Are the Models of the Triply Charged Gallium Vacancy and Doubly Charged Gallium Interstitial Alive or Dead?

1995 ◽  
Vol 378 ◽  
Author(s):  
R. M. Cohen ◽  
C. Y. Chen ◽  
W. M. Li ◽  
D. S. Simons ◽  
P. H. Chi
Keyword(s):  
Negative Charge ◽  
Growth Conditions ◽  
Gallium Vacancy ◽  
Group Iii ◽  
Multiply Charged ◽  
Diffusion Mechanisms ◽  
P Type ◽  
Doubly Charged ◽  
Charged Defects ◽  
Positively Charged

AbstractWe have found that the measured diffusivity can be quite different than predicted by recent models of multiply-charged defects. Key problems dealing with the measurement and the interpretation of diffusion mechanisms are discussed. Using a few common variations in GaAs epilayer growth, we have obtained diffusivities which range over several orders of magnitude at the same temperature. Making use of the relatively weak In-As bond, we have used In as a marker to measure group III interdiffusion, DIII. DIII is consistent with the results of others using Al as a marker in n-type GaAs, but orders of magnitude smaller than predicted by the triply charged Ga vacancy, V3−Ga, model of Tan and Gosele. Although diffusion can be attributed to a negatively charged vacancy in n-type GaAs, In is found to often move by a kick-out mechanism in p-type GaAs. It appears likely that many early experiments with n- and p-type GaAs-AlAs interdiffusion were affected by large concentrations of Ga interstitials, IGa, caused by Fermi energy pinning at the growing surface. We present the first direct experimental evidence for the existence of a positively charged Ga interstitial. Our results, combined with those of others, suggest that VGa has a single negative charge associated with it. Because epilayer growth conditions appear to cause the point defect concentrations to deviate substantially from equilibrium, we conclude that the exact charge states of VGa and IGa still remain to be determined.

Effect of Fermi Level Pinning at the Surface During OMVPE Growth

1995 ◽  
Vol 378 ◽  
Author(s):  
R. M. Cohen ◽  
C. Y. Chen ◽  
W. M. Li ◽  
D. S. Simons ◽  
P. H. Chi
Keyword(s):  
Fermi Level ◽  
Fermi Energy ◽  
Growth Conditions ◽  
Ambient Conditions ◽  
Group Iii ◽  
Fermi Level Pinning ◽  
Zn Concentration ◽  
Excess Concentration ◽  
P Type ◽  
Positively Charged

AbstractDuring organometallic vapor phase epitaxy of GaAs, the Fermi energy is found to be pinned ≈200 meV below the intrinsic Fermi energy on a (lOO)-oriented surface. This was determined by making the first comparison of Zn concentration, Nzn. obtained from growth with that obtained at equilibrium, all under the same nominal ambient conditions. Donor solubility has been found to be virtually unchanged during growth of n- or p-type GaAs, and this is strong evidence that the Fermi level remains pinned at essentially the same energy during growth of n- or p-type GaAs. Consistent with Fermi level pinning, we find (1) the NZn is supersaturated in the epilayer for the ambient growth conditions used, (2) a large excess concentration of positively charged Ga interstitials can be grown into n-type GaAs and which diffuses into nearby p-type layers, causing (3) the Zn diffusivity, DZn ∼10−13 cm2/s, out of buried npn layers to be essentially independent of the ambient conditions. Annealing of a heavily Zn-doped layer at the surface can lead to 10−16<DZn<10−13 cm2/s at T=800°C simply by varying the Zn partial pressure over its commonly used range. Use of In-doped spikes in n- and p-type GaAs suggest that interstitial point defects have a strong effect on the group III diffusion.

