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Compound semiconductors: defects and relocation of atoms during growth sputtering and diffusion
KTH, Superseded Departments, Electronics.ORCID iD: 0000-0002-0292-224X
1997 (English)Doctoral thesis, comprehensive summary (Other scientific)
Place, publisher, year, edition, pages
Stockholm: KTH , 1997. , viii, 48 p.
Series
Trita-FTE, ISSN 0284-0545 ; 1997:10
Keyword [en]
secondary ion mass spectrometry (SIMS), cascade mixing, redistribution, diffusion, defects, passivation, SiC, A1xGa1-xAs
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
URN: urn:nbn:se:kth:diva-2545ISBN: 99-2452010-6 OAI: oai:DiVA.org:kth-2545DiVA: diva2:8172
Public defence
1997-09-08, 00:00 (English)
Note
QC 20100524Available from: 2000-01-01 Created: 2000-01-01 Last updated: 2010-05-24Bibliographically approved
List of papers
1. Sputter profiling of AlGaAs/GaAs superlattice structures using oxygen and argon ions
Open this publication in new window or tab >>Sputter profiling of AlGaAs/GaAs superlattice structures using oxygen and argon ions
Show others...
1993 (English)In: Applied Surface Science, ISSN 0169-4332, E-ISSN 1873-5584, Vol. 70-71, no 1, 40-43 p.Article in journal (Refereed) Published
Abstract [en]

Broadening of Al sputter profiles in AlxGa1-xAs/GaAs structures has been investigated using secondary ion mass spectrometry. The depth profiling was carried out with 32O+2 ions and 40Ar+ ions using net primary energies of 1.8, 2.2, 3.2 and 5.7 keV. The decay lengths of the Al profiles show a pronounced increase with increasing sputtering ion energy caused by ballistic mixing. Moreover, in the O+2 case the λ-values degrade with eroded depth, indicating that beam-induced surface roughening takes place during profiling and in particular, this holds for high x-values. The results are discussed in terms of a semi-empirical model for ion-beam-induced broadening developed by Zalm and Vriezema.

National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-13011 (URN)10.1016/0169-4332(93)90394-Q (DOI)
Note
QC 20100524Available from: 2010-05-24 Created: 2010-05-24 Last updated: 2017-12-12Bibliographically approved
2. Influence of layer thickness and primary ion on profile broadening during sputtering of Al0.5Ga0.5As/GaAs structures
Open this publication in new window or tab >>Influence of layer thickness and primary ion on profile broadening during sputtering of Al0.5Ga0.5As/GaAs structures
1994 (English)In: Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, ISSN 0168-583X, Vol. 85, no 1-4, 395-398 p.Article in journal (Refereed) Published
Abstract [en]

Broadening of secondary ion mass spectrometry depth profiles for Al in Al0.5Ga0.5As/GaAs structures, where the layer thicknesses vary from two monolayers to 1000 Å, is investigated. The experiments were performed in the net primary energy range 1.8–13.2 keV with 40Ar+ ions and 84Kr+ ions. The broadening is mainly determined by ballistic mixing, and no dependence on the Al0.5Ga0.5As layer thickness is revealed. Good agreement is found with a semi-empirical mixing model published recently by Zalm and Vriezema and [Nucl. Instr. and Meth. B 67 (1992) 467] although a small contribution from surface roughness occurs. The surface roughness develops initially but saturates already after the first Al0.5Ga0.5As layer.

National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-13013 (URN)10.1016/0168-583X(94)95852-1 (DOI)
Note
QC 20100524Available from: 2010-05-24 Created: 2010-05-24 Last updated: 2010-05-24Bibliographically approved
3. Cascade mixing in AlxGa1-xAs/GaAs during sputter profiling by noble-gas ions
Open this publication in new window or tab >>Cascade mixing in AlxGa1-xAs/GaAs during sputter profiling by noble-gas ions
1999 (English)In: Physical Review B Condensed Matter, ISSN 0163-1829, E-ISSN 1095-3795, Vol. 60, no 20, 14302-14310 p.Article in journal (Refereed) Published
Abstract [en]

