Air-gap embedding GaN template for enhanced emission from light-emitting diodes

Selective growth by metal-organic chemical vapor deposition (MOCVD), and electrochemical etching of a heavily Si-doped GaN (n+-GaN) interlayer were employed to obtain air-gaps embedded in a u-GaN layer. As confirmed by Raman spectroscopy, the introduction of an n+-GaN, which was later etched to obtain air-gaps, also enhanced the strain-compliance of GaN epilayer on sapphire substrate. An enhanced electroluminescence emission was observed from the light-emitting diodes (LEDs) fabricated on the air-gap embedding template. Using theoretical LED simulation, it was discerned that the increase in optical emission from the LED was caused predominantly by the redirection of photons at GaN/air-gap interface. Finite-difference time domain (FDTD) simulation method was employed to understand the mechanism of optical emission enhancement and its spatial variation over the LED surface.