The Shape Control of ZnO Based Nanostructures

2006 ◽  
Vol 6 (11) ◽  
pp. 3628-3632
Author(s):  
M. N. Jung ◽  
S. Y. Ha ◽  
H. S. Kim ◽  
H. J. Ko ◽  
H. Ko ◽  
...  
Keyword(s):  
Growth Temperature ◽  
Shape Control ◽  
Deep Level ◽  
Growth Parameters ◽  
Stoichiometric Composition ◽  
Growth Conditions ◽  
Second Phase ◽  
Gas Flux ◽  
Carrier Gas ◽  
Si Substrates

Tetrapod-shape ZnO nanostructures are formed on Si substrates by vapor phase transportation method. The effects of two important growth parameters, growth temperature and VI/II ratio, are investigated. The growth temperature is varied in the range from 600 °C to 900 °C to control the vapor pressure of group II-element and the formation process of nanostructures. VI/II ratio was changed by adjusting the flux of carrier gas which affects indirectly the supplying rate of group VI-element. From the scanning electron microscopy (SEM), systematic variation of shape including cluster, rod, wire and tetrapod was observed. ZnO tetrapods, formed at 800 °C under the carrier gas flux of 0.5 cc/mm2 min, show considerably uniform shape with 100 nm thick and 1 ∼ 1.5 μm long legs. Also stoichiometric composition (O/Zn ∼ 1) was observed without any second phase structures. While, the decrease of growth temperature and the increase of carrier gas flux, results in the irregular shaped nanostructures with non-stoichiometric composition. The excellent luminescence properties, strong excitonic UV emission at 3.25 eV without deep level emission, indicate that the high crystalline quality tetrapod structures can be formed at the optimized growth conditions.

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.`

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.

scholarly journals Influence of Showerhead–Sample Distance (GAP) in MOVPE Close Coupled Showerhead Reactor on GaN Growth

Materials ◽  
2019 ◽  
Vol 12 (20) ◽  
pp. 3375
Author(s):  
Robert Czernecki ◽  
Karolina Moszak ◽  
Wojciech Olszewski ◽  
Ewa Grzanka ◽  
Mike Leszczynski
Keyword(s):  
Growth Rate ◽  
Growth Temperature ◽  
Research Reactor ◽  
Growth Parameters ◽  
Sample Surface ◽  
Growth Pressure ◽  
Carrier Gas ◽  
Sample Distance ◽  
Main Growth

The distance between the showerhead and the sample surface (GAP) is one of the main growth parameters of the commonly used research reactor, Close Coupled Showerhead. We examine its influence on the growth rate of GaN layers deposited under various conditions (growth temperature, carrier gas, V/III ratio and growth pressure). Regardless of other growth parameters, increasing the GAP value leads to a reduction in the growth rate.

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.

Impurity Effects in the Growth of 4H-SiC Crystals by Physical Vapor Transport

1999 ◽  
Vol 572 ◽  
Author(s):  
V. Balakrishna ◽  
G. Augustine ◽  
R. H. Hopkins
Keyword(s):  
Electronic Device ◽  
Defect Density ◽  
Growth Parameters ◽  
Large Diameter ◽  
Growth Conditions ◽  
High Resistivity ◽  
Growth Surface ◽  
Second Phase ◽  
Impurity Effects ◽  
Growth Environment

ABSTRACTSiC is an important wide bandgap semiconductor material for high temperature and high power electronic device applications. Purity improvements in the growth environment has resulted in a two-fold benefit during growth: (a) minimized inconsistencies in the background doping resulting in high resistivity (>5000 ohm-cm) wafer yield increase from 10–15% to 70-85%, and (b) decrease in micropipe formation. Growth parameters play an important role in determining the perfection and properties of the SiC crystals, and are extremely critical in the growth of large diameter crystals. Several aspects of growth are vital in obtaining highly perfect, large diameter crystals, such as: (i) optimized furnace design, (ii) high purity growth environment, and (iii) carefully controlled growth conditions. Although significant reduction in micropipe density has been achieved by improvements in the growth process, more stringent device requirements mandate further reduction in the defect density. In-depth understanding of the mechanisms of micropipe formation is essential in order to devise approaches to eliminate them. Experiments have been performed to understand the role of growth conditions and ambient purity on crystal perfection by intentionally introducing arrays of impurity sites on one half of the growth surface. Results clearly suggest that presence of impurities or second phase inclusions during start or during growth can result in the nucleation of micropipes. Insights obtained from these studies were instrumental in the growth of ultra-low micropipe density (less than 2 micropipes cm−2 ) in 1.5 inch diameter boules.

