MOCVD Regrowth and Surface Morphology Study of Distributed Bragg Reflector Structures on Photonic Crystal Layers

Photonic-crystal surface-emitting lasers (PCSELs) are a new type of semiconductor laser with the potential for high-power output and high-beam-quality operation. Integrating a distributed Bragg reflector (DBR) into PCSELs can significantly enhance device performance. However, the growth of high-aluminum-content DBRs on photonic crystal layers with buried air holes presents two major challenges. First, the low mobility of aluminum atoms increases the propagation of surface roughness from the substrate into the DBR, increasing defect density. Second, the high growth temperatures required for DBR growth can deform the thermally unstable air holes. In this work, we investigated a metal–organic chemical vapor deposition (MOCVD) regrowth process for fabricating DBRs on PCSELs. By adjusting the epitaxial growth temperature and V/III ratio, we effectively controlled the diffusion of adatoms on both the sample surface and inside the holes. As a result, the root mean square (RMS) surface roughness decreased by ~96%, and uniform buried air holes were obtained, with a filling factor of ~ 18.8% and a depth of ~ 270 nm, without significant deformation. Finally, we fabricated a PCSEL device with a DBR structure, exhibiting a beam divergence angle of ~ 0.5° and a peak power of about 0.86 W. This study provides a key process solution for the development of PCSELs with high-quality DBR structures, enabling further improvement in optical output performance.