Photonic crystal interactions with electroluminescence from zinc sulfide thin films doped with erbium trifluoride

Photonic crystal (PC) interactions with the near-infrared emission at a wavelength of 1550 nm from zinc sulfide (ZnS) doped with erbium trifluoride (ErF3) have been studied in alternating current thin film electroluminescent (ACTFEL) devices. An objective of this study was to determine if propagation of light parallel to the surface would be frustrated by the PC and result in the increase of light intensity emitted perpendicularly to the surface. The thin film phosphor light emitting layer was deposited by radio frequency (RF) planar magnetron sputtering of a 1.5 mol% ErF3-doped ZnS target and an undoped ZnS target onto the substrate stack consisting of an insulating Al2O3-TiO2 (ATO) layer on a transparent conducting indium-tin oxide (ITO) layer on glass. A honeycomb structured PC was fabricated into the ZnS:ErF3 layer by electron beam lithography on a polymer masking layer and the pattern was transferred into the ZnS:ErF3 layer by argon sputtering. An insulating thin film layer of yttria-stabilized-zirconia (YSZ) or barium tantalate (BaTa2O6) was deposited into the honeycomb structure of holes, creating the photonic crystal structure with a dielectric mismatch between the ZnS:ErF3 layer of 20 or 11, for the YSZ and BaTa2O6 respectively. Aluminum was then deposited as the top electrode in order to complete the ACTFEL device. The photonic band gaps were modeled for 13 input parameters including dielectric mismatch and honeycomb structure to determine the parameters of hole diameter and lattice spacing needed to achieve a photonic band gap for light at 1550 nm. For the structures used in this study, the lattice constant and hole diameter typically were on the order of 1000 nm and 350 nm respectively. The BaTa 2O6 structured PC affected the angularly resolved emission characteristics of the 1550 nm light by an ∼18% increase in the light emitted at ∼15 degrees off normal to the face of the device when compared to control devices. The angularly resolved emission of this device at 550 nm light was unchanged from the control devices. The YSZ structured PC ACTFEL device showed a two fold increase in 1550 nm light intensity versus a device without a PC structure as compared to the emission of 550 nm light which should not be effected by the PC structure. Analyses of the light scattering and reflection caused by the structure of the PC do not prove sufficient to explain the increase in 1550 nm emission of the PC device. Therefore, the increase in light intensity at 1550 nm is attributed to the PC effect of frustration of parallel light propagation to the surface resulting in the increase of light emitted perpendicularly to the surface. (Full text of this dissertation may be available via the University of Florida Libraries web site. Please check http://www.uflib.ufl.edu/etd.html)...