Low Resistance Ohmic Contact on (100) β-Ga₂O₃ Substrate with Laser Annealing Using Ti/Au

<tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\beta-\text{Ga}z\mathrm{O}_{3}$</tex> is considered as a potential candidate for the next generation of power electronics and optoelectronic devices due to their ultra-high breakdown voltage. Ohmic contact between metal and <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\text{Ga}_{2}\mathrm{O}_{3}$</tex> with low specific contact resistivity and good thermal stability is required to achieve high-performance power devices. It is extremely challenging for <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\beta- \text{Ga}_{2}\mathrm{O}_{3}$</tex> to form ohmic contacts compared to narrow-band gap semiconductors for Schottky contact are formed between <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\beta- \text{Ga}_{2}\mathrm{O}_{3}$</tex> and the majority of metals. The current research on <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\text{Ga}_{2}\mathrm{O}_{3}$</tex> ohmic contact electrodes and practical device applications is focused on the multi-metallic Ti/Au stack following rapid thermal annealing (RTA). In this study, we adopt the innovative approach of replacing the conventional RTA with laser annealing and investigate the electrical characteristics, surface topography and interfacial reactions at different laser fluences to illustrate the ohmic contact formation mechanism and the effect of different laser fluences on electrode characteristics. The transmission line measurement (TLM) was used to extract the specific contact resistance <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$(\mathrm{p}_{\mathrm{c}})$</tex> and a minimum <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\mathrm{p}_{\mathrm{c}}$</tex> of 1.24 <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\times 10^{-4}\Omega\cdot \text{cm}^{2}$</tex> was obtained for the sample annealed at 0.15 <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\mathrm{J}\cdot \text{cm}^{-2}$</tex> with ameliorative surface roughness. The discovery offers a novel approach to the annealing process of <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\text{Ga}_{2}\mathrm{O}_{3}$</tex> ohmic contact electrodes.