Vertical GaN-Based LEDs With Naturally Textured Surface Formed by Patterned Sapphire Substrate With Self-Assembled Ag Nanodots as Etching Mask

We propose a new pattern-transfer method comprising laser liftoff and wafer bonding process; the former was used to separate GaN-based epitaxial layers from patterned sapphire substrates (PSSs) with self-assembled surface nanodots, and the latter was used to combine the epitaxial layers with the Si substrate. The nanodots on the PSS surface were formed by dry etching with self-assembled Ag nanoislands as an etching mask. The fabricated vertical GaN-based light-emitting diodes (VLEDs) presented an in situ nanotextured surface. At a driving current of 350 mA, the VLEDs increased the output power by ~17% compared with the conventional VLEDs without a nanotextured surface. The main enhancement can be attributed to the increase in light-extraction efficiency of photons emitted inside the LEDs.