Thin as Paper, New Transistor Handles 8,000 Volts

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  • July 22, 2020

The most commonly used components in electronic devices are metal oxide semiconductor field-effect transistors, or MOSFETs. They’re essential for switching high-power electronics on and off instantly. Now, research by University at Buffalo engineers may improve the design and efficiency of these transistors and provide a breakthrough for electric vehicles.

The researchers discovered that MOSFETs based on gallium oxide can dramatically reduce the size and weight of automotive batteries. Thin as a paper sheet, the gallium oxide transistors can manage extremely high voltages of more than 8kV. The research was published in the June edition of IEEE Electron Device Letters.

Two features distinguish gallium oxide MOSFETs:

  • Gallium oxide bandgap
  • Passivation layer

The research focused on gallium oxide due to its bandgap, the amount of energy required to push an electron into a conducting stateThe most common material in power electronics, silicon, has a 1.1eV bandgap. In contrast, gallium oxide has an ultrawide 4.8eV bandgap. This causes a high electric field density of ~ 8MV/cm. 

Materials with wide bandgaps can manage more power than ones with lower bandgaps. Because of this, gallium oxide MOSFETs can be as thin as a sheet of paper. 

Gallium oxide MOSFETs can manage high voltages with a small size due to passivation, a chemical process that coats the device in an epoxy-based polymer commonly used in microelectronics (SU-8). The purpose of the process is to reduce the chemical reactivity of a surface. Research has shown that passivation improves breakdown voltages. 

“The passivation layer is a simple, efficient and cost-effective way to boost the performance of gallium oxide transistors,” said Uttam Singisetti, associate professor of electrical engineering at the University at Buffalo.

Ultimately, this new transistor could result in electronic systems that have increased efficiency and decreased size for use in locomotives, electric cars and airplanes to allow longer times between charge cycles.

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