scholarly journals Growth of GaN from elemental Gallium and Ammonia via Modified Sandwich Growth Technique

2004 ◽  
Vol 831 ◽  
Author(s):  
E. Berkman ◽  
R. Collazo ◽  
R. Schlesser ◽  
Z. Sitar
Keyword(s):  
Growth Rate ◽  
Gas Flow ◽  
Transport Model ◽  
Theoretical Calculations ◽  
Substrate Surface ◽  
Maximum Growth ◽  
Direct Reaction ◽  
Pure Nitrogen ◽  
Flow Rates ◽  
Reactor Pressure

ABSTRACTGallium nitride (GaN) films were grown on (0001) sapphire substrates at 1050°C by controlled evaporation of gallium (Ga) metal and reaction with ammonia (NH3) at a total reactor pressure of 800 Torr. Pure nitrogen (N2) was flowed directly above the molten Ga source to prevented direct reaction between the molten Ga and ammonia, which causes Ga spattering and GaN crust formation. At the same time, this substantially enhanced the Ga transport to the substrate. A simple mass-transport model based on total reactor pressure, gas flow rates and source temperature was developed and verified. The theoretical calculations and growth rate measurements at different ammonia flow rates and reactor pressures showed that the maximum growth rate was controlled by transport of both Ga species and reactive ammonia to the substrate surface.

Optimizing diamond growth for an atmospheric oxyacetylene torch

1997 ◽  
Vol 12 (5) ◽  
pp. 1237-1252 ◽  
Author(s):  
Lua'y A. Zeatoun ◽  
Philip W. Morrison
Keyword(s):  
Growth Rate ◽  
Surface Temperature ◽  
Flow Rate ◽  
Gas Flow ◽  
Substrate Surface ◽  
Diamond Films ◽  
Diamond Growth ◽  
Statistical Experimental Design ◽  
Gas Flow Rate ◽  
Open Flame

Diamond growth conditions for an atmospheric combustion flame have been optimized using statistical experimental design. Films are grown on a molybdenum bolt for 40 min at a distance of 1 mm from the flame cone. The diamond films have been characterized using Raman spectroscopy, x-ray diffraction, and scanning electron microscope. The input process variables are varied over a range of conditions: total gas flow rate Q = 2–4 standard liter/min, substrate surface temperature Ts = 800–1000 °C, and flow ratio of O2/C2H2 = R = 0.93–0.99. The experimental response outputs are growth rate, full width half maximum (FWHM) of the diamond Raman peak, Raman diamond fraction (β) in the film, ratio of luminescence to diamond peak height (LR), and the relative intensity of the {220}, {311}, {400}, and {331} orientations. The film quality indices FWHM, β, and LR improve by increasing the gas ratio (R), by increasing substrate surface temperature (Ts), and lowering the growth rate by decreasing total gas flow rate. Diamond film shows a small amount texturing in {220} and {400} orientation at low R and Ts. At high R and low Ts crystals are oriented with the {111} direction normal to the substrate surface. Jet and boundary layer theory have been applied to understand the growth rate, the thickness profile, and the morphological instability of the diamond films. Surface Damkühler calculation shows that the deposition process is marginally controlled by mass transfer. Growth rate of an open flame is higher than for an enclosed flame, while the Raman quality measurements of the enclosed flame are more uniform than open flame over the range of the comparison.

Design and Characteristics of a Novel Close-Spaced Reactor for Organometallic Epitaxy

1990 ◽  
Vol 204 ◽  
Author(s):  
P.B. Chinoy ◽  
S.K. Ghandhi
Keyword(s):  
Gas Flow ◽  
Deposition Efficiency ◽  
Organometallic Vapor Phase Epitaxy ◽  
Operating Characteristics ◽  
Stagnation Flow ◽  
Large Area ◽  
Flow Rates ◽  
Acceptable Quality ◽  
Nozzle Temperature ◽  
Reactor Pressure

