Dieletric Interfaces on Doped Diamond Surfaces

Project: Research project

Description

Overview:
Diamond is a wide band gap semiconductor with outstanding semiconductor properties that have long been recognized for high power and high frequency applications. Diamond has the highest known thermal conductivity which enables high power operation, and the high electron and hole mobilities of diamond are unusual compared to all other wide band gap semiconductors and support both high power and high frequency applications.

Intellectual Merit:
In recent years there has been an explosion of diamond device studies. Two notable advances contributed to this renaissance of diamond device studies: 1) the growth of n-type layers using phosphorus as a dopant, and 2) the commercial availability of high quality substrates prepared by plasma enhanced chemical vapor deposition (PECVD). One of the greatest challenges to advancing diamond devices is the development of stable, low defect dielectric layers that confine electrons and holes in the conduction and valence band of diamond.
This study will include the preparation of doped diamond surfaces by microwave plasma enhanced CVD growth of epitaxial layers on single crystal substrates. Commercially obtained (100) and (111) substrates will be employed. The doping level will be optimized for photoemission measurements. The substrates will enable a careful study of the surface electronic states of clean surfaces and surfaces terminated with hydrogen, oxygen and fluorine. A unique aspect of diamond is that the surface electron affinity varies by more 3 eV depending on the termination, and the goal of this component will be to determine the electron affinity, band bending, work function, surface Fermi level position and presence of surface states on the p- and n-type surfaces. The well characterized doped diamond surfaces will be used with in situ photoemission measurements to determine the band offsets of wide bandgap oxide dielectric layers on clean, and H, O, and F terminated, p- and n-type diamond. The use of doped diamond substrates is expected to show different surface band bending for p- and n-type surfaces and potentially different surface and interface Fermi level positions due to surface and interface states. The results will establish a model for band alignment that considers the work function model and the charge neutrality or interface dipole model. Three projects will establish the interface properties for specific dielectric interfaces that each have unique character: i) high work function and high electron affinity oxides (e.g. MoO3, or V2O5) that have shown unusual surface transfer doping characteristics; ii) water as a dielectric and the potential of photochemical processes on doped diamond, and iii) ultra-wide band gap fluoride layers (specifically AlF3) prepared by ALD that take advantage of the F-terminated diamond surface.
The result will be a comprehensive study of the band alignment of dielectric layers on wide band gap diamond that should provide guidance on device design for this rapidly developing wide band gap semiconductor.

Broader Impacts:
The research presented here addresses one of the greatest challenges in advancing diamond electronics. The research could enable high power, high frequency and high temperature devices that are not possible with any other material. In addition, the project provides laboratory training for students to advance the science and technology that will drive this field. This project will also collaborate with ASU Sundial, a program which supports retention and diversity in the physical sciences. The activities developed with Sundial will include research related workshops and the development of an outreach-level scientific conference, geared at community members and local high school and community college students and teachers, with an expected attendance of over 200. The goals of these activities is to increase access to science careers to students who are traditionally under-represented, by improving retention and educational enrichment opportunities for these students.
StatusActive
Effective start/end date7/1/176/30/20

Funding

  • National Science Foundation (NSF): $430,000.00

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diamonds
students
broadband
electron affinity
photoelectric emission
alignment
vapor deposition
physical sciences
oxides
instructors
hole mobility
electron mobility
electronics
Fermi surfaces
availability
fluorine
fluorides
phosphorus
explosions
conduction bands