Spyridon (Spyros) Pavlidis received the European Microwave Conference (EuMC) Young Engineer Prize at the 45th European Microwave Conference (part of European Microwave Week), held September 6-11 in Paris, France. A Ph.D. student in the Georgia Tech School of Electrical and Computer Engineering (ECE), Pavlidis is the first student from Tech to win this honor.

This award is given to a young engineer who presented an outstanding paper at the European Microwave Conference and who is under the age of 30, the first author on the paper, and the presenter in an oral or poster session.

Pavlidis’ work was sponsored by I2R Nanowave, based in Atlanta, as well as by his Air Force Research Lab (AFRL)/Oak Ridge Institute for Science and Education (ORISE) fellowship. He is co-advised by ECE Professors Oliver Brand and John Papapolymerou.

Pavlidis was recognized for his paper entitled “A 5.4W X-Band Gallium Nitride (GaN) Power Amplifier in an Encapsulated Organic Package;” his coauthors on the paper are Ahmet Cagri Ulusoy, a research engineer in the Georgia Electronic Design Center (GEDC), and Papapolymerou.

High performance radar and telecommunications systems place stringent requirements on both electronics and packaging. In recent years, GaN, a wide bandgap semiconductor compound from the III-V groups in the periodic table, has received much attention due to its ability to handle high power and operate at microwave- and millimeter-wave frequencies. Therefore, power amplifiers (PAs) made with GaN technology are characterized by large power densities and have been traditionally wire-bonded on high thermal conductivity substrates, such as copper (Cu) or aluminum nitride (AlN). These materials are expensive and/or lossy, which can limit the overall system's performance. On the other hand, liquid crystal polymer (LCP), an organic laminate that is low-cost, ultra thin (down to 25 microns), near hermetic, and low-loss up to 170 GHz has been overlooked due to its poor thermal conductivity.

In the team's work, this thermal limitation is overcome through using a multi-layer stack-up of LCP that permits a GaN device or MMIC to be encapsulated within the package structure, while simultaneously attaching the backside of the chip to a heatsink. Moreover, the chip is flip-chip bonded instead of wire-bonded, reducing interconnect parasitics and improving wideband performance. The thermal performance of the package and its impact on device reliability were evaluated using a combination of infrared (IR) temperature and pulsed current-voltage (I-V) measurements. Ultimately, the full potential of this package was demonstrated through the design, fabrication, and characterization of an X-Band (8-12 GHz) PA. At 10.2 GHz, the PA showed a power added efficiency (PAE) of 38% and saturated output power (PSAT) of 5.4W under continuous-wave (CW) operation, or 49% PAE and 7W PSAT when pulsed at 50% duty cycle.

This is the first time that an encapsulated flip-chip based package using organics has been demonstrated for reliable and high-power operation of GaN amplifiers. With the thermal and RF performance of this package verified, future work will focus on the design of a wideband PA in order to leverage the advantages of the flip-chip interconnect.

This team’s paper was also recognized as a top four finalist for the overall EuMC Microwave Prize for the best contributed paper to the conference. Approximately 900 papers were submitted for consideration, of which only 50% were accepted for presentation and publication. Therefore, the paper was considered to be in the top 4 out of 450 entries, or in the top 1%.

Cutline for group photo: Pictured with Spyros Pavlidis (center) are Wilhelm Gruener (left), employee of Airbus Defence and Space, which sponsored the EuMC Young Engineer Prize, and Jean-François Villemazet (right), employee of Thales Alenia Space and EuMC 2015 co-chair.