Phase segregation in GaAs layers grown at low temperature

1991 ◽  
Vol 49 ◽  
pp. 860-861
Author(s):  
Zuzanna Liliental ◽  
Roar Kilaas
Keyword(s):  
Growth Temperature ◽  
Growth Parameters ◽  
Flux Ratio ◽  
Phase Segregation ◽  
Lattice Parameter ◽  
High Resistivity ◽  
Active Device ◽  
Circuit Performance ◽  
Gaas Buffer Layer ◽  
Lt Gaas

GaAs device and circuit performance may be impaired by substrate conduction. One such effect, called sidegating, leads to undesirable cross-talk between neighboring devices. This problem can be avoided by isolating the active device layer from the substrate with a GaAs buffer layer grown by molecular beam epitaxy (MBE) at low temperatures (LT GaAs). The LT GaAs layers show high resistivity, a large trap density, and breakdown strengths about ten times that of semi-insulating GaAs. These layers are grown at a substrate temperature of ~ 200°C. A large (~1 at.%) excess of As in these as-grown layers causes an increase (~0.1%) in the GaAs lattice parameter.The crystal structure of these layers is very sensitive to the growth parameters such as: growth temperature, As/Ga flux ratio and growth rate. With decreasing growth temperature a higher As concentration can be incorporated and only a smaller layer thickness of high crystal perfection can be grown.

Electrical And Structural Properties Of LT-GaAs: Influence Of As/Ga Flux Ratio And Growth Temperature

1996 ◽  
Vol 442 ◽  
Author(s):  
M. Luysberg ◽  
H. Sohn ◽  
A. Prasad ◽  
P. Specht ◽  
H. Fujioka ◽  
...  
Keyword(s):  
Structural Properties ◽  
Point Defects ◽  
Growth Temperature ◽  
Conduction Mechanism ◽  
Growth Parameters ◽  
Flux Ratio ◽  
Growth Conditions ◽  
High Resistivity ◽  
Antisite Defects ◽  
Band Conduction

AbstracThe deposition of GaAs by MBE at low temperatures results in a material of unique properties. However, up to now the control and understanding of the electrical and structural properties are unsatisfactory. To investigate the influence of growth parameters on the formation of point defects and electrical properties, the substrate temperature and the As/Ga flux ratio were systematically varied. In a well defined parameter range the lattice expansion was found to be dominated by the formation of As antisite defects. After annealing a high resistivity is obtained independent of the growth conditions. A strong influence of the growth temperature on the band conduction mechanism is observed, whereas a variation of the As/Ga flux ratio induces only slight changes of the temperature dependence of the conductivity.

Structure and Orientation of As Precipitates in LT-MBE Grown GaAs

1991 ◽  
Vol 49 ◽  
pp. 900-901 ◽  
Author(s):  
Alain Claverie ◽  
Zuzanna Liliental-Weber
Keyword(s):  
Transport Properties ◽  
Layer Thickness ◽  
Growth Temperature ◽  
Low Temperatures ◽  
Lattice Parameter ◽  
Crystalline Quality ◽  
Insulating Properties ◽  
Lt Gaas

GaAs layers grown by MBE at low temperatures (in the 200°C range, LT-GaAs) have been reported to have very interesting electronic and transport properties. Previous studies have shown that, before annealing, the crystalline quality of the layers is related to the growth temperature. Lowering the temperature or increasing the layer thickness generally results in some columnar polycrystalline growth. For the best “temperature-thickness” combinations, the layers may be very As rich (up to 1.25%) resulting in an up to 0.15% increase of the lattice parameter, consistent with the excess As. Only after annealing are the technologically important semi-insulating properties of these layers observed. When annealed in As atmosphere at about 600°C a decrease of the lattice parameter to the substrate value is observed. TEM studies show formation of precipitates which are supposed to be As related since the average As concentration remains almost unchanged upon annealing.

