Semiconductors doped with erbium are attractive materials for optoelectronic devices due to the fact that characteristic Er³⁺ emissions meet technologically important spectral ranges, and semiconductor host provides the possibility of electrical excitation. Due to low thermal quenching of erbium luminescence, GaN:Er was recently extensively studied and devices based on this material were demonstrated. However, the optimization of the emission requires a better understanding of the excitation mechanisms.

We studied infrared and green erbium photoluminescence (PL) of MBE-grown GaN:Er with above- and below-band-gap excitation methods. In the latter case, the excitation wavelengths resonant and nonresonant with Er³⁺ transitions were also used. The PL spectra obtained in these conditions are similar, but the decay kinetics change with the excitation method. This enables us to distinguish emissions related with isolated and defect-coupled Er³⁺ centers.

To obtain the electroluminescence (EL) electrical contacts were made, and characteristic infrared and green emissions of Er³⁺ were observed. Electrical characteristics of this device and the dependence of its emission on the current and temperature were studied.

When electrical and optical excitations are combined, we observe that electroluminescence is altered by additional illumination. The below-band-gap illumination leads to a slight enhancement of EL, while with above-band-gap illumination very strong quenching of EL is observed. This indicates that both excitation mechanisms proceed via common steps within the excitation path, and as a result, they are perturbed by each other.