Improved Performance of (11bar 22) Semipolar InGaN/GaN Light-Emitting Diodes Grown Using a Hemispherically Patterned SiO2 Mask

In this paper, we report on the improved performance of (11 (2) over bar2) semipolar InGaN/GaN light-emitting diodes (LEDs) grown using a hemispherically patterned SiO2 mask on an m-plane sapphire substrate (HP-SiO2), in comparison with a planar m-plane sapphire substrate and a hemispherically patterned m-plane sapphire substrate (HPSS), by metalorganic chemical vapor deposition. The full widths at half maximum of X-ray rocking curves for the on- and off-axes planes of the GaN layers on HP-SiO2 were the narrowest of the three samples. Cross-sectional transmission electron microscopy images showed larger low defect areas of GaN layers on HP-SiO2 than on HPSS. The electroluminescence results showed that the optical powers of LEDs on HPSS and HP-SiO2 increased by approximately 2.7 and 6 times, respectively, over that of m-planar sapphire at 100 mA. Our results suggest that the introduction of HP-SiO2 is very effective to improve the crystal quality as well as the light extraction efficiency of semipolar InGaN LEDs. (C) 2013 The Japan Society of Applied Physics