Contacting Mechanically Exfoliated β-Ga2O3Nanobelts for (Opto)electronic Device Applications

We systematically investigated the properties of metal contacts deposited on exfoliated β-Ga 2 O 3 nanobelts. Unintentionally doped β-Ga 2 O 3 was mechanically exfoliated from bulk β-Ga 2 O 3 crystal and transferred onto SiO 2 /Si substrate having a back gate configuration. Electrodes were formed by depositing Ti/Au or Ni/Au onto the transferred β-Ga 2 O 3 nanobelts, followed by rapid thermal annealing (RTA) with different ambient gases and temperatures. Using scanning transmission electron microscopy (STEM) and energy-dispersive X-ray spectroscopy (EDS), it was shown that titanium reacts with oxygen to form titanium oxide, which has ohmic behavior. In contrast, nickel does not form an ohmic contact despite 600°C thermal treatment. The lower oxygen partial pressure in a nitrogen atmosphere as compared to air results in more oxygen vacancies within the Ga 2 O 3 nanobelts during RTA and a …