Heteroepitaxy and Characterization of Low-Dislocation-Density GaN on Periodically Grooved Substrates

2000 ◽  
Vol 639 ◽  
Author(s):  
T. Detchprohm ◽  
M. Yano ◽  
R. Nakamura ◽  
S. Sano ◽  
S. Mochiduki ◽  
...  
Keyword(s):  
Dislocation Density ◽  
New Method ◽  
Growth Technique ◽  
New Approach ◽  
Density Area ◽  
Low Dislocation Density ◽  
Dislocation Densities ◽  
Movpe Growth

ABSTRACTWe have developed a new method to prepare low-dislocation-density GaN by using periodically grooved substrates in a conventional MOVPE growth technique. This new approach was demonstrated for GaN grown on periodically grooved α-Al2O3(0001), 6H-SiC(0001)Si and Si(111) substrates. Dislocation densities were 2×107 cm−2 in low-dislocation-density area.

scholarly journals Hydropyrolysis: Implications for Radiocarbon Pretreatment and Characterization of Black Carbon

Radiocarbon ◽  
2010 ◽  
Vol 52 (3) ◽  
pp. 1336-1350 ◽  
Author(s):  
P L Ascough ◽  
M I Bird ◽  
W Meredith ◽  
R E Wood ◽  
C E Snape ◽  
...  
Keyword(s):  
Black Carbon ◽  
Radiocarbon Dating ◽  
Elevated Temperatures ◽  
New Method ◽  
Humic Material ◽  
New Approach ◽  
Pyrogenic Carbon ◽  
Organic Components ◽  
Diagenetic Alteration

Charcoal is the result of natural and anthropogenic burning events, when biomass is exposed to elevated temperatures under conditions of restricted oxygen. This process produces a range of materials, collectively known as pyrogenic carbon, the most inert fraction of which is known as black carbon (BC). BC degrades extremely slowly and is resistant to diagenetic alteration involving the addition of exogenous carbon, making it a useful target substance for radiocarbon dating particularly of more ancient samples, where contamination issues are critical. We present results of tests using a new method for the quantification and isolation of BC, known as hydropyrolysis (hypy). Results show controlled reductive removal of non-BC organic components in charcoal samples, including lignocellulosic and humic material. The process is reproducible and rapid, making hypy a promising new approach not only for isolation of purified BC for 14C measurement but also in quantification of different labile and resistant sample C fractions.

Monolithic Integration of III-V Microcavity Leds on Silicon Drivers using Conformal Epitaxy

1998 ◽  
Vol 535 ◽  
Author(s):  
B. Gérard ◽  
X. Marcadet ◽  
P. Etienne ◽  
D. Pribat ◽  
D. Friedrich ◽  
...  
Keyword(s):  
Cmos Technology ◽  
High Crystalline Quality ◽  
Growth Technique ◽  
Si Substrates ◽  
Active Structures ◽  
Gaas Substrates ◽  
Low Dislocation Density ◽  
Dislocation Densities ◽  
The Impact

AbstractConformal epitaxy is an epitaxial growth technique capable of yielding low dislocation density III-V films on Silicon. In this technique, the growth of the III-V material occurs parallel to the silicon substrate, from the edge of a previously deposited III-V seed, the vertical growth being stopped by an overhanging capping layer. As an example, conformal GaAs layers on Silicon, presenting dislocation densities below 105cm−2, have been obtained using selective vapor phase epitaxy. These layers have then been used as high quality GaAs on Si substrates for subsequent vertical MBE regrowth of active structures. In this paper, we report on the integration of surface-emitting microcavity LEDs with their silicon drivers using this conformal growth technique. The global technology concept and the design of the active structures are first presented. The compatibility of the conformal growth technique with CMOS technology is then checked: the impact of the integration process on the performances of the drivers is for example quantified. Characterisations of the high crystalline quality of the conformal layers and of the LEDs structures grown on it are then shown. The electro-optical characteristics of the LEDs on Si are finally compared to those of reference LEDs on GaAs substrates in order to prove the efficiency of the integration procedure.

