GaN blue light-emitting diodes with a peak emission wavelength of approximately 461nm were fabricated on a c-face lens patterned sapphire substrate and an unpatterned sapphire substrate by metal organic chemical vapour deposition. The crystal structure of an epitaxial GaN film was improved by using the patterned sapphire substrate. The peak wavelengths with electroluminescence intensities of 462 and 464nm were measured for patterned sapphire substrates and unpatterned sapphire substrate light-emitting diodes using a 20mA injection current. It was found that the electroluminescence intensity of the light-emitting diodes grown on the lens patterned sapphire substrate was about 61% higher than that of the light-emitting diodes prepared on the unpatterned sapphire substrate. The emission angle of the patterned sapphire substrate light-emitting diodes increased by 1.5 times compared with that of the unpatterned sapphire substrate unpatterned sapphire substrate light-emitting diodes. The luminous intensities of both light-emitting diodes increased similarly on both circular and square reflectors. The output power of the patterned sapphire substrate light-emitting diodes was 33% greater than that of the light-emitting diode unpatterned sapphire substrate. In addition, the reduction in full width at half maximum in the ω-scan rocking curves of GaN on the patterned sapphire substrate suggested an improved crystal quality. These significant improvements in output power and emission angle resulted from the enhanced light extraction and the reduced threading dislocation density using the patterned sapphire substrate method.

Improvements in Optical Power and Emission Angle of Blue Light Emitting Diodes Using Patterned Sapphire Substrates with Low Threading Dislocation Densities. S.M.Jeong, S.Kissinger, Y.H.Ra, S.H.Yun, D.W.Kim, S.J.Lee, H.K.Ahn, J.S.Kim, C.R.Lee: Japanese Journal of Applied Physics, 2010, 49, 04DH02