation ◽  
Simultaneous Generation ◽  
Burgers Vector ◽  
X Ray ◽  
Transmission Electron

Defect formation in 4H-SiC(0001) and (000-1) epitaxy is investigated by grazing incidence synchrotron reflection X-ray topography and transmission electron microscopy. Frank-type faults, which are terminated by four Frank partials with a 1/4[0001] type Burgers vector with the same sign on four different basal planes, are confirmed to be formed by conversion of a 1c threading edge dislocation (TSD) in the substrate as well as simultaneous generation of a 1c TSD during epitaxy. The collation between the topography appearance and the microscopic structure and the variety of Frank faults are shown. Formation of carrot defects and threading dislocation clusters are also investigated.

Photo Modified Growth of GaAs by Chemical Beam Epitaxy

1998 ◽  
Vol 510 ◽  
Author(s):  
R. Jothilingam ◽  
T. Farrell ◽  
T.B. Joyce ◽  
P.J. Goodhew
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Growth Rate ◽  
Electrical Power ◽  
Xenon Lamp ◽  
Chemical Beam Epitaxy ◽  
Cross Sectional ◽  
Transmission Electron ◽  
Substrate Temperatures ◽  
Laser Reflectometry

AbstractWe report the photo modified growth of GaAs by chemical beam epitaxy at substrate temperatures in the range 335 to 670°C using triethygallium (TEG) and arsine. A mercury-xenon lamp (electrical power 200 W) provided the irradiation for the photoassisted growth. The growth was monitored in real time by laser reflectometry (LR) using a 670 nm semiconductor laser, and the optically determined growth rate agreed with that obtained from the layer thickness measured by cross sectional transmission electron microscopy. The observed photo-enhancement of the growth rate at low substrate temperatures and inhibition at high substrate temperatures is thermal in origin, consistent with raising the substrate temperature by 10±3°C. Cross sectional transmission electron microscopy showed that the photoassisted layers are essentially free from dislocations

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