A light-emitting device (LED) is described which exhibits high extraction
efficiency and an emission profile which is substantially more
directional than from a Lambertian source. The device comprises a light
generating layer disposed between first and second layers of
semiconductor material, each having a different type of doping. An upper
surface of the first layer has a tiling arrangement of inverted pyramidal
or inverted frustro-pyramidal indentations in the semiconductor material
filled by a material of different refractive index and which together
comprise a photonic band structure. The indentations and their tiling
arrangement are configured for efficient extraction of light from the
device via the upper surface of the first layer and in a beam that is
substantially more directional than from a Lambertian source. An enhanced
device employs a reflector beneath the second layer to utilise the
microcavity effect. A method for fabricating the device is also described
which employs anisotropic wet etching to produce the inverted pyramidal
or inverted frustro-pyramidal indentations.