Optimization of the emission characteristics of light emitting diodes by surface plasmons and surface waveguide modes

In this letter, the influence of metal films and dielectric waveguides on the radiation characteristics of light emitting diodes (LEDs) is investigated. Cross and hexagonal surface grating structures are used to excite surface plasmons and waveguide modes in these media. A beam divergence as small as 17 degrees is achieved for a hexagonal grating coated with a 40 nm Ag film. The maximum quantum efficiency is found for a hexagonal grating with a 10-nm-thick Au film and a 250-nm-thick dielectric layer. The optical power emitted by this LED into the solid angle from -30 degrees to 30 degrees is 10% higher than that of an LED without metal film and dielectric layer. (C) 2000 American Institute of Physics. [S0003- 6951(00)04941-X].