The Role of Sn <i>δ</i>-Doping in Tailoring Channel Properties for High-Voltage <i>α</i>-Ga₂O₃ MESFETs

This study investigates the role of Sn δ-doping in tailoring the channel properties of α-Ga<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><roman>2</roman></sub>O<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><roman>3</roman></sub> MESFETs for high-voltage applications. By varying the Sn δ-doping durations, the electron concentration in the channel layer is effectively modulated, increasing from 3.6 × 10<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><roman>16</roman></sup> to 2.5 × 10<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><roman>19</roman></sup> cm<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-<roman>3</roman></sup> as the doping time extends from 40 to 80 s. At 80 s, the channel layer exhibits a sheet resistance of 0.3 kΩ/sq and a specific contact resistivity of 2.68 × 10<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-<roman>4</roman></sup> Ω⋅cm<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><roman>2</roman></sup>. However, excessive leakage current at the Schottky junction makes this condition unsuitable for MESFET operation. In contrast, α-Ga<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><roman>2</roman></sub>O<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><roman>3</roman></sub> MESFETs with a 60-s Sn δ-doping achieve an optimal balance between electrical performance and leakage control, delivering a high ON/OFF current ratio of 8.25 × 10<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><roman>8</roman></sup>, a specific ON-resistance of 257.5 mΩ⋅cm<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><roman>2</roman></sup>, an OFF-state breakdown voltage of 1210 V, and power figure-of-merit of 5.68 MW/cm<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><roman>2</roman></sup>. These findings suggest the critical role of Sn δ-doping in optimizing channel properties for high-performance, high-voltage α-Ga<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><roman>2</roman></sub>O<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><roman>3</roman></sub>-based power devices.