| Autor: |
Geenen, F., Constant, A., Solano, E., Deduytsche, D., Mocuta, C., Coppens, P., Detavernier, C. |
| Předmět: |
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| Zdroj: |
Journal of Applied Physics; 6/7/2020, Vol. 127 Issue 21, p1-15, 15p, 5 Diagrams, 2 Charts, 15 Graphs |
| Abstrakt: |
Wide-bandgap nitride semiconductors are currently in development for high-power electronic applications. Compositional layered heterostructures of such nitrides result in a high polarization field at the interface, enabling a higher electron mobility, a higher power density, and a higher conversion efficiency. Further optimization of such GaN-based high-electron-mobility transistors can be achieved by evolving from a top Al x Ga 1 − x N barrier toward AlN or even In y Al 1 − y N. An ongoing challenge in using such hexagonal nitride semiconductors is the formation of a low-resistive, Au-free, ohmic contact far below 1 Ω mm. In this paper, we investigate the formation of ohmic contacts by Ti–Al–TiN-based metalization as a function of different annealing temperatures (up to 950 ° C), Ti–Al ratios (from 15 up to 35 at. %) and nitride barrier composition ( Al x Ga 1 − x N , GaN, AlN, and In y Al 1 − y N). Contacts processed on AlxGa1–x/GaN, and AlN/GaN heterostructures result in low contact resistance of, respectively, 0.30 and 0.55 Ω mm , whereas the same contact stack on In y Al 1 − y N results in resistance values of 1.7 Ω mm. The observed solid-phase reaction of such Ti–Al–TiN stacks were found to be identical for all investigated barrier compositions (e.g., Al x Ga 1 − x N , GaN, AlN, and In y Al 1 − y N), including the preferential grain alignment to the epitaxial nitride layer. The best performing ohmic contacts are formed when the bottom Ti-layer is totally consumed and when an epitaxially-aligned metal layer is present, either epitaxial Al (for a contact which is relatively Al-rich and annealed to a temperature below 660 ° C) or ternary Ti 2 AlN (for a relatively Ti-rich contact annealed up to 850 ° C). The observation that the solid-phase reaction is identical on all investigated nitrides suggests that a further decrease of the contact resistance will be largely dependent on an optimization of the nitride barriers themselves. [ABSTRACT FROM AUTHOR] |
| Databáze: |
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