Pretreatment by selective ion-implantation for epitaxial lateral overgrowth of GaN on patterned sapphire substrate

Epitaxial lateral overgrowth (ELO) process of gallium nitride (GaN) films on cone-shaped patterned sapphire substrate (PSS), which was pretreated by ion-implantation was performed by using a metal organic chemical vapor deposition. A 250-nm-thick silicon dioxide (SiO₂) mask was covered on the planar surface of the PSS to protect them from ion-implantation damages, whereas the cone-shaped patterns of the PSS were exposed to collide with the N⁺ ions. The ion-implantation pretreatment was selectively carried out on the cone-shaped pattern of PSS at 67.5keV with a high dose of 5×10¹⁷ cm^-2. As a result of ion-implantation pretreatment, nucleation growth of GaN poly-grains was inhibited on the cone-shaped patterns with various crystal planes, such as c-like plane, R-like plane, and n-like plane. Surface roughness and crystal quality of GaN films grown on ion-implanted PSS were improved owing to the inhibition of nucleation growth on the patterns. The ion-implantation pretreatment is a very promising technique in the ELO process of GaN on an uneven substrate such as a cone-shaped PSS that includes various crystal planes.