A self-assembled double-island buffer structure for improving GaN-based materials grown on Si substrates

This paper reports a new method to reduce threading dislocation density in GaN epilayers grown on (111) Si substrates by metalorganic chemical vapor deposition. This method utilizes an in- situ SiN_x mask to produce a self-assembled double-island structure, which effectively reduces threading dislocation density from 9.6 × 10⁹ cm^-2 to 2.6 × 10⁹ cm^-2 without using any lithographic and regrowth processes. InGaN light-emitting diodes fabricated on the double-island buffer layer exhibit nearly 20% improvement on the optical output power as well as less energy localization effect, compared to those without the double-island buffer layer. The mechanisms of double-island formation as well as dislocation reduction are proposed based on transmission electron microscopy investigations.