A Study on the Impact of Dislocation Density on Leakage Current in Vertical GaN-on-GaN p-n Diodes

The impact of dislocation density on off-state leakage current in avalanche-capable gallium nitride (GaN)-on-GaN vertical p-n diodes is experimentally demonstrated and studied. At first, the presence of avalanche breakdown was confirmed on p-n diodes grown on bulk GaN substrates with dislocation density ranging from 1e4 to 1e6 cm
⁻²
. The impact of dislocation density on off-state leakage current was then compared and analyzed on devices with confirmed stable avalanche behavior. The devices in the 1e6-cm
⁻²
region show higher leakage current and a more variable-range-hopping-dominated leakage process, while the Poole–Frenkel effect starts showing more influence on the devices in the 1e4-cm
⁻²
region, especially under medium and high average electric field beyond 1.0 MV
$\cdot $
cm
⁻¹
.