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Janzén , Erik
Alternative names
Publications (10 of 573) Show all publications
Stenberg, P., Danielsson, Ö., Erdtman, E., Sukkaew, P., Ojamäe, L., Janzén, E. & Pedersen, H. (2017). Matching precursor kinetics to afford a more robust CVD chemistry: a case study of the C chemistry for silicon carbide using SiF4 as Si precursor. Journal of Materials Chemistry C, 5, 5818-5823
Open this publication in new window or tab >>Matching precursor kinetics to afford a more robust CVD chemistry: a case study of the C chemistry for silicon carbide using SiF4 as Si precursor
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2017 (English)In: Journal of Materials Chemistry C, ISSN 2050-7526, E-ISSN 2050-7534, Vol. 5, p. 5818-5823Article in journal (Refereed) Published
Abstract [en]

Chemical Vapor Deposition (CVD) is one of the technology platforms forming the backbone of the semiconductor industry and is vital in the production of electronic devices. To upscale a CVD process from the lab to the fab, large area uniformity and high run-to-run reproducibility are needed. We show by a combination of experiments and gas phase kinetics modeling that the combinations of Si and C precursors with the most well-matched gas phase chemistry kinetics gives the largest area of of homoepitaxial growth of SiC. Comparing CH4, C2H4 and C3H8 as carbon precursors to the SiF4 silicon precursor, CH4 with the slowest kinetics renders the most robust CVD chemistry with large area epitaxial growth and low temperature sensitivity. We further show by quantum chemical modeling how the surface chemistry is impeded by the presence of F in the system which limits the amount of available surface sites for the C to adsorb.

Place, publisher, year, edition, pages
Royal Society of Chemistry, 2017
National Category
Chemical Sciences
Identifiers
urn:nbn:se:liu:diva-137446 (URN)10.1039/c7tc00138j (DOI)000403571200024 ()
Note

Funding agencies: Knut & Alice Wallenberg Foundation (KAW) project Isotopic Control for Ultimate Material Properties; Swedish Foundation for Strategic Research project SiC - the Material for Energy-Saving Power Electronics [EM11-0034]; Swedish Government Strategic Research

Available from: 2017-05-16 Created: 2017-05-16 Last updated: 2018-08-09
Schmidt, S., Czigany, Z., Wissting, J., Greczynski, G., Janzén, E., Jensen, J., . . . Hultman, L. (2016). A comparative study of direct current magnetron sputtering and high power impulse magnetron sputtering processes for CNX thin film growth with different inert gases. Diamond and related materials, 64, 13-26
Open this publication in new window or tab >>A comparative study of direct current magnetron sputtering and high power impulse magnetron sputtering processes for CNX thin film growth with different inert gases
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2016 (English)In: Diamond and related materials, ISSN 0925-9635, E-ISSN 1879-0062, Vol. 64, p. 13-26Article in journal (Refereed) Published
Abstract [en]

Reactive direct current magnetron sputtering (DCMS) and high power impulse magnetron sputtering (HiPIMS) discharges of carbon in different inert gas mixtures (N-2/Ne, N-2/Ar, and N-2/Kr) were investigated for the growth of carbon-nitride (CNX) thin films. Ion mass spectrometry showed that energies of abundant plasma cations are governed by the inert gas and the N-2-to-inert gas flow ratios. The population of ion species depends on the sputter mode; HiPIMS yields approximately ten times higher flux ratios of ions originating from the target to process gas ions than DCMS. Exceptional are discharges in Ne with N-2-to-Ne flow ratios <20%. Here, cation energies and the amount of target ions are highest without influence on the sputter mode. CNX thin films were deposited in 14% N-2/inert gas mixtures at substrate temperatures of 110 degrees C and 430 degrees C. The film properties show a correlation to the substrate temperature, the applied inert gas and sputter mode. The mechanical performance of the films is mainly governed by their morphology and composition, but not by their microstructure. Amorphous and fullerene-like CN0.14 films exhibiting a hardness of similar to 15 GPa and an elastic recovery of similar to 90% were deposited at 110 degrees C in reactive Kr atmosphere by DCMS and HiPIMS.

