Closing the yellow gap with Eu- and Tb-doped GaN: one luminescent host resulting in three colours

Abstract

Gallium nitride (GaN) is a key material when it comes to light-emitting diodes (LEDs) and has pushed the LED revolution in lighting and displays. The concept of down-conversion of a GaN-based blue LED offers the possibility to provide efficient generation of monochromatic, high-color purity light resulting in a highly efficient warm-white all-nitride phosphor-converted light emitting diode (pc-LED). Although the down conversion of blue light from InGaN LEDs has become a dominant technique for producing white light, there are still some technical challenges, e.g. the immiscibility of GaN and InN and the lattice mismatch between the substrate and InGaN, that have to be overcome. Here we demonstrate the doping of bulk GaN with europium, terbium and the combination of both resulting in intriguing luminescence properties, pushing the role of GaN:Eu,Tb as a chief component in future light emitting diodes. This colour tuning proves that one luminescence host can provide three colours (red, green and orange) and that even the so called “yellow gap” could be closed with a III-nitride. By using one material for all colours, it will be possible to overcome the technical challenges in building up LED devices, which will open up new capabilities for modern highly efficient phosphors.

Eu- and Tb-adsorbed Si3N4and Ge3N4: tuning the colours with one luminescent host

“…This effect could be proven in the meantime for other doped nitrides 31 e.g. , GaN 31,32 (see Fig. 2e), and carbodiimides as well.…”

“…Silicon nitride (Si 3 N 4 ) materials have been found to meet these requirements due to its rigid lattices with highly covalent network and high thermal stability. 31,32 However, looking at the literature indicates that there are only a few investigations concerning rare-earth doped silicon nitride materials. In most cases only Eu- and Tb-doped α-Si 3 N 4 thin films and nanowires illustrating broad band emission are concerned.…”

“…As well novel is the fact that a pure nitride host material shows green luminescence, 31,32 till now this could only be realized by oxynitrides and oxonitridosilicates. 18,50–53…”

“…As well novel is the fact that a pure nitride host material shows green luminescence, 31,32 till now this could only be realized by oxynitrides and oxonitridosilicates. 18,[50][51][52][53] Just recently we demonstrated that the so called "yellow gap" could be closed for bulk GaN via co-doping with europium and terbium.…”

“…18,[50][51][52][53] Just recently we demonstrated that the so called "yellow gap" could be closed for bulk GaN via co-doping with europium and terbium. 32 Co-doping really opens up a multitude of degrees of freedom to customize and adapt a luminescent material to specic needs.…”