Improvement of crystal quality and optical property in (11-22) semipolar InGaN/GaN light emitting diodes grown on hemi-spherically patterned SiO2 mask

We report the improved crystal quality and optical property in (11-22) semipolar InGaN/GaN light emitting diodes (LEDs) grown on hemi-spherically patterned SiO2 mask on m-plane sapphire substrate (HP-SiO2) compared with the m-plane sapphire substrate (m-planar), using metalorganic chemical vapor deposition (MOCVD). The photoluminescence (PL) results showed that the integrated intensity of the near band edge (NBE) emission of the GaN layer grown on HP-SiO2 was increased by 3 times as high as that of m-planar. The full width at half maximums (FWHMs) of X-ray rocking curves for the on- and off-axis planes of the GaN layers on HP-SiO2 were narrower down than on m-planar, which indicates that the crystal quality of the semipolar GaN layers on HP-SiO2 was considerably improved as compared with that on m-planar by reducing defects such as perfect/partial dislocations and basal stacking faults. Cross-sectional transmission electron microscopy (TEM) images also showed the reduction of dislocation density in GaN layers on HP-SiO2 than on m-planar. The optical power of InGaN/GaN LEDs with HP-SiO2 was increased by 1.7 and 7.3 times at injection current of 20 mA and 100 mA, respectively, in comparison with the m-planar LEDs.