| AVS 64th International Symposium & Exhibition | |
| Electronic Materials and Photonics Division | Wednesday Sessions |
| Session EM+2D+MI+MN-WeA |
| Session: | Materials and Devices for Quantum Information Processing |
| Presenter: | Steven Vitale, MIT Lincoln Laboratory |
| Authors: | S.A. Vitale, MIT Lincoln Laboratory J.O. Varghese, MIT Lincoln Laboratory M.F. Marchant, MIT Lincoln Laboratory T. Wade, MIT Lincoln Laboratory M.W. Geis, MIT Lincoln Laboratory T.H. Fedynyshyn, MIT Lincoln Laboratory D.M. Lennon, MIT Lincoln Laboratory M.A. Hollis, MIT Lincoln Laboratory |
| Correspondent: | Click to Email |
Diamond possesses extraordinary semiconductor properties including carrier mobility, saturation velocity, and thermal conductivity which far exceed those of silicon and essentially all other semiconductor materials. In spite of these incredible qualities diamond has not yet become a mainstream transistor material, for two primary reasons. First, existing small single-crystal substrates have not been able to take advantage of commercial microelectronics processing equipment and growth of wafer-scale single-crystal diamond has not been vigorously pursued. Second, deep donor and acceptor levels in diamond imply that the impurity ionization fraction is quite low at room temperature which results in low carrier density in conventional FET architectures.
However the situation has changed dramatically in the past few years. Plasma-enhanced CVD promises to create large-wafer single-crystal diamond through mosaic or novel catalytic growth.1 Additionally, the discovery of the diamond surface FET has addressed the problem of low carrier density.2 Together, these advancements may allow development of practical diamond transistors with unparalleled performance for high-power, high-frequency applications. Many unit process and process integration challenges remain to develop diamond surface FETs into commercial technology. This paper will report on the state of the art in diamond surface FET technology and will examine current unmet needs.We have developed diamond surface FETs with current densities in excess of 100 mA/mm. This is enabled by a novel surface activation process using a high concentration of NO2 in air to react with a hydrogen-plasma-treated diamond surface. The electron accepting nature of the modified surface abstracts an electron from the diamond, resulting in a 2D hole gas (2DHG) in the diamond. We measure a hole mobility of 30-130 cm2/V-s and a repeatable surface resistance of ~ 1.5 kΩ sq-1 using this technique. 2DHG formation has been demonstrated using other surface moieties as well, including photoacid radical generators and trinitrotoluene. Pros and cons of these different surface adsorbates will be discussed. The performance of Au, Mo, Pt, Al, Pd, Ti, Cr contacts, as well as combinations of these metals will be presented, with a record-low diamond contact resistance of 0.6 ohm-mm and good ohmic behavior.
1 M. Schreck, et al, Sci. Rep. 7, 44462 (2017).
2 M. Kasu, Japanese Journal of Applied Physics 56, 01AA01 (2017).