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Publications (10 of 214) Show all publications
Tian, K., Hallén, A., Qi, J., Ma, S., Fei, X., Zhang, A. & Liu, W. (2019). An Improved 4H-SiC Trench-Gate MOSFET With Low ON-Resistance and Switching Loss. IEEE Transactions on Electron Devices, 66(5), 2307-2313, Article ID 8681267.
Open this publication in new window or tab >>An Improved 4H-SiC Trench-Gate MOSFET With Low ON-Resistance and Switching Loss
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2019 (English)In: IEEE Transactions on Electron Devices, ISSN 0018-9383, E-ISSN 1557-9646, Vol. 66, no 5, p. 2307-2313, article id 8681267Article in journal (Refereed) Published
Abstract [en]

In this paper, an improved 4H-SiC U-shaped trench-gate metal-oxide-semiconductor field-effect transistors (UMOSFETs) structure with low ON-resistance (R ON ) and switching energy loss is proposed. The novel structure features an added n-type region, which reduces ON-resistance of the device significantly while maintaining the breakdown voltage (V BR ). In addition, the gate of the improved structure is designed as a p-n junction to reduce the switching energy loss. Simulations by Sentaurus TCAD are carried out to reveal the working mechanism of this improved structure. For the static performance, the ON-resistance and the figure of merit (FOM = V BR 2 /R ON ) of the optimized structure are improved by 40% and 44%, respectively, as compared to a conventional trench MOSFET without the added n-type region and modified gate. For the dynamic performance, the turn-on time (T ON ) and turn-off time (T OFF ) of the proposed structure are both shorter than that of the conventional structure, bringing a 43% and 30% reduction in turn-on energy loss and total switching energy loss (E SW ). © 2019 IEEE.

Place, publisher, year, edition, pages
Institute of Electrical and Electronics Engineers Inc., 2019
Keywords
Breakdown voltage, ON-resistance, silicon carbide, switching energy loss, U-shaped trench-gate metal-oxide-semiconductor field-effect transistors (UMOSFETs), Dielectric devices, Electric breakdown, Energy dissipation, Metallic compounds, Metals, MOS devices, Oxide semiconductors, Semiconducting silicon compounds, Semiconductor junctions, Switching, Transistors, Wide band gap semiconductors, Conventional structures, Dynamic performance, Improved structures, Optimized structures, Switching energy, Trench gates, Trench-gate mosfet, MOSFET devices
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-252507 (URN)10.1109/TED.2019.2905636 (DOI)2-s2.0-85064973294 (Scopus ID)
Note

QC 20190710

Available from: 2019-07-10 Created: 2019-07-10 Last updated: 2019-07-10Bibliographically approved
Tian, K., Hallén, A., Qi, J., Ma, S., Fei, X., Zhang, A. & Liu, W. (2019). An Improved 4H-SiC Trench-Gate MOSFET With Low ON-Resistance and Switching Loss. IEEE Transactions on Electron Devices, 66(5), 2307-2313
Open this publication in new window or tab >>An Improved 4H-SiC Trench-Gate MOSFET With Low ON-Resistance and Switching Loss
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2019 (English)In: IEEE Transactions on Electron Devices, ISSN 0018-9383, E-ISSN 1557-9646, Vol. 66, no 5, p. 2307-2313Article in journal (Refereed) Published
Abstract [en]

In this paper, an improved 4H-SiC U-shaped trench-gate metal-oxide-semiconductor field-effect transistors (UMOSFETs) structure with low ON-resistance (R-ON) and switching energy loss is proposed. The novel structure features an added n-type region, which reduces ON-resistance of the device significantly while maintaining the breakdown voltage (V-BR). In addition, the gate of the improved structure is designed as a p-n junction to reduce the switching energy loss. Simulations by Sentaurus TCAD are carried out to reveal the working mechanism of this improved structure. For the static performance, the ON-resistance and the figure of merit (FOM = V-BR(2)/R-ON) of the optimized structure are improved by 40% and 44%, respectively, as compared to a conventional trench MOSFET without the added n-type region and modified gate. For the dynamic performance, the turn-on time (T-ON) and turn-off time (T-OFF) of the proposed structure are both shorter than that of the conventional structure, bringing a 43% and 30% reduction in turn-on energy loss and total switching energy loss (E-SW).

