Dependence of Sheet Hole Concentrations on Growth Kinetics of a Carbon Doped Electron Beam Heated Graphite Source in GaAs and Al0.3GaD0.7As Films Grown by Solid Source MBE

1995 ◽  
Vol 378 ◽  
Author(s):  
D. L. Sato ◽  
F. J. Szalkowski ◽  
H. P. Lee
Keyword(s):  
Electron Beam ◽  
Surface Segregation ◽  
Carbon Sources ◽  
Growth Conditions ◽  
Growth Surface ◽  
Photoluminescence Intensity ◽  
Beam Source ◽  
Atomic Carbon ◽  
Gaas Films ◽  
Carbon Beam

AbstractA series of carbon delta- and uniformly- doped GaAs and Al0.3Ga0.7As films have been grown by solid source Molecular Beam Epitaxy using an electron-beam heated graphite rod as the dopant source. In contrast to heated filament carbon sources, this electron-beam source produces atomic carbon C1, rather than C3 as the predominant species. The purpose of these experiments was to compare measured sheet carrier concentration of delta-doped GaAs and Al0.3Ga0.7As films under fixed growth conditions and with similar carbon beam fluxes using this electron-beam source. The films were characterized by Hall-effect measurements. The Al0.3Ga0.7As films have consistently higher hole sheet carrier concentrations than GaAs films with similar carbon fluxes. Delta-doped Al0.3Ga0.7 As sheet carrier concentrations of up to 2.2×1013 cm−2 were measured, and thin uniformly-doped Al0.3Ga0.7 As carrier densities were measured up to 5.7×1020 cm−3. The uniformly doped Al0.3Ga0.7As films appear to have higher atomic carbon activation than this delta-doped Al0.3Ga0.7As films. These results can be possibly explained in terms of several concurrent processes involving C-C pairing, stronger Al-C bonding, and dopant surface segregation taking place on the growth surface of the delta-doped layer. Photoluminescence intensity measurements of uniformly-doped GaAs shows degradation at hole concentrations greater then 1018 cm−3 and bandgap contraction at hole densities greater than mid 1018 cm−3.

Near-Surface Aggregation of Sn In Heavily Sn-Doped GaAs Films Grown By Molecular Beam Epitaxy

1985 ◽  
Vol 43 ◽  
pp. 368-369
Author(s):  
S. H. Chen
Keyword(s):  
Molecular Beam Epitaxy ◽  
Cross Section ◽  
Electron Spectroscopy ◽  
Molecular Beam ◽  
Surface Segregation ◽  
Secondary Ion Mass Spectrometry ◽  
Specimen Preparation ◽  
Near Surface ◽  
Gaas Films ◽  
Secondary Ion

Sn has been used extensively as an n-type dopant in GaAs grown by molecular-beam epitaxy (MBE). The surface accumulation of Sn during the growth of Sn-doped GaAs has been observed by several investigators. It is still not clear whether the accumulation of Sn is a kinetically hindered process, as proposed first by Wood and Joyce, or surface segregation due to thermodynamic factors. The proposed donor-incorporation mechanisms were based on experimental results from such techniques as secondary ion mass spectrometry, Auger electron spectroscopy, and C-V measurements. In the present study, electron microscopy was used in combination with cross-section specimen preparation. The information on the morphology and microstructure of the surface accumulation can be obtained in a fine scale and may confirm several suggestions from indirect experimental evidence in the previous studies.

ELECTRON BEAM SOURCE MOLECULAR BEAM EPITAXY OF AlxGa1-xAs GRADED BAND GAP DEVICE STRUCTURES

1988 ◽  
Vol 49 (C4) ◽  
pp. C4-607-C4-614
Author(s):  
R. J. MALIK ◽  
A. F.J. LEVI ◽  
B. F. LEVINE ◽  
R. C. MILLER ◽  
D. V. LANG ◽  
...  
Keyword(s):  
Electron Beam ◽  
Molecular Beam Epitaxy ◽  
Band Gap ◽  
Molecular Beam ◽  
Beam Source ◽  
Device Structures ◽  
Graded Band Gap

Assimilation of various organic carbon sources by Haematococcus strains

2009 ◽  
Vol 57 (2) ◽  
pp. 231-237
Author(s):  
M. Zych ◽  
A. Stolarczyk ◽  
K. Maca ◽  
A. Banaś ◽  
K. Termińska-Pabis ◽  
...  
Keyword(s):  
Organic Carbon ◽  
Organic Compounds ◽  
Present Experiment ◽  
Carbon Sources ◽  
Growth Conditions ◽  
Mixotrophic Growth ◽  
Naturally Occurring ◽  
Organic Carbon Sources ◽  
Secondary Carotenoids ◽  
Colour Changes

Differences in the assimilation of individual organic compounds (5 mM sugars and L-asparagine) under mixotrophic growth conditions were described for three naturally occurring Haematococcus strains.The effects of assimilation were measured by the growth intensity and size of algal cells, and the effect of colour changes in the cultures was observed. Some compounds caused the cell colouration to change from green to yellow, being the result of chlorophyll disappearance and the accumulation of yellow secondary carotenoids. In the present experiment none of the cultures turned red, thus excluding the intense accumulation of the commercially interesting carotenoid, astaxanthin.

