Avalanche Stability Improvement by Boron Implanted GaN JTE Structures with Reduced Trap Density

In this work, we examined improvement of vertical GaN p-n diodes with boron-implanted junction termination extension (JTE), focusing on breakdown voltage stability under avalanche stress. In the JTE technique, acceptors in the p-type epitaxial layer are compensated to achieve charge balance by introducing donor levels caused by boron implantation. We demonstrate significant suppression of avalanche walkout for 1.2 kV p-n diodes with the JTE structure and high temperature annealing of up to 900
${}^{\circ}\mathrm{C}$
to reduce deep trap density after the implantation. The p-n diodes fabricated with the new process condition on 4-inch freestanding GaN substrates demonstrate good reverse characteristics over the entire wafer and high avalanche capability with positive temperature coefficient of breakdown voltage.