In this work we present a systematic study on the conduction properties in vertical GaN trench MISFETs grown and manufactured on different free standing GaN substrates. It is shown that devices manufactured on ammonothermal substrates have superior conduction current density higher than 4 kA/cm2, specific on‑state resistance as low as 1.1 ± 0.1 mWcm2 and channel sheet resistance of 19.6 ± 0.9 Wmm. It is further shown that scaling these devices to large gate periphery is not limited by current spreading in the drift region, low channel mobility or by self‑heating. The conduction properties of devices manufactured on ammonothermal GaN substrates are found to be the most suitable for pulsed laser driving applications.