Place, publisher, year, edition, pages
ELSEVIER SCIENCE SA, 2016
Keywords
Magnetron sputtering; Inert gases; Plasma analysis; Langmuir probe measurement; CNX film stress; CNX hardness
National Category
Inorganic Chemistry Condensed Matter Physics
Identifiers
urn:nbn:se:liu:diva-128146 (URN)10.1016/j.diamond.2016.01.009 (DOI)000374608100003 ()
Note

Funding Agencies|Carl Tryggers Foundation for Scientific Research; Hungarian Academy of Sciences

Available from: 2016-05-19 Created: 2016-05-19 Last updated: 2017-11-30
Danielsson, Ö., Li, X., Ojamäe, L., Janzén, E., Pedersen, H. & Forsberg, U. (2016). A model for carbon incorporation from trimethyl gallium in chemical vapor deposition of gallium nitride. Journal of Materials Chemistry, 4(4), 863-871
Open this publication in new window or tab >>A model for carbon incorporation from trimethyl gallium in chemical vapor deposition of gallium nitride
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2016 (English)In: Journal of Materials Chemistry, ISSN 0959-9428, E-ISSN 1364-5501, Vol. 4, no 4, p. 863-871Article in journal (Refereed) Published
Abstract [en]

Gallium nitride (GaN) semiconductor material can become semi-insulating when doping with carbon. Semi-insulating buffer layers are utilized to prevent leakage currents in GaN high power devices. Carbon is inherently present during chemical vapor deposition (CVD) of GaN from the use of trimethyl gallium (TMGa) as precursor. TMGa decomposes in the gas phase, releasing its methyl groups, which could act as carbon source for doping. It is previously known that the carbon doping levels can be controlled by tuning the CVD process parameters, such as temperature, pressure and precursor flow rates. However, the mechanism for carbon incorporation from TMGa is not yet understood. In this paper, a model for predicting carbon incorporation from TMGa in GaN layers grown by CVD is proposed. The model is based on ab initio quantum chemical calculations of molecular adsorption and reaction energies. Using Computational Fluid Dynamics, with a chemical kinetic model for decomposition of the precursors and reactions in the gas phase, to calculate gas phase compositions at realistic process conditions, together with the proposed model, we obtain good correlations with measurements, for both carbon doping concentrations and growth rates, when varying the inlet NH3/TMGa ratio. When varying temperature (800 – 1050°C), the model overpredicts carbon doping concentrations at the lower temperatures, but predicts growth rates well, and the agreement with measured carbon doping concentrations is good above 1000°C.

Place, publisher, year, edition, pages
Royal Society of Chemistry, 2016
National Category
Physical Sciences Physical Chemistry
Identifiers
urn:nbn:se:liu:diva-118113 (URN)10.1039/c5tc03989d (DOI)000368839700027 ()
Note

Funding agencies: Swedish Foundation for Strategic Research (SSF); Swedish Defence Material Administration (FMV)

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Available from: 2015-05-22 Created: 2015-05-22 Last updated: 2017-12-04Bibliographically approved
Bergsten, J., Li, X., Nilsson, D., Danielsson, Ö., Pedersen, H., Janzén, E., . . . Rorsman, N. (2016). AlGaN/GaN high electron mobility transistors with intentionally doped GaN buffer using propane as carbon precursor. Japanese Journal of Applied Physics, 55, 05FK02-1-05FK02-4, Article ID 05FK02.
Open this publication in new window or tab >>AlGaN/GaN high electron mobility transistors with intentionally doped GaN buffer using propane as carbon precursor
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2016 (English)In: Japanese Journal of Applied Physics, ISSN 0021-4922, E-ISSN 1347-4065, Vol. 55, p. 05FK02-1-05FK02-4, article id 05FK02Article in journal (Refereed) Published
Abstract [en]

