A Nonpolar a-Plane GaN Grown on a Hemispherical Patterned r-Plane Sapphire Substrate

Abstract

A high-quality a-plane GaN layer with a pit-free, mirror-like surface was grown on a hemispherical patterned r-plane sapphire substrate (PSS) by metal–organic chemical vapor deposition. The use of the r-plane PSS reduced the density of defects such as basal plane staking faults and threading dislocations of the a-plane GaN. The low-temperature-photoluminescence intensity of the emissions at 3.25 and 3.39 eV related with the defects increased along with the near-band-edge emission at 3.46 eV. The intensity of yellow emission at 2.2 eV on the PSS was remarkably decreased, which indicates the improvement of the crystal quality because of the defect reduction. The InGaN light emitting diode grown on the PSS showed an output power of 7.4 mW at 100 mA, which was about 7 times higher than that on the planar substrate.

Improved Performance of (112̄2) Semipolar InGaN/GaN Light-Emitting Diodes Grown Using a Hemispherically Patterned SiO2 Mask

“…[15][16][17][18] Additionally, a hemispherically patterned sapphire substrate (HPSS) has been used to reduce defect density as well as to improve the light extraction efficiency of (11 20) nonpolar and (11 22) semipolar InGaN/GaN LEDs. 19,20) Actually, many defects were reduced in nonpolar and semipolar GaN layers grown on HPSS. However, in case of (11 22) semipolar structures, some defects were generated in the interface between GaN nuclei and hemispherical patterns.…”

Semipolar GaN Films on Prism Stripe Patterneda-Plane Sapphire Substrates

“…7,8 If a hemispherical pattern was applied on the r-plane sapphire, it was able to reduce the defect density. [9][10][11] Okada and Okuno have reported that nonpolar m-plane GaN films can be grown on patterned a-plane sapphire substrates if a pattern with c-plane sidewalls is adopted. [12][13][14] In this study, periodic prism stripe patterns were introduced onto aplane sapphire substrates for GaN growth.…”