UV light-emitting diodes grown on GaN templates with selective-area Si implantation.

Abstract

This study demonstrates that selective-area Si implantation performed on the GaN templates instead of conventional dielectric layers, such as SiO2 or SiNx, serves as the mask layer for the epitaxial lateral overgrowth (ELOG) process. Although the substantial mask layer is absent on the templates, selective growth initially occurs on the implantation-free area and then evolves a lateral overgrowth on the Si-implanted area during the regrowth process. This selective growth is attributed to that the crystal structure of the Si-implanted area subjected to the high doses of ion bombardment produces an amorphous surface layer, thereby leading to a lattice mismatch to the regrown GaN layer. Microstructural analyses reveal that the density of the threading dislocations above the Si-implanted regions is markedly lower than the GaN layer in the implantation-free regions. Consequentially, UV LEDs fabricated on the Si-implanted GaN templates exhibit relatively higher light output and lower leakage current compared with those of LEDs grown on ELOG-free GaN templates.