Ultra-Wide Bandgap Ga${}_2$O${}_3$-on-SiC MOSFETs

Abstract

Ulta-wide bandgap semiconductors based on $\beta$-Ga${}_2$O${}_3$ offer the potential to achieve higher power switching performance, efficiency, and lower manufacturing cost than today's wide bandgap power semiconductors. However, the most critical challenge to the commercialization of Ga${}_2$O${}_3$ electronics is overheating, which impacts the device's performance and reliability. We fabricated a Ga${}_2$O${}_3$/4H-SiC composite wafer using a fusion-bonding method. A low temperature ($\le$ 600 ${}^{\circ }$C) epitaxy and device processing approach based on low-temperature (LT) metalorganic vapor phase epitaxy is developed to grow a Ga${}_2$O${}_3$ epitaxial channel layer on the composite wafer and subsequently fabricate into Ga${}_2$O${}_3$ power MOSFETs. This LT approach is essential to preserve the structural integrity of the composite wafer. These LT-grown epitaxial Ga${}_2$O${}_3$ MOSFETs deliver high thermal performance (56% reduction in channel temperature), high voltage blocking capabilities up to 2.45 kV, and power figures of merit of $\sim$ 300 MW/cm${}^2$, which is a record high for any heterogeneously integrated Ga${}_2$O${}_3$ devices reported to date. This work is the first realization of multi-kilovolt homoepitaxial Ga${}_2$O${}_3$ power MOSFETs fabricated on a composite substrate with high heat transfer performance which delivers state-of-the-art power density values while running much cooler than those on native substrates. Thermal characterization and modeling results reveal that a Ga${}_2$O${}_3$/diamond composite wafer with a reduced Ga${}_2$O${}_3$ thickness ($\sim$ 1 $\mu$m) and thinner bonding interlayer ($<$ 10 nm) can reduce the device thermal impedance to a level lower than today's GaN-on-SiC power switches.

17 pages, 9 figures