Ultra-Wide-Bandgap Power Electronics

June 1, 2018

Sandia National Laboratories, Albuquerque, New Mexico

Power electronics used for routing, control, and conversion of electrical power traditionally utilize silicon semiconductors. These systems tend to be bulky, require active cooling, and are inadequate for applications demanding portable power conversion requirements (e.g., distributed power generation, vehicles, and satellites).

Researchers have grown ultra-wide-bandgap (UWBG) AlGaN materials, and from them, fabricated an Al_0.3Ga_0.7N PiN diode with a breakdown voltage greater than 1600V, and an AlN/Al_0.85Ga_0.15N high electron mobility transistor with a breakdown voltage greater than 800V. These devices can be used as building blocks to make next-generation power electronics for transferring electrical power from a source to a load, and converting voltages, currents, and frequencies.

The UWBG power semiconductor devices can eventually miniaturize and vastly improve the performance and efficiency of power systems for electrical power grids, electric vehicles, computer power supplies, and motors. The device performance, defined by breakdown voltage and electrical conductivity, is ultimately determined by the bandgap of the material utilized. Compared with silicon (Si), and even with commercial state-of-the-art wide-bandgap (WBG) materials, UWBG AlGaN materials (with bandgaps larger than SiC and GaN) have the potential to dramatically improve device performance and operate at even higher voltages, frequencies, and temperatures.

Different materials for power semiconductor devices are compared through a Figure of Merit (FOM) that quantifies the tradeoff between electrical conductivity and breakdown voltage. The FOM scales with the seventh power of the bandgap; thus, realizing devices in wide-bandgap GaN rather than Si improves FOM by 870 times. Another factor of 37 times is gained in FOM by moving to ultra-wide-bandgap AlN from wide-bandgap GaN.

Because these power electronic devices could enable 10 times faster switching speeds than the current state of the art, passive components in the power circuits can be smaller, and thus virtually every electrical power conversion system can be miniaturized commensurately. At the same time, the devices can function at higher operating temperatures without active cooling, and in high-radiation environments such as outer space.

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