Contributing to history: Yulin He wins CS MANTECH award

2/15/2023 Cassandra Smith

Written by Cassandra Smith

The University of Illinois Urbana-Champaign is leading in ultrafast transistor research. That domination has spanned decades and is evident today. A student with The Grainger College of Engineering earned a prestigious award for her paper contributing to that heritage. 

The Journey Begins

The project was started in 2016 by student Yu-Ting Peng (Electrical & Computer Engineering). She graduated in 2021 (Now works for Apple) and passed on the work to Yulin He, her mentee. He, an undergraduate student in HMNTL, continued building on Peng’s work and the legacy of this work that started more than 30 years ago. 

The hybrid etching process was exhibited by producing double heterojunction bipolar transistors (DHBTs) from 4-inch epitaxial wafers commercially grown by MBE (IntelliEpi) on semi-insulating InP substrates. “Compared to previously reported devices, the InP DHBTs of this work—with a thicker collector and lateral scaling, well controlled by hybrid etching—achieve a higher breakdown voltage at the same fT," said He in Compound Semiconductor. Formed with a combination of both dry and wet etching, the transistors give a breakdown voltage of more than 11 V, an fT of 135 GHz, and an fmax of 245 GHz (see Figure 1). This form of InP DHBT is promising for millimeter-wave 5G. The value for fmax  is around four times that for the 5G millimeter-wave bands found at 26 GHz, 28 GHz, and 39 GHz. The high breakdown voltage makes the device agreeable for operating in the 3-5 V range while allowing for any voltage fluctuations. These devices will play in future mobile networks and other applications. 

Graphic of Yulin He and team's work.
Figure 1

HSIC group has conducted microwave and millimeter-wave transistor and integrated circuit (IC) research since 1991. Principal Investigator Dr. Milton Feng (Electrical & Computer Engineering) said their research has helped establish a lot of the wireless ICs around the U.S. “We made [the] first reliable GaAsP HBT (collaborated with Professors Stillman and Holonyak group for dissevered C-doped in HBT base) for 3/4G Power Amplifier[s] used in industry since 1991.” In 2002, they reported the world record transistor speed (> 700 GHz) at IEDM, a prestigious device conference. Their work put UIUC on the map for their excellence in transistor research and He’s paper continued to show that tradition.

The group’s most recent work was not easy. Feng stated it does not happen overnight and He echoed his sentiment by applauding the university for their dedication to this project. She said they had high standards in their lab and constantly asked for maintenance work to help with result replication. 

Hard Work Pays Off

With great effort came great reward for He. She received the “Best Student Paper” award through CS MANTECH. This organization creates “a forum for members of the compound semiconductor community to exchange and discuss new ideas to better serve the public in general,” according to their website. 

He said to be involved with their conference is a great honor. While most of the conference population is comprised of members of industry, there are some who come from universities. He stated those students are encouraged to participate in the lively discussion of what’s next for technology and treated like colleagues. “It’s the greatest conference I’ve ever been to,” she said. 

“It is a great honor for her to receive the award in the 2022 International CS MANTECH since this is the first paper she wrote and presented in the prestigious conference,” said Feng. “I am very proud of her high-quality research and [it is] well-deserved.” Feng said He will get to go to the 2023 conference in Orlando, Florida in May. 

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This story was published February 15, 2023.