Integrated Selective Growth of Diamond and GaN for Maximum Heat Extraction from Electronic Devices

Texas State University - San Marcos, San Marcos TX

Investigators

Abstract

Diamond, as an electronic material, has the best heat conduction properties and is readily produced by commercial equipment and processes. Gallium nitride is a semiconductor material that has seen recent commercial success in high efficiency light emitting diode bulbs, radio wave communications and radars, and power conversion switches. However, the full potential of gallium nitride is limited by the material's inability to efficiently conduct heat. Therefore, the project's aim is to combine diamond and gallium nitride in a novel approach that will focus on (1) the processes that produce both materials, (2) an in-depth characterization of the electronic and thermal properties (emphasizing heat flow), (3) fabrication of test structures, and (4) thermal conduction simulations. There are broad needs for combining diamond's thermal benefits within individual circuitry that comprises today's electronics. Transistors and switches (the backbone of the entire high-tech industry) are well known to produce substantial heat, and the problem is continually getting worse as devices become smaller and the density of electronic components packed together on circuit boards increases. (In personal electronics, consider how hot smart phones and laptops become during regular usage.) Specific applications that will benefit from the research include electric vehicles, power conversion for flexible integration of renewable energy sources to the nation's power grid, radar systems and communications systems for first-responder, defense and civilian uses. The research will result in basic and applied knowledge regarding the diamond-gallium nitride interface. Results will be published in peer-reviewed journals and presented at national and international conferences. Student engagement and education efforts will take place through research and classroom experiences and a strong culture of undergraduate research at the affiliate's institution. The primary goal of the research is to develop a novel diamond-GaN interface and fully characterize its thermal transport characteristics. Innovative materials research will involve three-dimensional integration of GaN on diamond to significantly improve thermal management in high-power electronics. The high thermal conductivity of diamond makes it highly attractive for mitigating self-heating effects that plague the efficiency of switches and power transistors. An innovative path will be developed to selectively grow diamond and GaN to achieve close proximity to the current-carrying GaN two-dimensional electron gas for efficient heat removal. Systematic studies will focus on material growth and characterization. Characterization will emphasize interfaces of these materials and its impact on heat flow. Fabrication of electrical and electrothermal test structures will be conducted. These will be used in combination with electrical and optical measurements to investigate the effects of deposition and heterointerface quality on fundamental properties, including and thermal boundary resistance (TBR). The impact of these material properties on transistor operational limits will be examined with the aid of simulations. Selective diamond deposition will provide understanding to improve diamond quality, interface properties, and manage stresses resulting from thermal expansion mismatches. The impact of the growth steps, particularly of the diamond-GaN interfaces, on material and device properties will be studied by physical and optical methods. Test structures will be measured to determine thermal conductivity and TBR. Extensive characterization will correlate crystal quality and defect properties with these key macroscopic quantities in thermal transport and electrical performance. The research will result in basic and applied knowledge regarding material deposition and properties of the diamond?GaN interface region. Results will be published in peer-reviewed journals and presented at national and international conferences. 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.