Oliver Haeberlen

Si, SiC and GaN power devices: An unbiased view on key performance indicators

This paper discusses key parameters such as capacitances & switching losses for silicon, SiC and GaN power devices with respect to applications in switch mode power supplies. Whereas wide bandgap devices deliver roughly one order of magnitude lower charges stored in the output capacitance, the energy equivalent is nearly on par with latest generation super junction devices. Silicon devices will hence prevail in classic hard switching applications at moderate switching frequencies whereas SiC and GaN based power devices will play to their full benefits in resonant topologies at moderate to high switching frequencies.

GaN virtual prototyping: From traps modeling to system-level cascode optimization

The present paper focuses on the system-level optimization of GaN technology for high voltage applications. We will show that a key requirement for the future success of the GaN technology is the full system-optimization achieved by a simultaneous optimization of technology, packaging and applications. We will also show that Virtual Prototyping (VP) becomes, in GaN technology, a fundamental tool that allows not only to have a fundamental understanding of the device properties but more importantly it allows to strongly link device optimization, technology and system-level performance. In the present paper we will describe our view on the system-level optimization of high voltage GaN technology and present detailed simulations and comparison with experiments for both normally on isolated GaN transistors and cascoded GaN devices in real switching applications.

Off-state breakdown characteristics of AlGaN/GaN MIS-HEMTs for switching power applications

A consistent description of breakdown characteristics in ohmic-to-ohmic, ohmic-to-substrate and HEMT structures has been achieved by means of device simulations for a depletion-mode AlGaN/GaN MIS-HEMT technology on Si substrate suited for power switching applications. For relatively short gate-drain distances or ohmic-to-ohmic spacings, source-drain punch-through is suggested to be the limiting breakdown mechanism in either HEMTs under off-state conditions or ohmic-to-ohmic isolation test structures, respectively. The mechanism ultimately limiting the HEMT off-state voltage blocking capability is instead the vertical drain-to-substrate breakdown for long gate-drain spacings. The latter phenomenon is induced, in HEMTs on a low-resistivity p-type substrate like those considered here, by the triggering of a high-field carrier generation mechanism rather than by carrier injection.

Perspective of loss mechanisms for silicon and wide band-gap power devices

With the commercial availability of GaN and SiC-based power semiconductor devices having significantly improved material characteristics, there is a need to discuss the perspective of the underlying physical loss mechanisms of these devices versus their silicon counterparts. This article will compare latest generation Superjunction power transistors versus e-mode GaN HEMTs and SiC MOSFETs in terms of semiconductor losses and their potential for further improvement. A short application section will give practical information on best matching circuits for each device concept.