Low energy electron excited nanoscale luminescence spectroscopy of erbium doped AIN

Abstract

We have investigated the optical activity of Er3+ ions in AlN via depth-resolved, (5 nm to 250 nm), low energy electron-excited nanoscale (LEEN) luminescence spectroscopy and compared it with the luminescence of an Er-free AlN film. For the Er-free film, there was no emission in the IR from the AlN at any depth, and at higher energies we measured only a broad, weak feature between 1.7–3.25 eV along with an O defect related feature at 3.8 eV, which is significantly enhanced toward the surface. We found strong emission in the AlN:Er films from the first excited → ground state transition of Er3+ at 0.80 eV along with many other excited state transitions, although the features are broad compared to those of GaN:Er. The AlN:Er luminescence saturates near a concentration of 1021 cm−3, at which point we also observe enhanced O defect related luminescence uniformly distributed throughout the film. This finding suggests a role for O in activating the Er at low Er concentrations, while inhibiting the Er activity at high O concentrations.