EL-2 Defect Formation and Carbon Incorporation in GaAs grown by Organometallic Vapor Phase Epitaxy

1989 ◽  
Vol 163 ◽  
Author(s):  
R. Venkatasubramanian ◽  
J.M. Borrego ◽  
S.K. Ghandhi
Keyword(s):  
Partial Pressure ◽  
Vapor Phase ◽  
Growth Temperature ◽  
Defect Formation ◽  
Deep Level ◽  
Growth Conditions ◽  
Vapor Phase Epitaxy ◽  
Organometallic Vapor Phase Epitaxy ◽  
Surface Species ◽  
Phase Loss

AbstractThe anti-site defect AsGa, EL-2, is used to understand the nature of arsenic surface species during the Organometallic Vapor Phase Epitaxy(OMVPE) of GaAs. The concentration of EL-2 in unintentionally doped n-GaAs, measured by Deep Level Transient Spectroscopy, is presented as a function of AsH3 partial pressure, TMGa partial pressure and the growth temperature. Based on this data, a model for EL-2 incorporation in OMVPE GaAs is developed in which all surface species As-H, are converted to As2 at around 765 ° C. Under the same set of growth conditions, relative carbon levels measured by 4K Photoluminescence, suggest that the increase in carbon levels with growth temperature is due to the gas-phase loss of H radical from the As-H species.

Oxygen Doping of GaAs During Omvpe Controlled Introduction of Impurity Complexes

1993 ◽  
Vol 325 ◽  
Author(s):  
Y. Park ◽  
M. Skowronski ◽  
T.S. Rosseel ◽  
M.O. Manasreh
Keyword(s):  
Low Temperature ◽  
Deep Level ◽  
Growth Conditions ◽  
Near Band Edge ◽  
Second Phase ◽  
Temperature Growth ◽  
Temperature Deposition ◽  
Localized Vibrational Modes ◽  
Secondary Ion ◽  
Reactor Pressure

AbstractGaAs epilayers have been grown by Organo-Metallic Vapor Phase Epitaxy using dimethylaluminum methoxide as a dopant source. This compound contains a strong aluminumoxygen bond which is thought to remain intact during low temperature deposition and result in the incorporation of Al-O as a complex. Incorporation of aluminum and oxygen was investigated by Secondary Ion Mass Spectroscopy as a function of growth conditions: growth temperature, growth rate, V/III ratio, reactor pressure and dopant mole fraction. High doping levels up to 1020 cm−3 (for both oxygen and aluminum) were achieved without degradation of surface morphology andlor precipitation of a second phase. Oxygen concentration is lower than that of aluminum for all investigated growth conditions but at low deposition temperatures oxygen/aluminum ratios approach 1, indicating that Al-O is incorporated as a pair. Infrared absorption measurements in the 600-1200 cm−1 range did not detect well known isolated oxygen localized vibrational modes (LVM). Also in layers grown at low temperatures the intensity of isolated aluminum LVM at 362 cm−1 is much smaller than the concentration obtained by SIMS. Both observations prove that oxygen not only is incorporated as an Al-O pair but remains bonded in the bulk of the layer. Low temperature photoluminescence measurements indicate that the A1-O complex is electrically active in GaAs, forms a deep level within the GaAs band gap, and serves as an efficient non-radiative recombination center. Near band edge luminescence intensity correlates well incorporation of oxygen. The Al-O pairs act as deep acceptors in GaAs and cause the compensation of shallow tellurium donors.

Deep Electron and Hole Traps in 6H-SiC Bulk Crystals Grown by the Halide Chemical Vapor Deposition

2006 ◽  
Vol 527-529 ◽  
pp. 497-500 ◽  
Author(s):  
Sung Wook Huh ◽  
A.Y. Polyakov ◽  
Hun Jae Chung ◽  
Saurav Nigam ◽  
Marek Skowronski ◽  
...  
Keyword(s):  
Chemical Vapor Deposition ◽  
Growth Temperature ◽  
Vapor Deposition ◽  
Deep Level ◽  
Chemical Vapor ◽  
Growth Conditions ◽  
Bulk Crystals ◽  
Native Defects ◽  
Transient Spectroscopy ◽  
Electron And Hole Traps

