Emission enhancement and its mechanism of Eu-doped GaN by strain engineering

Eu-doped GaN (GaN:Eu) is an attractive material for red emission from GaN based light-emitting diodes (LEDs). In GaN:Eu, the Eu ions form multiple luminescent centers that differ in fractional percentage and affinity for capturing energy from the GaN host. We investigated the effects of compressive strain on the PL intensity from GaN:Eu using superlattices. It was found that the PL intensity from a particular Eu center, which is brightest under current injection, could be controlled by varying the magnitude of the in-plane compressive strain. This resulted in a 1.9 times enhancement of the PL intensity. Moreover, it was revealed that this enhancement was mainly due to an increase in the fractional percentage of this Eu luminescent center. This observation suggests that the fractional percentage of the Eu luminescent center could be manipulated by the in-plane compressive strain for the development of brighter GaN:Eu based red LEDs.