scholarly journals Elastic Energy in Inas Quantum Dot-in-a-Well Structures

2014 ◽  
Vol 2 ◽  
pp. 30-34
Author(s):  
Erick Velázquez-Lozada ◽  
G.M. Camacho-González ◽  
J. Quino-Cerdan
Keyword(s):  
Quantum Wells ◽  
Elastic Strain ◽  
Gaas Substrate ◽  
Buffer Layers ◽  
Epitaxial Layers ◽  
X Ray Diffraction ◽  
Bulk Gaas ◽  
X Ray ◽  
Fitting Procedure ◽  
Diffraction Peaks

The photoluminescence (PL), its temperature dependence and X ray diffraction (XRD) have been studied in the symmetric In0.15Ga1-0.15As/GaAs quantum wells (QWs) with embedded InAs quantum dots (QDs), obtained with the variation of QD growth temperatures (470-535°C). The increase of QD growth temperatures is accompanied by the enlargement of QD lateral sizes (from 12 up to 28 nm) and by the shift non monotonically of PL peak positions. The fitting procedure has been applied on the base of Varshni analysis to the temperature dependences of PL peaks. The obtained Varshni parameters testify that in studied QD structures the process of In/Ga interdiffusion between QDs and capping/buffer layers takes place partially. However, this process cannot explain the difference in PL peak positions. The XRD study has revealed the high intensity peaks at 2Θ= 31.6-31.8o (Kα1, Kα2) that correspond to the X ray diffraction of the Kα1 and Kα2 lines of Cu source from the (200) crystal planes of cubic GaAs. It was shown that the XRD peak is the superposition of the diffraction from the GaAs substrate and GaAs layers of quantum wells. The position of diffraction peaks related to the cubic GaAs substrate coincides with the very well know XRD data for the bulk GaAs. It means that the elastic strain in the GaAs substrate has been relaxed. At the same time the peak positions of the (200) diffraction peaks in GaAs epitaxial layers shift to the high angles in comparison with the bulk GaAs, testifying the compression strain in GaAs epitaxial layers. The minimum of elastic strain is detected in the structure with QD grown at 510°C that manifests itself by the higher QD PL intensity and lower the PL peak energy.

InAs Quantum Dots Grown on an AlGaAsSb Strain-Relief Buffer

2000 ◽  
Vol 642 ◽  
Author(s):  
A.L. Gray ◽  
L. R. Dawson ◽  
Y. Lin ◽  
A. Stintz ◽  
Y.-C. Xin ◽  
...  
Keyword(s):  
Quantum Dots ◽  
Cross Section ◽  
Gaas Substrate ◽  
Buffer Layers ◽  
Threading Dislocations ◽  
X Ray Diffraction ◽  
Strain Relief ◽  
Inas Quantum Dots ◽  
X Ray ◽  
Transmission Electron

ABSTRACTAn In(Ga)As-based self-assembled quantum dot laser test structure grown on strain-relief Al0.5Ga0.5As1-ySby strain-relief buffer layers (0≤y ≤ 0.24) on a GaAs substrate is investigated in an effort to increase dot size and therefore extend the emission wavelength over conventional InAs quantum dots on GaAs platforms. Cross-section transmission electron microscopy, and high-resolution x-ray diffraction are used to monitor the dislocation filtering process and morphology in the buffer layers. Results show that the buffer layers act as an efficient dislocation filter by drastically reducing threading dislocations, thus providing a relaxed, low dislocation, compositionally modulated Al0.5Ga0.5Sb0.24As0.76 substrate for large (500Å height x 300Å width) defect -free InAs quantum dots. Photoluminescence shows a ground-state emission of the InAs quantum dots at 1.45 μm.

A profile-fitting procedure for analysis of broadened X-ray diffraction peaks. I. Methodology. Erratum

1989 ◽  
Vol 22 (2) ◽  
pp. 184-184 ◽  
Author(s):  
S. Enzo ◽  
G. Fagherazzi ◽  
A. Benedetti ◽  
S. Polizzi
Keyword(s):  
X Ray Diffraction ◽  
Correct Equation ◽  
X Ray ◽  
Fitting Procedure ◽  
Profile Fitting ◽  
Diffraction Peaks

Equation (18) of the paper by Enzo, Fagherazzi, Benedetti & Polizzi [J. Appl. Cryst. (1988). 21, 536–542] is in error. The correct equation is: A(2θ) = exp [−a|(2θ − 2θ 0)/cot 2θ 0|].

Spontaneous Lateral Modulations in InAlAs Buffer Layers Grown by MBE on InP Substrates

1995 ◽  
Vol 417 ◽  
Author(s):  
F. Peiró ◽  
A. Cornet ◽  
J. C. Ferrer ◽  
J. R. Morante ◽  
G. Halkias ◽  
...  
Keyword(s):  
Quantum Wells ◽  
Molecular Beam ◽  
Buffer Layers ◽  
Single Quantum ◽  
X Ray Diffraction ◽  
Single Quantum Well ◽  
Quantum Well Structures ◽  
X Ray ◽  
Transmission Electron ◽  
Inp Substrates

AbstractTransmission Electron Microscopy (TEM) and X-ray Diffraction (XRD) have been used to analyze the spontaneous appearance of lateral composition modulations in InyAl1−yAs (yIn.≅ 50%) buffer layers of single quantum well structures grown by molecular beam epitaxy on exact and vicinal (100) InP substrates, at growth temperatures in the range of 530°C–580°C. The influence of the growth temperature, substrate misorientation and epilayer mismatch on the InAlAs lateral modulation is discussed. The development of a self-induced quantum-wire like morphology in the In0.53Ga0.47As single quantum wells grown over the modulated buffers is also commented on.

