Hydrogen Passivation of Be-Acceptors in AiGaAs/GaAs Quantum Well Structures

1998 ◽  
Vol 513 ◽  
Author(s):  
Q. X. Zhaoa ◽  
U. Södervall ◽  
M. Willandera ◽  
B. O. Fimland ◽  
D. Crawford ◽  
...  
Keyword(s):  
Quantum Wells ◽  
Molecular Beam ◽  
Secondary Ion Mass Spectrometry ◽  
Hydrogen Passivation ◽  
Quantum Well Structures ◽  
Significant Difference ◽  
20 Nm ◽  
First Time ◽  
Secondary Ion ◽  
Gas Pressures

ABSTRACTHigh quality Al0.3Ga0.7As/GaAs quantum wells with centrally doped Be-acceptors were grown by molecular beam epitaxy (MBE). The well width is either 10 nm or 20 nm, and the concentration of Be-acceptors is varied between 5× 1016/cm3 and 2×1018/cm3. The structures were treated systematically by dc H-plasma at different sample temperatures, gas pressures and cooling down procedures. The passivation of Be-acceptors were characterized by photoluminescence spectroscopy and secondary ion mass spectrometry (SIMS). Without causing degradation of the A1GaAs/GaAs interfaces, we have obtained, for the first time, a deactivation of above 80% of the Be-acceptors. The influence of the Be-doping on the bandgap excitons in the QW structures is also investigated in detail. A significant difference is found in comparison with the earlier reports for 150 Å wide quantum wells, in which different samples were used for different doping concentrations.

Effect of the oxidation of a silicide layer on dopant diffusion in the underlying silicon

1999 ◽  
Vol 568 ◽  
Author(s):  
L. Kappius ◽  
A. K. Tyagi ◽  
U. Breuer ◽  
H. L. Bay ◽  
S. Manti
Keyword(s):  
Mass Spectrometry ◽  
Molecular Beam ◽  
Secondary Ion Mass Spectrometry ◽  
Enhanced Diffusion ◽  
Depth Profiles ◽  
Silicide Layer ◽  
Before And After ◽  
Sb Doping ◽  
20 Nm ◽  
Secondary Ion

ABSTRACTWe have studied the influence of an epitaxial silicide layer on the diffusion of B and Sb in silicon. B and Sb doping superlattices have been grown by molecular beam epitaxy. They were then covered with a 20 nm thick CoSi2 layer. Test samples were also grown without silicide. Samples were oxidized at various temperatures ranging from 800°C to 1200°C for times that ensured sufficient broadening of the spikes. Another set of samples was annealed at the same times and temperatures in N2. Dopant depth profiles were measured before and after diffusion by secondary ion mass spectrometry (SIMS). At the test samples we observed thermal diffusion of B and Sb, oxidation enhanced diffusion of B and oxidation retarded diffusion of Sb, all in accordance with the literature. In contrast to this, oxidized silicide capped samples showed a retardation of B diffusion by a factor of 2 - 10 as compared to thermal diffusivity and an enhancement of Sb diffusion by a factor of 1 - 2.

Aspects of high-resolution imaging with a scanning ion microprobe

1986 ◽  
Vol 44 ◽  
pp. 750-751
Author(s):  
R. Levi-Setti ◽  
J. M. Chabala ◽  
Y. L. Wang
Keyword(s):  
Metal Ion ◽  
Secondary Ion Mass Spectrometry ◽  
Chromatic Aberration ◽  
Ion Source ◽  
Ion Microprobe ◽  
Emission Pattern ◽  
Intrinsic Resolution ◽  
Resolution Imaging ◽  
20 Nm ◽  
Secondary Ion

We have shown the feasibility of 20 nm lateral resolution in both topographic and elemental imaging using probes of this size from a liquid metal ion source (LMIS) scanning ion microprobe (SIM). This performance, which approaches the intrinsic resolution limits of secondary ion mass spectrometry (SIMS), was attained by limiting the size of the beam defining aperture (5μm) to subtend a semiangle at the source of 0.16 mr. The ensuing probe current, in our chromatic-aberration limited optical system, was 1.6 pA with Ga+ or In+ sources. Although unique applications of such low current probes have been demonstrated,) the stringent alignment requirements which they imposed made their routine use impractical. For instance, the occasional tendency of the LMIS to shift its emission pattern caused severe misalignment problems.

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.

scholarly journals Optimization of growth of InGaAs/InP quantum wells using photoluminescence and secondary ion mass spectrometry

2000 ◽  
Vol 23 (3) ◽  
pp. 207-209
Author(s):  
S. Bhunia ◽  
P. Banerji ◽  
T. K. Chaudhuri ◽  
A. R. Haldar ◽  
D. N. Bose ◽  
...  
Keyword(s):  
Mass Spectrometry ◽  
Quantum Wells ◽  
Secondary Ion Mass Spectrometry ◽  
Ion Mass Spectrometry ◽  
Secondary Ion

Direct visualization of a vast cortical calcium compartment in Paramecium by secondary ion mass spectrometry (SIMS) microscopy: possible involvement in exocytosis

1995 ◽  
Vol 108 (5) ◽  
pp. 1895-1909 ◽  
Author(s):  
N. Stelly ◽  
S. Halpern ◽  
G. Nicolas ◽  
P. Fragu ◽  
A. Adoutte
Keyword(s):  
Mass Spectrometry ◽  
Secondary Ion Mass Spectrometry ◽  
Membrane Vesicles ◽  
Cell Periphery ◽  
A Value ◽  
External Reference ◽  
Ion Mass Spectrometry ◽  
First Time ◽  
Secondary Ion

