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Bergman, Peder, Professor
Publications (10 of 193) Show all publications
Ayedh, H. M., Baathen, M. E., Galeckas, A., ul-Hassan, J., Bergman, P., Nipoti, R., . . . Svensson, B. G. (2018). (Invited) Controlling the Carbon Vacancy in 4H-SiC by Thermal Processing. ECS Transactions, 86(12), 91-97
Open this publication in new window or tab >>(Invited) Controlling the Carbon Vacancy in 4H-SiC by Thermal Processing
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2018 (English)In: ECS Transactions, ISSN 1938-5862, E-ISSN 1938-6737, ECS Transactions, Vol. 86, no 12, p. 91-97Article in journal (Refereed) Published
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-SiC. 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 µm thick epi-layers.

Place, publisher, year, edition, pages
Electrochemical Society, 2018
National Category
Materials Chemistry
Identifiers
urn:nbn:se:liu:diva-160924 (URN)10.1149/08612.0091ecst (DOI)2-s2.0-85058420747 (Scopus ID)
Available from: 2019-10-15 Created: 2019-10-15 Last updated: 2019-10-21Bibliographically approved
Lilja, L., Farkas, I., Booker, I., ul-Hassan, J., Janzén, E. & Bergman, P. (2017). Influence of n-Type Doping Levels on Carrier Lifetime in 4H-SiC Epitaxial Layers. In: Silicon Carbide and Related Materials 2016: . Paper presented at 11th European Conference on Silicone Carbide & Related Materials, Halkidiki, Greece, 25-29 September, 2016 (pp. 238-241). Trans Tech Publications Ltd, 897
Open this publication in new window or tab >>Influence of n-Type Doping Levels on Carrier Lifetime in 4H-SiC Epitaxial Layers
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2017 (English)In: Silicon Carbide and Related Materials 2016, Trans Tech Publications Ltd , 2017, Vol. 897, p. 238-241Conference paper, Published paper (Refereed)
Abstract [en]

In this study we have grown thick 4H-SiC epitaxial layers with different n-type doping levels in the range 1E15 cm-3 to mid 1E18 cm-3, in order to investigate the influence on carrier lifetime. The epilayers were grown with identical growth conditions except the doping level on comparable substrates, in order to minimize the influence of other parameters than the n-type doping level. We have found a drastic decrease in carrier lifetime with increasing n-type doping level. Epilayers were further characterized with low temperature photoluminescence and deep level transient spectroscopy.

Place, publisher, year, edition, pages
Trans Tech Publications Ltd, 2017
Series
Materials Science Forum, ISSN 1662-9752
Keywords
Auger Recombination, Carrier Lifetime, Epitaxial Growth, Chemical Vapor Deposition (CVD), Photoluminescence
National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:liu:diva-160906 (URN)10.4028/www.scientific.net/MSF.897.238 (DOI)2-s2.0-85020038744 (Scopus ID)
Conference
11th European Conference on Silicone Carbide & Related Materials, Halkidiki, Greece, 25-29 September, 2016
Available from: 2019-10-14 Created: 2019-10-14 Last updated: 2019-10-24Bibliographically approved
Seed Ahmed, H. A., Swart, H. C., Bergman, P. & Kroon, R. E. (2016). Concentration quenching of Eu2+ doped Ca2BO3Cl. Materials research bulletin, 75, 47-50
Open this publication in new window or tab >>Concentration quenching of Eu2+ doped Ca2BO3Cl
2016 (English)In: Materials research bulletin, ISSN 0025-5408, E-ISSN 1873-4227, Vol. 75, p. 47-50Article in journal (Refereed) Published
Abstract [en]

With the aim of determining the concentration quenching mechanism of Eu2+ doped Ca2BO3Cl, a series of phosphors with a varied Eu2+ concentration (Ca2-xBO3Cl:xEu(2+)) was synthesized by the solid state reaction method. The phase structure was determined by X-ray diffraction. Photoluminescence (PL) measurements showed broad excitation and emission signatures of the allowed f-d transition of Eu2+ ions. The PL emission intensity was found to be increased by increasing the concentration of Eu2+ ions up to x=0.03 and then decreased as a result of the concentration quenching effect. The lifetime of the emission from the Eu2+ ions was measured and the decrease in the lifetime with increasing Eu2+ concentration confirmed that non-radiative energy transfer occurred between Eu2+ ions. From the luminescence data, the value of the critical transfer distance was calculated as 1.5 nm and the corresponding concentration quenching mechanism was verified to be a dipole-dipole interaction. (C) 2015 Elsevier Ltd. All rights reserved.