The effect of cascade mixing on profile broadening during secondary-ion mass spectrometry (SIMS) analysis has been thoroughly investigated for AlxGa1-xAs/GaAs structures of five different compositions (x=0.1, 0.3, 0.5, 0.73, or 1) and layers with varying thicknesses (from one monolayer to 1000 Å). The SIMS analyses were performed using primary sputtering ions of 20Ne+, 40Ar+, 84Kr+, and 136Xe+ with an impact energy (E) ranging from 1.8 to 13.2 keV and an angle of incidence, with respect to the surface normal (θ), from 62° to 35°. Within the experimental accuracy, the decay length of the trailing edge was found to be proportional to E1/2cosθ where the proportionality constant displays a relatively weak dependence on primary ion mass. However, the leading edge is strongly affected by the extension of the collision cascade as demonstrated by a comparison of the results for the different ions at a given energy. As long as the cascade is fully developed before reaching an interface no dependence on the sample depth is obtained for the profile broadening. Furthermore, the decay length for the trailing edges is extracted in the dilute limit and no effect of the marker thickness or the x value is revealed. A numerical treatment of the profile broadening within a diffusional model, where the diffusion coefficient is assumed to be proportional to the energy deposited in elastic collisions, gives a surprisingly good agreement with the experimental data.

National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-13017 (URN)10.1103/PhysRevB.60.14302 (DOI)
Note
QC 20100524Available from: 2010-05-24 Created: 2010-05-24 Last updated: 2017-12-12Bibliographically approved
4. Diffusion of hydrogen in 6H silicon carbide
Open this publication in new window or tab >>Diffusion of hydrogen in 6H silicon carbide
1996 (English)In: III-nitride, SiC and diamond materials for electronic devices: Proceedings of the Symposium, San Francisco, CA; UNITED STATES; 8-12 Apr. 1996., 1996, 625-630 p.Conference paper, Published paper (Other academic)
Abstract [en]

6H polytype silicon carbide (SiC) samples of n-type have been implanted with 50-keV H(+) ions and subsequently annealed at temperatures between 200 and 1150 C. Using depth profiling by secondary ion mass spectrometry, the motion of hydrogen is observed in the implanted region for temperatures above 700 C. A diffusion coefficient of about 10 exp -14 sq cm/s is extracted at 800 C with an approximate activation energy of about 3.5 eV. Hydrogen displays strong interaction with the implantation-induced defects, and stable hydrogen-defect complexes are formed. These complexes anneal out at temperatures in excess of 900 C, and are tentatively identified as carbon-hydrogen centers at a Si vacancy.

Keyword
SILICON CARBIDES, HYDROGEN IONS, IONIC DIFFUSION, N-TYPE SEMICONDUCTORS, DIFFUSION COEFFICIENT, CRYSTAL DEFECTS, GASEOUS DIFFUSION, ANNEALING, MASS SPECTROSCOPY
National Category
Engineering and Technology
Identifiers
urn:nbn:se:kth:diva-13019 (URN)
Note
QC 20100524Available from: 2010-05-24 Created: 2010-05-24 Last updated: 2010-05-24Bibliographically approved
5. LITHIUM PASSIVATION OF ZN AND CD ACCEPTORS IN P-TYPE GAAS
Open this publication in new window or tab >>LITHIUM PASSIVATION OF ZN AND CD ACCEPTORS IN P-TYPE GAAS
1993 (English)In: Physical Review B Condensed Matter, ISSN 0163-1829, E-ISSN 1095-3795, Vol. 48, no 16, 12345-12348 p.Article in journal (Refereed) Published
Abstract [en]

We report lithium passivation of the shallow acceptors Zn and Cd in p-type GaAs which we attribute to the formation of neutral Li-Zn and Li-Cd complexes. Similar to hydrogen, another group-I element, lithium strongly reduces the concentration of free holes when introduced into p-type GaAs. The passivation is inferred from an increase of both the hole mobility and the resisitivity throughout the bulk of the sample. It is observed most clearly for Li concentrations comparable to the shallow-acceptor concentration. In addition, compensation of shallow acceptors by randomly distributed donors is present in varying degree in the Li-diffused samples. Unlike hydrogenation of n-type GaAs, Li doping shows no evidence of neutralizing shallow donors in GaAs.

National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-13027 (URN)A1993ME60100109 ()
Note
QC 20100524Available from: 2010-05-24 Created: 2010-05-24 Last updated: 2017-12-12Bibliographically approved
6. Control of Al and B doping transients in 6H and 4H SiC grown by vapor phase epitaxy
Open this publication in new window or tab >>Control of Al and B doping transients in 6H and 4H SiC grown by vapor phase epitaxy
1997 (English)In: Journal of Electronic Materials, ISSN 0361-5235, E-ISSN 1543-186X, Vol. 26, no 3, 187-192 p.Article in journal (Refereed) Published
Abstract [en]

