Electrical properties of thermally annealed β-Ga₂O₃ metal-semiconductor field-effect transistors with Pt/Au Schottky contacts

The electrical properties of the metal-semiconductor field-effect transistors (MESFETs) based on quasi-two-dimensional β-Ga₂O₃ n-channel and Pt/Au Schottky gate electrode were analyzed with cumulative temperature and time of thermal annealing. Mechanical exfoliation was used to prepare the β-Ga₂O₃ microflakes and the fabricated device was thermally annealed using either a rapid thermal annealing (RTA) equipment or a furnace. Raman spectroscopy was also employed to investigate the robustness of the mechanically exfoliated β-Ga₂O₃ microflakes. The devices survived a high temperature up to 700°C (RTA) and endured thermal annealing for an extended time of 90 minutes at 500°C. The stable performance was observed from the β-Ga₂O₃ MESFET until the Schottky barrier height decreased substantially and the current modulation deteriorated significantly after an RTA at 700°C. The obvious change in Schottky diode characteristics and the color contrast over the whole source and drain electrodes also confirmed the failure of MESFET operation after 120 minutes of annealing at 500°C. The thermal stability of the electronic devices based on β-Ga₂O₃ microflakes motivates further studies including power switching electronics under harsh environments.