Experimental Realization of 1400-2100 nm Broadband Emission for Wide Bandwidth Optical Communication in Er-Tm Codoped ZnO Film and Device

1400-2100 nm broadband emission is achieved in Er-Tm codoped ZnO (ETZO) films at an excitation of photon energies higher than the bandgap of ZnO. Room temperature (RT) and temperature-dependent photoluminescence (PL) spectra of the films annealed at different temperatures, together with their corresponding structural characterization results, reveal that the defect states of ZnO play an important role in the energy transfer (ET) processes for the broadband emission. At low temperatures, an intensive defect-related peak at 1938 nm concomitantly with a much-enhanced broadband emission was observed in the PL spectra. A dominant ET channel from ZnO to Tm3+ ions by the recombination of the defect-related state is suggested. The important role of the defect states for the broadband emission is further confirmed. Moreover, RT electroluminescence (EL) is also realized in the ETZO films with an Al/Ni/ETZO/p-Si/Al device structure, and a similar broadband emission spectrum was observed, illustrating the same lumine...