☰

β-Ga₂O₃ Power Devices

Gallium Oxide (Ga₂O₃), particularly its most stable form, β-Ga₂O₃, is a fascinating transparent oxide semiconductor with unique properties. Its exceptional wide bandgap of 4.8 eV transcends the category of “wide bandgap (WBG)” materials, placing it firmly in the realm of “Ultra-WBG” semiconductors. This opens exciting possibilities for its application in power electronics.

Doping β-Ga₂O₃ with Si, Ge, or Sn effectively enables n-type conductivity with remarkable efficiency. This paves the way for its potential application in the power electronics field, currently led by Silicon Carbide (SiC) and Gallium Nitride (GaN). In fact, according to Baliga's Figure of Merit (BFoM), a key measure of performance, β-Ga₂O₃ boasts one of the highest values among all known WBG materials. This remarkable combination of properties makes β-Ga₂O₃ a promising contender in the power electronics arena. Its potential to surpass established players like SiC and GaN is generating significant research interest, suggesting a bright future for this innovative material.

High current/breakdown MOSFETs and diodes are demonstrated in Ga₂O₃, showing its immense potential for high power applications. RF devices are also being investigated with the hope of achieving high frequency applications. Our work is mainly on fabrication and characterization of high breakdown voltage β-Ga₂O₃ MOSFET. We held a few records, including the first demonstration of Ga₂O₃ enhancement mode MOSFET (reported in 2016 Device Research Conference), the first kilo-volt breakdown field-plated Ga₂O₃ MOSFET at 1.85 kV (published on IEEE-Electron Device Letters(EDL)) and the highest breakdown voltage of 8 kV among all lateral MOSFETs ever made in any material (published on IEEE-EDL, reported on various news outlets). And we are continuing working on pushing the performance boundary by using innovative power MOSFET architecutre and designs.

Gold Rush for P-type/Current Blocking Layer in β-Ga₂O₃

For years, achieving p-type doping in gallium oxide (Ga₂O₃) has remained a tantalizing challenge, a persistent thorn in the side of researchers everywhere. While Ga₂O₃ boasts many remarkable properties, the absence of a suitable conducting blocking layer (CBL) stands as the main obstacle to realizing its full potential in vertical devices, a crucial step for its widespread adoption.

Despite theoretical predictions suggesting inherent limitations due to self-trapping holes in the valence band, the pursuit of an effective p-type dopant has never faltered. Recent glimmers of hope have emerged with findings that magnesium and nitrogen can partially compensate electrons, illuminating a path through the previously uncharted territory. This is just the beginning of a thrilling journey: the quest for effective p-type doping or current blocking in Ga₂O₃ for vertical power devices. To this end, we are heavily invested in the diffusion doping technology, especially utilizing Mg doped spin-on-glass as the diffusion source, to form an effective CBL. Its success promises to propel this versatile material towards a bright future in next-generation power electronics. This era is what the experts called 'The dawn of gallium oxide microelectronics’.

Application in Power Converters

To power the growing trend of electrification across industries, from electric vehicles to renewable energy farms, we need efficient and compact technology for converting electricity. This is where wide bandgap materials like silicon carbide (SiC), gallium nitride (GaN), and gallium oxide (Ga₂O₃) come in. Compared to traditional silicon (Si), these materials have a much higher “bandgap” energy, allowing them to handle significantly higher power levels. By incorporating them into power conversion devices, we can dramatically reduce energy losses while also shrinking the overall size of the systems. This paves the way for advancements in electrification throughout our lives.

Superior Material Properties

Substrate Economics

Imagine Ga₂O₃ power devices as affordable as silicon, thanks to well-established melt-growth technology. This method slashes costs by dramatically reducing the need for expensive substrates and epitaxial layers, which currently account for 70% of the total cost in SiC and GaN devices. This innovative technique enables Ga₂O₃ wafer size to grow at a rate three times faster than GaN and SiC. Remarkably, it took less than a decade to go from the first 2-inch wafer to demonstrating a 6-inch wafer, showcasing the rapid development potential.