Abstract
Structural and luminescence properties of In‐rich In__~x~__ Ga~1−x~ N (0.71 ≤ x ≤ 1) layers are comprehensively studied. The layers were grown on (0001) sapphire substrates by radio‐frequency plasma‐assisted molecular‐beam epitaxy, employing two types of underlying structures: low‐temperature‐grown InN (LT‐InN) buffer layers and high‐temperature‐grown InN templates grown on LT‐InN buffer layers. The insertion of the InN templates has improved not only surface morphology but also both a ‐axis and c ‐axis orientations of In‐rich In__~x~__ Ga~1−x~ N layers. In addition, by using InN templates of dramatically improved crystalline quality with the full width at half maximum of (0002) X‐ray rocking curves as narrow as 1 arcmin, which have been recently achieved by optimizing nitridation conditions of sapphire substrates, the crystalline quality of In~0.8~Ga~0.2~N layers was even further improved. On the other hand, however, photoluminescence (PL) line width showed no noticeable variation between the In__~x~__ Ga~1−x~ N layers grown on InN templates and those on LT‐InN buffer layers. Possible factors that determine PL line width and compositional fluctuation of these In‐rich In__~x~__ Ga~1−x~ N are discussed. Interference fringes of X‐ray diffraction (ω –2__θ__ scan) have been observed from the high crystalline‐quality InN templates of the excellent c ‐axis orientation for the first time. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)