| Rare earth (RE) doping of GaN has led to a new full color phosphor system for electroluminescent (EL) flat panel displays. GaN films doped with ∼1 at. % Eu, Er, and Tm dopants emit pure red, green, and blue emission colors, respectively. As a host for RE luminescent centers, GaN possesses many properties which are ideal for bright full color EL. Specifically, GaN has excellent high field transport characteristics, is chemically and thermally rugged, and incorporates well the RE dopants. With preliminary optimization of GaN:RE phosphors and proper design of EL device structure, GaN:RE phosphors have been advanced in luminous efficiency by two orders of magnitude, to nearly within an order of magnitude of commercially required display efficiencies (∼1 lm/W).; GaN:RE phosphors have been operated in direct current and alternating current thin film electroluminescent device structures. Alternating current GaN:RE EL devices require GaN deposition on amorphous dielectric layers which prevent catastrophic breakdown of the EL display devices at high operating voltage. Alternating current GaN:RE EL devices have been shown compatible with commercial display fabrication techniques, such as formation on low-cost transparent glass substrates. GaN:RE phosphors have also been implemented in a thin/thick film/ceramic substrate hybrid structure which is promising for high yield, large area (>17&inches; diagonal), full color displays which can be manufactured at less than half the cost of plasma displays. Using some of the specific advantages of GaN:RE phosphors, such as high temperature stability, GaN:RE thin film phosphors have been integrated with a novel display technique which advantageously combines utilization of standard flat panel display glass substrates and high-yield screen printing of a high permittivity thick film dielectric layer. Operation lifetimes exceeding 1000 hrs at >95% initial brightness have been achieved. This novel display structure has also been advanced to very high contrast device operation. |
