Numerically Investigating the Impact of High-k Buried Field-Plate Termination on the Catastrophic Mirror Failure for GaN-Based Laser Diodes

In this work, we find that shallow-level acceptor-type defects can make a relevant contribution to the catastrophic optical mirror damage (COMD) for gallium nitride (GaN)-based Fabry-Pérot (FP) laser diodes (LDs). These charged acceptor-type defects function as negatively charged centers that capture the injected holes and enhance nonradiative recombination at the cavity facets. This significantly enhances the self-heating effect and causes thermally induced facet degradation. To address this challenge, we propose introducing a high-k HfO₂ buried field-plate termination. The high-k HfO₂ buried field-plate enables the stronger electric field magnitude in the GaN region underneath the high-k HfO₂ region, which generates the valence band barrier height and achieves hole confinement. With the developed physical models on the facet, we find that the proposed structure can suppress facet degradation by reducing surface recombination and decreasing the facet temperature. As a result, our design delays the onset of nonradiative-recombination-induced heat in the facet region and enhances the COMD threshold.