Mechanism of light emission excited by Joule heating in ZnO crystals

Emission of light was observed in ZnO single crystals under Joule heating at high temperatures. This thermally induced emission (thermal emission) appeared at temperatures higher than 600 °C and exhibited itself as a band peaked at 500–520 nm whose intensity increased and maximum shifted towards longer wavelengths as temperature increased. Photoluminescence, thermal emission (TE) and transmission spectra were measured at different temperatures in the range of 20–1100 °C. It was concluded that the TE resulted from radiative recombination of thermally generated equilibrium carriers through some local centers. ► Observed emission of visible light in ZnO single crystals by Joule heating at high temperatures. ► Thermal emission maximum shifted towards the long wavelength side with temperature increase. ► Thermal emission in ZnO resulted from radiative recombination of thermally generated equilibrium carriers through some local centers.