ABSTRACTA novel, close-spaced, inverted, stagnation flow, organometallic vapor phase epitaxy (OMVPE) reactor has been designed and fabricated for achieving high deposition efficiency and good large-area uniformity for solar cell applications. A computer model for this reactor, which is based on the conservation of mass, momentum, energy and species equations, has been used for predicting its operating characteristics. Due to the close spacing between the nozzle and susceptor, extensive measurements of the nozzle temperature were carried out for different reactor conditions and compared with simulation results. The maximum nozzle temperature was about 110°C showing the feasibility of GaAs growth from trimethylgallium and arsine. GaAs epitaxial layers were grown at different susceptor-nozzle distances, gas flow rates, reactor pressures and susceptor temperatures. The morphology, electrical properties and thickness uniformity of the layers were found to be of an acceptable quality. The measured and computed deposition efficiencies were found to be independent of reactor pressure and increasing with decreasing gas flow rates. The highest gallium deposition efficiency achieved was about 42%.

Investigation of the Mechanism and Growth Kinetics of Homoepitaxial 4H-SiC Growth Using CH3Cl Carbon Precursor

2006 ◽  
Vol 527-529 ◽  
pp. 171-174 ◽  
Author(s):  
Huang De Lin ◽  
Jeffery L. Wyatt ◽  
Yaroslav Koshka
Keyword(s):  
Growth Rate ◽  
Gas Flow ◽  
Linear Trend ◽  
Maximum Growth ◽  
Maximum Growth Rate ◽  
Gas Flow Rate ◽  
Flow Conditions ◽  
Precursor Decomposition ◽  
Carrier Gas Flow ◽  
Kinetics Of

In this work, the mechanism of the epitaxial growth of 4H SiC using CH3Cl as the carbon source gas was investigated. The experiments were conducted with a H2 carrier gas flow rate reduced in comparison to the standard conditions used for device-quality, full-wafer C3H8 growth. Low-H2 conditions have been found favorable for investigating the differences between the two gas systems. A non-linear trend of the growth rate dependence on CH3Cl flow was observed. This dependence was quantitatively different for C3H8 growth, which serves as an indication of different kinetics of CH3Cl and C3H8 precursor decomposition, as well as differences in Si droplet formation and dissociation. The maximum growth rate that we were able to achieve was by a factor of two higher for the CH3Cl precursor than for the C3H8 precursor at the same temperature and flow conditions. The growth on lower off-axis angle substrates produced surface morphology degradation similar for both CH3Cl and C3H8 precursor systems.

Nucleation and growth rate influence on microstructure and critical currents of TFA-YBa2Cu3O7 under low-pressure conditions

2010 ◽  
Vol 25 (12) ◽  
pp. 2371-2379 ◽  
Author(s):  
H. Chen ◽  
K. Zalamova ◽  
A. Pomar ◽  
X. Granados ◽  
T. Puig ◽  
...  
Keyword(s):  
Growth Rate ◽  
Total Pressure ◽  
Gas Flow ◽  
Film Growth ◽  
Water Pressure ◽  
Maximum Growth ◽  
Low Pressure ◽  
Critical Currents ◽  
Growth Step ◽  
Ybco Films

The effects of variable conversion parameters on the microstructure and critical currents of TFA-derived YBa2Cu3O7 (YBCO) films annealed under low-pressure conditions were investigated, accompanied by the analysis of their relationship with the nucleation process and the growth rate. It is found that non-c-axis oriented YBCO grains are formed under high supersaturation conditions, i.e., by increasing oxygen pressure, water pressure, or temperature. The optimal PH2O–PO2 window for preparation of completely c-axis oriented YBCO films expands as the total pressure rises from 50 to 100 mbar due to the decrease of supersaturation at enhanced total pressure; the corresponding maximum growth rate is only slightly increased up to 0.6 nm/s. Additionally, it is shown that the gas flow needs to be high enough to avoid random nucleation of YBCO grains. A single gas-flow–water-pressure diagram, showing simultaneously the film-growth rate, allows visualizing the cross-linked influence of processing parameters to achieve c-axis oriented YBCO films with Jc above 1 MA/cm2 in one single growth step.

