Cathodoluminescence study of GaN-infilled opal nanocomposites

Abstract

In this study, three-dimensional ordered synthetic opals formed by spheres of 230 nm impregnated with GaN have been investigated. In some of the samples gold and platinum were also introduced. The potential applications of GaN-opal assemblies include use in large surface area (of the order of 10 m_2/cm_3 GaN-based light-emitting devices at a high density of elements. Also, the photonic crystal properties of perfect opal-GaN composites, characterized by the presence of a photonic band gap in the visible range, allow a substantial modification of the emitting properties of GaN-based nanodevices in this spectral region. The optical properties of GaN synthesized within interconnected opal voids have been investigated by cathodoluminescence (CL) in a scanning electron microscope. X-ray spectra have been obtained in order to test the quality of the GaN inside the voids. All CL spectra of the samples show a predominant emission centered at about 2.7 eV which is attributed to the opal matrix. CL spectra also reveal some differences in the spectral distribution of the luminescence which depends on the electron beam-sample orientation. Inhibition of the band edge emission of GaN has been observed in most of the samples. A possible correlation of this effect with the existence of a photonic band gap in the samples is discussed.