National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-252987 (URN)10.1109/TED.2019.2905636 (DOI)000466028500041 ()
Note

QC 20190814

Available from: 2019-08-14 Created: 2019-08-14 Last updated: 2019-08-14Bibliographically approved
Azarov, A., Aarseth, B. L., Vines, L., Hallén, A., Monakhov, E. & Kuznetsov, A. (2019). Defect annealing kinetics in ZnO implanted with Zn substituting elements: Zn interstitials and Li redistribution. Journal of Applied Physics, 125(7), Article ID 075703.
Open this publication in new window or tab >>Defect annealing kinetics in ZnO implanted with Zn substituting elements: Zn interstitials and Li redistribution
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2019 (English)In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 125, no 7, article id 075703Article in journal (Refereed) Published
Abstract [en]

It is known that the behavior of residual Li in ion implanted ZnO depends on the preferential localization of the implants, in particular, forming characteristic Li depleted or Li pile-up regions for Zn or O sublattice occupation of the implants due to the corresponding excess generation of Zn and O interstitials in accordance with the so-called "+1 model." However, the present study reveals that conditions for the radiation damage annealing introduce additional complexity into the interpretation of the Li redistribution trends. Specifically, four implants residing predominantly in the Zn-sublattice, but exhibiting different lattice recovery routes, were considered. Analyzing Li redistribution trends in these samples, it is clearly shown that Li behavior depends on the defect annealing kinetics which is a strong function of the implanted fluence and ion species. Thus, Li depleted and Li pile-up regions (or even combinations of the two) were observed and correlated with the defect evolution in the samples. It is discussed how the observed Li redistribution trends can be used for better understanding a thermal evolution of point defects in ZnO and, in particular, energetics and migration properties of Zn interstitials.

Place, publisher, year, edition, pages
AMER INST PHYSICS, 2019
National Category
Other Physics Topics
Identifiers
urn:nbn:se:kth:diva-246261 (URN)10.1063/1.5083226 (DOI)000459401100033 ()2-s2.0-85061705252 (Scopus ID)
Note

QC 20190326

Available from: 2019-03-26 Created: 2019-03-26 Last updated: 2019-04-04Bibliographically approved
Majdi, S., Gabrysch, M., Suntornwipat, N., Burmeister, F., Jonsson, R., Kovi, K. K. & Hallén, A. (2019). High-temperature deep-level transient spectroscopy system for defect studies in wide-bandgap semiconductors. Review of Scientific Instruments, 90(6), Article ID 063903.
Open this publication in new window or tab >>High-temperature deep-level transient spectroscopy system for defect studies in wide-bandgap semiconductors
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2019 (English)In: Review of Scientific Instruments, ISSN 0034-6748, E-ISSN 1089-7623, Vol. 90, no 6, article id 063903Article in journal (Refereed) Published
Abstract [en]

Full investigation of deep defect states and impurities in wide-bandgap materials by employing commercial transient capacitance spectroscopy is a challenge, demanding very high temperatures. Therefore, a high-temperature deep-level transient spectroscopy (HT-DLTS) system was developed for measurements up to 1100 K. The upper limit of the temperature range allows for the study of deep defects and trap centers in the bandgap, deeper than previously reported by DLTS characterization in any material. Performance of the system was tested by carrying out measurements on the well-known intrinsic defects in n-type 4H-SiC in the temperature range 300-950 K. Experimental observations performed on 4H-SiC Schottky diodes were in good agreement with the literature. However, the DLTS measurements were restricted by the operation and quality of the electrodes.

Place, publisher, year, edition, pages
AMER INST PHYSICS, 2019
National Category
Atom and Molecular Physics and Optics
Identifiers
urn:nbn:se:kth:diva-255499 (URN)10.1063/1.5097755 (DOI)000474601100062 ()31255019 (PubMedID)2-s2.0-85067838307 (Scopus ID)
Note

QC 20190925

Available from: 2019-09-25 Created: 2019-09-25 Last updated: 2019-09-25Bibliographically approved
Woerle, J., Prokscha, T., Hallén, A. & Grossner, U. (2019). Interaction of low-energy muons with defect profiles in proton-irradiated Si and 4H-SiC. Physical Review B, 100(11), Article ID 115202.
Open this publication in new window or tab >>Interaction of low-energy muons with defect profiles in proton-irradiated Si and 4H-SiC
2019 (English)In: Physical Review B, ISSN 2469-9950, E-ISSN 2469-9969, Vol. 100, no 11, article id 115202Article in journal (Refereed) Published
Abstract [en]

