Change search
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
4H-SiC power BJTs with high current gain and low on-resistance
KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP.
KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP.
KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP.ORCID iD: 0000-0001-8108-2631
KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP.ORCID iD: 0000-0002-5845-3032
2007 (English)In: Materials Science Forum, ISSN 0255-5476, E-ISSN 1662-9752, Vol. 556-557, 767-770 p.Article in journal (Refereed) Published
Abstract [en]

4H-SiC BJTs have been fabricated with varying geometrical designs. The maximum value of the current gain was about 30 at I-c=85 mA, V-CE=14 V and room temperature (RT) for a 20 mu m emitter width structure. A collector-emitter voltage drop V-CE of 2 V at a forward collector current 55 mA (J(C) = 128 A/cm(2)) was obtained and a specific on-resistance of 15.4 m Omega center dot cm(2) was extracted at RT. Optimum emitter finger widths and base-contact implant distances were derived from measurement. The temperature dependent DC IN characteristics of the BJTs have been studied resulting in 45 % reduction of the gain and 75 % increase of the on-resistance at 225 degrees C compared to RT. Forward-bias stress on SiC BJTs was investigated and about 20 % reduction of the initial current gain was found after 27.5 hours. Resistive switching measurements with packaged SiC BJTs were performed showing a resistive fast turn-on with a VCE fall-time of 90 ns. The results indicate that significantly faster switching can be obtained by actively controlling the base current.

Place, publisher, year, edition, pages
2007. Vol. 556-557, 767-770 p.
Keyword [en]
bipolar junction transistors; current gain; switching; degradation
National Category
Engineering and Technology
Identifiers
URN: urn:nbn:se:kth:diva-7933DOI: 10.4028/www.scientific.net/MSF.556-557.767ISI: 000249653900182Scopus ID: 2-s2.0-38449112149OAI: oai:DiVA.org:kth-7933DiVA: diva2:13116
Note
QC 20100819Available from: 2008-01-30 Created: 2008-01-30 Last updated: 2017-12-14Bibliographically approved
In thesis
1. Fabrication and Characterization of Silicon Carbide Power Bipolar Junction Transistors
Open this publication in new window or tab >>Fabrication and Characterization of Silicon Carbide Power Bipolar Junction Transistors
2008 (English)Doctoral thesis, comprehensive summary (Other scientific)
Abstract [en]

Silicon carbide bipolar junction transistors (BJTs) are attractive power switching devices because of the unique material properties of SiC with high breakdown electric field, high thermal conductivity and high saturated drift velocity of electrons. The SiC BJT has potential for very low specific on-resistances and this together with high temperature operation makes it very suitable for applications with high power densities. For SiC BJTs the common emitter current gain (β), the specific on-resistance (RSP_ON), and the breakdown voltage are important to optimize for competition with silicon based power devices. In this thesis, power SiC BJTs with high current gain β ≈ 60 , low on-resistance RSP_ON ≈ 5 mΩcm2, and high breakdown voltage BVCEO ≈ 1200 V have been demonstrated. The 1200 V SiC BJT that has been demonstrated has about 80 % lower on-state power losses compared to a typical 1200 V Si IGBT chip.

A continuous epitaxial growth of the base-emitter layers has been used to reduce interface defects and thus improve the current gain. A significant influence of surface recombination on the current gain was identified by comparing the experiments with device simulations. In order to reduce the surface recombination, different passivation layers were investigated in SiC BJTs, and thermal oxidation in N2O ambient was identified as an efficient passivation method to increase the current gain.

To obtain a low contact resistance, especially to the p-type base contact, is one critical issue to fabricate SiC power BJTs with low on-resistance. Low temperature anneal (~ 800 oC) of a p-type Ni/Ti/Al contact on 4H-SiC has been demonstrated. The contact resistivity on the ion implanted base region of the BJT was 1.3 × 10-4 Ωcm2 after annealing. The Ni/Ti/Al p-type ohmic contact was adapted to 4H-SiC BJTs fabrication indicating that the base contact plays a role for achieving a low on-resistance of SiC BJTs.

To achieve a high breakdown voltage, optimized junction termination is important in a power device. A guard ring assisted Junction Termination Extension (JTE) structure was used to improve the breakdown voltage of the SiC BJTs. The highest breakdown voltage of the fabricated SiC BJTs was obtained for devices with guard ring assisted JTE using the base contact implant step for a simultaneous formation of guard rings.

As a new approach to fabricate SiC BJTs, epitaxial regrowth of an extrinsic base layer was demonstrated. SiC BJTs without any ion implantation were successfully demonstrated using epitaxial regrowth of a highly doped p-type region and an etched JTE using the epitaxial base. A maximum current gain of 42 was measured for a 1.8 mm × 1.8 mm BJT with a stable and reproducible open base breakdown voltage of 1800 V.

Place, publisher, year, edition, pages
Stockholm: KTH, 2008. xvi, 74 p.
Series
Trita-ICT/MAP AVH, ISSN 1653-7610 ; 2008:01
Keyword
silicon carbide, power device, BJT, current gain, specific on resistance (RSP_ON), breakdown voltage, forward voltage drop, surface recombination, ohmic contact.
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-4623 (URN)
Public defence
2008-02-15, Sal E, Forum, Isafjordsgatan 39, Kista, Stockholm, 10:15
Opponent
Supervisors
Note
QC 20100819Available from: 2008-01-30 Created: 2008-01-30 Last updated: 2010-08-19Bibliographically approved

Open Access in DiVA

No full text

Other links

Publisher's full textScopus

Authority records BETA

Zetterling, Carl-Mikael

Search in DiVA

By author/editor
Lee, Hyung-SeokDomeij, MartinZetterling, Carl-MikaelÖstling, Mikael
By organisation
Microelectronics and Applied Physics, MAP
In the same journal
Materials Science Forum
Engineering and Technology

Search outside of DiVA

GoogleGoogle Scholar

doi
urn-nbn

Altmetric score

doi
urn-nbn
Total: 93 hits
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf