Stimulated emission of Cr²⁺ ions in ZnS:Cr thin-film electroluminescent structures

摘要

First observation of stimulated Cr²⁺ emission in ZnS:Cr electroluminescentud(EL) impact-excited thin-film waveguide structures is reported. The structures consist ofudthe following thin films deposited on a glass substrate: a transparent In₂O₃:Sn electrode,udan insulator SiO₂/Al₂O₃ layer (~270 nm), an EL ZnS:Cr film (~600 nm), the sameudinsulator layer, and an Al electrode. The stimulated character of the emission recordedudthrough the edge of the structure is evidenced by the following. With increasing theudapplied voltage, a broad band with three waveguide mode maxima in the edge emissionudspectrum changes into an intensifying and narrowing band. The maximum of this band isudthe same as that of the Cr²⁺ emission band recorded through the face, i.e. through theudIn₂O₃:Sn electrode (1.75 and ~2.6 µm at the Cr concentrations (5-7)*10¹⁹ and (2-ud3)*10²⁰ cm⁻³, respectively). The five-fold narrowing is observed when increasing theudvoltage by ~4% in the case of the lower Cr concentration. The voltage and frequencyuddependences of the edge emission are stronger than those for the face emission. A smalludmanifestation of the gain occurrence in the ZnS:Cr TFELS is also observed in the faceudemission. The possibility to create a new type of electrically pumped lasers with theudimpact excitation mechanism is discussed.