Ying is a Ph.D. student in the Georgia Tech School of Electrical and Computer Engineering (ECE). He works in the SiGe Devices and Circuits Group, where he is advised by John D. Cressler, ECE’s Schlumberger Chair Professor in Electronics. 

Ying's award-winning paper, “DC and RF Variability of SiGe HBTs Operating Down to Deep Cryogenic Temperatures,” was co-authored with J.W. Teng, G.N. Tzintzarov, A.P. Omprakash, S.G. Rao, U. Raghunathan, A. Ildefonso, and S. Fernandez—all students in the SiGe Devices and Circuits Group–and Cressler. This work studies the effect of temperature on the variability of silicon germanium (SiGe) heterojunction bipolar transistors (HBTs) down to a cryogenic temperature of 7 K (-266 °C).

For cryogenic applications such as quantum computing, it is desirable to operate electronics near the physical qubit. The further the qubit sits from the processing circuits, the more noise gets introduced in between them, and the signal to noise ratio degrades. However, bringing the electronics closer to the qubit is challenging, because the qubit is situated at cryogenic temperatures as low as a few tens of millikelvin. 

Because of those conditions, extensive testing and modeling is needed for successful design of any circuits and systems at those temperatures. Though SiGe HBTs have been a good candidate for cryogenic circuits, potential concerns for SiGe HBTs need to be mitigated, one of which is the increasing variability. This work quantifies the variability through measurement data and is the first work to report such data. The information and guidelines provided in this work can lead to more consistent circuit performance and higher yield for cryogenic circuits.