Influence of Growth Parameters on the Deep Level Spectrum in MBE-Grown n-GaN

2003 ◽  
Vol 798 ◽  
Author(s):  
A. R. Arehart ◽  
C. Poblenz ◽  
B. Heying ◽  
J. S. Speck ◽  
U. K. Mishra ◽  
...  
Keyword(s):  
Point Defect ◽  
Growth Temperature ◽  
Deep Level ◽  
Growth Parameters ◽  
Strong Dependence ◽  
Flux Ratio ◽  
Physical Point ◽  
Valence Bands ◽  
The Impact ◽  
N Flux

ABSTRACTThe impact of growth temperature and Ga/N flux ratio on deep levels in GaN grown by molecular beam epitaxy (MBE) is systematically investigated using both deep level optical spectroscopy (DLOS) and deep level transient spectroscopy (DLTS) in a study designed to map out the presence and concentration of defects over a defined region of the MBE GaN growth phase diagram. A series of Si-doped GaN films were grown to cover a substrate temperature range and a Ga/N flux ratio range that spans from the N stable to the Ga droplet regimes along both variables. Identical growth templates were used to eliminate variations in dislocations between samples so that point defect variations could be tracked. For these samples, traps are detected at EC-Et=0.25, 0.60, 0.90, 1.35, 2.40, 3.04, and 3.28 eV. The near valence bands states at EC–3.04 and EC–3.28 eV are found to be strongly dependent on Ga/N flux with decreased concentrations as a function of increasing Ga flux toward the Ga droplet regime, but with little effect from growth temperature. The EC-1.35 eV level shows a strong dependence on growth temperature and only slight dependence on Ga/N flux ratio. In contrast, the concentration of the EC-Et=0.25, 0.90 eV levels increased with increasing Ga flux toward the Ga droplet regime, while the EC-Et=0.60 shows no dependence. The variation in concentration of the EC-2.40 eV level that has been related to VGa was difficult to quantify, but tends to increase towards nitrogen rich growth. The dependencies for the detected states with respect to growth temperature and Ga/N flux ratio suggest different physical point defect sources.

scholarly journals Indium-Incorporation with InxGa1-xN Layers on GaN-Microdisks by Plasma-Assisted Molecular Beam Epitaxy

Crystals ◽  
2019 ◽  
Vol 9 (6) ◽  
pp. 308 ◽  
Author(s):  
ChengDa Tsai ◽  
Ikai Lo ◽  
YingChieh Wang ◽  
ChenChi Yang ◽  
HongYi Yang ◽  
...  
Keyword(s):  
Molecular Beam Epitaxy ◽  
Quantum Wells ◽  
Growth Temperature ◽  
Molecular Beam ◽  
Growth Parameters ◽  
Flux Ratio ◽  
Indium Content ◽  
High Indium Content

Indium-incorporation with InxGa1-xN layers on GaN-microdisks has been systematically studied against growth parameters by plasma-assisted molecular beam epitaxy. The indium content (x) of InxGa1-xN layer increased to 44.2% with an In/(In + Ga) flux ratio of up to 0.6 for a growth temperature of 620 °C, and quickly dropped with a flux ratio of 0.8. At a fixed In/(In + Ga) flux ratio of 0.6, we found that the indium content decreased as the growth temperature increased from 600 °C to 720 °C and dropped to zero at 780 °C. By adjusting the growth parameters, we demonstrated an appropriate InxGa1-xN layer as a buffer to grow high-indium-content InxGa1-xN/GaN microdisk quantum wells for micro-LED applications.

Laser Quality AlGaAs-GaAs Quantum Wells Grown on Low Temperature GaAs

1991 ◽  
Vol 241 ◽  
Author(s):  
Y. Hwang ◽  
D. Zhang ◽  
T. Zhang ◽  
M. Mytych ◽  
R. M. Kolbas
Keyword(s):  
Molecular Beam Epitaxy ◽  
Low Temperature ◽  
Quantum Wells ◽  
Barrier Layer ◽  
Molecular Beam ◽  
Optical Quality ◽  
First Order ◽  
Gaas Buffer Layer ◽  
Low Temperature Gaas ◽  
Lt Gaas

