We have investigated Nb single and Nb/Au metallization schemes for the formation of thermally stable ohmic contacts to p-GaN. It is shown that the as-deposited Nb and Nb/Au contacts exhibit rectifying behavior. However, both the contacts produce ohmic characteristics when annealed at 850°C. Measurements show that the 850°C Nb/Au and Nb contacts yield a specific contact resistance of 1.9 × 10-3 and 2 × 10-2 Ωcm2, respectively. Schottky barrier heights are found to decrease with increasing annealing temperature. A comparison of the XRD and electrical results shows that the formation of gallide phases, such as Ga-Nb and Ga-Au compounds, play a role in forming ohmic contacts. Atomic force microscopy results show that the surface morphology of the Nb contacts is fairly stable up to 850°C, while the Nb/Au contacts are slightly degraded upon annealing at 850°C.
- Ohmic contacts
- Schottky barrier heights
ASJC Scopus subject areas
- Electronic, Optical and Magnetic Materials
- Condensed Matter Physics
- Electrical and Electronic Engineering
- Materials Chemistry