| AVS 54th International Symposium | |
| Electronic Materials and Processing | Wednesday Sessions |
| Session EM-WeM |
| Session: | Contacts, Interfaces and Defects in Semiconductors |
| Presenter: | M.A. Miller, The Pennsylvania State University |
| Authors: | M.A. Miller, The Pennsylvania State University S.E. Mohney, The Pennsylvania State University |
| Correspondent: | Click to Email |
We have investigated the use of Ag in place of Au in V- and Ti-based ohmic contacts to Al0.27Ga0.73N/GaN heterostructures for high electron mobility transistors. An optimized V/Al/V/Ag contact provided a specific contact resistance of 1.7x10-6 Ohm-cm2 when annealed at 825°C for 60s in N2. As measured by atomic force microscopy, the contacts had a root-mean-square roughness of 4.5 nm over a 10 x 10 micron area, which was much smoother than the analogous Au-bearing metallizations. An optimized Ti/Al/Ti/Ag contact provided a higher minimum specific contact resistance of 7.4x10-6 Ohm-cm2, and the Ti/Al/Ti/Ag contacts were not as smooth as the V/Al/V/Ag contacts, perhaps due to the higher annealing temperatures necessary to minimize the resistance of the Ti-based contacts. The specific contact resistance and morphology of the V/Al/V/Ag contacts were also superior to those of the more conventional Ti/Al/Ti/Au and V/Al/V/Au contacts tested. Transmission electron microscopy revealed a very limited reaction of the annealed V/Al/V/Ag metallization with the semiconductor, leaving the AlGaN layer intact. The majority of the AlGaN interface is contacted by Ag-bearing phases. Silver has a lower work function than Au and may facilitate the formation of a low-resistance ohmic contact.