Place, publisher, year, edition, pages
PERGAMON-ELSEVIER SCIENCE LTD, 2016
Keywords
Optical materials; X-ray diffraction; Luminescence; Optical properties; Phosphors
National Category
Chemical Sciences
Identifiers
urn:nbn:se:liu:diva-124619 (URN)10.1016/j.materresbull.2015.11.024 (DOI)000368220300008 ()
Note

Funding Agencies|South African Research Chairs Initiative of the Department of Science and Technology; National Research Foundation of South Africa; University of the Free State

Available from: 2016-02-09 Created: 2016-02-08 Last updated: 2017-11-30
Yagoub, M. Y., Swart, H. C., Bergman, P. & Coetsee, E. (2016). Enhanced Pr3+ photoluminescence by energy transfer in SrF2:Eu2+, Pr3+ phosphor. AIP Advances, 6(2), 025204
Open this publication in new window or tab >>Enhanced Pr3+ photoluminescence by energy transfer in SrF2:Eu2+, Pr3+ phosphor
2016 (English)In: AIP Advances, ISSN 2158-3226, E-ISSN 2158-3226, Vol. 6, no 2, p. 025204-Article in journal (Refereed) Published
Abstract [en]

Efficient energy transfer was demonstrated in the SrF2:Eu2+, Pr3+ phosphor synthesized by the co-precipitation method. Results obtained with X-ray diffraction (XRD), scanning electron microscopy (SEM), x-ray spectroscopy (XPS), photoluminescence (PL) and decay curves proposed the UV-Vis energy transfer process. The energy transfer process between the Eu2+ and Pr3+ ions in SrF2 was investigated to evaluate the potential of the Eu2+ ion as a sensitizer for the Pr3+ ion. The results proposed that Eu2+ could be a good sensitizer for absorbing the UV photons and efficiently enhancing the Pr3+ emission intensity. The energy transfer process was effective until concentration quenching for the Pr3+ ions occurred. The concentration quenching was attributed to cross-relaxation between the Pr3+ ions. (C) 2016 Author(s).

Place, publisher, year, edition, pages
AMER INST PHYSICS, 2016
National Category
Chemical Sciences
Identifiers
urn:nbn:se:liu:diva-126843 (URN)10.1063/1.4941833 (DOI)000371739000055 ()
Note

Funding Agencies|South African Research Chairs Initiative of the Department of Science and Technology; National Research Foundation of South Africa; National Research Foundation (NRF); Cluster program of the University of the Free State

Available from: 2016-04-05 Created: 2016-04-05 Last updated: 2017-11-30
Lilja, L., ul-Hassan, J., Janzén, E. & Bergman, P. (2016). Smooth 4H-SiC epilayers grown with high growth rates with silane/propane chemistry using 4° off-cut substrates. In: Fabrizio Roccaforte, Francesco La Via, Roberta Nipoti, Danilo Crippa, Filippo Giannazzo and Mario Saggio (Ed.), Silicon Carbide and Related Materials 2015: . Paper presented at The 16th International Conference on Silicon Carbide and Related Materials (ICSCRM2015), Giardini Naxos, Sicily, Italy, October 4th October 9th, 2015. (pp. 209-212). Trans Tech Publications, 858
Open this publication in new window or tab >>Smooth 4H-SiC epilayers grown with high growth rates with silane/propane chemistry using 4° off-cut substrates
2016 (English)In: Silicon Carbide and Related Materials 2015 / [ed] Fabrizio Roccaforte, Francesco La Via, Roberta Nipoti, Danilo Crippa, Filippo Giannazzo and Mario Saggio, Trans Tech Publications, 2016, Vol. 858, p. 209-212Conference paper, Published paper (Refereed)
Abstract [en]

4H-SiC epilayers with very smooth surfaces were grown with high growth rates on 4° off-cut substrates using standard silane/propane chemistry. Specular surfaces with RMS values below 0.2 nm are presented for epilayers grown with growth rates up to 30 μm/h using horizontal hot-wall chemical vapor deposition, with up to 100 μm thickness. Optimization of in-situ etching conditions and C/Si ratio are presented.

