Mechanism of light emission excited by Joule heating in ZnO crystals Original Research Article

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.