Study of Ti contacts to corundum α-Ga<sub>2</sub>O<sub>3</sub>
Fabien Massabuau, David G. Nicol, Francesca Adams, John Jarman, Joseph W. Roberts, András Kovács, Paul R. Chalker, Rachel A. Oliver
Abstract
Abstract We present a study of the electrical, structural and chemical properties of Ti contacts on atomic layer deposited α -Ga 2 O 3 film. Ti forms an ohmic contact with α -Ga 2 O 3 . The contact performance is highly dependent on the post-evaporation annealing temperature, where an improved conductivity is obtained when annealing at 450 °C, and a strong degradation when annealing at higher temperatures. Structural and chemical characterisation by transmission electron microscopy techniques reveal that the electrical improvement or degradation of the contact upon annealing can be attributed to oxidation of the Ti metallic layer by the Ga 2 O 3 film in combination with the possibility for Ti diffusion into the Au layer. The results highlight that the grain boundaries and inclusions in the Ga 2 O 3 film provide fast diffusion pathways for this reaction, leaving the α -Ga 2 O 3 crystallites relatively unaffected—this result differs from previous reports conducted on β -Ga 2 O 3 . This study underlines the necessity for a phase-specific and growth method-specific study of contacts on Ga 2 O 3 devices.