Place, publisher, year, edition, pages
Trans Tech Publications, 2016
Series
Materials Science Forum, ISSN 1662-9752 ; 858
Keywords
Atomic force microscopy, Chemical vapor deposition, Epitaxial growth, Silicon carbide
National Category
Materials Engineering
Identifiers
urn:nbn:se:liu:diva-153288 (URN)10.4028/www.scientific.net/MSF.858.209 (DOI)
Conference
The 16th International Conference on Silicon Carbide and Related Materials (ICSCRM2015), Giardini Naxos, Sicily, Italy, October 4th October 9th, 2015.
Available from: 2018-12-10 Created: 2018-12-10 Last updated: 2019-01-10
Salemi, A., Elahipanah, H., Buono, B., Hallen, A., Ul-Hassan, J., Bergman, P., . . . Ostling, M. (2015). Conductivity Modulated On-axis 4H-SiC 10+kV PiN Diodes. In: 2015 IEEE 27TH INTERNATIONAL SYMPOSIUM ON POWER SEMICONDUCTOR DEVICES and ICS (ISPSD): . Paper presented at 27th International Symposium on Power Semiconductor Devices and ICs (ISPSD) (pp. 269-272). IEEE
Open this publication in new window or tab >>Conductivity Modulated On-axis 4H-SiC 10+kV PiN Diodes
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2015 (English)In: 2015 IEEE 27TH INTERNATIONAL SYMPOSIUM ON POWER SEMICONDUCTOR DEVICES and ICS (ISPSD), IEEE , 2015, p. 269-272Conference paper, Published paper (Refereed)
Abstract [en]

Degradation-free ultrahigh-voltage (> 10 kV) PiN diodes using on-axis 4H-SiC with low forward voltage drop (V-F = 3.3 V at 100 A/cm(2)) and low differential on-resistance (R-ON = 3.4 m Omega.cm(2)) are fabricated, measured, and analyzed by device simulation. The devices show stable on-state characteristics over a broad temperature range up to 300 degrees C. They show no breakdown up to 10 kV, i.e., the highest blocking capability for 4H-SiC devices using on-axis to date. The minority carrier lifetime (tau(P)) is measured after epitaxial growth by time resolved photoluminescence (TRPL) technique at room temperature. The tau(P) is measured again after device fabrication by open circuit voltage decay (OCVD) up to 500 K.

Place, publisher, year, edition, pages
IEEE, 2015
Series
Proceedings of the International Symposium on Power Semiconductor Devices & ICs, ISSN 1063-6854
Keywords
On-axis 4H-SiC; PiN diode; ultrahigh-voltage; lifetime enhancement; V-F; on-resistance; OCVD; breakdown voltage; bipolar degradation-free
National Category
Chemical Sciences
Identifiers
urn:nbn:se:liu:diva-126278 (URN)000370717300066 ()978-1-4799-6261-7 (ISBN)
Conference
27th International Symposium on Power Semiconductor Devices and ICs (ISPSD)
Available from: 2016-03-21 Created: 2016-03-21 Last updated: 2016-03-21
Lilja, L., Ul-Hassan, J., Janzén, E. & Bergman, P. (2015). In-grown stacking-faults in 4H-SiC epilayers grown on 2 degrees off-cut substrates. Physica status solidi. B, Basic research, 252(6), 1319-1324
Open this publication in new window or tab >>In-grown stacking-faults in 4H-SiC epilayers grown on 2 degrees off-cut substrates
2015 (English)In: Physica status solidi. B, Basic research, ISSN 0370-1972, E-ISSN 1521-3951, Vol. 252, no 6, p. 1319-1324Article in journal (Refereed) Published
Abstract [en]