ABSTRACTIn this work we demonstrate that photopumped quantum wellheterostructure lasers with excellent optical quality can be grown ontop of a LT GaAs buffer layer by molecular beam epitaxy. Hightemperature thermal annealing of these lasers blue-shifts the laseremission wavelengths but the presence/absence of a LT GaAs layerhad little effect on the overall laser thresholds. Also, to first order itwas not necessary to include an AlAs barrier layer to preventadverse effects (as has been necessary in the gate stack of MESFETs to prevent carrier compensation).

scholarly journals Characterisation of III?V Multilayers Grown by Low-pressure Metal Organic Vapour-phase Epitaxy

1993 ◽  
Vol 46 (3) ◽  
pp. 435
Author(s):  
C Jagadish ◽  
A Clark ◽  
G Li ◽  
CA Larson ◽  
N Hauser ◽  
...  
Keyword(s):  
Gallium Arsenide ◽  
Growth Temperature ◽  
Deep Level ◽  
Growth Parameters ◽  
Low Pressure ◽  
Vapour Phase ◽  
Growth Conditions ◽  
Vapour Phase Epitaxy ◽  
Metal Organic ◽  
Organic Vapour

Undoped and doped layers of gallium arsenide and aluminium gallium arsenide have been grown on gallium arsenide by low-pressure metal organic vapour-phase epitaxy (MOVPE). Delta doping and growth on silicon substrates have also been attempted. Of particular interest in the present study has been the influence of growth parameters, such as growth temperature, group III mole fraction and dopant flow, on the electrical and physical properties of gallium arsenide layers. An increase in growth temperature leads to increased doping efficiency in the case of silicon, whereas the opposite is true in the case of zinc. Deep level transient spectroscopy (DTLS) studies on undoped GaAs layers showed two levels, the expected EL2 level and a carbon-related level. The determination of optimum growth conditions has allowed good quality GaAs and AlGaAs epitaxial layers to be produced for a range of applications.`

On the Structure and Some Properties of LaCo Co-substituted NiZn Ferrites Prepared Using the Standard Ceramic Technique

2016 ◽  
Vol 35 (4) ◽  
pp. 417-423 ◽  
Author(s):  
Xiaofei Niu ◽  
Xiansong Liu ◽  
Xin Huang ◽  
Kai Huang ◽  
Yuqi Ma ◽  
...  
Keyword(s):  
Grain Size ◽  
Power Loss ◽  
Low Frequency ◽  
Secondary Phase ◽  
Lattice Parameter ◽  
Initial Permeability ◽  
High Resistivity ◽  
X Ray Diffraction ◽  
Ferrite Sample ◽  
Higher Power

AbstractZn0.5Ni0.5-xCoxFe2-yLayO4 ferrites (with x=0, 0.02 and y=0, 0.02) were prepared by an industrial method using the standard ceramic technique and sintered at 1,250°C in air. X-ray diffraction (XRD) was used to obtain the phase formation of the NiZn ferrites. The microstructure of ferrites was investigated by scanning electron microscopy (SEM). The XRD reveals that lattice parameter (a) is decreased and a secondary phase (LaFeO3) is formed in the La–Co co-substituted NiZn ferrite sample, meanwhile, the grain size (D) of this sample decreased obviously by observing SEM photographs. Vibrating sample magnetometry (VSM), B-H analyzer, impedance analyzer and electrometer were carried out in order to characterize some properties of the ferrites. This investigation indicates that, La–Co co-substituted NiZn ferrite sample has higher power loss (Pcv) than other samples at low frequency with an increase in coercive field (Hc) and magnetocrystalline anisotropy (K1), a decrease in initial permeability (μi) and saturation magnetization (Ms). However, at high frequency, the power loss of La–Co co-substituted sample is low, which is attributed to high resistivity (ρ), small grain size (D), less number of Fe2+ ions and low porosity (P).