AlGaN/GaN high electron mobility transistors (HEMTs) fabricated on a heterostructure grown by metalorganic chemical vapor deposition using analternative method of carbon (C) doping the buffer are characterized. C-doping is achieved by using propane as precursor, as compared to tuningthe growth process parameters to control C-incorporation from the gallium precursor. This approach allows for optimization of the GaN growthconditions without compromising material quality to achieve semi-insulating properties. The HEMTs are evaluated in terms of isolation anddispersion. Good isolation with OFF-state currents of 2 ' 10%6A/mm, breakdown fields of 70V/μm, and low drain induced barrier lowering of0.13mV/V are found. Dispersive effects are examined using pulsed current–voltage measurements. Current collapse and knee walkout effectslimit the maximum output power to 1.3W/mm. With further optimization of the C-doping profile and GaN material quality this method should offer aversatile approach to decrease dispersive effects in GaN HEMTs.

Place, publisher, year, edition, pages
Institute of Physics Publishing (IOPP), 2016
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:liu:diva-128077 (URN)10.7567/JJAP.55.05FK02 (DOI)000374697600081 ()
Funder
Swedish Foundation for Strategic Research Swedish Research Council
Available from: 2016-05-16 Created: 2016-05-16 Last updated: 2017-11-30
Schubert, M., Korlacki, R., Knight, S., Hofmann, T., Schoeche, S., Darakchieva, V., . . . Higashiwaki, M. (2016). Anisotropy, phonon modes, and free charge carrier parameters in monoclinic beta-gallium oxide single crystals. PHYSICAL REVIEW B, 93(12), 125209
Open this publication in new window or tab >>Anisotropy, phonon modes, and free charge carrier parameters in monoclinic beta-gallium oxide single crystals
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2016 (English)In: PHYSICAL REVIEW B, ISSN 2469-9950, Vol. 93, no 12, p. 125209-Article in journal (Refereed) Published
Abstract [en]

We derive a dielectric function tensor model approach to render the optical response of monoclinic and triclinic symmetry materials with multiple uncoupled infrared and far-infrared active modes. We apply our model approach to monoclinic beta-Ga2O3 single-crystal samples. Surfaces cut under different angles from a bulk crystal, (010) and ((2) over bar 01), are investigated by generalized spectroscopic ellipsometry within infrared and far-infrared spectral regions. We determine the frequency dependence of 4 independent beta-Ga2O3 Cartesian dielectric function tensor elements by matching large sets of experimental data using a point-by-point data inversion approach. From matching our monoclinic model to the obtained 4 dielectric function tensor components, we determine all infrared and far-infrared active transverse optic phonon modes with A(u) and B-u symmetry, and their eigenvectors within the monoclinic lattice. We find excellent agreement between our model results and results of density functional theory calculations. We derive and discuss the frequencies of longitudinal optical phonons in beta-Ga2O3. We derive and report density and anisotropic mobility parameters of the free charge carriers within the tin-doped crystals. We discuss the occurrence of longitudinal phonon plasmon coupled modes in beta-Ga2O3 and provide their frequencies and eigenvectors. We also discuss and present monoclinic dielectric constants for static electric fields and frequencies above the reststrahlen range, and we provide a generalization of the Lyddane-Sachs-Teller relation for monoclinic lattices with infrared and far-infrared active modes. We find that the generalized Lyddane-Sachs-Teller relation is fulfilled excellently for beta-Ga2O3.