4H-SiC epilayers were grown on 2 degrees off-cut substrates using standard silane/propane chemistry, with the aim of characterizing in-grown stacking faults. The stacking faults were analyzed with low temperature photoluminescence spectroscopy, room temperature photoluminescence mappings, room temperature cathodoluminescence and synchrotron white beam X-ray topography. At least three different types of in-grown stacking faults were observed, including double Shockley stacking faults, triple Shockley stacking faults and bar-shaped stacking faults. Those stacking faults are all previously found in 4 degrees and 8 degrees off-cut epilayers; however, the geometrical size is larger in epilayers grown on 2 degrees off-cut substrates due to lower off-cut angle. The stacking faults were formed close to the epilayer/substrate interface during the epitaxial growth. (C) 2015 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim

Place, publisher, year, edition, pages
WILEY-V C H VERLAG GMBH, 2015
Keywords
chemical vapor deposition; epitaxy; photoluminescence; SiC; stacking faults
National Category
Chemical Sciences
Identifiers
urn:nbn:se:liu:diva-120065 (URN)10.1002/pssb.201451710 (DOI)000355756200018 ()
Note

Funding Agencies|Swedish Research Council (VR); Advanced Functional Materials (AFM); Swedish Foundation for Strategic Research (SSF)

Available from: 2015-07-06 Created: 2015-07-06 Last updated: 2019-10-14
Yagoub, M. Y. A., Swart, H. C., Noto, L. L., Bergman, P. & Coetsee, E. (2015). Surface Characterization and Photoluminescence Properties of Ce3+, Eu Co-Doped SrF2 Nanophosphor. Materials, 8(5), 2361-2375
Open this publication in new window or tab >>Surface Characterization and Photoluminescence Properties of Ce3+, Eu Co-Doped SrF2 Nanophosphor
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2015 (English)In: Materials, ISSN 1996-1944, E-ISSN 1996-1944, Vol. 8, no 5, p. 2361-2375Article in journal (Refereed) Published
Abstract [en]

SrF2:Eu,Ce3+ nanophosphors were successfully synthesized by the hydrothermal method during down-shifting investigations for solar cell applications. The phosphors were characterized by X-ray diffraction (XRD), scanning Auger nanoprobe, time of flight-secondary ion mass spectrometry (TOF-SIMS), X-ray photoelectron spectroscopy (XPS) and photoluminescence (PL) spectroscopy. XRD showed that the crystallite size calculated with Scherrers equation was in the nanometre scale. XPS confirmed the formation of the matrix and the presence of the dopants in the SrF2 host. The PL of the nanophosphor samples were studied using different excitation sources. The phenomenon of energy transfer from Ce3+ to Eu2+ has been demonstrated.

Place, publisher, year, edition, pages
MDPI, 2015
Keywords
SrF2; cerium; TOF-SIMS; XPS; shake-down; energy transfer
National Category
Chemical Sciences
Identifiers
urn:nbn:se:liu:diva-120292 (URN)10.3390/ma8052361 (DOI)000356879100022 ()
Note

Funding Agencies|South African Research Chairs Initiative of the Department of Science and Technology; National Research Foundation of South Africa; National Research Foundation (NRF); University of the Free State

Available from: 2015-07-24 Created: 2015-07-24 Last updated: 2017-12-04
Shevchenko, E. A., Toropov, A. A., Nechaev, D. V., Jmerik, V. N., Shubina, T. V., Ivanov, S. V., . . . Monemar, B. (2014). AlGaN Quantum Well Heterostructures for Mid-Ultraviolet Emitters with Improved Room Temperature Quantum Efficiency. Paper presented at 43rd Jaszowiec International School and Conference on the Physics of Semiconductors. Acta Physica Polonica. A, 126(5), 1140-1142
Open this publication in new window or tab >>AlGaN Quantum Well Heterostructures for Mid-Ultraviolet Emitters with Improved Room Temperature Quantum Efficiency
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2014 (English)In: Acta Physica Polonica. A, ISSN 0587-4246, E-ISSN 1898-794X, Vol. 126, no 5, p. 1140-1142Article in journal (Refereed) Published
Abstract [en]