Heteroepitaxial Lateral Overgrowth of GaN on Periodically Grooved Substrates: A New Approach for Growing Low-Dislocation-Density GaN Single Crystals

2001 ◽  
Vol 40 (Part 2, No. 1A/B) ◽  
pp. L16-L19 ◽  
Author(s):  
Theeradetch Detchprohm ◽  
Masahiro Yano ◽  
Shigekazu Sano ◽  
Ryo Nakamura ◽  
Shingo Mochiduki ◽  
...  
Keyword(s):  
Dislocation Density ◽  
Single Crystals ◽  
New Approach ◽  
Lateral Overgrowth ◽  
Low Dislocation Density

Microwave performance and structural characterization of MBE-grown AlGaN/GaN HEMTs on low dislocation density GaN substrates

2007 ◽  
Vol 305 (2) ◽  
pp. 340-345 ◽  
Author(s):  
D.F. Storm ◽  
D.S. Katzer ◽  
J.A. Roussos ◽  
J.A. Mittereder ◽  
R. Bass ◽  
...  
Keyword(s):  
Dislocation Density ◽  
Structural Characterization ◽  
Low Dislocation Density ◽  
Gan Hemts

The Study of Flower-Shaped Structure Dislocation in 4 Inch Germanium Single Crystal

2011 ◽  
Vol 685 ◽  
pp. 141-146 ◽  
Author(s):  
Miao Miao Li ◽  
Xiao Ping Su ◽  
De Shen Feng ◽  
Jian Long Zuo ◽  
Nan Li ◽  
...  
Keyword(s):  
Solar Cells ◽  
Dislocation Density ◽  
Single Crystal ◽  
Single Crystals ◽  
Czochralski Method ◽  
Structure Defects ◽  
Germanium Single Crystal ◽  
Low Dislocation Density ◽  
Dislocation Densities

As the key component of single junction GaAs/Ge solar cells and GaAs/Ge solar cells, the quality of germanium single crystal affects the properties of space solar cell directly. The dislocation of germanium single crystals is the main impact factor on solar cells efficiency. Through measuring dislocation densities in the different positions of 4 inch <100> germanium single crystals produced by Czochralski method, we found that flower-shaped structure dislocations pattern was mainly caused by the inclusions. This paper briefly analyzed dislocations produced by inclusions, chemical etching pits method. SEM and EDS measurement methods were also employed to study the flower-shaped structure defects. A germanium single crystal with low dislocation density was obtained and the special defects were almost eliminated. The germanium single crystal with low dislocation density (PV) was obtained, which could meet the requirement of the GaAs/Ge solar cells.

Norm inequalities involving derivatives

1978 ◽  
Vol 82 (1-2) ◽  
pp. 51-70 ◽  
Author(s):  
W. D. Evans ◽  
A. Zettl
Keyword(s):  
General Class ◽  
New Method ◽  
Elementary Operator ◽  
Best Constant ◽  
New Approach ◽  
Theoretic Proof ◽  
General Class Of Functions ◽  
Image Position ◽  
Class Of Functions

SynopisisA new method for studying inequalities of the type ‖y(r)‖2<ε‖Sk−ry(k)‖2 + K(ε)‖S−ry‖2 and ‖y′‖2≦ Kp(S)‖Sy″‖ ‖S−1y‖ is presented here. With this new approach we obtain new and far reaching extensions of previously known inequalities of this sort as well as simpler proofs of the known cases. In addition we obtain an inequality of type ‖Sy′‖<ε‖(Sy′)′‖ + K(ε)‖y‖ for a general class of functions S. Also we give an elementary operator-theoretic proof of Everitt's characterization of the best constant as well as all cases of equality for

