Stark structure of the spectrum and decay kinetics of the Er3+ photoluminescence in pseudoamorphous a-nc-GaN films

Abstract

Amorphous films containing nanocrystalline inclusions, a-nc-GaN, were codoped with Er in the course of magnetron sputtering. Intense intracenter emission of Er3+ ions in the wavelength region λ=1510–1550 nm was obtained only after multistage annealing at temperatures of 650–770°C. The intracenter emission was excited indirectly through electron-hole pair generation in the a-nc-GaN matrix by a pulsed nitrogen laser. Subsequent recombination via a number of localized states in the band gap transferred the excitation energy to the Er3+ ions. Measurements of photoluminescence (PL) spectra carried out with time resolution in various annealing stages at different temperatures in the range 77–500 K and in the course of decay permitted us to establish the Stark nature of the PL spectrum and to reveal the dynamic and nonequilibrium character of redistribution of the intracenter emission energy among the Stark modes in the course of the excitation pulse relaxation. The information thus obtained was used to interpret the dominant hot-mode contribution and the complex decay kinetics.