Fabrication of Pyramidal Patterned Sapphire Substrates for High-Efficiency InGaN-Based Light Emitting Diodes
- 1 January 2006
- journal article
- Published by The Electrochemical Society in Journal of the Electrochemical Society
- Vol. 153 (8), G765-G770
- https://doi.org/10.1149/1.2209587
Abstract
In this study, a wet-etched pyramidal patterned sapphire substrate (PSS) was used to fabricate the near-ultraviolet InGaN-based light-emitting diodes (LEDs). The pyramidal PSS was etched using a 3H2SO4:1H3PO43H2SO4:1H3PO4 mixture solution and the activation energy of this reaction is determined to be 28.2kcal∕mol28.2kcal∕mol . Three symmetric sidewall facets of the etched pyramidal hole were {112¯k¯}{112¯k¯} on the (0001) sapphire. It was found that the GaN epi layer grew laterally from the top of the pyramid pit and overhung the cavity. An evident reduction in dislocation density of the GaN-on-PSS sample can be confirmed by the etch-pit-density, double-crystal X-ray, and micro photoluminescence measurement results. Under a 20mA20mA forward injection current, the output power of the conventional and pyramidal PSS LEDs (in epoxy lamp form, λD=400nmλD=400nm ) were 7.45 and 9.35mW9.35mW , respectively. A 25% enhancement in output power was achieved in the pyramidal PSS LED as compared with that of the conventional LED sample. The enhanced output power is not only due to the improvement of the internal quantum efficiency upon decreasing the dislocation density, but also due to the enhancement of the extraction efficiency using a pyramidal PSS. From light-tracing calculation, the pyramidal reflector arrays can offer more probability of escaping photons from the GaN/sapphire interface, resulting in an increase in light extracting efficiency.Keywords
This publication has 23 references indexed in Scilit:
- Enhancement in external quantum efficiency of blue light-emitting diode by photonic crystal surface gratingElectronics Letters, 2005
- Increase in the extraction efficiency of GaN-based light-emitting diodes via surface rougheningApplied Physics Letters, 2004
- Light emission and microstructure of Mg-doped AlGaN grown on patterned sapphireApplied Physics Letters, 2003
- Phosphor-Conversion White Light Emitting Diode Using InGaN Near-Ultraviolet ChipJapanese Journal of Applied Physics, 2002
- High Output Power InGaN Ultraviolet Light-Emitting Diodes Fabricated on Patterned Substrates Using Metalorganic Vapor Phase Epitaxyphysica status solidi (a), 2001
- GaN microdisk light emitting diodesApplied Physics Letters, 2000
- High-quality coalescence of laterally overgrown GaN stripes on GaN/sapphire seed layersApplied Physics Letters, 1999
- GaN epitaxial lateral overgrowth and optical characterizationApplied Physics Letters, 1998
- Hydride vapor-phase epitaxy growth of high-quality GaN bulk single crystal by epitaxial lateral overgrowthJournal of Crystal Growth, 1998
- Dislocation density reduction via lateral epitaxy in selectively grown GaN structuresApplied Physics Letters, 1997