Patent ID: 7700962

Claim:
A light-emitting device (LED) comprising: a first layer comprising a first semiconductor material having a first type of doping; a second layer comprising a second semiconductor material having a second type of doping; and, a light-generating layer disposed between the first and second layers, wherein the first layer has an upper surface distal the light-generating layer and a lower surface proximate the light-generating layer and wherein light generated in the light-generating layer emerges from the LED structure through the upper surface of the first layer, the first layer further comprising a tiling arrangement of inverted pyramidal or inverted frustro-pyramidal indentations in the first semiconductor material extending from the upper surface towards the light-generating layer and comprising a material of different refractive index to the first semiconductor material, wherein the tiling arrangement of indentations and surrounding first semiconductor material comprise a photonic band structure, and wherein the indentations and their tiling arrangement comprise a photonic quasicrystal tiling pattern and the pitch of the tiling arrangement is greater than or equal to 1.5 μm, whereby light emerging from the LED structure through the upper surface is substantially more directional than from a Lambertian source.