U of I researchers overcome significant hurdle to making high-power semiconductors

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Gallium oxide (Ga2O3) is an inorganic chemical compound of gallium and oxygen that is water-insoluble and appears as a white, odorless, crystalline powder.

Thanks to its ultrawide bandgap, gallium oxide has many promising applications in power electronics. Compared to leading semiconductor materials, silicon (SiC), and gallium nitride (GaN), gallium oxide offers potentially significant performance improvement.

But there’s an issue exclusive to gallium oxide, and that is its complex crystal structure that is tough to control during the semiconductor fabrication process.

Now, researchers at the University of Illinois have unveiled a new technique that allows making high-power semiconductors based on gallium oxide.

New Fabrication Technique for Gallium Oxide High-Power Semiconductors

As a member of an emerging class of wide bandgap materials, gallium oxide, more specifically beta-gallium oxide (β-Ga2O3), has a great potential as a high-power semiconductor material.

Yet, it suffers from a similar major setback as silicon. Transistors made of these materials can only get smaller and smaller as the laws of physics allow them to be until we can’t go any further.

As a solution to this semiconductor fabrication bottleneck, electrical engineers at the University of Illinois (U. of I.) have thought of “going vertical”  to increase the surface area on a chip.

They were able to achieve this thanks to a new technique they developed called metal-assisted chemical etching, or MacEtch for short. Per the researchers, this method is “superior to traditional ‘dry’ etching techniques because it is far less damaging to delicate semiconductor surfaces, such as beta-gallium oxide.”

Using MacEtch with a chemical solution based on gallium oxide crystals, the U. of I. team etched semiconductor into 3D fin-like structures that increase the chip’s surface area. With room for more transistors, the chip’s power will significantly increase while its footprint remains the same.

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While the research demonstrates the MacEtch technique’s potential in serving the semiconductor industry, there are two main shortcomings that the team needs to remedy.

First, the etching itself is too slow due to the complex crystal structure of gallium oxide. Second, the 3D fins obtained aren’t perfectly vertical, a requirement for efficient power use.

The method produced triangular, trapezoidal, and tapered fins, but the researchers were surprised to find that these shapes still perform better than the flat, unetched surfaces.

“We are not sure why this is the case, but we are starting to get some clues by performing atomic-level characterizations of the material. The bottom line is that we have shown it is possible to use the MacEtch process to fabricate beta-gallium oxide, a potentially low-cost alternative to gallium nitride, with good interface quality.”

The team thinks that by increasing the etch rate, they would be able to improve the process and produce more vertical fins, and this is what they’d be focussing on next.

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