Building Blocks for GaN Power Switches

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CREDIT: Zongyang Hu" height="521" width="820">

A state-of-the-art design of GaN p-n junction diodes that has resulted in near-unity ideality factor, avalanche breakdown capability, and record-breaking power performance. Insets show a GaN p-n diode fabricated on a high-quality bulk GaN substrate and light emission from the junction under forward bias.
CREDIT: Zongyang Hu

The work is significant because many researchers around the globe are working to find ways to make GaN materials reliable for use within future electronics. Due to the presence of defects with high concentrations in typical GaN materials today, GaN-based devices often operate at a fraction of what GaN is truly capable of.

It’s worth noting that, in 2014, a Nobel Prize in physics was awarded to three scientists for making seminal and breakthrough contributions to the field of GaN-based LEDs. Though operating at compromised conditions, GaN LEDs are helping to shift the global lighting industry to a much more energy-efficient, solid-state lighting era.

The work led by Xing at Cornell University is the first report of GaN p-n diodes with near-ideal performance in all aspects simultaneously: a unity ideality factor, avalanche breakdown voltage, and about a two-fold improvement in device figure-of-merits over previous records.

“Our results are an important step toward understanding the intrinsic properties and the true potential of GaN,” Hu noted. “And these achievements are only possible in high-quality GaN device structures (an effort led by IQE engineers) prepared on high-quality GaN bulk substrates and with precisely tuned fabrication technologies (an effort led by Dr. Kazuki Nomoto, a research associate at Cornell University).”

One big surprise for the team came in the form of unexpectedly low differential-on-resistance of the GaN diode. “It’s as if the body of the entire p-n diode is transparent to the current flow without resistance,” he said. “We believe this is due to high-level injection of minority carriers and their long lifetime, and are exploring it further.”

The team’s work is part of the U.S. Department of Energy’s (DOE) Advanced Research Projects Agency-Energy (ARPA-E) “SWITCHES” program, monitored by Dr. Timothy Heidel. “Leading one of these projects, we at Cornell, in collaboration with our industrial partners IQE, Qorvo, and UTRC, have established an integrated plan to develop three terminal GaN power transistors, package them, and insert them into circuits and products,” Xing said.

Beyond the DOE ARPA-E project, the team is open to collaboration with any researchers or companies interested in helping drive GaN power electronics to its fruition.

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