We report on optical studies of exciton localization and recombination kinetics in two single 2.2 nm thick AlxGa1-xN/Alx+0.1Ga0.9-xN quantum well structures (x = 0.55 and 0.6) grown by plasma assisted molecular beam epitaxy on a c-sapphire substrate. Strong localization potential inherent for both the quantum well and barrier regions results in merging of the quantum well and barrier emission spectra into a single broad line centered at 285 nm (x = 0.55) and 275 nm (x = 0.6). Time-resolved photoluminescence measurements revealed surprising temperature stability of the photoluminescence decay time constant (approximate to 400 ps) relevant to the recombination of the quantum well localized excitons. This observation implies nearly constant quantum efficiency of the quantum well emission in the whole range from 4.6 to 300 K.

Place, publisher, year, edition, pages
POLISH ACAD SCIENCES INST PHYSICS, 2014
National Category
Physical Sciences Chemical Sciences
Identifiers
urn:nbn:se:liu:diva-113203 (URN)10.12693/APhysPolA.126.1140 (DOI)000346069100026 ()2-s2.0-84916894578 (Scopus ID)
Conference
43rd Jaszowiec International School and Conference on the Physics of Semiconductors
Available from: 2015-01-13 Created: 2015-01-12 Last updated: 2017-12-05
Booker, I. D., Ul Hassan, J., Lilja, L., Beyer, F., Karhu, R., Bergman, J. P., . . . Janzén, E. (2014). Carrier Lifetime Controlling Defects Z(1/2) and RB1 in Standard and Chlorinated Chemistry Grown 4H-SiC. Crystal Growth & Design, 14(8), 4104-4110
Open this publication in new window or tab >>Carrier Lifetime Controlling Defects Z(1/2) and RB1 in Standard and Chlorinated Chemistry Grown 4H-SiC
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2014 (English)In: Crystal Growth & Design, ISSN 1528-7483, E-ISSN 1528-7505, Vol. 14, no 8, p. 4104-4110Article in journal (Refereed) Published
Abstract [en]

4H-SiC epilayers grown by standard and chlorinated chemistry were analyzed for their minority carrier lifetime and deep level recombination centers using time-resolved photoluminescence (TRPL) and standard deep level transient spectroscopy (DLTS). Next to the well-known Z(1/2) deep level a second effective lifetime killer, RB1 (activation energy 1.05 eV, electron capture cross section 2 x 10(-16) cm(2), suggested hole capture cross section (5 +/- 2) x 10(-15) cm(2)), is detected in chloride chemistry grown epilayers. Junction-DLTS and bulk recombination simulations are used to confirm the lifetime killing properties of this level. The measured RB1 concentration appears to be a function of the iron-related Fe1 level concentration, which is unintentionally introduced via the corrosion of reactor steel parts by the chlorinated chemistry. Reactor design and the growth zone temperature profile are thought to enable the formation of RB1 in the presence of iron contamination under conditions otherwise optimal for growth of material with very low Z(1/2) concentrations. The RB1 defect is either an intrinsic defect similar to RD1/2 or EH5 or a complex involving iron. Control of these corrosion issues allows the growth of material at a high growth rate and with high minority carrier lifetime based on Z(1/2) as the only bulk recombination center.

Place, publisher, year, edition, pages
American Chemical Society (ACS), 2014
National Category
Chemical Sciences
Identifiers
urn:nbn:se:liu:diva-110278 (URN)10.1021/cg5007154 (DOI)000340080400049 ()
Note

Funding Agencies|The Swedish Energy Agency; Swedish Research Council (VR); Swedish Foundation for Strategic Research (SSF); LG Innotek

Available from: 2014-09-05 Created: 2014-09-05 Last updated: 2017-12-05Bibliographically approved
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