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4H-silicon carbide-dielectric interface recombination analysis using free carrier absorption
KTH, School of Information and Communication Technology (ICT), Integrated Devices and Circuits.
KTH, School of Information and Communication Technology (ICT), Integrated Devices and Circuits.ORCID iD: 0000-0002-0292-224X
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2015 (English)In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 117, no 10, 105309Article in journal (Refereed) Published
Abstract [en]

In this paper, an alternative method to characterize the interface between 4H polytype of Silicon Carbide (4H-SiC) and passivating dielectric layers is established. The studies are made on dielectric-semiconductor test structures using Al2O3 as dielectric on 4H-SiC n-type epitaxial layers. Samples with different pre-and post-dielectric deposition preparations have been fabricated on epilayers of varying thicknesses. Effective lifetimes (tau(eff)) of all the samples were measured by an optical pump-probe method utilizing free carrier absorption (FCA) to analyse the influence of the 4H-SiC/dielectric interface on charge carrier recombination. The relative contribution to tau(eff) from the surfaces increases with decreasing epilayer thickness, and by analysing the data in combination with numerical modelling, it is possible to extract values of the surface recombination velocities (SRVs) for interfaces prepared in different ways. For instance, it is found that SRV for a standard cleaning procedure is 2 x 10(6) cm/s compared to a more elaborate RCA process, yielding a more than 50 times lower value of 3.5 x 10(4) cm/s. Furthermore, the density of interface traps (D-it) is extracted from capacitance-voltage (CV) measurements using the Terman method and a comparison is made between the SRV extracted from FCA measurements and D(it)s extracted from CV measurements on the same structures fabricated with metal contacts. It is observed that the SRV increase scales linearly with the increase in Dit. The strong qualitative correlation between FCA and CV data shows that FCA is a useful characterization technique, which can also yield more quantitative information about the charge carrier dynamics at the interface.

Place, publisher, year, edition, pages
2015. Vol. 117, no 10, 105309
National Category
Other Physics Topics
Identifiers
URN: urn:nbn:se:kth:diva-164450DOI: 10.1063/1.4914521ISI: 000351442900065Scopus ID: 2-s2.0-84924859308OAI: oai:DiVA.org:kth-164450DiVA: diva2:807440
Note

QC 20150423

Available from: 2015-04-23 Created: 2015-04-17 Last updated: 2017-12-04Bibliographically approved
In thesis
1. Radiation Hardness of 4H-SiC Devices and Circuits
Open this publication in new window or tab >>Radiation Hardness of 4H-SiC Devices and Circuits
2017 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Advances in space and nuclear technologies are limited by the capabilities of the conventional silicon (Si) electronics. Hence, there is a need to explore materials beyond Si with enhanced properties to operate in extreme environments. In this regards, silicon carbide (4H-SiC), a wide bandgap semiconductor, provides suitable solutions. In this thesis, radiation effects of 4H-SiC bipolar devices, circuits and dielectrics for SiC are investigated under various radiation types. We have demonstrated for the first time the radiation hardness of 4H-SiC logic circuits exposed to extremely high doses (332 Mrad) of gamma radiation and protons. Comparisons with previously available literature show that our 4H-SiC bipolar junction transistor (BJT) is 2 orders of magnitude more tolerant under gamma radiation to existing Si-technology. 4H-SiC devices and circuits irradiated with 3 MeV protons show about one order of magnitude higher tolerance in comparison to Si.

Numerical simulations of the device showed that the ionization is most influential in the degradation process by introducing interface states and oxide charges that lower the current gain. Due to the gain reduction of the BJT, the voltage reference of the logic circuit has been affected and this, in turn, degrades the voltage transfer characteristics of the OR-NOR gates.

One of the key advantages of 4H-SiC over other wide bandgap materials is the possibility to thermally grow silicon oxide (SiO2) and process device in line with advanced silicon technology. However, there are still questions about the reliability of SiC/SiO2 interface under high power, high temperature and radiation rich environments. In this regard, aluminium oxide (Al2O3), a chemically and thermally stable dielectric, has been investigated. It has been shown that the surface cleaning treatment prior to deposition of a dielectric layer together with the post dielectric annealing has a crucial effect on interface and oxide quality. We have demonstrated a new method to evaluate the interface between dielectric/4H-SiC utilizing an optical free carrier absorption technique to quantitative measure the charge carrier trapping dynamics. The radiation hardness of Al2O3/4H-SiC is demonstrated and the data suggests that Al2O3 is better choice of dielectric for devices in radiation rich applications.

Place, publisher, year, edition, pages
KTH Royal Institute of Technology, 2017. 56 p.
Series
TRITA-ICT, 2017:04
Keyword
Silicon carbide, radiation hardness, protons, gamma radiation, bipolar junction transistors, aluminium oxide, surface recombination.
National Category
Engineering and Technology
Research subject
Information and Communication Technology
Identifiers
urn:nbn:se:kth:diva-199907 (URN)978-91-7729-252-4 (ISBN)
Public defence
2017-02-17, Ka-Sal C (Sal Sven-Olof Öhrvik), KTH, Kistagången 16, Kista, 10:00 (English)
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Supervisors
Note

QC 20170119

Available from: 2017-01-19 Created: 2017-01-17 Last updated: 2017-01-19Bibliographically approved

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Linnarsson, MargaretaLinnros, JanHallén, Anders

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