A Megawatt Milestone for Power Electronics

Power electronics are responsible for controlling the flow of electricity in everything from electric vehicles to industrial machinery. As these systems become more powerful, the semiconductors that make them work need to handle increasingly high voltages and currents without overheating or breaking down. Researchers have been developing new semiconductor materials to meet these demands, and a team from the University of Hong Kong, Virginia Tech, and Nanjing University has now demonstrated a gallium oxide power module capable of switching an impressive one megawatt of power.

The research, published in Nature Communications, describes a new approach to building high-power semiconductor modules using gallium oxide (Ga₂O₃), a semiconductor material with an ultra-wide bandgap. Compared with silicon, gallium oxide can withstand much stronger electric fields and operate at higher temperatures. These properties make it particularly attractive for applications that require short bursts of enormous electrical power, such as pulsed lasers, medical imaging equipment, and nuclear fusion systems.

The heat is on

But gallium oxide has a problem. Despite its impressive electrical properties, it doesn't conduct heat particularly well. That makes it difficult to prevent devices from overheating when large currents flow through them. Until now, gallium oxide power devices demonstrated in switching circuits have generally been limited to the kilowatt range.

The researchers solved this problem by redesigning how the semiconductor devices are packaged. Their approach uses a flip-chip configuration that places the active side of the gallium oxide die directly against a copper substrate, allowing heat to escape more efficiently. A thin layer of barium titanate (BaTiO₃), just 300 nanometers thick, helps control electric fields near the edges of the semiconductor, preventing electrical breakdown.

This arrangement also eliminates the need for a supporting post that would otherwise interfere with heat dissipation. Testing showed that the new packaging reduced thermal resistance by more than 50%, from 1.05 K/W to just 0.47 K/W. Individual devices could also withstand reverse voltages exceeding 2,000 volts and operate at temperatures up to 250 degrees Celsius.

One megawatt, six chips

To demonstrate the technology at a larger scale, the team combined six gallium oxide diode submodules into a single power module. The resulting device successfully switched 1,000 volts at 1,000 amps, achieving a peak switching power capacity of one megawatt. It operated with repetitive pulses at a frequency of 1 kHz and demonstrated a turn-off time of just 23 nanoseconds.

That's more than 100 times the switching power capacity previously demonstrated by ultra-wide bandgap semiconductor devices. The researchers also measured a pulsed power capacity density exceeding 1.8 MW/cm², outperforming comparable silicon and silicon carbide devices under the tested conditions.

There is still work to be done before gallium oxide modules like this find their way into commercial equipment. The demonstration focuses on pulsed-power operation rather than continuously delivering a megawatt, and the researchers have not established that the technology is ready for mass production. Nevertheless, the results show that gallium oxide could have a bright future in applications where handling enormous bursts of electrical power is necessary.