Numerical Investigation of Pulsed Chemical Vapor Deposition of Aluminum Nitride to Reduce Particle Formation

2011 ◽  
Author(s):  
Derek Endres ◽  
Sandip Mazumder
Keyword(s):  
Gas Phase ◽  
Direct Contact ◽  
Gas Flow ◽  
Film Growth ◽  
Chemical Vapor ◽  
Particle Formation ◽  
Group V ◽  
Flow Rates ◽  
Group Iii ◽  
Reactor Pressure

Particles of aluminum nitride (AlN) have been observed to form during epitaxial growth of AlN films by metal organic chemical vapor deposition (MOCVD). Particle formation is undesirable because particles do not contribute to the film growth, and are detrimental to the hydraulic system of the reactor. It is believed that particle formation is triggered by adducts that are formed when the group-III precursor, namely tri-methyl-aluminum (TMAl), and the group-V precursor, namely ammonia (NH3), come in direct contact in the gas-phase. Thus, one way to eliminate particle formation is to prevent the group-III and the group-V precursors from coming in direct contact at all in the gas-phase. In this article, pulsing of TMAl and NH3 is numerically investigated as a means to reduce AlN particle formation. The investigations are conducted using computational fluid dynamics (CFD) analysis with the inclusion of detailed chemical reaction mechanisms both in the gas-phase and at the surface. The CFD code is first validated for steady-state (non-pulsed) MOCVD of AlN against published data. Subsequently, it is exercised for pulsed MOCVD with various pulse widths, precursor gas flow rates, wafer temperature, and reactor pressure. It is found that in order to significantly reduce particle formation, the group-III and group-V precursors need to be separated by a carrier gas pulse, and the carrier gas pulse should be at least 5–6 times as long as the precursor gas pulses. The studies also reveal that with the same time-averaged precursor gas flow rates as steady injection (non-pulsed) conditions, pulsed MOCVD can result in higher film growth rates because the precursors are incorporated into the film, rather than being wasted as particles. The improvement in growth rate was noted for both horizontal and vertical reactors, and was found to be most pronounced for intermediate wafer temperature and intermediate reactor pressure.

scholarly journals Зависимость скорости роста и структуры III-V нитевидных нанокристаллов от площади сбора адатомов на поверхности подложки

2021 ◽  
Vol 47 (9) ◽  
pp. 37
Author(s):  
В.Г. Дубровский
Keyword(s):  
Growth Rate ◽  
Theoretical Analysis ◽  
Substrate Surface ◽  
Maximum Growth ◽  
Maximum Growth Rate ◽  
Crystal Phase ◽  
Wurtzite Phase ◽  
Group Iii ◽  
Gaas Nanowires ◽  
Vertical Growth Rate

A theoretical analysis is presented for the growth rate and structure of III-V nanowires depending on the collection area of group III adatoms on the substrate surface. An expression for the maximum possible nanowire vertical growth rate is obtained and different reasons are analyzed for its suppression in different technologies. It is shown that the maximum growth rate is proportional to the collection area and inversely proportional to the squared nanowire radius. It is demonstrated that self-catalyzed GaAs nanowires grow or shrink radially at large or small adatom collection areas, respectively, having the zincblende crystal phase in both cases. The wurtzite phase forms in GaAs nanowires growing only axially at the intermediate adatom collection areas.

Computational Experiment on CVD of SiC: Growth Rate, C/Si Ratio, Parasitic Phase Formation

2000 ◽  
Vol 616 ◽  
Author(s):  
Andrei N. Vorob'ev ◽  
Alexandre E. Komissarov ◽  
Maxim V. Bogdanov ◽  
Sergey Yu. Karpov ◽  
Olga V. Bord ◽  
...  
Keyword(s):  
Growth Rate ◽  
Phase Formation ◽  
Homogeneous Nucleation ◽  
Transport Model ◽  
Cluster Formation ◽  
Secondary Phase ◽  
Silicon Cluster ◽  
Rotating Disc ◽  
Flow Rates ◽  
Wide Range

AbstractThe heat and mass transport model extended to describe silicon cluster formation in the gas phase is employed for a numerical analysis of SiC CVD in a commercial vertical rotating disc reactor. The growth rate is studied as a function of precursor flow rates varied in a wide range of values. It is found that the growth rate is limited by the gas mixture depletion in silicon atoms due to homogeneous nucleation. The secondary phase formation on the growing surface is analyzed. The SiC growth window depending on the precursor flow rates is calculated, and a significant effect of the homogeneous nucleation on the window width is found. The model predicts that the Si/C ratio on the wafer can considerably differ from that at the reactor inlet.

