Layered mixed-anion compounds: Epitaxial growth, active function exploration, and device application

Abstract

Optoelectronic properties and device applications of layered mixed-anion compounds such as oxychalcogenide LaCuO Ch ( Ch = chalcogen) and oxypnictide La T MO Pn ( T M = 3d transition metal, Pn = pnicogen) are reviewed. Several distinctive functions have been found in these materials based on our original material exploration concept. Fabrication of high-quality epitaxial films of LaCuO Ch leads to clarifying the excellent electrical and optical properties such as high hole mobility of 8 cm 2/(V s) and heavy hole doping at >10 21 cm −3 in LaCuOSe, and sharp and tunable-wavelength photoluminescence in the solid–solution systems in LaCuO Ch. In addition, a room temperature operation of a light-emitting diode is demonstrated using LaCuOSe as a light-emitting layer. These results suggest that the layered oxychalcogenides have potential for light-emitting layers as well as transparent hole-injection layers in organic/inorganic light-emitting diodes. Furthermore, by extending the material system from the copper-based oxychalcogenides to isostructural compounds, transition metal-based oxypnictides La T MOP ( T M = Fe, Ni), we have found novel superconductors, LaFeOP and LaNiOP.