ERI: Integration of Diamond with Ga2O3 for High Performance Applications

Studying the growth of emerging ultrawide bandgap (UWBG) materials and devices is crucial due to the growing demand for power electronic devices that can efficiently handle increased electrical power and operate at higher speeds without failure. These devices are the essential components in electric vehicles, power transmission lines that transport electricity from generation sites to households and industries, and electronic systems designed for high-temperature and radiation environments such as jet engines, nuclear reactors, and spacecrafts.

Among UWBG materials, Gallium Oxide (Ga2O3) stands out as one of the most promising candidates for these applications due to its desirable electrical properties, good stability at high temperatures, radiation tolerance property, and abundance of electronic grade Ga2O3 wafers. Nevertheless, the limited thermal conductivity of Ga2O3 renders high-power devices fabricated from this material susceptible to failure.

Growing diamond is another promising UWBG material with the highest thermal conductivity among all materials. As a heat dissipation layer on Ga2O3, it can address the poor thermal conductivity associated with Ga2O3-based devices. Since diamond can be easily doped p-type, integration with n-type Ga2O3 would lead to the fabrication of a p-n junction.

However, the material quality of Ga2O3 drastically degrades in the harsh growth environment of diamond growth. This proposed work aims to address the ever-present challenges of growing delamination-free uniform and high-quality diamond film with a small thermal boundary resistance directly on UWBG oxides by incorporating an ultrathin quenched(Q)-carbon interlayer.

Prototype p-diamond/n-Ga2O3 devices will be fabricated to assess their compatibility and determine the device characteristics. The outcomes of this project will contribute to the design of advanced and more compatible Ga2O3-based power devices. An important aspect of this study involves training both undergraduate and graduate students.

Additionally, high school students will receive exposure to this research through summer workshop programs hosted at Texas State University. The project activities and outcomes will also be showcased through lab tours, demonstrations, visits to local schools, and on-site presentations, aiming to enhance scientific awareness among the public.

Ultrawide bandgap (UWBG) Gallium Oxide (Ga2O3) based electronic device systems have the potential to handle extraordinarily large power across a wide range of frequency bands for next-generation high-temperature, high-power, and high-frequency applications. Two major bottlenecks to harnessing the true potential of this immensely promising UWBG material are the absence of p-type Ga2O3, which limits the fabrication of homojunction devices, and its low thermal conductivity, which directly impacts the device performance and reliability.

In this regard, p-diamond/n-β-Ga2O3 integration offers potential solutions owing to diamond's superior thermal conductivity and p-type dopability. The diamond layer in the device can effectively dissipate heat during operation. However, lattice and thermal mismatch between Ga2O3 and diamond and issues related to harsh growth conditions for diamond are major challenges to implementing this concept.

This proposal aims to address the persistent issues of integrating p-type diamond films with UWBG n-type Ga2O3 layer by implementing a novel approach, i.e., incorporating an ultra-thin quenched carbon (Q-carbon) interlayer achieved by pulsed laser annealing between the Ga2O3 and diamond interface. The Q-carbon layer on Ga2O3 will provide the nucleation base for high-quality uniform coverage diamond growth, protect the Ga2O3 layer from damage during the growth process, and reduce the thermal misfit between Ga2O3 and diamond.

The project also aims to investigate the structural and electrical properties of each layer of the device and the heterointerface. Prototype Ga2O3-diamond p-n and p-i-n devices will be fabricated to measure the key performance parameters.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.