Fermi-Level effect and junction carrier concentration effect on p-Type dopant distribution in IlI-V Compound superlattices

1998 ◽  
Vol 535 ◽  
Author(s):  
Chang-Ho Chen ◽  
Ulrich M. Gösele ◽  
Teh Y. Tan
Keyword(s):  
Electric Field ◽  
Fermi Level ◽  
Hole Concentration ◽  
Equilibrium Concentration ◽  
Dopant Atom ◽  
Group Iii ◽  
Atom Diffusion ◽  
Segregation Phenomenon ◽  
P Type ◽  
Positively Charged

AbstractThe pronounced segregation phenomenon in the distribution of p-type dopants Zn and Be in GaAs and related III-V compound heterostructures has been explained quantitatively by treating simultaneously the processes of dopant atom diffusion, segregation, and the effect of heterojunction carrier concentrations on these two aspects. Segregation of a dopant species between two semiconductor heterostructure layers is described by a model incorporating (i) a chemical effect on the neutral species; and (ii) in addition, a Fermi-level effect on the ionized species. The process of Zn and Be diffusion in GaAs and related compounds is governed by the doubly-positively-charged group III element self-interstitials whose thermal equilibrium concentration and hence also the Zn and Be diffusivities exhibit also a Fermi-level dependence, i.e., in proportion to p2.A heterojunction is consisting of a space charge region with an electric field, in which the hole concentration is different from those in the bulk layers. This influences the junction region concentrations of and of Zn− or Be−, which in turn influence the distribution of the ionized acceptor atoms. The overall process involves diffusion and segregation of holes, , Zn− or Be−, and an ionized interstitial acceptor species. The junction electric field also changes with time and position.

Growth of GaN without Yellow Luminescence

1995 ◽  
Vol 395 ◽  
Author(s):  
X. Zhang ◽  
P. Kung ◽  
D. Walker ◽  
A. Saxler ◽  
M. Razeghi
Keyword(s):  
Vapor Deposition ◽  
Metalorganic Chemical Vapor Deposition ◽  
Deep Level ◽  
Chemical Vapor ◽  
Growth Conditions ◽  
Native Defect ◽  
Yellow Luminescence ◽  
Gallium Vacancy ◽  
Rich Condition

ABSTRACTWe report the growth and photoluminescence characterization of GaN grown on different substrates and under different growth conditions using metalorganic chemical vapor deposition. The deep-level yellow luminescence centered at around 2.2eV is attributed to native defect, most possibly the gallium vacancy. The yellow luminescence can be substantially reduced By growing GaN under Ga-rich condition or doping GaN with Ge or Mg.

Diffusion Mechanisms in Sige Alloys

1999 ◽  
Vol 568 ◽  
Author(s):  
Arthur F.W. Willoughby ◽  
Janet M. Bonar ◽  
Andrew D.N. Paine
Keyword(s):  
Diffusion Processes ◽  
Dopant Diffusion ◽  
Elemental Silicon ◽  
Self Diffusion ◽  
Si Substrates ◽  
Marker Layer ◽  
Diffusion Mechanisms ◽  
Silicon And Germanium ◽  
Charged Defects

ABSTRACTInterest in diffusion processes in SiGe alloys arises from their potential in HBT's, HFET's, and optoelectronics devices, where migration over distances as small as a few nanometres can be significant. Successful modelling of these processes requires a much improved understanding of the mechanisms of self- and dopant diffusion in the alloy, although recent progress has been made. It is the purpose of this review to set this in the context of diffusion processes in elemental silicon and germanium, and to identify how this can help to elucidate behaviour in the alloy. Firstly, self diffusion processes are reviewed, from general agreement that self-diffusion in germanium is dominated by neutral and acceptor vacancies, to the position in silicon which is still uncertain. Germanium diffusion in silicon, however, appears to be via both vacancy and interstitial processes, and in the bulk alloy there is evidence for a change in dominant mechanism at around 35 percent germanium. Next, a review of dopant diffusion begins with Sb, which appears to diffuse in germanium by a mechanism similar to self-diffusion, and in silicon via monovacancies also, from marker layer evidence. In SiGe, the effects of composition and strain in epitaxial layers on Si substrates are also consistent with diffusion via vacancies, but questions still remain on the role of charged defects. The use of Sb to monitor vacancy effects such as grown-in defects by low temperature MBE, are discussed. Lastly, progress in assessing the role of vacancies and interstitials in the diffusion of boron is reviewed, which is dominated by interstitials in silicon-rich alloys, but appears to change to domination by vacancies at around 40 percent germanium, although studies in pure germanium are greatly needed.

