SiC and GaN Devices in the Mainstream - Achievements, Challenges and Perspectives

1:00 pm - 1:40 pm

Silicon has been the primary selection for power semiconductor devices because the devices are cheap, readily available, reliable and well-known in general. However, silicon is more and more reaching its physical limits, such that the progress becomes slow and the required technology becomes expensive. The best alternative for powersemiconductor devices is wide band-gap materials because the on-resistance scales with about the cube of the material’s critical breakdown field. Consequently, silicon carbide (SiC) and gallium nitride (GaN) have made theirway into the mainstream of power semiconductor devices. While lateral GaN-HEMTs are yet limited to a few100 V of blocking capability and a few 10 A, vertical SiC MOSFET-technology has its sweet spot between 600 Vand 3.3 kV and is not limited in current.

However, the semiconductor chip itself is only part of the story. To fully exploit the benefits of WBG devices, the package and the circuitry around has to cope with the capabilities of the chip. In fact, WBG devices can switchmuch faster than silicon IGBTs and cause much lower switching losses. This would enable much higher operation frequencies and can reduce the size (and cost) of other circuit components significantly. To achieve that, parasitic components of the package, especially stray inductances, must be extremely low. Furthermore, the chip could survive much higher temperatures than silicon components, but the packaging materials have to withstand these higher temperatures as well, which usual package materials cannot. And higher temperature swings during operation are also critical because SiC is stiffer than silicon and introduces more stress into joints at the same temperature swing. Thus, the full potential of SiC and also GaN chips is by far not utilised yet.

On top, the materials themselves have their peculiarities. Under electron-hole-plasma operation the SiC crystal degrades due to expanding defects! And due to interface states, the inversion channels of the SiC-MOSFETsshow low electron mobilities. Some of the interface states get charged during gate bias and do not discharge quickly again, thus causing threshold drift or even permanent degradation. In GaN, the gate has its challenges, too, and the insulation of the device towards the substrate is still limiting the blocking capability and performance. After all, there is still considerable development effortrequired, while WBG is conquering a significant market share already.

Featured Speakers

Prof. Nando Kaminski (invited)

Professor and Director, University of Bremen

Nando Kaminski has been full professor for power semiconductor devices at University of Bremen since 2008. He has been one of two directors of the Institute for Electrical Drives, Power Electronics, and Devices (IALB). His research interests include alternative semiconductor materials, material basics, device concepts, simulation, packaging, reliability, influence of parasitics, and EMC.

From 1998 until 2008 Nando Kaminski was with ABB Semiconductors in Lenzburg, Switzerland. He worked on IGBTs, IGCTs, diodes, packaging, and reliability. He held various positions as project, team, laboratory, and customer support manager in R&D and quality before he finally became department manager and head of the IGBT module factory.

Nando Kaminski studied electrical engineering at the University of Bremen and finished with the Dipl.-Ing. degree (with distinction) in 1994. Afterwards until 1998, he was researcher and PhD-candidate at the former Daimler-Benz research institute in Frankfurt (Main), Germany. He worked on Silicon-Carbide power devices and received the Dr.-Ing. degree (summa cum laude) in 2001 from University of Bremen.