The Photoluminescence and TEM Studies of Patterned GaAs films on Si Substrate Grown by Molecular Beam Epitaxy

1988 ◽  
Vol 116 ◽  
Author(s):  
Henry P. Lee ◽  
Yi-He Huang ◽  
Xiaoming Liu ◽  
Hong Lin ◽  
John. S. Smith ◽  
...  
Keyword(s):  
Tensile Stress ◽  
Uniaxial Stress ◽  
Luminescence Spectra ◽  
Residual Tensile Stress ◽  
Photoluminescence Intensity ◽  
Patterned Substrate ◽  
Si Substrates ◽  
Gaas Films ◽  
Patterned Films ◽  
Window Area

AbstractPatterned epitaxial GaAs films have been formed on Si substrates by either growth over patterned substrate (selective -area epitaxy) or chemical etching of patterns after growth. The optical properties of these samples are studied by 77K photoluminescence (PL) and the defect structures are investigated by transmission electron microscope (TEM). The patterned substrate consisted of bare Si stripes with width ranging from 10 µm to 100 µm surrounded by Si3N4 films on both sides and a reference area of bare Si. For 1.5 µmiann d 3 µm thick films, PL intensities from the films inside the 10 µm stripe shows 140% and 75% increase over unpatterned areas while the residual tensile stress in the patterned films is very similar to that of the unpatterned area. The increase in the photoluminescence intensity is ascribed to the reduction of crystalline defects inside the the window area. In the chemically etched sample, the pattern consisted of 4 µm by 4 µm squares and 1 mm long stripes with widths ranging from 100 µm to 4 plm. From the shift of PL peaks, a monotonic decrease in the tensile stress versus stripe width is observed. In particular, when the width of the stripe is less than 7 µm. tensile stress becomes essentially uniaxial in agreement with the results obtained by Yacobi et al [16] on a GaAs on InP sample. The polarization of the luminescence spectra parallel and perpendicular to the uniaxial stress of a 4 µm wide stripe agrees well with theoretical prediction. It is also observed that tensile stress is almost completely relieved in the 4 µm by 4 muentc hed squares.

In Situ Monitoring of the Smear-Out of the Ge Profile in GAS Source SiGe MBE Using Rheed Intensity Oscillations

1992 ◽  
Vol 263 ◽  
Author(s):  
K. Werner ◽  
S. Butzke ◽  
J.W. Maes ◽  
O.F.Z. Schannen ◽  
J. Trommel ◽  
...  
Keyword(s):  
Growth Rate ◽  
Molecular Beam ◽  
Surface Segregation ◽  
Catalytic Effect ◽  
Growth Conditions ◽  
In Situ Monitoring ◽  
Marked Contrast ◽  
Si Substrates ◽  
Gas Source

ABSTRACTWe have studied the deposition of GexSi1−x layers on (100) Si substrates by gas source molecular beam epitaxy (GSMBE) using disilane and germane.The investigation of RHEED intensity oscillations during growth reveals the well known rate enhancement obtained when adding a small amount of germane to the disilane flux. However, when exposing a previously deposited Ge layer to a pure disilane flux the growth rate during the first few monolayers remains at an enhanced value but returns to its homoepitaxial value after about 10 to 15 monolayers. This behaviour was observed under a variety of growth conditions. It is in marked contrast to the experience obtained in conventional Si/Ge MBE and suggests a catalytic effect of the particular surface present during GSMBE growth. We propose that this effect is caused by the surface segregation of Ge species and leads to a smear-out of the Ge profile in the layer.

Nitrate removal using Brevundimonas diminuta MTCC 8486 from ground water

2009 ◽  
Vol 60 (2) ◽  
pp. 517-524 ◽  
Author(s):  
S. Kavitha ◽  
R. Selvakumar ◽  
M. Sathishkumar ◽  
K. Swaminathan ◽  
P. Lakshmanaperumalsamy ◽  
...  
Keyword(s):  
Carbon Source ◽  
Ground Water ◽  
Nitrate Removal ◽  
Carbon Sources ◽  
Treatment Plant ◽  
Growth Conditions ◽  
Pilot Scale ◽  
Biological Removal ◽  
Treatment Processes ◽  
Brevundimonas Diminuta

Brevundimonas diminuta MTCC 8486, isolated from marine soil of coastal area of Trivandrum, Kerala, was used for biological removal of nitrate from ground water collected from Kar village of Pali district, Rajasthan. The organism was found to be resistance for nitrate up to 10,000 mg L−1. The optimum growth conditions for biological removal of nitrate were established in batch culture. The effect of carbon sources on nitrate removal was investigated using mineral salt medium (MSM) containing 500 mg L−1 of nitrate to select the most effective carbon source. Among glucose and starch as carbon source, glucose at 1% concentration increased the growth (182±8.24 × 104 CFU mL−1) and induced maximum nitrate reduction (86.4%) at 72 h. The ground water collected from Kar village, Pali district of Rajasthan containing 460±5.92 mg L−1 of nitrate was subjected to three different treatment processes in pilot scale (T1 to T3). Higher removal of nitrate was observed in T2 process (88%) supplemented with 1% glucose. The system was scaled up to 10 L pilot scale treatment plant. At 72 h the nitrate removal was observed to be 95% in pilot scale plant. The residual nitrate level (23±0.41 mg L−1) in pilot scale treatment process was found to be below the permissible limit of WHO.

Sign in / Sign up

Export Citation Format

Share Document