Modified Physical Vapor Transport Growth of SiC - Control of Gas Phase Composition for Improved Process Conditions

2005 ◽  
Vol 483-485 ◽  
pp. 25-30 ◽  
Author(s):  
Peter J. Wellmann ◽  
Thomas L. Straubinger ◽  
Patrick Desperrier ◽  
Ralf Müller ◽  
Ulrike Künecke ◽  
...  
Keyword(s):  
Temperature Field ◽  
Phase Composition ◽  
Gas Phase ◽  
Growth Conditions ◽  
Vapor Transport ◽  
Physical Vapor Transport ◽  
Process Conditions ◽  
Growth Technique ◽  
Experimental Implementation ◽  
P Type

We review the development of a modified physical vapor transport (M-PVT) growth technique for the preparation of SiC single crystals which makes use of an additional gas pipe into the growth cell. While the gas phase composition is basically fixed in conventional physical vapor transport (PVT) growth by crucible design and temperature field, the gas inlet of the MPVT configuration allows the direct tuning of the gas phase composition for improved growth conditions. The phrase "additional" means that only small amounts of extra gases are supplied in order to fine-tune the gas phase composition. We discuss the experimental implementation of the extra gas pipe and present numerical simulations of temperature field and mass transport in the new growth configuration. The potential of the growth technique will be outlined by showing the improvements achieved for p-type doping of 4H-SiC with aluminum, i.e. [Al]=9⋅1019cm-3 and ρ<0.2Ωcm, and n-type doping of SiC with phosphorous, i.e. [P]=7.8⋅1017cm-3.

First Principles Investigation of the Stability and the Chemical Behavior of Hydrogen in ThCoH4

2011 ◽  
Vol 66 (3) ◽  
pp. 269-274
Author(s):  
Samir F. Matar
Keyword(s):  
Negative Charge ◽  
Geometry Optimization ◽  
Full Geometry Optimization ◽  
Intermetallic Matrix ◽  
Charge Analysis ◽  
The Stability ◽  
The One ◽  
Site Selective ◽  
Bader Charge Analysis ◽  
Positively Charged

We address the changes in the electronic structure brought by the insertion of hydrogen into ThCo leading to the experimentally observed ThCoH4. Full geometry optimization positions the hydrogen in three sites stabilized in the expanded intermetallic matrix. From a Bader charge analysis, hydrogen is found to be in a narrow iono-covalent (~−0.6) to covalent (~−0.3) bonding which should enable site-selective desorption. The overall chemical picture shows a positively charged Thδ+ with the negative charge redistributed over a complex anion {CoH4}δ− with δ~1.8. Nevertheless this charge transfer remains far from the one in the more ionic hydridocobaltate anion CoH54− in Mg2CoH5, due to the largely electropositive character of Mg.

Group III-Sb Metamorphic Buffer on Si for p-Channel all-III-V CMOS: Electrical Properties, Growth and Surface Defects

2015 ◽  
Vol 1790 ◽  
pp. 13-18
Author(s):  
Shun Sasaki ◽  
Shailesh Madisetti ◽  
Vadim Tokranov ◽  
Michael Yakimov ◽  
Makoto Hirayama ◽  
...  
Keyword(s):  
Surface Defects ◽  
Lattice Mismatch ◽  
Chemical Properties ◽  
Antiphase Domain ◽  
Hole Transport ◽  
Heteroepitaxial Growth ◽  
Group Iii ◽  
Similar Chemical ◽  
Unintentional Doping ◽  
P Type

ABSTRACTGroup III-Sb compound semiconductors are promising materials for future CMOS circuits. Especially, In1-xGaxSb is considered as a complimentary p-type channel material to n-type In1-xGaxAs MOSFET due to the superior hole transport properties and similar chemical properties in III-Sb’s to those of InGaAs. The heteroepitaxial growth of In1-xGaxSb on Si substrate has significant advantage for volume fabrication of III-V ICs. However large lattice mismatch between InGaSb and Si results in many growth-related defects (micro twins, threading dislocations and antiphase domain boundaries); these defects also act as deep acceptor levels. Accordingly, unintentional doping in InGaSb films causes additional scattering, increase junction leakages and affects the interface properties. In this paper, we studied the correlations between of defects and hole carrier densities in GaSb and strained In1-xGaxSb quantum well layers by using various designs of metamorphic superlattice buffers.

