Material synthesis and infrared optical properties of transition metal doped binary and ternary II-VI semiconductors

Abstract

ABSTRACTWe report on the material preparation and optical characterization of transition metal (Cr, Co) doped ternary cadmium chalcogenides for possible applications in mid-infrared (MIR) light source development. Cr2+ doped II-VI's (e.g. ZnSe, ZnS) have received significant attention for MIR solid-state laser development in the 2-3 μm region. Transition metal (TM) doped II-VI thin films are also currently being studied for the development of broadly tunable MIR sources pumped through electrical carrier-injection. In this paper, we present results of the material synthesis and IR spectroscopy of several Cr and Co doped cadmium chalcogenides including CdTe, CdMnTe, CdZnTe, CdMgTe, CdCaTe, and CdSrTe. Following the synthesis and purification of undoped II-VI materials, TM doping was achieved during in-situ Bridgman growth or through a thermal diffusion process. The Cr2+ doped II-VI materials were characterized by broad IR absorption bands centered at ∼1800–1900 nm and MIR emission extending from ∼2000–3500 nm. The emission lifetimes varied between 1-5 μs, depending on the Cr concentration and host composition. Co2+ doped cadmium chalcogenides exhibited several absorption bands in the infrared region and broad emission extending from ∼3-5 μm. Compared to Cr2+ doped II-VI's, the emission from Co2+ doped chalcogenides was significantly quenched at room-temperature due to the onset of non-radiative relaxations.