Development of High Growth Rate SiC Epi-Reactor with Controlled Thermal Gradient

2007 ◽  
Vol 556-557 ◽  
pp. 81-84
Author(s):  
Masahiko Ito ◽  
Hidekazu Tsuchida ◽  
Isaho Kamata ◽  
L. Storasta
Keyword(s):  
Growth Rate ◽  
Thermal Gradient ◽  
Gas Flow ◽  
Flow Behavior ◽  
High Growth ◽  
Maximum Growth ◽  
High Growth Rate ◽  
Maximum Growth Rate ◽  
Simulation Results ◽  
Growth Experiments

A vertical hot-wall type reactor, with a unique structure designed for controlling both gas flow behavior and thermal gradient (T/mm) on the susceptor surface, was developed. The simulation results indicate that depending on the height of the epitaxy room (h), the T/mm can be changed from a negative to a positive value. Preliminary epitaxial growth experiments resulted in a maximum growth rate of 51 μm/h, 4-inch area uniformity of σ/mean=1.7% for growth rate and σ/mean=21.5 % for doping concentration, and Z1/2 trap concentration of 9×1012 cm-3 at a growth rate of 43 μm/h.

Modeling of Halide Chemical Vapor Deposition of SiC

2006 ◽  
Author(s):  
Rong Wang ◽  
Ronghui Ma ◽  
Govindhan Dhanaraj ◽  
Yi Chen ◽  
Michael Dudley
Keyword(s):  
Growth Rate ◽  
Chemical Vapor Deposition ◽  
Vapor Deposition ◽  
Transport Model ◽  
Substrate Surface ◽  
Chemical Vapor ◽  
High Growth ◽  
High Growth Rate ◽  
Gaseous Species ◽  
Gas Field

Halide chemical vapor deposition is used to grow thick SiC epilayers at high growth rate. In this paper we present simulation of HCVD process in a horizontal hot wall reactor. A reaction mechanism for Si-C-Cl-H system is proposed for deposition of SiC using SiCl4/C3H8/H2 mixture. A model for transport of momentum and energy is developed to determine the gas field velocity and temperature distribution. Chemical reactions in the gas phase and on the substrate surface are incorporated into the transport model for predicting gas species transport and deposition. The effects of graphite etching are also accounted for in the model. Numerical simulation is performed to predict growth rate of the film as a function of temperature and gaseous species flow rates.

Convection Effects in Epitaxial Reactors: an Experimental and Theoretical Study

1988 ◽  
Vol 144 ◽  
Author(s):  
P. B. Chinoy ◽  
P. D. Agnello ◽  
S. K. Ghandhia
Keyword(s):  
Mathematical Model ◽  
Growth Rate ◽  
Energy Transfer ◽  
Natural Convection ◽  
Gas Flow ◽  
Theoretical Study ◽  
Excellent Correlation ◽  
Flow Rates ◽  
Wide Range ◽  
Experimental Vehicle

ABSTRACTAn experimental and theoretical study has been undertaken of the effects of natural and forced convection in horizontal epitaxial reactors. The epitaxial growth of GaAs was used as the experimental vehicle for this study. A mathematical model for mass, momentum and energy transfer in the reactor was developed. Excellent correlation between modeled and experimental results was demonstrated over a wide range of reactor pressures and susceptor geometries. Recirculation of hot gases, caused by natural convection, was found to result in a strong pressure dependence of growth rate at higher susceptor slopes. Low reactor pressures have been shown to be a more effective way to eliminate recirculation than high gas flow rates.

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