Place, publisher, year, edition, pages
AMER PHYSICAL SOC, 2016
National Category
Chemical Sciences
Identifiers
urn:nbn:se:liu:diva-127273 (URN)10.1103/PhysRevB.93.125209 (DOI)000372412400003 ()
Note

Funding Agencies|National Science Foundation (NSF) through the Center for Nanohybrid Functional Materials [EPS-1004094]; Nebraska Materials Research Science and Engineering Center [DMR-1420645]; Swedish Research Council (VR) [2013-5580, 2010-3848]; Swedish Governmental Agency for Innovation Systems (VINNOVA) under the VINNMER international qualification program [2011-03486, 2014-04712]; Swedish Foundation for Strategic Research (SSF) [FFL12-0181, RIF14-055]; Linkoping Linnaeus Initiative on Nanoscale Functional Materials (LiLiNFM) - VR; University of Nebraska-Lincoln; J. A. Woollam Co., Inc.; J. A. Woollam Foundation; [CMMI 1337856]; [EAR 1521428]

Available from: 2016-04-20 Created: 2016-04-19 Last updated: 2016-05-10
Minamisawa, R. A., Mihaila, A., Farkas, I., Teodorescu, V. S., Afanasev, V. V., Chih-Wei, C.-W., . . . Rahimo, M. (2016). Characterization of a n+3C/n-4H SiC heterojunction diode. Applied Physics Letters, 108(14), 143502
Open this publication in new window or tab >>Characterization of a n+3C/n-4H SiC heterojunction diode
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2016 (English)In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 108, no 14, p. 143502-Article in journal (Refereed) Published
Abstract [en]

We report on the fabrication of n+3C/n-4H SiC heterojunction diodes (HJDs) potentially promising the ultimate thermal stability of the junction. The diodes were systematically analyzed by TEM, X-ray diffraction, AFM, and secondary ion mass spectroscopy, indicating the formation of epitaxial 3C-SiC crystal on top of 4H-SiC substrate with continuous interface, low surface roughness, and up to similar to 7 x 10(17) cm(-3) dopant impurity concentration. The conduction band off-set is about 1 V as extracted from CV measurements, while the valence bands of both SiC polytypes are aligned. The HJDs feature opening voltage of 1.65 V, consistent with the barrier height of about 1.5 eV extracted from CV measurement. We finally compare the electrical results of the n+3C/n-4H SiC heterojunction diodes with those featuring Si and Ge doped anodes in order to evaluate current challenges involved in the fabrication of such devices. (C) 2016 AIP Publishing LLC.

Place, publisher, year, edition, pages
American Institute of Physics (AIP), 2016
National Category
Chemical Sciences
Identifiers
urn:nbn:se:liu:diva-127776 (URN)10.1063/1.4945332 (DOI)000374230700040 ()
Available from: 2016-05-12 Created: 2016-05-12 Last updated: 2017-11-30
Booker, I. D., Farkas, I., Ivanov, I. G., Ul Hassan, J. & Janzén, E. (2016). Chloride-based SiC growth on a-axis 4H-€“SiC substrates. Paper presented at 6th South African Conference on Photonic Materials (SACPM 2015), Mabula Game Lodge, South Africa, 4 – 8 May 2015. Physica. B, Condensed matter, 480, 23-25
Open this publication in new window or tab >>Chloride-based SiC growth on a-axis 4H-€“SiC substrates
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2016 (English)In: Physica. B, Condensed matter, ISSN 0921-4526, E-ISSN 1873-2135, Vol. 480, p. 23-25Article in journal (Refereed) Published
Abstract [en]

Abstract SiC has, during the last few years, become increasingly important as a power-device material for high voltage applications. The thick, low-doped voltage-supporting epitaxial layer is normally grown by CVD on 4° off-cut 4H–SiC substrates at a growth rate of 5 – 10 ÎŒ m / h using silane (SiH4) and propane (C3H8) or ethylene (C2H4) as precursors. The concentrations of epitaxial defects and dislocations depend to a large extent on the underlying substrate but can also be influenced by the actual epitaxial growth process. Here we will present a study on the properties of the epitaxial layers grown by a Cl-based technique on an a-axis (90° off-cut from c-direction) 4H–SiC substrate.

