Normally-OFF GaN MIS-HEMT With F⁻ Doped Gate Insulator Using Standard Ion Implantation

Abstract

A normally-OFF GaN metal-insulator-gate high electron mobility transistors with fluorine doped gate insulator has been fabricated using standard ion implantation technique. Fluorine ions with negative charges were doped lightly into both the gate insulator and the partially recessed barrier layer, resulting in high positive threshold voltage ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${V} _{\mathrm{ th}}$ </tex-math></inline-formula> ) for the device, meanwhile preserving low ON-resistance. Compared to the fluorine-free and recess-free device, only about 16% increase of ON-resistance was observed for the F <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">−</sup> doped devices. The fabricated F <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">−</sup> doped device exhibits a threshold voltage of +0.68 V at <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${I} _{\mathrm{ DS}}= 5~\mu \text{A}$ </tex-math></inline-formula> /mm, a current density of 620 mA/mm, an OFF-state breakdown voltage of 800 V, and high ON/OFF current ratio of 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">10</sup> . For thermal stability consideration of fluorine dopant, the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${V} _{\mathrm{ th}}$ </tex-math></inline-formula> -thermal stability test and positive bias temperature instability test were also discussed.