Contacting Mechanically Exfoliated beta-Ga2O3 Nanobelts for (Opto)electronic Device Applications

Abstract

We systematically investigated the properties of metal contacts deposited on exfoliated beta-Ga2O3 nanobelts. Unintentionally doped beta-Ga2O3 was mechanically exfoliated from bulk beta-Ga2O3 crystal and transferred onto SiO2/Si substrate having a back gate configuration. Electrodes were formed by depositing Ti/Au or Ni/Au onto the transferred beta-Ga2O3 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 degrees C thermal treatment. The lower oxygen partial pressure in a nitrogen atmosphere as compared to air results in more oxygen vacancies within the Ga2O3 nanobelts during RTA and a negative threshold voltage shift. A decreased current level after high temperature annealing can be ascribed to significant outward diffusion of oxygen and gallium atoms and to oxidation of the metal electrode. Our results can pave a route to demonstrating high performance beta-Ga2O3 nanobelt-based (opto)electronic devices. (C) 2016 The Electrochemical Society. All rights reserved.