Abstract
We present a study of the electrical, structural and chemical properties of Ti contacts on atomic layer deposited α-Ga2O3 film. Ti forms an ohmic contact with α-Ga2O3. 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 Ga2O3 film in combination with the possibility for Ti diffusion into the Au layer. The results highlight that the grain boundaries and inclusions in the Ga2O3 film provide fast diffusion pathways for this reaction, leaving the α-Ga2O3 crystallites relatively unaffected—this result differs from previous reports conducted on β-Ga2O3. This study underlines the necessity for a phase-specific and growth method-specific study of contacts on Ga2O3 devices.
Highlights
In recent years, Ga2O3 has emerged as one of the most promising wide bandgap semiconductor materials for high-power electronic and ultraviolet optoelectronic applications [1]
250 nm films of unintentionally n-doped α-Ga2O3 were grown on 1 × 1 cm2 c-plane sapphire substrates by plasma-enhanced atomic layer deposition (PEALD) using an Oxford Instruments OpAL PEALD reactor at a temperature of 250 ◦C—full description of the growth process can be found in reference [14]
Shipley s1813 positive photoresist was developed with MF-319, an aqueous developer containing dilute tetramethylammonium hydroxide (TMAH), after a short post-exposure treatment with chlorobenzene to produce the undercut profile required for the metal lift-off process
Summary
Ga2O3 has emerged as one of the most promising wide bandgap semiconductor materials for high-power electronic and ultraviolet optoelectronic applications [1]. Abstract We present a study of the electrical, structural and chemical properties of Ti contacts on atomic layer deposited α-Ga2O3 film.
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