Nanotexturing of GaN light-emitting diode material through mask-less dry etching

Abstract

We describe a new technique for random surface texturing of a gallium nitride (GaN)light-emitting diode wafer through a mask-less dry etch process. This involves depositing asub-monolayer film of silica nanospheres (typical diameter of 200 nm) and then subjectingthe coated wafer to a dry etch process with enhanced physical bombardment. The silicaspheres acting as nanotargets get sputtered and silica fragments are randomly deposited onthe GaN epi-layer. Subsequently, the reactive component of the dry etch plasma etchesthrough the exposed GaN surface. Silica fragments act as nanoparticles, locally maskingthe underlying GaN. The etch rate is much reduced at these sites and consequently arough topography develops. Scanning electron microscopy (SEM) and atomicforce microscopy (AFM) inspections show that random topographic features atthe scale of a few tens of nanometres are formed. Optical measurements usingangle-resolved photoluminescence show that GaN light-emitting diode material thusroughened has the capability to extract more light from within the epilayers.