Fabricating Ultralow Dislocation Density Microlight-Emitting Diodes on a Silicon Substrate via an Epitaxial Lateral Overgrowth Method

Abstract

Microlight-emitting diodes were fabricated using an original substrate (ELO GaN on silicon; EGOS). The EGOS substrate was fabricated by growing a GaN layer on a (111)-plane silicon substrate via the epitaxial lateral overgrowth technique. The EGOS substrate has a wide mask that formed an open area. The widths of the ELO mask and open area are 51.5 and 3.5 μm, respectively. Whole micro-LEDs could be formed within the wing area by widening its width, which has a low defect density. Because the adjacent ELO layers do not coalesce into each other, gaps are present between the ELO layers. The EGOS substrate exhibits a ridge structure that is formed via the dry-etched method, facilitating the removal of the chips from the EGOS substrate. The optimizing growth condition of the ELO GaN layer was realizing 3.2 μm in thickness even though the width of the LEO layer is over 47 μm. Cathode luminescence measurement did not show dislocations at the wing area of the ELO layer. The micro-LEDs fabricated via this method emitted at 424 nm, proving the feasibility of the method. The original substrate with an ELO layer can be used as a platform to fabricate many kinds of microlight sources with an ultralow dislocation density.