Transparent Conductive Electrodes of β-Ga₂O₃/Ag/β-Ga₂O₃ Multilayer for Ultraviolet Emitters

Abstract

We investigated the optical and electrical properties of a β-Ga₂O₃/Ag/β-Ga₂O₃ multilayer transparent conductive electrode deposited on an α-Al2O₃ (0001) substrate. For the deposition of a continuous Ag layer, we preliminarily performed anultraviolet-ozone pretreatment of the Ga₂O₃ bottom layer. To obtain a stable β-phase of Ga₂O₃, the β-Ga₂O₃/Ag/β-Ga₂O₃ multilayer was annealed at 700 °C under N₂ atmosphere. The transmittance and sheet resistance of the β-Ga₂O₃/Ag/β-Ga₂O₃ multilayer were critically affected by the surface morphology and thickness of the Ag interlayer. The multilayer with optimized thicknesses (β-Ga₂O₃ top layer: 30 nm; Ag interlayer: 12 nm; β-Ga₂O₃ bottom layer: 60 nm) exhibited a resistance of 8.48 Ωsq^-1, an average optical transmittance of 87.16% in the ultraviolet wavelength range from 300 to 350 nm, and a figure of merit of 29.81 × 10^-3 Ω^-1.