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Beshkova, Milena
Publications (10 of 11) Show all publications
Scajev, P., Onufnjevs, P., Manolis, G., Karaliunas, M., Nargelas, S., Jegenyes, N., . . . Jarasionas, K. (2012). On applicability of time-resolved optical techniques for characterization of differently grown 3C-SiC crystals and heterostructures. In: Daniel Alquier (Ed.), HETEROSIC and WASMPE 2011. Paper presented at 4th Workshop on Advanced Semiconductor Materials and Devices for Power Electronics Applications, 27-30 June 2011, Tours, France (pp. 159-163). Trans Tech Publications Inc., 711
Open this publication in new window or tab >>On applicability of time-resolved optical techniques for characterization of differently grown 3C-SiC crystals and heterostructures
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2012 (English)In: HETEROSIC and WASMPE 2011 / [ed] Daniel Alquier, Trans Tech Publications Inc., 2012, Vol. 711, p. 159-163Conference paper, Published paper (Refereed)
Abstract [en]

We applied a number of time-resolved optical techniques for investigation of optical and photoelectrical properties of cubic SiC grown by different technologies on different substrates. The excess carriers were injected by a short laser pulse and their dynamics was monitored by free-carrier absorption, light-induced transient grating, and photoluminescence techniques in a wide excitation range. Combining an optical and electrical probe beam delay, we found that free carrier lifetimes in differently grown layers vary from few ns up to 20 mu s. Temperature dependences of carrier diffusivity and lifetime revealed a pronounced carrier trapping in thin sublimation grown layers. In free-standing layers and thick sublimation layers, the ambipolar mobility was found the highest (120 cm(2)/Vs at room temperature). A linear correlation between the room-temperature band edge emission and carrier lifetime in differently grown layers was attributed to defect density, strongly dependent on the used growth conditions.

Place, publisher, year, edition, pages
Trans Tech Publications Inc., 2012
Series
Materials Science Forum, ISSN 0255-5476 ; 711
Keywords
Cubic silicon carbide; light-induced transient grating; free carrier absorption; doping; mobility; carrier lifetime; carrier trapping
National Category
Natural Sciences
Identifiers
urn:nbn:se:liu:diva-89787 (URN)10.4028/www.scientific.net/MSF.711.159 (DOI)000302673900029 ()
Conference
4th Workshop on Advanced Semiconductor Materials and Devices for Power Electronics Applications, 27-30 June 2011, Tours, France
Available from: 2013-03-06 Created: 2013-03-06 Last updated: 2013-03-14
Beshkova, M., Birch, J., Syväjärvi, M. & Yakimova, R. (2012). Sublimation epitaxy of 3C-SiC grown at Si- and C-rich conditions. Vacuum, 86(10), 1595-1599
Open this publication in new window or tab >>Sublimation epitaxy of 3C-SiC grown at Si- and C-rich conditions
2012 (English)In: Vacuum, ISSN 0042-207X, E-ISSN 1879-2715, Vol. 86, no 10, p. 1595-1599Article in journal (Refereed) Published
Abstract [en]

3C-SiC layers have been grown by using sublimation epitaxy at a source temperature of 2000 degrees C, under vacuum conditions (andlt;10(-5) mbar) on well oriented (on-axis) 6H-SiC (0001) substrates. Close space sublimation growth geometry has been used in a RF-heated furnace employing high-purity graphite crucible with a possibility to change the growth environment from Si vapor-rich to C vapor-rich. The optical microscopy in transmission mode reveals continuous 3C-domains for 3C-SiC with less than 0.4% 6H-inclusions for the layer grown at Si-rich conditions, and separate 3C-SiC domains for the layer grown at C-rich conditions. The type of 6H-inclusions for layers with continuous domain structure investigated by Atomic Force Microscopy (AFM) is discussed. 2Theta-omega scan shows 0006 and 111 peaks coming from the substrate and the layer, respectively with a higher intensity of the 111 peak for 3C-SiC grown at Si-rich conditions which is related with the continuous character of the 3C-SiC domains.

