Study of a-Plane GaN Epitaxial Lateral Overgrowth Using Carbonized Photoresist Mask on r-Plane Sapphire

Abstract

Epitaxial lateral overgrowth (ELO) a-plane GaN samples were successfully grown on masked sapphire (11̄02) substrates using an in-situ carbonized photoresist (PR) mask by a metalorganic chemical vapor deposition (MOCVD) method. The PR masks for the ELO process were prepared using conventional lithography in the form of a stripe with an opening of 4 µm and a period of 12 µm. The stripe-patterned PR was annealed at 1100 °C in a H2 atmosphere. The stripes were aligned parallel to the <11̄00>GaN direction. The ELO process of GaN was strongly dependent on the direction of the stripes. Overall, the PR masks on the r-plane sapphire substrate were carbonized during the heating step before the main growth, so that the carbonized PR mask acted as an ELO mask. The study results confirmed the promising potential of the ELO process using an in-situ carbonized PR mask on r-plane sapphire.

Effective Chemical Lift-Off for Air-Tunnel GaN on a Trapezoid-Patterned Sapphire Substrate

“…Selective area growth, which is suitable for a PSS with various planes, reduces the threading dislocation density at the bottom layer of the PSS by creating a template with epitaxial lateral overgrowth (ELOG) [11][12][13]. The ELOG process can significantly reduce defects such as threading dislocations caused by the large lattice mismatch and difference in the thermal expansion coefficient of the sapphire substrate and GaN film [14,15].…”