Suppression of cracks and V-shaped defects, and improvement of reflectivity of GaN/AlGaN distributed Bragg reflectors by insertion of multiple interlayers

Abstract

GaN/AlxGa1–xN distributed Bragg reflectors (DBRs) for the near‐ultraviolet region have been grown on sapphire substrates by metal‐organic chemical vapor deposition. In order to suppress the generation of cracks and V‐shaped defects on the surface of the DBRs, AlGaN/AlN superlattices and step‐graded multiple AlGaN layers were inserted prior to or during the growth of the DBRs. By optimizing those layers, the reflectivity of a 40‐pair GaN/Al0.35Ga0.65N DBR was increased up to 96% without any cracks and V‐shaped defects. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Crack-Free AlN/GaN Distributed Bragg Reflectors on AlN Templates

“…Considering nitride semiconductor-based DBRs, combinations of AlN/GaN, [5][6][7][8][9][10] AlGaN/GaN, [11][12][13][14] AlInN/ GaN, [15][16][17][18] and AlGaN/AlN 19,20) have been reported. AlN/ GaN DBRs have the highest refractive index contrast (Án=n ¼ 0:16) 21) among nitride semiconductor materials.…”

“…25) Several research groups have attempted to suppress crack formation by inserting AlN/GaN or AlGaN/GaN superlattice structures in DBR structures. 11,26,27) In this study, AlN templates are used for the growth of AlN/GaN DBRs for the first time, instead of GaN templates. Although DBRs on GaN templates receive tensile stress, DBRs on AlN templates receive compressive stress, generally preventing crack formation.…”