Muon spin rotation (mu SR) with low-energy muons is a powerful nuclear method where electrical and magnetic properties of thin films can be investigated in a depth-resolved manner. Here, we present a study on proton-irradiated Si and 4H-SiC where the formation of the hydrogen-like muonium (Mu) is analyzed as a function of the proton dose. While the Mu formation is strongly suppressed in the highly defective region of the shallow proton stopping profile, the Mu signal quickly recovers for higher muon energies where the muons reach the untreated semiconductor bulk. A lower sensitivity limit of low-energy mu SR to crystal defects of around 10(17) to 10(18) cm(-3) is estimated. Our results demonstrate the high potential of this technique to nondestructively probe near-surface regions without the need for electronic device fabrication and to provide valuable complementary information when investigating defects in semiconductors.

Place, publisher, year, edition, pages
AMER PHYSICAL SOC, 2019
National Category
Other Physics Topics
Identifiers
urn:nbn:se:kth:diva-261305 (URN)10.1103/PhysRevB.100.115202 (DOI)000486636700004 ()2-s2.0-85072805848 (Scopus ID)
Note

QC 20191008

Available from: 2019-10-08 Created: 2019-10-08 Last updated: 2019-10-08Bibliographically approved
Ayedh, H. M., Bathen, M. E., Galeckas, A., Hassan, J. U., Bergman, J. P., Nipoti, R., . . . Svensson, B. G. (2018). Controlling the carbon vacancy in 4H-SiC by thermal processing. In: ECS Transactions: . Paper presented at Symposium on Gallium Nitride and Silicon Carbide Power Technologies 8 - AiMES 2018, ECS and SMEQ Joint International Meeting, 30 September 2018 through 4 October 2018 (pp. 91-97). Electrochemical Society Inc. (12)
Open this publication in new window or tab >>Controlling the carbon vacancy in 4H-SiC by thermal processing
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2018 (English)In: ECS Transactions, Electrochemical Society Inc. , 2018, no 12, p. 91-97Conference paper, Published paper (Refereed)
Abstract [en]

The carbon vacancy (Vc) is perhaps the most prominent point defect in silicon carbide (SiC) and it is an efficient charge carrier lifetime killer in high-purity epitaxial layers of 4H-SÌC. The Vc concentration needs to be controlled and minimized for optimum materials and device performance, and an approach based on post-growth thermal processing under C-rich ambient conditions is presented. It utilizes thermodynamic equilibration and after heat treatment at 1500 °C for 1 h, the Vc concentration is shown to be reduced by a factor-25 relative to that in as-grown state-of-the-art epi-layers. Concurrently, a considerable enhancement of the carrier lifetime occurs throughout the whole of >40 urn thick epi-layers. 

Place, publisher, year, edition, pages
Electrochemical Society Inc., 2018
Keywords
Carbon, Carrier lifetime, Gallium nitride, Heat treatment, III-V semiconductors, After-heat treatment, Ambient conditions, As-grown, Carbon vacancy, Device performance, High purity, Silicon carbides (SiC), State of the art, Silicon carbide
National Category
Materials Chemistry
Identifiers
urn:nbn:se:kth:diva-246562 (URN)10.1149/08612.0091ecst (DOI)2-s2.0-85058420747 (Scopus ID)
Conference
Symposium on Gallium Nitride and Silicon Carbide Power Technologies 8 - AiMES 2018, ECS and SMEQ Joint International Meeting, 30 September 2018 through 4 October 2018
Note

QC 20190527

Available from: 2019-05-27 Created: 2019-05-27 Last updated: 2019-05-27Bibliographically approved
Suvanam, S. S., Larsen, J., Ross, N., Kosyak, V., Hallén, A. & Björkman, C. P. (2018). Extreme radiation hard thin film CZTSSe solar cell. Solar Energy Materials and Solar Cells, 185, 16-20
Open this publication in new window or tab >>Extreme radiation hard thin film CZTSSe solar cell
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2018 (English)In: Solar Energy Materials and Solar Cells, ISSN 0927-0248, E-ISSN 1879-3398, Vol. 185, p. 16-20Article in journal (Refereed) Published
Abstract [en]