Place, publisher, year, edition, pages
Elsevier, 2012
Keywords
3C-SiC, Sublimation heteroepitaxy, Morphology, AFM, HRXRD
National Category
Engineering and Technology
Identifiers
urn:nbn:se:liu:diva-79641 (URN)10.1016/j.vacuum.2012.03.020 (DOI)000306390200032 ()
Note
Funding Agencies|European Community through the MANSiC|MRTN-CT-2006-035735|Available from: 2012-08-13 Created: 2012-08-13 Last updated: 2017-12-07
Zoulis, G., Sun, J. W., Beshkova, M., Vasiliauskas, R., Juillaguet, S., Peyre, H., . . . Camassel, J. (2010). Investigation of Low Doped n-Type and p-Type 3C-SiC Layers Grown on 6H-SiC Substrates by Sublimation Epitaxy. In: Silicon Carbide and Related Materials 2009: . Paper presented at Silicon Carbide and Related Materials 2009 (pp. 179-182). , 645
Open this publication in new window or tab >>Investigation of Low Doped n-Type and p-Type 3C-SiC Layers Grown on 6H-SiC Substrates by Sublimation Epitaxy
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2010 (English)In: Silicon Carbide and Related Materials 2009, 2010, Vol. 645, p. 179-182Conference paper, Published paper (Refereed)
Abstract [en]

Both, n-type and p-type 3C-SiC samples grown on 6H-SiC substrates by sublimation epitaxy have been investigated. From low temperature photoluminescence studies, we demonstrate a low level of residual (n and/or p-type) doping with weak compensation, which is confirmed by secondary ion mass spectroscopy in the case of p-type samples.

Series
Materials Science Forum
Keywords
Epitaxial Growth, Low Temperature Photoluminescence
National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:liu:diva-128857 (URN)10.4028/www.scientific.net/MSF.645-648.179 (DOI)
Conference
Silicon Carbide and Related Materials 2009
Available from: 2016-06-02 Created: 2016-06-02 Last updated: 2018-08-02
Beshkova, M., Lorenzzi, J., Jegenyes, N., Birch, J., Syväjärvi, M., Ferro, G. & Yakimova, R. (2010). Properties of 3C-SiC Grown by Sublimation Epitaxy on Different Type of Substrates. In: Materials Science Forum, Vols. 645-648. Paper presented at ICSCRM2009 (pp. 183-186). Transtec Publications; 1999, 645-648
Open this publication in new window or tab >>Properties of 3C-SiC Grown by Sublimation Epitaxy on Different Type of Substrates
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2010 (English)In: Materials Science Forum, Vols. 645-648, Transtec Publications; 1999 , 2010, Vol. 645-648, p. 183-186Conference paper, Published paper (Refereed)
Abstract [en]

3C-SiC layers have been grown by using sublimation epitaxy at a temperature of 2000 degrees C, on different types of on-axis 6H-SiC(0001) substrates. The influence of the type of substrate on the morphology of the layers investigated by Atomic Force Microscopy (AFM) is discussed. Stacking faults are studied by reciprocal space map (RSM) which shows that double positions domains exists.

Place, publisher, year, edition, pages
Transtec Publications; 1999, 2010
Keywords
3C-SiC; Sublimation Epitaxy; morphology; AFM; HRXRD
National Category
Engineering and Technology
Identifiers
urn:nbn:se:liu:diva-58208 (URN)10.4028/www.scientific.net/MSF.645-648.183 (DOI)000279657600043 ()
Conference
ICSCRM2009
Available from: 2010-08-10 Created: 2010-08-09 Last updated: 2010-12-08
Beshkova, M., Syväjärvi, M., Vasiliauskas, R., Birch, J. & Yakimova, R. (2009). Properties of 3C-SiC Grown by Sublimation Epitaxy. In: ECSCRM2008,2008.
Open this publication in new window or tab >>Properties of 3C-SiC Grown by Sublimation Epitaxy
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2009 (English)In: ECSCRM2008,2008, 2009Conference paper, Published paper (Refereed)
Abstract [en]

  

National Category
Natural Sciences
Identifiers
urn:nbn:se:liu:diva-43442 (URN)73852 (Local ID)73852 (Archive number)73852 (OAI)
Available from: 2009-10-10 Created: 2009-10-10
Beshkova, M., Syväjärvi, M., Vasiliauskas, R., Birch, J. & Yakimova, R. (2009). Structural Properties of 3C-SiC Grown by Sublimation Epitaxy. In: ECSCRM2009,2009: . Paper presented at 7th European Conference on Silicon Carbide and Related Materials, ECSCRM 2008; Barcelona; Spain (pp. 181-184). Materials Science Forum Vols. 615-617: Trans Tech Publications
Open this publication in new window or tab >>Structural Properties of 3C-SiC Grown by Sublimation Epitaxy
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2009 (English)In: ECSCRM2009,2009, Materials Science Forum Vols. 615-617: Trans Tech Publications , 2009, p. 181-184Conference paper, Published paper (Refereed)
Abstract [en]

