Formation conditions of random laser cavities in annealed ZnO epilayers

The possibilities to realize room-temperature random laser action in ZnO epilayers with MgO as the buffer layer are studied. It is found that the formation of random laser cavities inside the ZnO epilayers can be achieved by post-growth annealing. Incoherent and coherent random lasing phenomena are observed from ZnO epilayers with (220)- and [200]-oriented MgO buffer layers, respectively. Lasing linewidth of the ZnO epilayers with incoherent and coherent feedback under 355-nm optical excitation is found to be ∼4 and ∼0.4 nm, respectively.