Origins of lasing emission in a resonance-controlled ZnO random laser

We investigate the origins of lasing emission in a scatterer-resonance-controlled random laser made of ZnO nanopowder over a wide temperature range (20–300 K). At higher temperatures (>150 K), the lasing emission appears around exciton recombination energies and the lasing threshold carrier density is comparable to the Mott density, indicating that the resonance-controlled random laser is going toward showing excitonic lasing; at lower temperatures, random lasing is caused by usual electron–hole plasma recombination because of the threshold carrier density being much larger than the Mott density. (paper)