Enhanced Red Emission of Eu,O-Codoped GaN Embedded in a Photonic Crystal Nanocavity with Hexagonal Air Holes

Abstract

In this work, we fabricate a nitride-based photonic crystal (PhC) nanocavity with an embedded active layer for unexplored red regions using simplified selective wet etching of an ${\mathrm{Al}}_{0.82}{\mathrm{In}}_{0.18}\mathrm{N}$ sacrificial layer. Eu,O-codoped $\mathrm{Ga}\mathrm{N}$ ($\mathrm{Ga}\mathrm{N}$:$\mathrm{Eu}$,$\mathrm{O}$) is embedded in L7-type two-dimensional-PhC (2D-PhC) nanocavities with hexagonal holes. Room-temperature photoluminescence (PL) shows $\mathrm{Eu}$ emission coupled to the cavity modes at wavelengths around 620 nm. The quality factor of the fundamental mode in an L7 nanocavity is 5400, which is comparable to those of state-of-the-art 2D-PhC nanocavities with embedded nitride-based active layers for the blue and ultraviolet regions. We show that the Purcell effect due to the small mode volumes of the 2D-PhC nanocavities and enhanced light extraction lead to a 54-fold increase in the integrated PL intensity per unit area with respect to the typical $\mathrm{Ga}\mathrm{N}$:$\mathrm{Eu}$,$\mathrm{O}$ emission.