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A Comprehensive Study on the Geometrical Effects in High Power 4H-SiC BJTs
KTH, School of Information and Communication Technology (ICT), Integrated Devices and Circuits.ORCID iD: 0000-0002-7510-9639
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: 0000-0001-8108-2631
KTH, School of Information and Communication Technology (ICT), Integrated Devices and Circuits.
2016 (English)In: IEEE Transactions on Electron Devices, ISSN 0018-9383, E-ISSN 1557-9646Article in journal (Refereed) Published
Abstract [en]

Geometrical effects on the forward characteristics of high-power bipolar junction transistors are studied.An implantation-free area optimized junction termination is implemented in order to have a stable breakdown voltage. The effect of varying the emitter-base geometry, i.e., the emitter width (WE), the base width (WB), emitter contact–emitter edge distance (Wn), and base contact–emitter edge (Wp) on the on-state characteristics is studied in the different emitter cell geometries. The emitter size effect shows the highest influence on the current gain (β). It shows a significant effect on the β (single finger design, about 61%; square cell geometry, about 98%;hexagon cell geometry, about 90%). The base size effect also shows a significant improvement on the β of about 23% at a given WE.

Place, publisher, year, edition, pages
Institute of Electrical and Electronics Engineers (IEEE), 2016.
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
URN: urn:nbn:se:kth:diva-197700DOI: 10.1109/TED.2016.2631303OAI: oai:DiVA.org:kth-197700DiVA: diva2:1052927
Note

QC 20161208

Available from: 2016-12-07 Created: 2016-12-07 Last updated: 2016-12-09Bibliographically approved
In thesis
1. Silicon Carbide Technology for High- and Ultra-High-Voltage Bipolar Junction Transistors and PiN Diodes
Open this publication in new window or tab >>Silicon Carbide Technology for High- and Ultra-High-Voltage Bipolar Junction Transistors and PiN Diodes
2017 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Silicon carbide (SiC) is an attractive material for high-voltage and high-temperature electronic applications owing to the wide bandgap, high critical electric field, and high thermal conductivity. High- and ultra-high-voltage silicon carbide bipolar devices, such as bipolar junction transistors (BJTs) and PiN diodes, have the advantage of a low ON-resistance due to conductivity modulation compared to unipolar devices. However, in order to be fully competitive with unipolar devices, it is important to further improve the off-state and on-state characteristics, such as breakdown voltage, leakage current, common-emitter current gain, switching, current density, and ON-resistance.

In order to achieve a high breakdown voltage with a low leakage current, an efficient and easy to fabricate junction edge protection or termination is needed. Among different proposed junction edge protections, a mesa design integrated with junction termination extensions (JTEs) is a powerful approach. In this work, implantation-free 4H-SiC BJTs in two classes of voltage, i.e., 6 kV-class and 15 kV-class with an efficient and optimized implantation-free junction termination (O-JTE) and multiple-shallow-trench junction termination extension (ST-JTE) are designed, fabricated and characterized. These terminations result in high termination efficiency of 92% and 93%, respectively.

The 6 kV-class BJTs shows a maximum current gain of β = 44. A comprehensive study on the geometrical design is done in order to improve the on-state performances. For the first time, new cell geometries (square and hexagon) are presented for the SiC BJTs. The results show a significant improvement of the on-state characteristics because of a better utilization of the base area. At a given current gain, new cell geometries show a 42% higher current density and 21% lower ON-resistance. The results of this study, including an optimized fabrication process, are utilized in the 15 kV-class BJTs where a record high current gain of β = 139 is achieved.

Ultra-high-voltage PiN diodes in two classes of voltage, i.e., 10+ kV using on-axis 4H-SiC and 15 kV-class off-axis 4H-SiC, are presented. O-JTE is utilized for 15 kV-class PiN diodes, while three steps ion-implantation are used to form the JTE in 10+ kV PiN diodes. Carbon implantation followed by high-temperature annealing is also performed for the 10+ kV PiN diodes in order to enhance the lifetime. Both type diodes depict conductivity modulation in the drift layer. No bipolar degradation is observed in 10+ kV PiN diodes.

Place, publisher, year, edition, pages
KTH Royal Institute of Technology, 2017. 126 p.
Series
TRITA-ICT, 2017:02
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Research subject
Information and Communication Technology
Identifiers
urn:nbn:se:kth:diva-197913 (URN)978-91-7729-183-1 (ISBN)
Public defence
2017-01-20, Ka-Sal C (Sal Sven-Olof Öhrvik), KTH, Kistagången 16, Kista, 10:00 (English)
Opponent
Supervisors
Funder
StandUpSwedish Energy AgencySwedish Research Council
Note

QC 20161209

Available from: 2016-12-09 Created: 2016-12-09 Last updated: 2016-12-21Bibliographically approved

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Salemi, ArashElahipanah, HosseinZetterling, Calr-MikaelÖstling, Mikael
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