In this work, we have demonstrated the extreme radiation hardness of thin film CZTSSe solar cells. Thin film solar cells with CZTSSe, CZTS and CIGS absorber layers were irradiated with 3 MeV protons. No degradation in device parameters was observed until a displacement damage dose of 2 × 1010 MeV/g for CZTS and CZTSSe. CIGS solar cells degraded by 13% at the same dose. For the highest proton dose both the CZTSSe and CZTS degraded by 16% while CIGS suffered from 34% degradation in efficiency. The degradation in efficiency maybe attributed to the reduction in the minority carrier lifetime due to radiation induced lattice defects. Comparisons with previously available literature show that our CZTS technology has superior radiation hardness by about two orders of magnitude compared to existing state of the art Si and GaAs technology.

Place, publisher, year, edition, pages
Elsevier, 2018
Keywords
CZTSSe, Proton radiation, Radiation hardness, Space solar cells
National Category
Other Engineering and Technologies not elsewhere specified
Identifiers
urn:nbn:se:kth:diva-228694 (URN)10.1016/j.solmat.2018.05.012 (DOI)000437816100003 ()2-s2.0-85046621751 (Scopus ID)
Note

QC 20180530

Available from: 2018-05-30 Created: 2018-05-30 Last updated: 2018-07-27Bibliographically approved
Chulapakorn, T., Primetzhofer, D., Sychugov, I., Suvanam, S. S., Linnros, J. & Hallén, A. (2018). Impact of H-uptake by forming gas annealing and ion implantation on photoluminescence of Si-nanoparticles. Physica Status Solidi (a) applications and materials science, 215(3), Article ID 1700444.
Open this publication in new window or tab >>Impact of H-uptake by forming gas annealing and ion implantation on photoluminescence of Si-nanoparticles
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2018 (English)In: Physica Status Solidi (a) applications and materials science, ISSN 1862-6300, E-ISSN 1862-6319, Vol. 215, no 3, article id 1700444Article in journal (Refereed) Published
Abstract [en]

Silicon nanoparticles (SiNPs) are formed by implanting 70 keV Si+ into a SiO2-film and subsequent thermal annealing. SiNP samples are further annealed in forming gas. Another group of samples containing SiNP is implanted by 7.5 keV H+ and subsequently annealed in N2-atmosphere at 450 °C to reduce implantation damage. Nuclear reaction analysis (NRA) is employed to establish depth profiles of the H-concentration. Enhanced hydrogen concentrations are found close to the SiO2surface, with particularly high concentrations for the as-implanted SiO2. However, no detectable uptake of hydrogen is observed by NRA for samples treated by forming gas annealing (FGA). H-concentrations detected after H-implantation follow calculated implantation profiles. Photoluminescence (PL) spectroscopy is performed at room temperature to observe the SiNP PL. Whereas FGA is found to increase PL under certain conditions, i.e., annealing at high temperatures, increasing implantation fluence of H reduces the SiNP PL. Hydrogen implantation also introduces additional defect PL. After low-temperature annealing, the SiNP PL is found to improve, but the process is not found equivalently efficient as conventional FGA.

Place, publisher, year, edition, pages
John Wiley & Sons, 2018
Keywords
H-quantification, nuclear reaction analysis, photoluminescence, silicon nanoparticles
National Category
Nano Technology
Identifiers
urn:nbn:se:kth:diva-219544 (URN)10.1002/pssa.201700444 (DOI)000424387300006 ()2-s2.0-85031427795 (Scopus ID)
Funder
Swedish Research Council
Note

QC 20171219

Available from: 2017-12-17 Created: 2017-12-17 Last updated: 2018-02-22Bibliographically approved
Suvanam, S. S., Usman, M., Martin, D., Yazdi, M. G., Linnarsson, M. K., Tempez, A., . . . Hallén, A. (2018). Improved interface and electrical properties of atomic layer deposited Al2O3/4H-SiC. Applied Surface Science, 433, 108-115
Open this publication in new window or tab >>Improved interface and electrical properties of atomic layer deposited Al2O3/4H-SiC
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2018 (English)In: Applied Surface Science, ISSN 0169-4332, E-ISSN 1873-5584, Vol. 433, p. 108-115Article in journal (Refereed) Published
Abstract [en]

In this paper we demonstrate a process optimization of atomic layer deposited Al2O3 on 4H-SiC resulting in an improved interface and electrical properties. For this purpose the samples have been treated with two pre deposition surface cleaning processes, namely CP1 and CP2. The former is a typical surface cleaning procedure used in SiC processing while the latter have an additional weak RCA1 cleaning step. In addition to the cleaning and deposition, the effects of post dielectric annealing (PDA) at various temperatures in N2O ambient have been investigated. Analyses by scanning electron microscopy show the presence of structural defects on the Al2O3 surface after annealing at 500 and 800 °C. These defects disappear after annealing at 1100 °C, possibly due to densification of the Al2O3 film. Interface analyses have been performed using X-ray photoelectron spectroscopy (XPS) and time-of-flight medium energy ion scattering (ToF MEIS). Both these measurements show the formation of an interfacial SiOx (0 < x < 2) layer for both the CP1 and CP2, displaying an increased thickness for higher temperatures. Furthermore, the quality of the sub-oxide interfacial layer was found to depend on the pre deposition cleaning. In conclusion, an improved interface with better electrical properties is shown for the CP2 sample annealed at 1100 °C, resulting in lower oxide charges, strongly reduced flatband voltage and leakage current, as well as higher breakdown voltage.

Place, publisher, year, edition, pages
Elsevier, 2018
Keywords
4H-SiC, Al2O3, High-K dielectric, Interface trap densities, Annealing, Atomic layer deposition, Cleaning, Deposition, Optimization, Scanning electron microscopy, Silicon carbide, Surface cleaning, Surface defects, Atomic layer deposited, Interface analysis, Interface trap density, Medium energy ion scattering, Structural defect, Surface cleaning procedure, X ray photoelectron spectroscopy
National Category
Materials Engineering
Identifiers
urn:nbn:se:kth:diva-223127 (URN)10.1016/j.apsusc.2017.10.006 (DOI)000418883800014 ()2-s2.0-85031746823 (Scopus ID)
Funder
Swedish Research Council, D0674701
Note

QC 20180327

Available from: 2018-03-27 Created: 2018-03-27 Last updated: 2018-04-11Bibliographically approved
Ayedh, H. M., Nipoti, R., Hallén, A. & Svensson, B. G. (2018). Kinetics modeling of the carbon vacancy thermal equilibration in 4H-SiC. In: International Conference on Silicon Carbide and Related Materials, ICSCRM 2017: . Paper presented at 17 September 2017 through 22 September 2017 (pp. 233-236). Trans Tech Publications
Open this publication in new window or tab >>Kinetics modeling of the carbon vacancy thermal equilibration in 4H-SiC
2018 (English)In: International Conference on Silicon Carbide and Related Materials, ICSCRM 2017, Trans Tech Publications, 2018, p. 233-236Conference paper, Published paper (Refereed)
Abstract [en]

The carbon vacancy (VC) is a major limiting-defect of minority carrier lifetime in n-type 4H-SiC epitaxial layers and it is readily formed during high temperature processing. In this study, a kinetics model is put forward to address the thermodynamic equilibration of VC, elucidating the possible atomistic mechanisms that control the VC equilibration under C-rich conditions. Frenkel pair generation, injection of carbon interstitials (Ci’s) from the C-rich surface, followed by recombination with VC’s, and diffusion of VC’s towards the surface appear to be the major mechanisms involved. The modelling results show a close agreement with experimental deep-level transient spectroscopy (DLTS) depth profiles of VC after annealing at different temperatures.

Place, publisher, year, edition, pages
Trans Tech Publications, 2018
Keywords
4H-SiC, Carbon vacancy, Diffusion, Kinetics model, Thermodynamic equilibrium, Carbon, Carrier lifetime, Deep level transient spectroscopy, Kinetics, Atomistic mechanism, High-temperature processing, Kinetics modeling, Minority carrier lifetimes, Thermal equilibrations, Thermodynamic equilibria, Silicon carbide
National Category
Metallurgy and Metallic Materials
Identifiers
urn:nbn:se:kth:diva-236387 (URN)10.4028/www.scientific.net/MSF.924.233 (DOI)2-s2.0-85049002040 (Scopus ID)9783035711455 (ISBN)
Conference
17 September 2017 through 22 September 2017
Note

QC 20181101

Available from: 2018-11-01 Created: 2018-11-01 Last updated: 2018-11-01Bibliographically approved
Organisations
Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0002-8760-1137

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