Deep electron and hole traps were studied in a series of high purity 6H-SiC single crystals grown by Halide Chemical Vapor Deposition (HCVD) method at various C/Si flow ratios and at temperatures between 2000 oC and 2100 oC. Characterization included Low Temperature Photoluminescence (LTPL), Deep Level Transient Spectroscopy (DLTS), Minority Carrier Transient Spectroscopy (MCTS), and Thermal Admittance Spectroscopy (TAS) measurements. Concentrations of all deep traps were shown to strongly decrease with increased C/Si flow ratio and with increased growth temperature. The results indicate that the majority of deep centers in 6H-SiC crystals grown by HCVD are due to native defects or complexes of native defects promoted by Si-rich growth conditions. The observed growth temperature dependence of residual donor concentration and traps density is explained by increasing the effective C/Si ratio at higher temperatures for the same nominal ratio of C and Si flows.

scholarly journals Self-Catalyzed InSb/InAs Quantum Dot Nanowires

Nanomaterials ◽  
2021 ◽  
Vol 11 (1) ◽  
pp. 179
Author(s):  
Omer Arif ◽  
Valentina Zannier ◽  
Francesca Rossi ◽  
Daniele Ercolani ◽  
Fabio Beltram ◽  
...  
Keyword(s):  
Quantum Dot ◽  
Quantum Wells ◽  
Growth Temperature ◽  
Growth Rates ◽  
Radial Growth ◽  
Growth Parameters ◽  
Chemical Beam Epitaxy ◽  
Si Substrates ◽  
Single Defect ◽  
Inas Quantum Dot

The nanowire platform offers great opportunities for improving the quality and range of applications of semiconductor quantum wells and dots. Here, we present the self-catalyzed growth of InAs/InSb/InAs axial heterostructured nanowires with a single defect-free InSb quantum dot, on Si substrates, by chemical beam epitaxy. A systematic variation of the growth parameters for the InAs top segment has been investigated and the resulting nanowire morphology analyzed. We found that the growth temperature strongly influences the axial and radial growth rates of the top InAs segment. As a consequence, we can reduce the InAs shell thickness around the InSb quantum dot by increasing the InAs growth temperature. Moreover, we observed that both axial and radial growth rates are enhanced by the As line pressure as long as the In droplet on the top of the nanowire is preserved. Finally, the time evolution of the diameter along the entire length of the nanowires allowed us to understand that there are two In diffusion paths contributing to the radial InAs growth and that the interplay of these two mechanisms together with the total length of the nanowires determine the final shape of the nanowires. This study provides insights in understanding the growth mechanisms of self-catalyzed InSb/InAs quantum dot nanowires, and our results can be extended also to the growth of other self-catalyzed heterostructured nanowires, providing useful guidelines for the realization of quantum structures with the desired morphology and properties.

scholarly journals Growth of NbO2 by Molecular-Beam Epitaxy and Characterization of its Metal-Insulator Transition

MRS Advances ◽  
2017 ◽  
Vol 2 (52) ◽  
pp. 3031-3036 ◽  
Author(s):  
Lindsey E. Noskin ◽  
Ariel Seidner H. ◽  
Darrell G. Schlom
Keyword(s):  
Electrical Resistivity ◽  
Molecular Beam Epitaxy ◽  
Growth Temperature ◽  
Molecular Beam ◽  
Film Growth ◽  
Growth Parameters ◽  
Growth Conditions ◽  
Lower Growth ◽  
Rutile Structure ◽  
Partial Pressures

ABSTRACTThin films of NbO2 are synthesized by oxide molecular-beam epitaxy on (001) MgF2 substrates, which are isostructural (rutile structure) with NbO2. Two growth parameters are systematically varied in order to identify appropriate growth conditions: growth temperature and the partial pressure of O2 during film growth. θ-2θ X-ray diffraction measurements identify two dominant phases in this system at background oxygen pressures in the (0.2–6)×10–7 Torr range: rutile NbO2 is favored at higher growth temperature, while Nb2O5 forms at lower growth temperature. Electrical resistivity measurements were made between 350 K and 675 K on three epitaxial NbO2 films in a nitrogen ambient. These measurements show that NbO2 films grown in higher partial pressures of molecular oxygen have larger temperature-dependent changes in electrical resistivity and higher resistivity at room temperature.

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