Temperature-Dependent Characteristics of Field-Effect Mobility in MOCVD-Grown β-Ga₂O₃MOSFETs on Sapphire Substrate

<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> MOSFETs were fabricated based on the heteroepitaxial <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> film grown on the sapphire substrate by metalorganic chemical vapor deposition (MOCVD). Thanks to the high epitaxial quality and an optimized Si+ implantation and activation process, a high field effect mobility <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$(\mu_{\mathrm{F}\mathrm{E}})$</tex> of 35 cm<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup>/V·s was achieved at a high carrier density <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$(n_{\mathrm{e}})$</tex> near the surface exceeding 10<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">18</sup> cm<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">−3</sup>. As the temperature rises, the density of ionized impurities increases, and Coulombic scattering becomes the dominant mechanism, resulting in the enhancement of <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\mu_{\mathrm{F}\mathrm{E}}$</tex> from 35 cm<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup>/V·s to 55 cm<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup>/V·s when the temperature increases from 25°C to 300°C. The <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\mu_{\mathrm{F}\mathrm{E}}$</tex> is the highest reported for heteroepitaxial Ga<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf>O<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</inf> devices on sapphire substrates.