Enhanced forward emission from ZnO via surface plasmons

By using metal-insulator-metal (MIM) as the cap layer, we have enhanced the photoluminescent emission from ZnO in the forward direction via coupling of surface plasmons. The basic principle behind the enhancement involves two steps. First, the overall light emission efficiency of ZnO is increased significantly due to the coupling and scattering of nonradiative surface plasmons at the metal/ZnO interface. The forward emission is then increased by enhanced transmission due to the excitation of radiative surface plasmons in the MIM structure. As a result, the forward emission from MIM/ZnO is found to be 7 and 3.5 times stronger than that from uncapped ZnO and M/ZnO. We expect that the MIM structure could evolve as an effective means in fabricating high brightness light emitting diodes from semiconductors. (C) 2007 American Institute of Physics.