Electrically pumped near-ultraviolet lasing from ZnO/MgO core/shell nanowires

Electrically pumped near-ultraviolet lasing was achieved in a metal/insulator/semiconductor laser diode based on ZnO/MgO core/shell nanowires. The nanowire diode shows higher emission intensity at relatively low operating current density compared with the planar device. The improved efficiency is attributed to enhanced exciton oscillator strength and superior carrier transport properties of single-crystalline ZnO nanowires, and effective surface passivation by MgO coating. Random laser action was confirmed by the calculation of quality factor and the real-time changes of lasing spectra. The results reveal that the MgO coating serves as electron blocking, hole supplying and surface passivation layer for the nanowire heterostructure. (C) 2011 American Institute of Physics. [doi:10.1063/1.3625925]