University at Buffalo Engineers Develop A Transistor That Can Handle 8,000 VoltsJune 23, 2020 by Luke James
The gallium oxide-based MOSFET, which is about as thin as a single sheet of paper, could help make large and bulky batteries and power systems, such as those used in electric vehicles, smaller.
Metal-oxide semiconductor field-effect transistors (MOSFETs) are commonly used components in all kinds of electronic devices, however, they are especially prevalent in the automotive sector where they are a crucial component used to switch high-power electronics on and off extremely quickly.
Now, University at Buffalo electrical engineers aim to take MOSFETs one step further by basing them on gallium oxide, something which has enabled the team to work out how to handle extremely high voltages of more than 8,000 V.
In a study published by the research team in the June edition of IEEE Electron Device Letters, the team of electrical engineers describe how their tiny electronic switch is able to handle such a high voltage despite its super small and thin profile.
Gallium Oxide’s ‘Elite’ Bandgap
The Buffalo research team have been studying the potential of gallium oxide for quite some time, and previous works by the team include exploring transistors made from the material. Their reason for placing so much focus on gallium oxide is its bandgap—the amount of energy required to jolt an electron into a conducting state.
Systems that use materials with wider bandgaps can be thinner, lighter, and handle more power than systems that use materials with lower bandgaps. Gallium oxide’s bandgap is around 4.8 electron volts which, according to the research team, places it among an “elite” group of materials.
In contrast, the most commonly used material in power electronics, silicon, has a bandgap of 1.1 electron volts, and potential replacements for silicon such as silicon carbide (SiC) and gallium nitride (GaN) have about 3.4 and 3.3 electron volts respectively. It is because of gallium oxide’s ultrawide bandgap that the team’s electronic switch could be thinned down to the width of a piece of paper.
MOSFETS, like the one pictured above, are used to power electric vehicles and other electronic devices. The Buffalo team's gallium oxide design may make them more efficient. Image credited to SparkFun Electronics
As for the material’s ability to handle such a high voltage despite being so small, this was achieved using a chemical process known as “passivation.” This involves coating the electronic switch device in a layer of SU-8, an epoxy-based polymer commonly used in microelectronics, to reduce the chemical reactivity of its surface.
Following tests, the team’s results demonstrated that the transistor can handle 8,032 volts before breaking down, which is more than transistors designed from SiC and GaN. And the higher the breakdown voltage, the more power a device is able to handle. "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.
Smaller and More Efficient Electronic Systems
The research team’s new transistor could lead to smaller and more efficient electronic systems that control and convert electric power in applications such as electric vehicles, airplanes, and locomotives.
“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,” Singisetti added. With more efficient electronic power systems, these vehicles could travel further and run for longer between charge cycles.