Nanopore morphology in porous GaN template and its effect on the LEDs emission

Abstract

GaN grown on sapphire is electrochemically etched in HF and in KOH. Etching in HF results in a network of nanopillars while that etched in KOH results in a network of pores. The higher density of voids from the network of pores shows the highest strain relaxation for a 1.2 µm thick GaN overgrown on the porous templates. In general, a light-emitting diode (LED) on the porous templates gives about 1.5 times higher intensity and a spectral envelop shift towards the red due to a higher In incorporation. The higher intensity is attributed to enhanced light extraction due to light scattering at the voids formed from the pores and improved material quality with dislocation reduction. The formation of larger overgrowth GaN islands which merges to give a continuous GaN film over the porous template reduced the dislocation density and also accounted for higher strain relaxation for the growth of the quantum dots (QDs) and quantum well layers. This reduced the extent of peak shift of LEDs grown on porous GaN template and improved its performance.