Low-Resistance Ni/Ag Contacts on GaN-Based p-Channel Heterojunction Field-Effect Transistor
Yuanlei Zhang, Zhiwei Sun, Weisheng Wang, Ye Liang, Miao Cui, Yinchao Zhao, Huiqing Wen, Wen Liu
Abstract
In this work, we have demonstrated the Ni/Ag contacts on p-channel heterostructure field-effect transistors (p-HFETs) based on the p-GaN/AlGaN/GaN/Si platform. Using an optimal contact condition, where Ni/Ag (1/120 nm) was deposited and annealed at 550 °C for 180 s in <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\text{O}_{{2}}$ </tex-math></inline-formula> ambient, a low contact resistance ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$27.44 \Omega \cdot $ </tex-math></inline-formula> mm at 50 mA/mm) and a low Schottky barrier height (SBH) (0.479 eV) have been obtained. The p-HFETs with Ni/Ag contacts exhibit a very slight Schottky character, resulting in a satisfactory ON-resistance ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${R} _{ \mathrm{\scriptscriptstyle ON}}$ </tex-math></inline-formula> ) of 2.1 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\text{k}\Omega \cdot $ </tex-math></inline-formula> mm. Furthermore, the p-HFETs exhibit excellent electrical properties including a 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">${V} _{{\text {th}}}$ </tex-math></inline-formula> ) of −1.91 V, an ON-state current ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${I} _{ \mathrm{\scriptscriptstyle ON}}$ </tex-math></inline-formula> ) of 2.46 mA/mm, and an <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${I} _{ \mathrm{\scriptscriptstyle ON}}/{I} _{ \mathrm{\scriptscriptstyle OFF}}$ </tex-math></inline-formula> ratio of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${\sim } 10^{{6}}$ </tex-math></inline-formula> . These results present a great potential of cost-effective Ni/Ag contacts on p-HFETs.