Vertical Ga<sub>2</sub>O<sub>3</sub> MOSFET With Magnesium Diffused Current Blocking Layer
Ke Zeng, Rohith Soman, Zhengliang Bian, Seungbin Jeong, Srabanti Chowdhury
Abstract
Vertical MOSFET is a critical milestone in the gallium oxide (Ga <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> ) roadmap. However, the lack of an effective current blocking layer in Ga <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> , which is essential for any DMOS-like (double-diffused MOSFET) transistors has proved to be the main barrier to the achievement of a vertical MOSFET. Here, we report two novel findings -first, a selective diffusion doping technique utilizing magnesium (Mg) doping spin-on-glass (SOG) as a dopant source to form a current blocking layer (CBL), and second, the first demonstration of a vertical Ga <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> MOSFET with the Mg diffused CBL- Vertical Diffused Barrier Field-Effect-Transistor (VDBFET). The device exhibits an excellent field-effect-transistor (FET) behavior with a high on-off ratio of 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">9</sup> and a decent saturation. Due to the unique nature of the Mg-doped region, the transistor is normally-off with a turn-on voltage of ~7 V. An on-current of 0.15 kA/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> is measured with a gate voltage ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${V}_{g}$ </tex-math></inline-formula> ) of 12 V, and a drain voltage ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${V}_{d}$ </tex-math></inline-formula> ) of 15 V. The three terminal breakdown voltage measured at a <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${V}_{g}$ </tex-math></inline-formula> of 0V is 72 V. The successful demonstration of the first Ga <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> VDBFET significantly brightens the prospect for its application in high power electronics.