Over the last seven decades, the silicon technology has dominated solid state electronics. However, the silicon-based semiconductor technology cannot handle the power levels and switching frequencies anticipated by the next generation of power applications. This EAGER project aims to create the prototype of high power diamond based transistors with properties that are beyond the scope of current devices in terms of operating frequency, power handling capacity, operating voltage, and operating environment. Such diamond based semiconductor devices can eliminate the majority of the power losses that currently occur during AC-to-DC and DC-to-AC electricial conversion, operate at voltages up to 30 times higher than silicon-based devices, and operate at temperatures above 300°C, twice what silicon electronics can tolerate. These devices may revolutionize power distribution and conditioning, allowing for a more versatile and stable power grid with efficient access to non-traditional power sources, to improved efficiencies for electric motor drives, and to improved microwave and millimeter wave sources. Many of these devices will be appropriate for operation in harsh chemical, biological, thermal, or radiological environments. This research will provide a proof of principle for diamond-based high voltage devices and high frequency devices and will also enable the accurate design of diamond based FETs, which will exploit advantages of increased temperature and voltage insensitivity of 2D structures. As a result, the research will lay the foundation for the development of wide bandgap (WBG) semiconductor diamond technologies, which will both outperform current Si, SiC and GaN high voltage device characteristics and will have much higher voltage and temperature tolerance.
The present NSF EAGER research project is to demonstrate a new transistor concept based on two dimensional hole gas (2DHG) channels in diamond thereby extending the basic science of diamond 2D transport channels to high-voltage devices as well as high frequency power devices. This objective will be achieved through correlations between experimental results with device design as well as with basic models of charge transport. Our proposed research will investigate the fundamental device physics of diamond based field effect transistors (FETs) for high power and high voltage applications. These diamond based FETs will exploit multiple sub surface nanometer thick boron ä-doped channels which have been fabricated via the precision control of chemical vapor deposition chemistry. The proposed plan is to achieve unique and innovative device structures through the fabrication of two dimensional conduction channels on single crystal (100) diamond epitaxial layers grown on diamond substrates. The research is based on the fundamental understanding of the delta doping and carrier channel formation in diamond 2D channel devices, and will employ the unique facilities available at the University of Maryland. The research approach consists of the design and fabrication of double delta doped FETs based on an optimized channel dopant profile, as well as utilization of insulating gate materials complex dielectrics for surface passivation. Device electrical performance will be characterized after fabrication. Investigations on ä-doped channel FETs will also consist of in depth device modeling and electrical and physical characterization of performance.
