Eu-doped Lu2O3 epitaxial films with an embedded nanoporous GaN distributed Bragg reflectors

Abstract

The GaN/nanoporous GaN (NP-GaN) distributed Bragg reflectors (DBRs) with high reflectivity (>95%) at specific wavelengths were designed and fabricated by an electrochemical (EC) etching technique, and then as-grown GaN and DBR were used to grow Eu-doped Lu2O3 high-quality films by Pulsed Laser Deposition (PLD) method. Structural analyses confirmed the thin film grown at 480 °C has highest crystalline quality. The epitaxial relationship between the film and substrate was determined as Lu2O3 (222)∥GaN (0002) with Lu2O3[1‾10]∥GaN[1‾21‾0]. The photoluminescence (PL) intensity of the Eu-doped Lu2O3 film with an embedded DBR substrate was 3.4 times higher than for reference film on as-grown GaN, which should be attributed to in-coupling and out-coupling of the excitation and emission lights. The enhancement effects of light-coupling were explained by multiple reflection model. Hence, this strategy can be used to enhance the optical signal intensity of scintillators by embedding DBR substrates with proper Bragg wavelength.