Growth and Characterization of High-Quality, Relaxed In _y Ga_1−y N Templates for Optoelectronic Applications

Abstract

Thick, high-quality InGaN layers can be used as templates for quantum well strain reduction in light-emitting diodes and as optical absorption layers in solar cell structures. Current InGaN growth technology, however, is primarily limited by V-pit formation and non-uniform indium composition. We report the growth and characterization of thick, strain-relaxed In _y Ga_{1− y} N layers, with 0.08 ≤ y ≤ 0.11, by metal organic chemical vapor deposition using the semibulk approach, which consists in periodic insertion of 2-nm GaN interlayers into the bulk In _y Ga_{1− y} N structure; these are then spike-annealed at 1000°C. Photoluminescence, x-ray diffraction, and scanning electron and atomic force microscopy revealed that the semibulk In _y Ga_{1− y} N had optical and electrical properties superior to those of conventional bulk In _y Ga_{1− y} N grown at the same temperature. Homogeneous indium content and substantial reduction of V-pit density were observed for the semibulk In _y Ga_{1− y} N films, even when grown above the critical layer thickness. Double-crystal x-ray diffraction rocking curves also revealed a one order of magnitude reduction of screw dislocation density in the semibulk In _y Ga_{1− y} N film compared with the bulk In _y Ga_{1− y} N film.