Abstract
A significant improvement of output power and external quantum efficiency (EQE)
for nonpolar a-plane (11-20) GaN light-emitting diodes (LEDs) on r-plane sapphire
substrates has been demonstrated by using embedded pyramid-shape air-gap arrays on
hexagonally patterned SiO<sub>2</sub> layer. The air-gap structure was realized based on
asymmetrical growth behavior of a-plane epitaxial lateral overgrowth (ELO) GaN along
+c-axis and -c-axis. The output power and EQE of the a-plane LEDs
with the air-gaps on patterned SiO<sub>2</sub> have increased by more than 50% when compared
to those of the conventional a-plane LEDs. Theoretical fit to the measured EQE suggested
that the significant improvement of EQE was mainly attributed to the increase in light
extraction efficiency (EXE). Light emission pattern analysis and ray-tracing simulation
revealed that the air-gap arrays on top of patterned SiO<sub>2</sub> enlarged the guided-light
scattering at the air-gap surface due to the significant refractive index contrast with
the GaN layer, followed by the improvement of EXE of nonpolar a-plane LEDs.
© 2013 IEEE
PDF Article
More Like This
Cited By
You do not have subscription access to this journal. Cited by links are available to subscribers only. You may subscribe either as an Optica member, or as an authorized user of your institution.
Contact your librarian or system administrator
or
Login to access Optica Member Subscription