Glancing angle X-ray diffraction and Auger electron spectroscopy have been used to investigate interfacial reactions between the Ni(20 nm)/Pt(30 nm)/Au(80 nm) contacts and p-GaN (p = 9.4×1016 cm-3). The metallization schemes were annealed at temperatures ranging from 500 to 700 °C for 30 s in a flowing Ar atmosphere. The anneal of the sample at 500 °C resulted in ohmic behavior with a specific contact resistance of 2.1×10-2Ωcm2. However, the anneal at temperatures ≥600 °C led to the degradation of the ohmic property. It is shown that Ga-(Pt,Ni) phases such as Ga3Pt5 and Ga4Ni3 and a Pt-Ni solid solution are formed upon annealing at 500 °C, while in addition to the Ga4Ni3, new phases of GaAu2 and GaAu are formed upon annealing at temperatures ≥600 °C. As for the Pt-Ni solid solution, the lattice parameter decreases significantly with increasing annealing temperatures. A qualitative explanation is given to describe why the characteristic of the contacts changed from ohmic to rectifying behavior with increasing temperature.
ASJC Scopus subject areas
- Electronic, Optical and Magnetic Materials
- Renewable Energy, Sustainability and the Environment
- Surfaces, Coatings and Films
- Materials Chemistry