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

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.

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

Australian Journal of Physics ◽

10.1071/ph930435 ◽

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.`

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

MRS Proceedings ◽

10.1557/proc-442-485 ◽

1996 ◽

Vol 442 ◽

Cited By ~ 6

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.

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Phase segregation in GaAs layers grown at low temperature

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100088610 ◽

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.

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Growth and Characterization of InSb films on Si (001)

MRS Proceedings ◽

10.1557/proc-1068-c02-05 ◽

2008 ◽

Vol 1068 ◽

Cited By ~ 1

Author(s):

Lien Tran ◽

Julia Dobbert ◽

Fariba Hatami ◽

W. Ted Masselink

Keyword(s):

Substrate Temperature ◽

Buffer Layer ◽

Growth Temperature ◽

Deep Level ◽

Flux Ratio ◽

Deep Levels ◽

Structural Quality ◽

Rocking Curve ◽

X Ray ◽

Native Oxides

ABSTRACTThe replacement of native oxides with deposited oxides in CMOS technology opens the door to replacing the Si with semiconductors without high-quality native oxides. For example, the use of InSb in logic applications could allow much lower operating voltages and power dissipation due to the InSb channels reaching saturation at significantly lower electric fields. Epitaxy of InSb onto Si could be done directly or using an intermediate layer such as GaP, GaAs, or InP. In the current work we describe the growth of InSb on Si (001) and discuss the structural and electrical properties of the resulting InSb films. The samples were characterized in terms of background electron concentration, mobility, deep level traps, Hall sensitivity, and x-ray rocking curve width.Samples were grown using molecular-beam epitaxy in a Riber-Compact 21T system. Antimony was supplied with a Veeco valved cracker cell. Vicinal Si(001) substrates offcut by 4º toward [110] were prepared by repeated oxidation and oxide-removal and then loaded into the MBE system. After the substrate temperature had been increased to about 820ºC, the surface shows a clear 24 reconstruction and appears to be free of oxide. This reconstruction remains until the substrate temperature reaches 1015ºC, at which temperature a 21 appears, indicating a dominance of double-height steps. After allowing the substrate to cool to the intended growth temperature for InSb, it is exposed to cracked Sb, resulting in the surface going from 21 to 11. This 11 reconstruction remains throughout the subsequent InSb deposition. InSb was deposited with a Sb/In flux ratio of about 5 and a growth rate of 0.2 nm/s. We have investigated growth temperatures between 300 and 420ºC for growth. To prevent the formation of the defects we introduced in some samples GaSb/AlSb supperlattice buffer layer. The best structural quality has been achieved at a growth temperature of 420ºC using GaSb/AlSb supperlattice buffer layer, resulting in our best electron mobility of 2.6104 cm2/Vs for a 2m film at room temperature. The samples grown at 420°C have the narrowest x-ray rocking curve width (FWHM of about 950 arcsec). Deep level noise spectra indicate the existence of the deep levels. The sample with the best crystal quality and highest mobility has the lowest traps. The deep levels have a temperature dependent behavior.

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The Shape Control of ZnO Based Nanostructures

Journal of Nanoscience and Nanotechnology ◽

10.1166/jnn.2006.17996 ◽

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.

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

Crystals ◽

10.3390/cryst9060308 ◽

2019 ◽

Vol 9 (6) ◽

pp. 308 ◽

Cited By ~ 1

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.

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Impact of Pseudomonas putida on the Growth Parameters of Fenugreek (Trigonella foenum- graecum L.): A Traditional Herbal Boon for Rural Areas

Science & Technology Journal ◽

10.22232/stj.2017.05.02.04 ◽

2017 ◽

Vol 5 (2) ◽

pp. 93-96

Author(s):

Shashi Kant Shukla ◽

◽

Awadhesh Kumar ◽

Anupam Dikshit ◽

◽

...

