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High Gamma Ray Tolerance for 4H-SiC Bipolar Circuits
KTH, School of Information and Communication Technology (ICT), Electronics, Integrated devices and circuits.
KTH.
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2016 (English)In: IEEE Transactions on Nuclear Science, ISSN 0018-9499, E-ISSN 1558-1578Article in journal (Refereed) Published
Abstract [en]

A high gamma radiation hardness of 4H-SiC circuits is performed. The OR NOR circuits are based on emitter coupled logic (ECL), using integrated bipolar NPN transistors. Gain degradation in individual bipolar junction transistors (BJT) is minimal up to a dose of 38 Mrad (SiO2), but for the dose of 332 Mrad (SiO2) a degradation of 52% is observed. The SiC BJTs show higher radiation hardness than existing Si-technology and high stability under temperature stress. It is proposed that the oxide charge-dominated recombination is the key base current recombination mechanism contributing to gain degradation. An improvement in the gain is seen after annealing at 400 °C for 1800 s due to the possible annealing of some of the oxide defects contributing to the oxide charge.

Place, publisher, year, edition, pages
IEEE Press, 2016.
Keyword [en]
Ionization radiation, 4H-SiC, Bipolar Junction Transistors, Gamma rays, Logic Circuits
National Category
Engineering and Technology
Identifiers
URN: urn:nbn:se:kth:diva-199901DOI: 10.1109/TNS.2016.2642899ISI: 000396813400012Scopus ID: 2-s2.0-85014561700OAI: oai:DiVA.org:kth-199901DiVA, id: diva2:1066160
Note

Qc 20170118

Available from: 2017-01-17 Created: 2017-01-17 Last updated: 2017-06-09Bibliographically 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. p. 56
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)
Opponent
Supervisors
Note

QC 20170119

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

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