PERFORMANCE OF PSEUDOMORPHIC ULTRAVIOLET LEDs GROWN ON BULK ALUMINUM NITRIDE SUBSTRATES

2011 ◽  
Vol 20 (03) ◽  
pp. 497-504 ◽  
Author(s):  
SHAWN R. GIBB ◽  
JAMES R. GRANDUSKY ◽  
MARK MENDRICK ◽  
LEO J. SCHOWALTER
Keyword(s):  
Dislocation Density ◽  
Published Data ◽  
Epitaxial Layers ◽  
Device Structure ◽  
Low Dislocation Density ◽  
High Aluminum Content ◽  
Current Densities ◽  
Pseudomorphic Growth ◽  
High Aluminum

Low dislocation density pseudomorphic epitaxial layers of Al x Ga 1- x N have been grown on c -face AlN substrates prepared from high quality bulk crystals. As reported previously, pseudomorphic growth yields very low dislocation density layers with atomically smooth surfaces throughout the active region of a full LED device structure. An advantage of the low dislocation density is the ability to n -type dope the high aluminum content Al x Ga 1- x N (x ~ 70%) epitaxial layers required for UVLED devices to obtain sheet resistances less than 350 Ohm/square for 0.5 μm thick layers. Here, we report on the characterization of our pseudomorphic epitaxial AlGaN layers via cathodoluminescence (CL) and on-wafer and initial packaged level characterization of fully fabricated pseudomorphic ultraviolet LEDs (PUVLEDs) with an emission wavelength between 250 - 265 nm. An additional benefit of PUVLED devices is the ability to run these devices at high input powers and current densities. Further, the aforementioned low dislocation density of the epitaxial structure results in improved device performance over previously published data. Mean output powers of greater than 4 mW were obtained on-wafer prior to thinning and roughening while output powers as high as 45 mW were achieved for packaged devices.

TEM Investigation of Arsenic Precipitates in Semi-Insulating GaAs

1991 ◽  
Vol 225 ◽  
Author(s):  
S. Yegnasubramanian ◽  
M. A. Shahid
Keyword(s):  
Electron Diffraction ◽  
Dislocation Density ◽  
Pattern Analysis ◽  
Vertical Gradient ◽  
Fine Particulates ◽  
Growth Technique ◽  
X Ray ◽  
Selected Area Electron Diffraction ◽  
Low Dislocation Density ◽  
Vertical Gradient Freeze

ABSTRACTThis paper presents a TEM investigation of undoped, semi-insulating GaAs crystals grown by the VGF (vertical gradient freeze) technique for microstructure and defects characterization. Energy dispersive X-ray spectrometry (EDS) and selected area electron diffraction (SAD) were used to characterize for composition and lattice spacings, respectively. TEM images of dislocations decorated with precipitate particles are presented. The particles were found to be arsenic rich. Regions of fine particulates were identified and a Moire pattern analysis was carried out. The occurrence of such defects in the low dislocation density VGF GaAs of the present study suggests that these are material related and not necessarily dependent on the growth technique.

Microstructure Characterization of Hot Deformed Fe-32%Ni Alloy

2011 ◽  
Vol 230-232 ◽  
pp. 154-158 ◽  
Author(s):  
Bao Jun Han
Keyword(s):  
Dislocation Density ◽  
Dynamic Equilibrium ◽  
Optical Microscope ◽  
Electron Back Scatter Diffraction ◽  
High Dislocation Density ◽  
Hot Deformation Behavior ◽  
Transmission Electron ◽  
Low Dislocation Density ◽  
Ni Alloy

Hot deformation behavior and microstructure evolution of Fe-32%Ni alloy were investigated when compressed at the temperature of 1000°C and a strain rate of 2×10-3s-1. The microstructures were analyzed using optical microscope (OM), electron back scatter diffraction (EBSD) and transmission electron microscope (TEM). The results show that the generation and development of dynamic recrystallization (DRX) can obviously refine the grains of Fe-32Ni% alloy and the DRX reached dynamic equilibrium when the strain was high. According to the TEM observations, the DRX microstructure can be categorized into three kinds: grains with low dislocation density, which are DRX nucleations; grains with low dislocation density around the grain boundary and high dislocation density in its interior which means that grains with dislocation density gradient and which are DRX grains in growth; grains with high dislocation density, which are fully work-hardened DRX grains.

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