Degradation of β-Ga<sub>2</sub>O<sub>3</sub> Vertical Ni/Au Schottky Diodes Under Forward Bias
Rujun Sun, Andrew R Balog, Haobo Yang, Nasim Alem, Michael A. Scarpulla
Abstract
Here we report on the degradation processes of Au/Ni/ <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\beta $ </tex-math></inline-formula> -Ga{2}O{3} Schottky diodes under forward bias stress which is related to their on-state reliability. In some diodes, we find a bias regime of electrical degradation occurring at a lower bias than those causing contact changes visible in optical microscopy. In this regime, the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\text{V}_{\text {bi}}$ </tex-math></inline-formula> increases but is associated with decreasing <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\text{I}_{\text {s}}$ </tex-math></inline-formula> . In the higher-bias regime associated with contact roughing and change in appearance caused by the metallurgical changes mentioned, the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\text{V}_{\text {bi}}$ </tex-math></inline-formula> continually increases with increased <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\text{I}_{\text {s}}$ </tex-math></inline-formula> , ideality factor, and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\text{R}_{\text {on}}$ </tex-math></inline-formula> . In regions near the failure point, the Ni adhesion layer actually diffuses through the Au layer, which recrystallizes, and forms NiO on the top surface. This work highlights the importance of developing more thermodynamically stable refractory contacts to <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\beta $ </tex-math></inline-formula> -Ga2O3 to enhance long-term reliability.