An effective approach to enhance the light output power of InGaN/GaN light emitting diodes (LED) was proposed using
pyramidal patterned sapphire substrates (PSS). The sapphire substrates were patterned by a selective chemical wet
etching technique. GaN-based LEDs were fabricated on patterned sapphire substrates through metal organic chemical
deposition (MOCVD). The LEDs fabricated on patterned sapphire substrates exhibit excellent device performance
compared to the conventional LEDs fabricated on planar sapphire substrates in the case of the same growth and device
fabricating conditions. The light output power of the LEDs fabricated on patterned sapphire substrates was about 37%
higher than that of LEDs on planar sapphire substrates at an injection current of 20 mA. The significant enhancement is
attributable to the improvement of the quality of GaN-based epilayers and improvement of the light extraction efficiency
by patterned sapphire substrates.
Patterning sapphire substrate can relax the stress in the nitride epilayer, reduce the threading dislocation density, and
significantly improve device performance. In this article, a wet-etching method for sapphire substrate is developed. The
effect of substrate surface topographies on the quality of the GaN epilayers and corresponding device performance are
investigated. The GaN epilayers grown on the wet-patterned sapphire substrates by MOCVD are characterized by
means of scanning electrical microscopy (SEM), atomic force microscopy (AFM), high-resolution x-ray diffraction
(HRXRD), and photoluminescence (PL) techniques. In comparison with the planar sapphire substrate, about a 22%
increase in device performance with light output power of 13.31 mW@20mA is measured for the InGaN/GaN blue
LEDs grown on the wet-patterned sapphire substrate.
Nano-patterning sapphire substrates technique has been developed for nitrides light-emitting diodes (LEDs) growths. It
is expected that the strain induced by the lattice misfits between the GaN epilayers and the sapphire substrates can be
effectively accommodated via the nano-trenches. The GaN epilayers grown on the nano-patterned sapphire substrates by
a low-pressure metal organic chemical vapor deposition (MOCVD) are characterized by means of scanning electron
microscopy (SEM), high-resolution x-ray diffraction (HRXRD) and photoluminescence (PL) techniques. In comparison
with the planar sapphire substrate, about 46% increment in device performance is measured for the InGaN/GaN blue
LEDs grown on the nano-patterned sapphire substrates.