Vertical GaN-on-Tungsten High Voltage pn-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 $1.52~\pm ~0.05$ m $\Omega \cdot $ cm2 to $1.15~\pm ~0.05$ m $\Omega \cdot $ cm2 and the blocking strength is not heavily compromised with its mean value reduced from $1015~\pm ~47$ V to $988~\pm ~57$ 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.