The present paper deals with morphological and structural investigation of 3C-SiC layers grown by sublimation epitaxy on on axis 6H-SiC(0001) at source temperature 2000 °C, under vacuum conditions (<10-5 mbar) and different temperature gradients in the range of 5-8 °C/mm. The layer grown at a temperature gradient 6 °C/mm has the largest average domain size of 0.4 mm2 assessed by optical microscope in transmission mode. The rocking curve full width at half maximum (FWHM) of (111) reflection is 43 arcsec which suggests good crystalline quality. The AFM image of the same layer shows steps with height 0.25 nm and 0.75 nm which are characteristic of a stacking fault free 3C-SiC surface and c-axis repeat height, respectively.

Place, publisher, year, edition, pages
Materials Science Forum Vols. 615-617: Trans Tech Publications, 2009
National Category
Natural Sciences
Identifiers
urn:nbn:se:liu:diva-45292 (URN)10.4028/www.scientific.net/MSF.615-617.181 (DOI)80736 (Local ID)978-087849334-0 (ISBN)80736 (Archive number)80736 (OAI)
Conference
7th European Conference on Silicon Carbide and Related Materials, ECSCRM 2008; Barcelona; Spain
Available from: 2009-10-10 Created: 2009-10-10 Last updated: 2014-08-29
Vasiliauskas, R., Syväjärvi, M., Beshkova, M. & Yakimova, R. (2009). Two-dimensional nucleation of cubic and 6H silicon carbide. In: ECSCRM2008,2008: . Paper presented at 7th European Conference on Silicon Carbide and Related Materials, ECSCRM 2008; Barcelona; Spain (pp. 189-192). Materials Science Forum Vols. 615-617: Trans Tech Publications
Open this publication in new window or tab >>Two-dimensional nucleation of cubic and 6H silicon carbide
2009 (English)In: ECSCRM2008,2008, Materials Science Forum Vols. 615-617: Trans Tech Publications , 2009, p. 189-192Conference paper, Published paper (Refereed)
Abstract [en]

The initial stage of heteroepitaxial growth of 3C-SiC and homoepitaxial growth of 6H-SiC on nominal 6H-SiC on-axis substrates has been studied. Before 3C-SiC starts to nucleate, 6H-SiC grows in a step-flow growth mode due to a slight off-orientation of the substrate surface already at about 1500oC. In the 1650-1700oC temperature interval 3C-SiC nucleates as 2D islands. A distance away from the 3C-SiC island 6H-SiC grows in step-flow mechanism. In the vicinity of the 3C-SiC islands the 6H-SiC growth steps start to change direction and even split into two steps with the equal height of 0.5 nm, which is approaching the unit cell size of cubic SiC. When the supersaturation is lower in comparison with the conditions for 3C-SiC growth, there is only formation of 6H-SiC, i.e. homoepitaxial growth. The growth mode of 6H-SiC is dependent on temperature. At the lowest temperature there is spiral growth while at higher temperature 2D nucleation is preferred.

Place, publisher, year, edition, pages
Materials Science Forum Vols. 615-617: Trans Tech Publications, 2009
National Category
Natural Sciences
Identifiers
urn:nbn:se:liu:diva-43441 (URN)10.4028/www.scientific.net/MSF.615-617.189 (DOI)73851 (Local ID)978-087849334-0 (ISBN)73851 (Archive number)73851 (OAI)
Conference
7th European Conference on Silicon Carbide and Related Materials, ECSCRM 2008; Barcelona; Spain
Available from: 2009-10-10 Created: 2009-10-10 Last updated: 2014-09-04
Beshkova, M., Grigorov, K. G., Zakhariev, Z., Abrashev, M., Massi, M. & Yakimova, R. (2007). Sublimation epitaxy of AlN layers grown by different conditions on 4H-SiC substrates. Journal of Optoelectronics and Advanced Materials, 9(1), 213-216
Open this publication in new window or tab >>Sublimation epitaxy of AlN layers grown by different conditions on 4H-SiC substrates
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2007 (English)In: Journal of Optoelectronics and Advanced Materials, ISSN 1454-4164, E-ISSN 1841-7132, Vol. 9, no 1, p. 213-216Article in journal (Refereed) Published
Abstract [en]

Epitaxial layers of aluminium nitride were grown at temperature 2100 degrees C on 10X10 mm(2) 4H-SiC substrates via a sublimation-recondensation method in an RF heated graphite furnace. The source material was polycrystalline sintered AIN. Growths of AIN layers in vacuum and pure nitrogen at 20 mbar were compared. MA maximum growth rate of 70 mu m/h was achieved in a pure N-2 atmosphere. The surface morphology reveals the hexagonal symmetry of the seeds, suggesting an epitaxial growth. This was confirmed by High-Resolution X-Ray Diffraction. The spectra showed a strong and well defined (0002) reflection positioned at 36.04 degrees in a symmetric theta-2 theta scan for both samples. Micro-Raman spectroscopy revealed that the films had a wurtzite structure. Rutherford Backscattering Spectrometry indicated the quality with a relative chi(min) parameter 0.68.