The atomic concentration profiles in 4H and 6H SiC created by Al and B doping turn-on and turn-off during vapor phase epitaxy (VPE) was investigated by secondary ion mass spectrometry (SIMS). It was found that dopant traces were adsorbed to the reactor walls and re-evaporated after the dopant precursor flow was switched off. This adsorption/re-evaporation process limits the doping dynamic range to about three orders of magnitude for Al, and two orders of magnitude for B. An order of magnitude in doping dynamics could be gained by simultaneously switching the gases and changing the C:Si precursor ratio. By adding a 10 min growth interruption with an H or HC1 etch at the doping turn-off, the background doping tail could be considerably suppressed. In total, a doping dynamics for Al of almost five orders of magnitude can be controlled within a 30 nm layer. For B, the dynamic range is more than three orders of magnitude, and the abruptness is most probably diffusion limited. Abackground doping level of 2 × 1015 cm−3 for Al and 2 × 1016 cm−3 for B was obtained. For Al, the background doping is most probably due to the adsorption/re-evaporation of dopants at the reactor walls; while for B, the background doping may in addition be limited by diffusion.

Keyword
Aluminum, Boron, Diffusion, Doping memory, Epitaxy, Silicon carbide
National Category
Engineering and Technology
Identifiers
urn:nbn:se:kth:diva-13024 (URN)10.1007/s11664-997-0148-y (DOI)
Note

QC 20100524

Available from: 2010-05-24 Created: 2010-05-24 Last updated: 2017-12-12Bibliographically approved
7. Electrically active point defects in n-type 4H–SiC
Open this publication in new window or tab >>Electrically active point defects in n-type 4H–SiC
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1998 (English)In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 84, no 3, 61-68 p.Article in journal (Refereed) Published
Abstract [en]

An electrically active defect has been observed at a level position of ∼ 0.70 eV below the conduction band edge (Ec) with an extrapolated capture cross section of ∼ 5×10−14 cm2 in epitaxial layers of 4H–SiC grown by vapor phase epitaxy with a concentration of approximately 1×1013 cm−3. Secondary ion mass spectrometry revealed no evidence of the transition metals Ti, V, and Cr. Furthermore, after electron irradiation with 2 MeV electrons, the 0.70 eV level is not observed to increase in concentration although three new levels are observed at approximately 0.32, 0.62, and 0.68 eV below Ec with extrapolated capture cross sections of 4×10−14, 4×10−14, and 5×10−15 cm2, respectively. However, the defects causing these levels are unstable and decay after a period of time at room temperature, resulting in the formation of the 0.70 eV level. Our results suggest strongly that the 0.70 eV level originates from a defect of intrinsic nature. The unstable behavior of the electron irradiation-induced defects at room temperature has not been observed in the 6H–SiC polytype.

National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-13025 (URN)10.1063/1.368247 (DOI)
Note

QC 20100524

Available from: 2010-05-24 Created: 2010-05-24 Last updated: 2017-12-12Bibliographically approved
8. Characterization of deep level defects in 4H and 6H SiC via DLTS, SIMS and MeV e-beam irradiation
Open this publication in new window or tab >>Characterization of deep level defects in 4H and 6H SiC via DLTS, SIMS and MeV e-beam irradiation
Show others...
1996 (English)In: III-nitride, SiC and diamond materials for electronic devices: Proceedings of the Symposium, San Francisco, CA; UNITED STATES; 8-12 Apr. 1996., 1996, 519-524 p.Conference paper, Published paper (Refereed)
Abstract [en]
Electrically active defects in both 4H and 6H polytypes of SiC have been observed through the use of deep level transient spectroscopy (DLTS). Schottky contacts were grown by VPE with doping concentrations, the epitaxial layer having a doping concentration in the range of 10 exp 14/cu cm to 10 exp 17/cu cm. Numerous levels have been found in the as-grown n-type 6H-SiC samples, and SIMS and MeV electron irradiation have been employed to correlate the defect levels to impurities or structural defects. In contrast, only a single level is observed in the as-grown 4H-SiC samples.
Keyword
SILICON CARBIDES, CRYSTAL DEFECTS, ELECTRON IRRADIATION, SCHOTTKY DIODES, VAPOR PHASE EPITAXY, MASS SPECTROSCOPY, ELECTRON BEAMS, TRANSIENT RESPONSE, TEMPERATURE DEPENDENCE
Identifiers
urn:nbn:se:kth:diva-13026 (URN)
Note
QC 20100524Available from: 2010-05-24 Created: 2010-05-24 Last updated: 2010-05-24Bibliographically approved

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