Paper TF1-FrM5
Near IR Electroluminescent Studies Of ZnS Photonic Crystal

Friday, October 19, 2007, 9:20 am, Room 602/603

The effects of a photonic crystal (PC) structure on outcoupling of light from an alternating current thin film electroluminescent (ACTFEL) device are being studied. The ACTFEL device consists of a thin film of ZnS doped with erbium sputter deposited onto an aluminum-titanium-oxide (ATO) thin insulating layer on an indium-tin-oxide (ITO) transparent conducting electrode on a glass substrate. Al top electrodes are vapor deposited onto the ZnS:Er phosphor, and light is emitted through the glass substrate. ZnS:Er has strong emissions in the near IR at 1550nm, but it has been shown that much of this light is lost laterally to total internal reflection and absorption. The PC structure allows light from these lost modes to be transferred to modes that outcouple from the device. The data show that a triangular array of circles of radius and lattice spacing of 264nm and 660nm, respectively, in the ZnS:Er layer of the ACTFEL device allow coupling of horizontal modes to vertical modes. The sensitivity of this coupling to the dimensions of the PC will be reported. The PC was created with electron-beam lithography using a PMMA resist over the ZnS:Er layer of the ACTFEL device. An Ar ion etch was used to etch the triangular array of holes into the ZnS:Er layer. FOx® flowable silicon oxide was spin coated into the holes to act as the contrasting dielectric layer to the ZnS:Er layer which enables the PC effect. Finally an aluminum electrode was vapor deposited on the backside of the device. The emissions of ACTFEL devices were analyzed using an optical spectrometer. A sevenfold increase in the vertical modes of 1550nm light emission was observed from a device with a PC structure.