Low Contact Resistivity of <10 Ω·mm for Au-Free Ohmic Contact on p-GaN/AlGaN/GaN

A robust Au-free p-type ohmic contact process with ultralow contact resistivity is developed on p-GaN/AlGaN/GaN, which demonstrates the potential of GaN CMOS to be compatible with Si CMOS process lines. A novel metal stack of Mg/Ni/Pt is designed, and ultralow contact resistivity of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$8 \; \Omega \cdot $ </tex-math></inline-formula>mm (<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${1}.{0} \times {10}^{-{5}} \; \Omega \cdot $ </tex-math></inline-formula>cm<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$^{{2}}\text {)}$ </tex-math></inline-formula> is achieved. It is revealed that the Ga vacancies on the p-GaN surface induced by Ni, and the Ni2O3 embed in the decomposed p-GaN are key to forming stable low resistivity ohmic contact.