CAREER: Enhancing GaN-on-Si high electron mobility transistor technology for high frequency and high power applications

This project is jointly funded by the Electrical, Communications and Cyber Systems (ECCS) and the Established Program to Stimulate Competitive Research (EPSCoR). GaN electronics attract much interest as the potential candidate to replace silicon electronics in a wide range of applications: spanning from 5G commercial wireless infrastructure, electronic warfare, and communications applications to consumer electronics, data centers, electric vehicles, electricity grid, and renewable energy systems.

The GaN electronics can be built on various kinds of substrates (i.e. Si and SiC), in which the GaN-on-Si seems to be the most promising technology due to its low cost and large scale capability. However, the GaN-on-Si technology is still premature and is inferior to the GaN-on-SiC technology.

A deep understanding of the real reasons for impeding its performance is indispensable. This proposal aims to provide insights to understand the fundamental problems of GaN-on-Si technology and develop the ability to enhance its performance. The successful implementation of this work is expected to revolutionize the GaN-on-Si high electron mobility transistor technology, which can be applied to high frequency and high power electronic systems.

What integrated into the research activities is a broad scope of educational and outreach efforts including educating young people with emerging device technology for miniaturization, integration and improved efficiency, developing new courses and internships, interacting with industry and disseminating K-12 Lithokit, which are beneficial for workforce development.

The proposed work addressing a number of fabrication process challenges facing GaN-on-Si technology that, if successful, will result in performance enhancement for both high frequency and high power applications. Specifically, through a novel self-aligned T-shaped gate process, we expect to revolutionize GaN-on-Si technology by enhancing its RF performance fT/fMAX to values comparable to its GaN-on-SiC counterpart and its power performance close to its theoretical limit.

The innovative self-aligned T-shape gate process where the T-foot length and stem height can be used to downscale the gate length and minimize the parasitic capacitance for improved RF performance and the T-head can be adopted as the field plate to enhance device power performance. In addition, the developed gate dielectrics and field plate technology can be further extended to other transistors for power applications.

The developed material and device parameters are of great value to all other GaN-related devices. The proposed research will not only advance the basic science and technology of the GaN-on-Si HEMTs, but also set an example for the investigation of the physical and chemical understanding of the relationship between material surface and interface properties and fabrication process and provide a deeper understanding of the relationship between the fabrication process and device performance.

The courses developed from this program will educate young people with emerging device technology for miniaturization, integration and improved efficiency, which is one of the NSF’s desired societal impacts. The new courses, internships, interactions with industry, and K-12 “Lithokit” will increase the audience exposed to the device field, and help expand the workforce.

In addition, through the collaborative industry programs, the potential to commercialize this technology has already attracted industry professionals, which will greatly impact semiconductor companies that fabricate chips.

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.