Yb³⁺-Doped GaN Nanoceramics as a New Material for Broad Band White Light Emission

The effect of grain boundary defects on the optoelectronic properties of Yb³⁺-doped GaN nanoceramics was investigated. Structural analysis confirmed crystallization in the wurtzite structure, with a maximum concentration of Yb³⁺ up to 3%. Optical spectroscopy in the visible range allowed us to confirm the defect nature of the obtained materials, and VUV measurements confirmed the presence of deep surface defects, which are active recombination centers for broad band white light emission. In the NIR range, the characteristic emission of the f-f Yb³⁺ transitions was confirmed, as well as energy transfer between the Yb³⁺ ions and the host. Laser-induced white emission (LIWE) was observed after irradiation with CW NIR laser diode in vacuum, revealing the excitation threshold and nonlinearity with increasing laser power density. The emission process was accompanied by efficient photoconductivity. The defined hysteresis contrast reaches a maximum of over 65% for undoped GaN, while the introduction of Yb³⁺ ions reduces the hysteresis, or optical capacitance, reaching a minimum value of almost 23% for the 3% Yb³⁺ sample. The obtained results clearly demonstrate that the obtained nanoceramics can behave as optically controllable memristive-like systems.