Phase Separation in InGaN/GaN Multiple Quantum Wells

1997 ◽  
Vol 482 ◽  
Author(s):  
M. D. Mccluskey ◽  
L. T. Romano ◽  
B. S. Krusor ◽  
D. P. Bour ◽  
C. Chua ◽  
...  
Keyword(s):  
Phase Separation ◽  
Active Region ◽  
Quantum Wells ◽  
Broad Peak ◽  
Multiple Quantum Wells ◽  
Multiple Quantum ◽  
X Ray Diffraction ◽  
X Ray ◽  
Diffraction Peaks

AbstractEvidence is presented for phase separation in In0.27Ga0.73N/GaN multiple quantum wells (MQW's). After annealing for 4 min at a temperature of 1100 °C, the absorption threshold at 2.95 eV is replaced by a broad peak at 2.65 eV. This peak is attributed to the formation of Inrich InGaN phases in the active region. X-ray diffraction measurements show a shift in the diffraction peaks toward GaN, consistent with the formation of an In-poor phase.

A profile-fitting procedure for analysis of broadened X-ray diffraction peaks. I. Methodology

1988 ◽  
Vol 21 (5) ◽  
pp. 536-542 ◽  
Author(s):  
S. Enzo ◽  
G. Fagherazzi ◽  
A. Benedetti ◽  
S. Polizzi
Keyword(s):  
X Ray Diffraction ◽  
X Ray ◽  
Fitting Procedure ◽  
Profile Fitting ◽  
Diffraction Peaks

Non-Polar GaN/AlN Superlattices on A-plane AlN (500nm) Buffer Layers Grown by RF-MBE

2004 ◽  
Vol 831 ◽  
Author(s):  
Takayuki Morita ◽  
Akihiko Kikuchi ◽  
Katsumi Kishino
Keyword(s):  
Molecular Beam ◽  
Growth Conditions ◽  
Buffer Layers ◽  
Structural Quality ◽  
X Ray Diffraction ◽  
X Ray ◽  
Sapphire Substrates ◽  
Frequency Plasma ◽  
Diffraction Peaks ◽  
Rich Side

ABSTRACTThe growth conditions of A-plane AlN and GaN epitaxial layers by radio-frequency plasma assisted molecular beam epitaxy on R-plane sapphire substrates were investigated. The growth temperature and V/III supply ratio dependency on structural quality and surface roughness was described. The optimum V/III ratio for A-plane GaN and AlN layers was shifted to nitrogen rich side compared to the C-plane layers. A-plane GaN/AlN superlattices (SLs) were also grown on R-plane sapphire substrates. The X-ray diffraction peaks from a primary and a 1st satellite were observed. From a comparison of low temperature photoluminescence peak wavelength between A-plane and C-plane SLs, the built-in electrostatic field originated from spontaneous and piezoelectric polarization is negligible for A-plane SLs.

Lattice distortion of thick epitaxial layers

1996 ◽  
Vol 11 (1) ◽  
pp. 50-54
Author(s):  
K. Bickmann ◽  
J. Hauck
Keyword(s):  
Lattice Distortion ◽  
Relative Volume ◽  
Lattice Parameters ◽  
Buffer Layers ◽  
Epitaxial Layers ◽  
X Ray Diffraction ◽  
X Ray ◽  
Gaas Substrates ◽  
Different Strains ◽  
Bond Method

Precise x-ray diffraction measurements between room temperature and ∼400 °C (Bond method) exhibit some details in the variations of strain in ∼ 1 μm thick epitaxial layers of GaAs, InP, CdTe, EuS, or SrS on Si or GaAs substrates. The lattice parameters of the cubic layers, which are deposited at high temperatures, deviate from the lattice parameters, a0, of small unconstrained single crystals by Δa/a0 = ∈0 ≲ 10−3. The layers adhere to the substrates below Tc and adopt different strains, ∈‖ and ∈⊥, parallel and perpendicular to the substrate. Frequently the Tc and ∈0 values vary on annealing at 160–400 °C. The ratio E = —(∈⊥ — ∈0)/(∈‖ — ∈0) remains constant for each sample. The change of the relative volume ΔV/V0 = ∈‖ (2—E) +∈0 (1 + E) at the variation of ∈0 can give rise to corrugations, blisters, or microcracks in the epitaxial layers. Stable epitaxial layers with constant ∈0 and Tc values can be obtained by deposition on buffer layers or stepped substrates.

Crystalline Alignment and In-plane Texture Improvement of Buffer Layers Deposited on NiW Tapes

2011 ◽  
Vol 1308 ◽  
Author(s):  
Linfei Liu ◽  
Yijie Li ◽  
Huaran Liu ◽  
Xiaokun Song ◽  
Dan Hong ◽  
...  
Keyword(s):  
Critical Current Density ◽  
Critical Current ◽  
Current Density ◽  
Buffer Layers ◽  
X Ray Diffraction ◽  
X Ray ◽  
Deposition Parameters ◽  
Current Densities ◽  
Diffraction Peaks ◽  
Deposition Conditions

ABSTRACTIn order to deposit YBCO coated conductor with high critical current densities on rolling assisted biaxially textured Ni-W tapes, this paper has systematically studied the influence of deposition conditions on the orientation, in-plane texture and surface morphology of buffers and superconducting layers. It was found that the crystalline alignment and the in-plane texture of cerium oxide cap-layers were well improved by optimizing deposition parameters. The full width at half maximum of phi-scan x-ray diffraction peaks were reduced from original values of 7-8 degrees to 5-6 degrees. A high critical current density of 4.6×106 A/cm2 has been achieved on optimized buffer layers. This value is comparable with the critical current density of YBCO thin films deposited on single crystalline substrates.

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