The plasma membrane of ciliates is underlaid by a vast continuous array of membrane vesicles known as cortical alveoli. Previous work had shown that a purified fraction of these vesicles actively pumps calcium, suggesting that alveoli may constitute a calcium-storage compartment. Here we provide direct confirmation of this hypothesis using in situ visualization of total cell calcium on sections of cryofixed and cryosubstituted cells analyzed by SIMS (secondary ion mass spectrometry) microscopy a method never previously applied to protists. A narrow, continuous, Ca-emitting zone located all along the cell periphery was observed on sections including the cortex. In contrast, Na and K were evenly distributed throughout the cell. Various controls confirmed that emission was from the alveoli, in particular, the emitting zone was still seen in mutants totally lacking trichocysts, the large exocytotic organelles docked at the cell surface, indicating that they make no major direct contribution to the emission. Calcium concentration within alveoli was quantified for the first time in SIMS microscopy using an external reference and was found to be in the range of 3 to 5 mM, a value similar to that for sarcoplasmic reticulum. After massive induction of trichocyst discharge, this concentration was found to decrease by about 50%, suggesting that the alveoli are the main source of the calcium involved in exocytosis.

Indium concentration fluctuations in InGaN/GaN quantum wells

2019 ◽  
Vol 34 (8) ◽  
pp. 1718-1723 ◽  
Author(s):  
Paweł Piotr Michałowski ◽  
Ewa Grzanka ◽  
Szymon Grzanka ◽  
Artur Lachowski ◽  
Grzegorz Staszczak ◽  
...  
Keyword(s):  
Mass Spectrometry ◽  
Quantum Wells ◽  
Secondary Ion Mass Spectrometry ◽  
Concentration Fluctuations ◽  
Specific Information ◽  
Indium Concentration ◽  
Ion Mass Spectrometry ◽  
Secondary Ion ◽  
Ingan Quantum Wells

Secondary ion mass spectrometry measurements can provide specific information on In fluctuations in InGaN quantum wells.

Direct analysis of alkaloids in natural Cinchona bark and commercial extracts using time-of-flight secondary ion mass spectrometry

2018 ◽  
Vol 10 (9) ◽  
pp. 950-958 ◽  
Author(s):  
Derick N. Ateacha ◽  
Ulrike Koch ◽  
Carsten Engelhard
Keyword(s):  
Mass Spectrometry ◽  
Secondary Ion Mass Spectrometry ◽  
Time Of Flight ◽  
Direct Analysis ◽  
Tof Sims ◽  
Ion Mass Spectrometry ◽  
First Time ◽  
Secondary Ion

Time-of-flight secondary ion mass spectrometry (ToF-SIMS) is used for the first time to characterize Cinchona alkaloids in natural Cinchona bark and commercial Cinchona extracts.

Photoluminescence Fatigue in Laterally-Ordered (GaP)2/(InP)2 Short-Period-Superlattices (SPS) Grown by Molecular Beam Epitaxy

1993 ◽  
Vol 325 ◽  
Author(s):  
X. C. Liu ◽  
S. Q. Gu ◽  
E. E. Reuter ◽  
S. G. Bishop ◽  
A. C. Chen ◽  
...  
Keyword(s):  
Molecular Beam Epitaxy ◽  
Quantum Well ◽  
Quantum Wells ◽  
Lower Energy ◽  
Molecular Beam ◽  
Continuous Illumination ◽  
Exciting Light ◽  
Quantum Well Structures ◽  
Short Period ◽  
Short Period Superlattices

AbstractSpontaneously laterally ordered (GaP)2/(InP)2 short period superlattices (SPS) grown by Molecular Beam Epitaxy (MBE) on nominal (100) GaAs substrates have been studied by photoluminescence (PL) spectroscopy. The samples studied included SPS comprising 110 pairs of (GaP)2/(InP)2 (total thickness σ90 nm) and multiquantum well structures in which quantum wells comprising 12 pairs of (GaP)2/(InP)2 SPS layers (thickness σ10 nm) are alternated with lattice-matched GaInP random alloy barrier layers. The 5K PL spectra include a σ1760 meV nearband edge band, and a much broader, lower energy (σ1670 meV) luminescence band that exhibits an unusual fatiguing behavior; its intensity diminishes monotonically during continuous illumination by the exciting light. This fatigued PL state is metastable at low temperatures. In the quantum well structure, although the relative intensity of the lower energy band is significantly weaker in comparison to the higher one, the fatiguing behavior still exists. However the fatiguing rate is slower in quantum well structures than that observed in the thick SPS film.

A Comparison of Magnesium and Beryllium Acceptors in GaN Grown by rf-Plasma Assisted Molecular Beam Epitaxy

2000 ◽  
Vol 639 ◽  
Author(s):  
A.J. Ptak ◽  
T.H. Myers ◽  
Lijun Wang ◽  
N.C. Giles ◽  
M. Moldovan ◽  
...  
Keyword(s):  
Atomic Hydrogen ◽  
Molecular Beam ◽  
Surface Segregation ◽  
Secondary Ion Mass Spectrometry ◽  
Rf Plasma ◽  
Dopant Incorporation ◽  
Optical Activation ◽  
P Type ◽  
Kinetics Of ◽  
Secondary Ion

ABSTRACTStep-doped structures of both magnesium and beryllium were grown in GaN and analyzed using secondary ion mass spectrometry. Dopant incorporation was studied as a function of substrate temperature and dopant flux for Ga-polarity and N-polarity GaN. Incorporation is different for each polarity, with Mg incorporating by up to a factor of 20 times more (30 times more with atomic hydrogen) on the Ga-face, while Be incorporates more readily on the N-face. The effect of atomic hydrogen on the incorporation kinetics of both Mg and Be is also discussed. Mg and Be both undergo surface segregation during growth. Photoluminescence measurements suggest that Be is a p-type dopant with an optical activation energy of approximately 100 meV.

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