Dielectric Interfaces on Doped Diamond Surfaces

Arizona State University, Scottsdale AZ

Investigators

Abstract

Non-technical description: Diamond is a crystalline material that shares the same crystal structure with silicon, which has formed the basis of modern electronics. Recent advances in laboratory growth methods have provided diamond plates suitable for fabricating electronic devices. Compared to silicon, the unique properties of diamond make it the ultimate semiconductor for power and high frequency electronics, where diamond electronics could enable more efficient electronic vehicles, a more efficient and smarter electronic grid, and more efficient communication systems. One of the greatest challenges to advancing diamond electronics is producing dielectric interfaces that can enable fabrication of transistors on diamond wafers. The outcomes of this research provides insight into the electronic properties of dielectric interfaces on diamond for a new generation of high power and high frequency devices. The research provides laboratory training for students to advance the science and technology that will drive this field. This project collaborates with Sundial, a program at Arizona State University which supports retention and diversity in the physical sciences. The activities developed with Sundial include research related workshops and an outreach-level scientific conference, geared to community members and local high school and community college students and teachers. The goals of these activities are to increase access to science careers to students who are traditionally under-represented, by improving retention and educational enrichment opportunities for these students. Technical description: One of the greatest challenges to advancing diamond electronics is the development of stable, low defect dielectric layers that confine electrons and holes in the conduction and valence band of diamond. This project uses doped epitaxial diamond layers prepared by microwave plasma enhanced chemical vapor deposition on single crystal substrates. A unique aspect of diamond is that the surface electron affinity varies by more than 3 eV by controlling the surface termination with H, O or F. A project goal is to determine the electron affinity, band bending, work function, surface Fermi level position and presence of surface states on the p- and n-type diamond surfaces. The well-characterized doped diamond surfaces are used with in situ photoemission measurements to determine the band offsets of wide bandgap dielectric layers on diamond. Three specific layers establish the unique interface properties: i) high work function and high electron affinity oxides (e.g. molybdenum oxide) that have shown unusual surface transfer doping characteristics; ii) water as a dielectric that enables photochemical processes on doped diamond, and iii) ultra-wide band gap fluoride layers that take advantage of the F-terminated diamond surface. The research provides a comprehensive understanding of the band alignment of dielectric layers on diamond and provides guidance for device design.