Introducing EeroQ’s Fabrication Engineer: Dr. Heejun Byeon
Dr. Heejun Byeon is EeroQ’s extremely talented and hardworking Fabrication Engineer. Heejun makes all of EeroQ’s single and multi-electron devices. In addition to his technical prowess in the cleanroom, Heejun brings many years of expertise with “electrons-on-helium.” Every week, our jaws drop when Heejun shows us beautiful microscope images of the quantum devices he is fabricating. He’s an indispensable part of the team, so we decided to ask Heejun some questions to highlight his crucial role at EeroQ, what he enjoys about his work, and why he thinks electrons trapped above the surface of superfluid helium are a compelling quantum computing platform.
Tell us a little about your background. When did you start at EeroQ? Where are you from? Did you work somewhere else before coming to EeroQ? What subject did you focus on for your PhD?
I worked at the Samsung LCD lab for seven years developing high-mobility thin film transistors for next-generation displays. Then, I joined and completed my PhD at Michigan State University from 2015 to 2020. During my PhD I performed the first experiments integrating high-frequency surface acoustic wave devices with electrons-on-helium, and my PhD supervisor was Prof. Johannes Pollanen, who is one of the co-founders and CSO of EeroQ. In 2021, I studied solid-state single photon emitters as a postdoctoral researcher at Sandia National Lab for one year. I started working at EeroQ in 2022.
A two-dimensional electron system floating above the superfluid helium surface is a very simple but interesting system at the same time. Its ultra-clean environment and lack of defects and impurities that exist in most other condensed matter systems make this system a perfect candidate for quantum computing due to the possibility of long-lived qubits.
What’s a problem or challenge that you were able to solve and tackle that has enabled technical progress at EeroQ?
To enable simple routing of on-chip electrodes and kill spurious modes of our superconducting microwave resonators, I set up an aluminum airbridge fabrication process. This is now a key process for every device EeroQ has made since then. Our Wonder Lake chip from Skywater, a semiconductor fabrication foundry, is a CMOS compatible electron-on-helium chip for future qubit operation. For this chip, I developed a cyclic dry etching process to remove electrostatic discharge damage to the device.
What are your main responsibilities at EeroQ? In other words, what does your day to day look like?
I’m in charge of fabricating electron-on-helium devices. I spend most of my time working in the Pritzker Nanofabrication Facility cleanroom located at the University of Chicago. Half of my work is running EeroQ’s whole fabrication process to make physical devices which will be measured and characterized. The other half is to develop new fabrication processes and to solve unexpected fab issues.
What is something you think you bring to the technical team that is unique or valuable?
I can fabricate new devices weekly once a new process is set up and stabilized. This can be a huge benefit especially for a start-up that needs to make progress quickly. The Pritzker Nanofabrication Facility is a multi-user facility and thus there is always some chance for unexpected issues to arise. Almost every fab issue can be quickly analyzed and solved due to my many years of experience at Samsung. I help EeroQ move faster by minimizing these unexpected fab delays.
Why did you decide to join EeroQ?
Electrons on helium are very familiar to me since it was my PhD research area. Theoretically, this system is well studied and a long spin coherence time is predicted. At the same time, large scalability can be also easily achieved with mature semiconductor technology. I’m really interested in physically building a qubit platform with electrons on helium and demonstrating this prediction. That’s why I joined EeroQ.
What’s your favorite part about working at EeroQ?
And finally, Heejun, we have a couple of bonus questions. What’s your favorite Fajita Friday food? What’s a fond memory that you have of EeroQ? What’s the best Chicago deep dish spot? And what’s your favorite Chicago weekend activity?