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 pyramidal or
frustro-pyramidal protrusions of semiconductor material surrounded by a
material of different refractive index which together comprise a photonic
band structure. The protrusions 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 utilize the microcavity effect. A
method for fabricating the device is also described which employs
anisotropic wet etching to produce the pyramidal or frustro-pyramidal
protrusions