Electron Paramagnetic Resonance Study of Carbon Antisite-Vacancy Pair in p-Type 4H-SiC

2007 ◽  
Vol 556-557 ◽  
pp. 453-456 ◽  
Author(s):  
T. Umeda ◽  
Norio Morishita ◽  
Takeshi Ohshima ◽  
Hisayoshi Itoh ◽  
Junichi Isoya
Keyword(s):  
Electron Paramagnetic Resonance ◽  
Electron Irradiation ◽  
Electron Paramagnetic Resonance Study ◽  
Dangling Bond ◽  
Charged State ◽  
Paramagnetic Resonance ◽  
Vacancy Pair ◽  
P Type ◽  
Electron Paramagnetic ◽  
Positively Charged

Carbon antisite-vacancy pair (CSiVC) is a fundamental defect in SiC, and is theoretically predicted to be very stable in p-type materials. However, this pair was found only in the form of a negatively charged state (i.e., the SI5 center = CSiVC −) in n-type and semi-insulating 4H-SiC, and yet, its presence has not been shown in p-type SiC. In this report, we present the first EPR observation on positively charged CSiVC pairs in p-type 4H-SiC. By carefully examining p-type samples after electron irradiation, we found a pair of new defects with C3v and C1h symmetries. They correspond to “c-axial” pairs (C3v) and “basal” pairs (C1h) of CSiVC +, respectively. The positively charged pairs are characterized by a strong 13C hyperfine interaction due to a dangling bond on a carbon antisite (CSi), which is successfully resolved for the c-axial pairs.

scholarly journals Formation and fragmentation of doubly and triply charged ions in the negative ion spectra of neutral N-glycans from viral and other glycoproteins

2021 ◽  
Author(s):  
David J. Harvey ◽  
Weston B. Struwe ◽  
Anna-Janina Behrens ◽  
Snezana Vasiljevic ◽  
Max Crispin
Keyword(s):  
Detailed Comparison ◽  
Negative Ion ◽  
Doubly Charged Ions ◽  
Multiply Charged ◽  
Structural Details ◽  
Different Types ◽  
Doubly Charged ◽  
Ion Collision ◽  
Charged Ions

AbstractStructural determination of N-glycans by mass spectrometry is ideally performed by negative ion collision-induced dissociation because the spectra are dominated by cross-ring fragments leading to ions that reveal structural details not available by many other methods. Most glycans form [M – H]- or [M + adduct]- ions but larger ones (above approx. m/z 2000) typically form doubly charged ions. Differences have been reported between the fragmentation of singly and doubly charged ions but a detailed comparison does not appear to have been reported. In addition to [M + adduct]- ions (this paper uses phosphate as the adduct) other doubly, triply, and quadruply charged ions of composition [Mn + (H2PO4)n]n- have been observed in mixtures of N-glycans released from viral and other glycoproteins. This paper explores the formation and fragmentation of these different types of multiply charged ions with particular reference to the presence of diagnostic fragments in the CID spectra and comments on how these ions can be used to characterize these glycans. Graphical abstract

N2 positively charged defects in diamond. A quantum mechanical investigation of the structural, electronic, EPR and vibrational properties

2020 ◽  
Vol 8 (15) ◽  
pp. 5239-5247 ◽  
Author(s):  
Giulio Di Palma ◽  
Francesco Silvio Gentile ◽  
Valentina Lacivita ◽  
William C. Mackrodt ◽  
Mauro Causà ◽  
...  
Keyword(s):  
Ab Initio ◽  
Quantum Mechanical ◽  
Vibrational Properties ◽  
Quantum Mechanical Calculations ◽  
Mechanical Investigation ◽  
Crystal Code ◽  
Charged Defects ◽  
Positively Charged ◽  
Vibrational Characterization

Structural, EPR and vibrational characterization of the N2, N+2 and N++2 defects in diamond from ab initio quantum-mechanical calculations with the CRYSTAL code.

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