This paper investigates GaN-based blue light-emitting diodes (LEDs) grown on sapphire substrates with selective-area Ar-ion implantation. The GaN-based epitaxial layers grown on the Ar-implanted sapphire substrates (Ar-ISS) exhibited selective growth and subsequent lateral growth because of different lattice constants between the implantation and implantation-free regions. As a result, air voids were formed at the GaN/sapphire interface, above the implanted regions and below the active layers of LEDs. We proposed the GaN layer growth mechanisms on the Ar-ISS, and characterized the LEDs with embedded air voids at the GaN/sapphire interface. Using a 20-mA current injection, the light output of the experimental LEDs was found to be 15% greater than that of conventional LEDs. This enhancement can be attributed to the light scattering at the textured GaN/air void interfaces, which increases the probability of photons escaping from the LEDs.