Development of mercury-free ultraviolet light emitting devices

We developed rare-earth doped phosphors for mercury-free narrowband ultraviolet light sources. The narrowband emission is a typical feature of the intra-orbital electron transition in the rare-earth Gd³⁺ ion. Al_1-xGd_xN epitaxial films were grown by using an ultra-pure reactive sputtering technique performed under molecular-beam epitaxial quality. A narrowband luminescence line from Gd³⁺ ions has been observed at 318 nm. We fabricated field-emission devices using Al_1-xGd_xN thin films and investigated detailed device characteristics. Furthermore, recently, we have successfully developed bright fluorescent lamps with an ultraviolet phosphor containing Gd³⁺ ions.