Light extraction enhancement of sapphire‐free InGaN LEDs using single‐ and double‐side surface roughening techniques

Abstract

AbstractWe compare the performance of three types of GaN‐based light‐emitting diodes (LEDs) epitaxially grown on patterned sapphire substrates (PSSs). For the devices with a single roughened p‐GaN surface, the light output power of the original LEDs with the PSS and Ag reflector (Sample A) is lower than that of thin‐film LEDs transferred onto Si carriers via glue bonding (Sample B). While the thin GaN LEDs with double‐side roughening (both p‐GaN and micropillar undoped‐GaN surfaces) and glue/Ag omnidirectional reflector (Sample C) shows much higher light output power than that of Sample B. As compared with the Sample A, the Sample C shows a performance enhancement of 50.3% in light output power and 46.3% in power efficiency at 350 mA. These results reflect that the contribution of the micropillar undoped‐GaN texturing for the light extraction is dominant. The employment of Si carrier decreases the junction temperature of the Sample C, a 46.6 °C lower than that of the conventional LEDs on PSS. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)