In conversation with Stefan Mönch

You work and write your thesis in the field of power electronics. What fascinates you about this subject?

Power electronics is theoretically able to convert energy nearly without losses. This basic concept motivates me to pursue the vision that one day every electric application is powered with maximum efficiency. The unfortunate reality, however, is that to date only few applications, such as solar inverters, use energy converters with an efficiency of over 99 percent. Most of the time, for example in billions of power supply units worldwide, a high transmission loss occurs and energy is wasted. The main reason for this problem is that silicon technology, even though it has been optimized for decades, increasingly reaches its physical limit and is not able to overcome the conflict between efficiency, compactness and cost. We at Fraunhofer IAF want to push these boundaries by researching alternative semiconductor materials that allow us to improve all three aspects at the same time.

What do you currently research, and what is your dissertation about?

In my research, I work with the semiconductor material gallium nitride (GaN) in order to approach the overarching goal of near loss-free electrical conversion. In my dissertation, I go even further by using GaN to increase more than just the efficiency:

I capitalize on the lateral geometry of GaN components via monolithic integration with the aim of realizing numerous functions and sensors, which used to be realized separately, in a single integrated GaN Power Circuit (GaN Power IC). I utilize GaN technology beyond the state of the art, considering that I reach better efficiency and higher compactness at the same time. However, the compactness of GaN ICs in combination with line voltage leads to capacitive coupling effects, a problem that is of no concern in common discrete circuits. My dissertation answers the question of how coupling effects occur and what impact they have on the performance of energy converters. With this new insight, we are able to take interdependency into account during the design of GaN ICs and even capitalize on their effect.

What’s more, these GaN circuits are as inexpensive as current solutions, since economical silicon is used as a carrier material (GaN-on-Si).

Where will your research be used?

GaN technology is not only a technological achievement, but also a real innovation for everyday applications. The first GaN technology has been available in electronic markets in the form of laptop chargers for a few weeks now. These devices are much more efficient and compact than former chargers, which makes them beneficial for end users. Additionally to common chargers, GaN power electronics will soon be used in many different applications that require high amounts of energy. We currently research GaN ICs for the use in e-cars or processor power supply. Wherever there is a need for large amounts of electrical energy, GaN is especially useful, as it allows saving this precious resource.

How can you combine your everyday work with your dissertation project?

Fraunhofer IAF provides me with the best possible environment for my dissertation. Our research builds upon an exceptional infrastructure and decades of expertise. Here I can do my dissertation exactly the way it should be: I can use state-of-the-art technology as a foundation and move beyond that point to study unknown aspects. In fact, the current state of GaN power electronics is actually based on the work, research and dissertations of my colleagues, which creates a motivating academic atmosphere.

In addition, the independence of the Fraunhofer-Gesellschaft offers enough freedom of research to realize novel ideas. At the same time, I get a feeling for industrial demands through projects, which allows me to keep my research relevant. Finally, the close collaboration with universities ensures that, alongside of developing technical solutions, we conduct close research of underlying scientific issues.

What do you cherish most about Freiburg and its surroundings?

The way to the institute is as short as the way into nature. Freiburg’s environment is very climate-friendly and has a comfortable city atmosphere, which fits the innovative research institute IAF perfectly. Here I can work on pioneering technologies for a sustainable and energy-efficient future.

What has been your personal highlight at Fraunhofer IAF?

To witness how the interplay of various people here at IAF allowed the idea of an integrated GaN circuit, an idea that I had years ago, to become reality in form of various devices that are being used by industrial research projects was great. The research results are not only an enormous achievement for us at Fraunhofer IAF, but they have become real highlights as they contribute to the improvement of everyday applications and even allow for completely new ones.

How would you describe Fraunhofer IAF briefly in three aspects?

Semiconductor innovation, application relevance and freedom of research.

Stefan Mönch researches at Fraunhofer IAF in the field of power electronics and writes his thesis on GaN Power ICs. Previously he worked as a research assistant at the University of Stuttgart, where he also did his bachelor’s and master’s degree in electro and information technology with focus on micro and power electronics.