Keyword(s):

Pseudomonas Putida ◽

Rural Areas ◽

Growth Parameters ◽

Leguminous Plant ◽

Food Protein ◽

Botany Department ◽

Medicinal Value ◽

Randomized Design ◽

Trigonella Foenum Graecum L ◽

The Impact

The present study aims the impact of Pseudomonas putida on different growth parameters of Trigonella sp., a leguminous plant to support the requirement of food, protein along with their medicinal value in the rural areas of India. A pot experiment was arranged based on completely randomized design with four replications at Biological Product Laboratory, Botany Department, University of Allahabad. Treatments were given at the seed level with one of control. Results indicated that application of P. putida significantly improved vegetative growth and showed an edge on the growth of the fenugreek as compared to the control.

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Aquatic Toxicity of Photocatalyst Nanoparticles to Green Microalgae Chlorella vulgaris

Water ◽

10.3390/w13010077 ◽

2020 ◽

Vol 13 (1) ◽

pp. 77

Author(s):

Cristina Adochite ◽

Luminita Andronic

Keyword(s):

Chlorella Vulgaris ◽

Advanced Oxidation Process ◽

Growth Parameters ◽

Aquatic Toxicity ◽

Basal Medium ◽

Inhibitory Effect ◽

Synthesis Methods ◽

Potent Inhibitory Effect ◽

Density Surface ◽

The Impact

In the last years, nanoparticles such as TiO2, ZnO, NiO, CuO and Fe2O3 were mainly used in wastewater applications. In addition to the positive aspects concerning using nanoparticles in the advanced oxidation process of wastewater containing pollutants, the impact of these nanoparticles on the environment must also be investigated. The toxicity of nanoparticles is generally investigated by the nanomaterials’ effect on green algae, especially on Chlorella vulgaris. In this review, several aspects are reviewed: the Chlorella vulgaris culture monitoring and growth parameters, the effect of different nanoparticles on Chlorella vulgaris, the toxicity of photocatalyst nanoparticles, and the mechanism of photocatalyst during oxidative stress on the photosynthetic mechanism of Chlorella vulgaris. The Bold basal medium (BBM) is generally recognized as an excellent standard cultivation medium for Chlorella vulgaris in the known environmental conditions such as temperature in the range 20–30 °C and light intensity of around 150 μE·m2·s−1 under a 16/8 h light/dark cycle. The nanoparticles synthesis methods influence the particle size, morphology, density, surface area to generate growth inhibition and further algal deaths at the nanoparticle-dependent concentration. Moreover, the results revealed that nanoparticles caused a more potent inhibitory effect on microalgal growth and severely disrupted algal cells’ membranes.

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Oil and Flower Production in Rosa damascena trigintipetala Dieck under Salinity Stress in Taif Region, Saudi Arabia

Sustainability ◽

10.3390/su13084547 ◽

2021 ◽

Vol 13 (8) ◽

pp. 4547

Author(s):

Mohamed E. El-Sharnouby ◽

Metwally M. Montaser ◽

Sliai M. Abdallah

Keyword(s):

Essential Oil ◽

Essential Oils ◽

Salinity Stress ◽

Growth Parameters ◽

Industrial Applications ◽

Rosa Damascena ◽

Flower Production ◽

Survival Percentage ◽

The Impact ◽

Tolerance To Salinity

The flower industry depends on oil and fragrance, which is addressed in the current work. Different concentrations of NaCl (0, 250, 500, 1000, and 1500 ppm) were applied to Taif rose plants (Rosa damascena var. trigintipetala Dieck) to evaluate their effects on growth and essential oil content. Results clearly indicated the highest survival percentage (98.3%) was seen in untreated plants compared to plants under salinity stress. Moreover, increasing the NaCl levels induced an adverse effect on the growth parameters of Taif rose plants, while some essential oil contents were increased to the maximum degree of their tolerance to salinity stress. The extracted essential oils were analyzed using GC/MS. The essential oils of Taif rose plants treated with 500 ppm NaCl recorded the highest values of citronellol, geraniol and phenylethyl alcohol contents (16.56, 8.67 and 9.87%), respectively. NaCl at 250 ppm produced the highest values of heneicosane (13.12%), and then decreased to the lowest value (7.79%) with the increase of NaCl to 1500 NaCl, compared to the control and other NaCl levels. The current results could highlight the impact of salinity stress on Rosa damascena Miller var. trigintipetala Dieck for better economic and industrial applications.

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