Keywords
AlN, sublimation epitaxy, HRXRD, RBS
National Category
Engineering and Technology
Identifiers
urn:nbn:se:liu:diva-48035 (URN)
Available from: 2009-10-11 Created: 2009-10-11 Last updated: 2017-12-13
Beshkova, M., Zakhariev, Z., Abrashev, M., Birch, J., Kakanakova-Georgieva, A. & Yakimova, R. (2004). Low-pressure sublimation epitaxy of AlN films - growth and characterization. Vacuum, 76, 143-146
Open this publication in new window or tab >>Low-pressure sublimation epitaxy of AlN films - growth and characterization
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2004 (English)In: Vacuum, ISSN 0042-207X, E-ISSN 1879-2715, Vol. 76, p. 143-146Article in journal (Refereed) Published
Abstract [en]

Epitaxial layers of aluminum nitride have been grown at temperatures 1900-2400degreesC on 10 x 10 mm(2) 4H-SiC substrate via sublimation recondensation in an RF heated graphite furnace. The source material was polycrystalline sintered AlN. A maximum growth rate of about 100 mum/h was achieved at 2400degreesC and seed to source distance of 1 mm. The surface morphology reflects the hexagonal symmetry of the seed suggesting an epitaxial growth. This was confirmed by X-ray diffraction (XRD). The spectra showed very strong and well-defined (0002) reflection position at around 36.04degrees in symmetric Theta-2Thetascans for all samples. Micro-Raman spectroscopy reveals that the films have a wurtzite structure. It is evidenced by the appearance of the A(1) (TO) (at 601 cm(-1)) and E-2((2)) (at 651 cm(-1)) lines in the spectra. Secondary-ion mass spectroscopy (SIMS) results showed a low concentration of carbon incorporation in the AlN films. A correlation between the growth conditions and properties of the AlN layers was established.

Keywords
AIN, sublimation, morphology, XRD, Raman
National Category
Natural Sciences
Identifiers
urn:nbn:se:liu:diva-40881 (URN)10.1016/j.vacuum.2004.07.052 (DOI)54459 (Local ID)54459 (Archive number)54459 (OAI)
Available from: 2009-10-10 Created: 2009-10-10 Last updated: 2017-12-13
Beshkova, M., Zakhariev, Z., Birch, J., Kakanakova-Georgieva, A. & Yakimova, R. (2003). Properties of AlN layers grown by sublimation epitaxy. In: Materials Science Forum, Vols. 433-436. Paper presented at ECSCRM2002 (pp. 995-998). , 433-4
Open this publication in new window or tab >>Properties of AlN layers grown by sublimation epitaxy
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2003 (English)In: Materials Science Forum, Vols. 433-436, 2003, Vol. 433-4, p. 995-998Conference paper, Published paper (Refereed)
Abstract [en]

Epitaxial layers of aluminum nitride (AlN)less than or equal to 80 mum thick have been grown at the temperatures 1900 and 2100 degreesC on 10x10mm(2) 4H-SiC substrates via sublimation recondensation in a RF heated graphite furnace. The source material was polyerystalline sintered AlN. A maximum growth rate of 80 mum/h was achieved at 2100degreesC and seed to source separation of I mm. The surface morphology reflects the hexagonal symmetry of the seed that suggesting an epitaxial growth. All crystals show strong and well defined single crystalline XRD patterns. Only the (002) reflection positioned at around 36.04 was observed in symmetric Theta-2Theta scan. The rocking curves FWHM (full width half maximum) and peak positions arc reported.

Keywords
AlN, growth rate, morphology, sublimation epitaxy, XRD
National Category
Engineering and Technology
Identifiers
urn:nbn:se:liu:diva-48570 (URN)
Conference
ECSCRM2002
Available from: 2009-10-11 Created: 2009-10-11 Last updated: 2010-12-08
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