Optoelectronic and structural characteristics of Er-doped amorphous AlN films

Abstract

This work reports on the optical, electronic, and structural properties of aluminum-nitrogen (AlN) films doped with Er. The films were deposited by conventional radio-frequency sputtering at 200°C in an atmosphere of pure nitrogen. Their main characteristics have been investigated by experimental techniques such as optical transmission, photo- and cathodoluminescence, Raman scattering, and x-ray photoelectron spectroscopy. All films exhibit Er3+-related optical emissions in the visible and infrared regions, which are considerably enhanced after thermal annealing and on measurements at low temperature. Moreover, Raman spectroscopy indicates that the films remain amorphous even after thermal treatment at 900°C. Based on the composition and on the structural and luminescent properties of these Er-doped amorphous AlN films it was possible to conclude that energy excitation of Er3+ ions takes place according to different routes when electrons or photons are used. In the former case, energy is transferred from the amorphous host to the Er3+ ions by carrier-mediated processes. As a result, relatively strong Er3+-related optical transitions can be observed in the ∼400–1600nm range. Excitation with 488.0nm photons also produces visible and infrared Er3+-related luminescence, but most of the optical excitation occurs through direct excitation of the F7∕24 level of Er3+. Finally, the role played by nitrogen atoms and thermal treatments on the achievement of light emission from the present AlN films is discussed and compared with the existing literature.