Vertical GaN-on-Tungsten High Voltage <i>pn</i>-Diodes From Sapphire-Grown GaN Membranes

In this work, we demonstrate vertical GaN pn-diodes for high voltage applications initially grown and processed on 4” sapphire substrates and then transferred to 4” tungsten substrates to achieve a fully vertical conduction path. Laser lift-off was used to separate the GaN-membrane device structures from the initial sapphire substrate. The diodes show improved forward conduction after the transfer process with on-state resistance reduced from <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$1.52~\pm ~0.05$ </tex-math></inline-formula> m<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\Omega \cdot $ </tex-math></inline-formula>cm2 to <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$1.15~\pm ~0.05$ </tex-math></inline-formula> m<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\Omega \cdot $ </tex-math></inline-formula>cm2 and the blocking strength is not heavily compromised with its mean value reduced from <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$1015~\pm ~47$ </tex-math></inline-formula> V to <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$988~\pm ~57$ </tex-math></inline-formula> V. High device yields of the membrane transfer procedure underscores this cost-competitive vertical GaN device technology for high-power applications without the need of expensive GaN substrates.