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.

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.

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.`

Impact of Buffered Layer Growth Conditions on Grown-In Vacancy Concentrations in Molecular Beam Epitaxy Silicon Germanium

2004 ◽  
Vol 809 ◽  
Author(s):  
Kareem M. Shoukri ◽  
Yaser M. Haddara ◽  
Andrew P. Knights ◽  
Paul G. Coleman ◽  
Mohammad M. Rahman ◽  
...  
Keyword(s):  
Molecular Beam Epitaxy ◽  
Buffer Layer ◽  
Point Defects ◽  
Growth Temperature ◽  
Silicon Germanium ◽  
Molecular Beam ◽  
Growth Conditions ◽  
Layer Growth ◽  
Vacancy Clusters ◽  
Temperature And Growth

ABSTRACTSilicon-Germanium (SiGe) has become increasingly attractive to semiconductor manufacturers over the last decade for use in high performance devices. In order to produce thin layers of device grade SiGe with low concentrations of point defects and well-controlled doping profiles, advanced growth and deposition techniques such as molecular beam epitaxy (MBE) are used. One of the key issues in modeling dopant diffusion during subsequent processing is the concentration of grown-in point defects. The incorporation of vacancy clusters and vacancy point defects in 200nm SiGe/Si layers grown by molecular beam epitaxy over different buffer layers has been observed using beam-based positron annihilation spectroscopy. Variables included the type of buffer layer, the growth temperature and growth rate for the buffer, and the growth temperature and growth rate for the top layer. Different growth conditions resulted in different relaxation amounts in the top layer, but in all samples the dislocation density was below 106 cm−2. Preliminary results indicate a correlation between the size, type and concentration of vacancy defects and the buffer layer growth temperature. At high buffer layer growth temperature of 500°C the vacancy point defect concentration is below the PAS detectable limit of approximately 1015 cm−3. As the buffer layer growth is decreased to a minimum value of 300°C, large vacancy clusters are observed in the buffered layer and vacancy point defects are observed in the SiGe film. These results are relevant to the role played by point defects grown-in at temperatures below ∼350°C in modeling dopant diffusion during processing.

Movpe Strip-Like Self-Organization of InAs Grown on InP Vicinal Surfaces

2000 ◽  
Vol 618 ◽  
Author(s):  
Laurent Auvray ◽  
Véronique Soulière ◽  
Hervé Dumont ◽  
Jacques Dazord ◽  
Yves Monteil ◽  
...  
Keyword(s):  
Surface Morphology ◽  
Growth Parameters ◽  
Flux Ratio ◽  
Growth Conditions ◽  
Thin Layers ◽  
Vicinal Surfaces ◽  
Force Microscopy ◽  
Atomic Force ◽  
Nominal Thickness ◽  
Inp Substrates

ABSTRACTWe have investigated the influence of MOVPE growth parameters on the surface morphology of InAs nanostructures grown on 0.2° misoriented (001)InP substrates. Thin layers of nominal thickness of about 3 and 6 ML were deposited at 500°C with V/Ill flux ratios ranging from 50 to 240. The samples were cool down from 500 to 350°C during 6 minutes under either arsine or phophine atmosphere. The influence of this step has been found to greatly determine the surface morphology of the nanostructures observed by atomic force microscopy. Dots self-aligned along the steps and forming a non continuous strip, regularly spaced every 3-4 terraces have been obtained. The morphology of the strips can be varied with the growth conditions (V/III flux ratio). In this work, we will propose a mechanism for the formation of the strips observed during the cooling under phosphine atmosphere taking into account an As » P exchange.

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.

Indium Gallium Nitride on Germanium by Molecular Beam Epitaxy

2011 ◽  
Vol 1324 ◽  
Author(s):  
R.R. Lieten ◽  
W.-J. Tseng ◽  
M. Leys ◽  
J.-P. Locquet ◽  
J. Dekoster
Keyword(s):  
Molecular Beam ◽  
Growth Parameters ◽  
Flux Ratio ◽  
Growth Conditions ◽  
Nitrogen Supply ◽  
Buffer Layers ◽  
Crystal Quality ◽  
Structural Quality ◽  
Nitride Layers ◽  
Ingan Alloys

ABSTRACTIndium containing III-Nitride layers are predominantly grown by heteroepitaxy on foreign substrates, most often Al2O3, SiC and Si. We have investigated the epitaxial growth of InxGa1-xN (InGaN) alloys on Ge substrates. First we looked at the influence of buffer layers between the InGaN and Ge substrate. When applying a high temperature (850 °C) GaN buffer, the InGaN showed superior crystal quality. Furthermore the influence of growth parameters on the structural quality and composition of InGaN layers has been looked into. For a fixed gallium and nitrogen supply, the indium beam flux was increased incrementally. For both nitrogen- as well as for metal (Ga + In) rich growth conditions, the In incorporation increases for increasing In flux. However, for metal rich growth conditions, segregation of metallic In is observed. An optimum in crystal quality is obtained for a metal:nitrogen flux ratio close to unity. The XRD FWHM of the GaN (0002) reflection increases significantly after InGaN growth. Apparently the presence of indium deteriorates the GaN buffer during InGaN growth. The mechanism of the effect is not known yet.

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.

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 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.

A Study of Point Defects and Cause of Nonstoichiometry in InSb Nanowires

2011 ◽  
Vol 1302 ◽  
Author(s):  
U. Philipose ◽  
Gopal Sapkota ◽  
Pradeep Gali ◽  
Prathyusha Nukala
Keyword(s):  
Point Defects ◽  
Growth Temperature ◽  
Defect Formation ◽  
Growth Parameters ◽  
Chemical Vapor ◽  
Metal Catalyst ◽  
Vapor Pressures ◽  
Experimental Findings ◽  
Good Agreement ◽  
Insb Nanowires

ABSTRACTSynthesis of InSb nanowires using chemical vapor deposition (CVD) is technically challenging due to the tuning of III-V vapor pressures. Growth parameters such as the choice of the metal catalyst, growth temperature and vapor pressure of constituents affect the morphology and stoichiometry of InSb nanowires. By controlling the growth temperature, it was possible to grow either stoichiometric InSb nanowires or In nanowires that contained no Sb within detectable limits. We present a simple model to show that the occurrence of native point defects in InSb is influenced by the growth kinetics and by the thermodynamics of defect formation. Results from this model are in good agreement with our experimental findings of the evidence of point defects in these nanowires.

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