Place, publisher, year, edition, pages
Elsevier, 2016
Keywords
4H–SiC; a-face; DLTS; Photoluminescence; Raman; Epitaxy
National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:liu:diva-123948 (URN)10.1016/j.physb.2015.08.038 (DOI)000365600300005 ()
Conference
6th South African Conference on Photonic Materials (SACPM 2015), Mabula Game Lodge, South Africa, 4 – 8 May 2015
Available from: 2016-01-14 Created: 2016-01-14 Last updated: 2017-11-30Bibliographically approved
Duc Tran, T., Pozina, G., Amano, H., Monemar, B., Janzén, E. & Hemmingsson, C. (2016). Deep level study of Mg-doped GaN using deep level transient spectroscopy and minority carrier transient spectroscopy. Physical Review B, 94(4), Article ID 045206.
Open this publication in new window or tab >>Deep level study of Mg-doped GaN using deep level transient spectroscopy and minority carrier transient spectroscopy
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2016 (English)In: Physical Review B, ISSN 2469-9950, Vol. 94, no 4, article id 045206Article in journal (Refereed) Published
Abstract [en]

Deep levels in Mg doped GaN have been studied using deep level transient spectroscopyand minority charge carrier transient spectroscopy. Two traps are revealed in the investigatedtemperature range. In the substrate, one electron trap labelled ET1 (EC – 0.158 eV) is observedand in the Mg-doped layer, one hole trap labelled HT1 has been revealed. By varying theelectric field, it is found that the hole trap HT1 exhibits an electric field enhanced hole emissionrate. Using four theoretical models based on 3-dimensional Coulombic Poole-Frenkel effect, 3-dimensional square well Poole-Frenkel effect, phonon assisted tunneling, and 1-dimensionalCoulombic Poole-Frenkel effect including phonon assisted tunneling, the experimental data arefitted in order to justify the field enhanced emission process. It is found that the 1-dimensionalCoulombic Poole-Frenkel model including phonon assisted tunneling is consistent with theexperimental data. Since the trap exhibits Poole-Frenkel effect, we suggest it is acceptor like.From the theoretical model, the zero field activation energy of HT1 and an estimate of the holecapture cross section have been determined as Ev+0.57 eV and 1.9x10-15 cm2, respectively.Since the level is only observed in Mg-doped material, it is suggested that the trap can beassociated with a Mg related defect.

Place, publisher, year, edition, pages
AMER PHYSICAL SOC, 2016
National Category
Physical Sciences
Identifiers
urn:nbn:se:liu:diva-121705 (URN)10.1103/PhysRevB.94.045206 (DOI)000381484500007 ()
Note

Funding agenices: Swedish Research Council [621-2010-3850]; Swedish Energy Agency [38338-1]

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Available from: 2015-10-02 Created: 2015-10-02 Last updated: 2016-09-26Bibliographically approved
Duc Tran, T., Pozina, G., Nguyen, T. S., Kordina, O., Janzén, E., Ohshima, T. & Hemmingsson, C. (2016). Deep levels in as-grown and electron-irradiated n-type GaN studied by deep level transient spectroscopy and minority carrier transient spectroscopy. Journal of Applied Physics, 119(9)
Open this publication in new window or tab >>Deep levels in as-grown and electron-irradiated n-type GaN studied by deep level transient spectroscopy and minority carrier transient spectroscopy
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2016 (English)In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 119, no 9Article in journal (Refereed) Published
Abstract [en]

By minority carrier transient spectroscopy on as-grown n-type bulk GaN produced by halide vapor phase epitaxy (HVPE) one hole trap labelled H1 (EV + 0.34 eV) has been detected. After 2 MeV-energy electron irradiation, the concentration of H1 increases and at fluences higher than 5×1014 cm-2, a second hole trap labelled H2 is observed. Simultaneously, the concentration of two electron traps, labelled T1 (EC - 0.12 eV) and T2 (EC - 0.23 eV) increases. By studying the increase of the concentration versus electron irradiation fluences, the introduction rate of T1 and T2 using 2 MeV-energy electrons was determined to 7X10-3 cm-1 and 0.9 cm-1, respectively. Due to the low introduction rate of T1 and the low threading dislocation density in the HVPE bulk GaN material, it is suggested that the defect is associated with a primary defect decorating extended structural defects. The high introduction rate of the trap H1 suggests that the H1 defect is associated with a primary intrinsic defect or a complex.

