Epitaxial Lateral Overgrowth of GaN Using High-Dose N⁺-Ion-Implantation

Abstract

Epitaxial lateral overgrowth (ELO) process has limited use in GaN devices due to the uneasiness of regrowth or the likeliness of contamination from the ELO mask, even though it is a method to reduce the dislocation density in GaN grown on sapphire substrate. Here we introduce a maskless and single-step ELO process using a high-dose N+-ion implantation. We employed a high-dose N+-ion implantation as an ELO mask instead of usual dielectric material such as SixNy or SiO2. The GaN layer was laterally grown over the ion implanted array formed in a stripe pattern of 4-µm-width, resulting in a complete coalescence after 30 min. TEM and photoluminescence analysis confirmed the reduced dislocation density of the ELO grown GaN layer.

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

“…Sapphire substrates were coated with a 0.9-1 m thick PR that was patterned in arrays of stripes with openings of 4 m wide and a period of 12 m using standard photolithography. 16) The stripes orientation was chosen parallel to the h1 100i GaN direction to realized vertical c-plane sidewalls. 17) Although some positive resist could be used in principle, we chose PR (AZ1512), a photocurable g, i-line positive resist, due to its low viscosity.…”