Influences of thickness and temperature of low temperature GaAs buffer layer on two-step MOVPE grown GaAs/Ge heterostructures

2020 ◽  
Vol 90 (2) ◽  
pp. 20301
Author(s):  
Ilkay Demir ◽  
Ahmet Emre Kasapoğlu ◽  
Hasan Feyzi Budak ◽  
Emre Gür ◽  
Sezai Elagoz
Keyword(s):  
Buffer Layer ◽  
Growth Parameters ◽  
Internal Quantum Efficiency ◽  
Optical Quality ◽  
Structural Quality ◽  
Atomic Step ◽  
Organic Vapor ◽  
Gaas Buffer Layer ◽  
Metal Organic ◽  
Low Temperature Gaas

We investigate influence of GaAs buffer layer (BL) growth parameters such as temperature and thickness on the structural, morphological, crystalline and optical quality of metal organic vapor phase epitaxy (MOVPE) grown heterostructures of GaAs on Ge. It was found that the optimal BL conditions significantly decrease the effects of anti-phase boundaries (APBs) even when grown on offcut Ge substrate by two-step growth technique with AsH3 pre-flow to promote double atomic step formation. It is observed that as the growth temperature increases, the growth rate of the GaAs BL increases, too. Improvement on the structural quality is observed up to BLs temperature of 535 °C, then it decreases. On the other hand, as the different thick BLs, 12, 25, 75 nm are considered, the epilayer grown on the 25 nm thick BL has shown the lowest full width at half maximum (FWHM) value, large photoluminescence peak intensity and internal quantum efficiency (IQE).

Structural and Electrical Characterization of Highly Tetrahedral-Coordinated Diamond-Like Carbon Films Grown by Pulsed-Laser Deposition

1994 ◽  
Vol 349 ◽  
Author(s):  
M. P. Siegal ◽  
T. A. Friedmann ◽  
S. R. Kurtz ◽  
D. R. Tallant ◽  
R. L. Simpson ◽  
...  
Keyword(s):  
Pulsed Laser Deposition ◽  
Growth Parameters ◽  
High Vacuum ◽  
Pulsed Laser ◽  
Electrical Characterization ◽  
Carbon Films ◽  
Laser Deposition ◽  
High Resistivity ◽  
Low Frequencies ◽  
Carbon Carbon Bond

ABSTRACTHighly tetrahedral-coordinated-amorphous-carbon (a-tC) films deposited by pulsed-laser deposition (PLD) on silicon substrates are studied. These films are grown at room-temperatures in a high-vacuum ambient. a-tC films grown in this manner have demonstrated stability to temperatures in excess of T = 1000°C, more than sufficient for any post-processing treatment or application. Film surfaces are optically smooth as determined both visually and by atomic-force microscopy. PLD growth parameters can be controlled to produce films with a range of sp2 - sp3 carbon-carbon bond ratios. Films with the highest yield of sp3 C-C bonds have high resistivity, with a dielectric permittivity constant s σ 4, measured capacitively at low frequencies (1 – 100 kHz). These a-tC films are p-type semiconductors as grown. Schottky barrier diode structures have been fabricated.

MOCVD Growth Of GaxIn1−xAs1−ySby and GaxIn1−xSb ALLOYS: Effect of Growth Parameters on Their Solid Compositions

1995 ◽  
Vol 415 ◽  
Author(s):  
Baolin Zhang ◽  
Tianming Zhou ◽  
Hong Jiang ◽  
Yongqiang Ning ◽  
Shuwei Li ◽  
...  
Keyword(s):  
Chemical Vapor Deposition ◽  
Growth Temperature ◽  
Vapor Deposition ◽  
Growth Kinetic ◽  
Metalorganic Chemical Vapor Deposition ◽  
Growth Parameters ◽  
Chemical Vapor ◽  
Mocvd Growth ◽  
Growth Temperature Dependence ◽  
Metalorganic Chemical

ABSTRACTQuaternary GaxIn1−xAs1−ySby and ternary GaxIn1−xSb alloys have been grown by metalorganic chemical vapor deposition (MOCVD). The effects of growth parameters on the solid compositions, x, y for GaxIn1−xAs1−ySby and x for GaxIn1−x Sb alloys are described in detail. Concentrations of the reactants have major effects on the corresponding solid compositions in the two kinds of alloys. The growth temperature dependence of the solid compositions in both GaxIn1−xAs1−ySby and GaxIn1−xSb was obviously observed and the growth kinetic factor was considered to account for this dependence. It was found that III/V ratio in vapor has a great effect on x in GaxIn1−xSb alloy but little effect on x and y in GaxIn1−xAs1−ySby alloy.

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