Keywords
Deep level, GaN, DLTS, irradiation
National Category
Physical Sciences
Identifiers
urn:nbn:se:liu:diva-121709 (URN)10.1063/1.4943029 (DOI)000372351900075 ()
Note

Funding agencies:  Swedish Research Council (VR); Swedish Energy Agency

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Available from: 2015-10-02 Created: 2015-10-02 Last updated: 2017-12-01Bibliographically approved
Booker, I. D., Janzén, E., Son, N. T., Hassan, J., Stenberg, P. & Sveinbjörnsson, E. (2016). Donor and double donor transitions of the carbon vacancy related EH6/7 deep level in 4H-SiC. Journal of Applied Physics, 119(23), Article ID 235703.
Open this publication in new window or tab >>Donor and double donor transitions of the carbon vacancy related EH6/7 deep level in 4H-SiC
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2016 (English)In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 119, no 23, article id 235703Article in journal (Refereed) Published
Abstract [en]

Using medium- and high-resolution multi-spectra fitting of deep level transient spectroscopy (DLTS), minority carrier transient spectroscopy (MCTS), optical O-DLTS and optical-electrical (OE)-MCTS measurements, we show that the EH6∕7 deep level in 4H-SiC is composed of two strongly overlapping, two electron emission processes with thermal activation energies of 1.49 eV and 1.58 eV for EH6 and 1.48 eV and 1.66 eV for EH7. The electron emission peaks of EH7 completely overlap while the emission peaks of EH6 occur offset at slightly different temperatures in the spectra. OE-MCTS measurements of the hole capture cross section σp 0(T) in p-type samples reveal a trap-Auger process, whereby hole capture into the defect occupied by two electrons leads to a recombination event and the ejection of the second electron into the conduction band. Values of the hole and electron capture cross sections σn(T) and σp(T) differ strongly due to the donor like nature of the deep levels and while all σn(T) have a negative temperature dependence, the σp(T) appear to be temperature independent. Average values at the DLTS measurement temperature (∼600 K) are σn 2+(T) ≈ 1 × 10−14 cm2, σn +(T) ≈ 1 × 10−14 cm2, and σp 0(T) ≈ 9 × 10−18 cm2 for EH6 and σn 2+(T) ≈ 2 × 10−14 cm2, σn +(T) ≈ 2 × 10−14 cm2, σp 0(T) ≈ 1 × 10−20 cm2 for EH7. Since EH7 has already been identified as a donor transition of the carbon vacancy, we propose that the EH6∕7 center in total represents the overlapping first and second donor transitions of the carbon vacancy defects on both inequivalent lattice sites.

Place, publisher, year, edition, pages
American Institute of Physics (AIP), 2016
Keywords
4H-SiC, DLTS, MCTS, Carbon vacancy, EH6/7; Z1/2, UT-1, Negative-U, Trap Auger, Deep level
National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:liu:diva-121544 (URN)10.1063/1.4954006 (DOI)000379038800035 ()
Funder
Swedish Foundation for Strategic Research Swedish Research Council
Note

At the time for thesis presentation publication was in status: Manuscript

Funding agencies: Swedish Foundation for Strategic Research (SSF); Swedish Research Council (VR)

Available from: 2015-09-24 Created: 2015-09-24 Last updated: 2017-12-01Bibliographically approved
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