MOSFET New gallium oxide-based transistor can handle 8,000 volts

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Researchers at the State University of New York Buffalo have developed transistors based on gallium oxide. Could they be a cheaper and more efficient alternative to transistors made from silicon carbide (SiC)?

Metal-oxide semiconductor field-effect transistors (MOSFETs) are components commonly used in electronic devices, however, they are most common in the automotive sector where they are used to switch high-power electronic systems on and off very quickly, a critical function.

Now, a new gallium oxide-based transistor, which is as thin as a piece of paper, is said to open up a plethora of potential opportunities for the development of compact, energy-efficient power electronics systems.

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Taking the MOSFET one step further

The transistor was developed by researchers at The State University of New York Buffalo (UB) who have been studying the potential of gallium oxide for several years and have published similar works involving gallium oxide transistors.

In particular, it is gallium oxide’s wider bandgap—the amount of energy required to jolt an electron into a conducting state—that has attracted particular attention from the UB research team. Systems that use materials with wider bandgaps can be thinner, lighter, and handle far more power than systems that use materials with lower bandgaps. At 4.8 electron volts, gallium oxide’s bandgap is over four times that of silicon’s (1.1 electron volts) placing it in an “elite” category of materials. It also has much higher bandgaps than other potential silicon replacements such as silicon carbide (SiC) with 3.4 electron volts and gallium nitride with 3.3 electron volts.

This time, the researchers decided to base a MOSFET on gallium oxide and found that despite its super small and thin profile thanks to the ultrawide bandgap, their transistor was able to handle extremely high voltages of 8,000 V.

Passivation

The material’s ability to handle such a high voltage stemmed from the use of a chemical process known as “passivation.” This involved coating the electronic switch device in a layer of epoxy-based polymer commonly used in microelectronics called SU-8. This reduced the chemical reactivity of the material’s surface.

After testing, the team’s results demonstrated that the transistor could handle up to 8,032 volts before breaking down, a far higher voltage than both SiC and GaN can handle. This is notable because the higher the breakdown voltage, the higher the power. "The passivation layer is a simple, efficient and cost-effective way to boost the performance of gallium oxide transistors,” says the study’s lead author, Uttam Singisetti.

Research & Development

Is gallium nitride (GaN) the silicon of the future?

It is thought that the UB team’s new ultrathin transistor could lead to the development of smaller and more efficient electronic systems that control and convert electric power. “To really push these technologies into the future, we need next-generation electronic components that can handle greater power loads without increasing the size of power electronics systems,” said Singisetti. With more efficient power systems, applications like electric vehicles could travel further between charge cycles.

The UB research team’s study can be found in the June edition of IEEE Electron Device Letters.

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