Saving energy through innovative GaN power switches

It is estimated that up to 25% of electrical energy is lost due to electronic energy conversions. In Europe, this means that up to 730 TWh is lost, or an equivalent of 365 megatons of CO₂. The electronic energy conversions (for example, from AC to DC, or DC to DC at different voltage levels) are realized by power electronic circuits that typically contain several power switches. These power switches are either realized as discrete semiconductor components such as (Schottky) diodes, MOSFETs, or IGBTs; or as part of an IC in which the power switches are incorporated with dedicated circuitry to drive and control the power switches.

The vast majority of power switches or power electronic circuits are – still today – using silicon as the active semiconductor. Yet wide band gap semiconductors such as SiC and GaN hold better cards when it comes to energy conversion. Material properties such as higher critical electric fields at breakdown, higher mobilities associated with two-dimensional electron gases, and higher saturation velocities outperform silicon’s properties. As a result, devices made in these wide band gap materials can operate at frequencies, voltages and current levels beyond the reach of silicon, opening new paths for more efficient and more dense power electronic switches and circuits.

Of course, silicon can rely on decades of technological advancements driven (also) by the digital revolution. Wide band gap materials need to catch up and one of the main challenges is the growth of these crystals and their efficient use in power devices. GaN is typically grown epitaxially onto a silicon substrate whereby a complex layer stack is built consisting of several III-nitride layers (also containing AlGaN). The PhD candidate will strive to develop an optimum epitaxial stack through innovative designs with the ultimate goal to boost the performance of the GaN power switches. Therefore, the candidate will have to:

• contribute to innovative epitaxial layer stack design by exploring several routes in the active layers (spacers, back-barrier design, use of multi-channel layers, polarization engineering…)
• use numerical simulations (so-called Technology Computer Aided Design or TCAD) to help with the design and optimization of the power switches
• perform and analyse electrical measurements on power switches
• help with technological processing in the III-V lab for short-loop testing

The PhD student joins a team with over a decade of experience in processing, characterization and analyzing GaN switches in a top-notch research environment including latest simulation, characterization and fab tools. The student will receive a training by highly skilled professionals.