Semiconductor light emitting device

A semiconductor light emitting device, comprising:

• a substrate;
• a plurality of GaN based semiconductor layers stacked on said substrate and made of different materials from that of said substrate;
• and
• an ohmic electrode formed on the top layer of said GaN based semiconductor layers, so that light generated in said GaN-based semiconductor layers is emitted from said ohmic electrode or from said substrate,
• wherein a plurality of protruding portions for scattering or diffracting light generated in said GaN based semiconductor layers are created in the surface of said substrate in a repeated pattern with a pitch larger than or equal to λ/4 and smaller than or equal 10 μm, where λ is the wavelength of a light emitted from said GaN based semiconductor layers.
• a planar shape of said protruding portions is approximately triangular or hexagonal,
• each component side of the planar shape of said protruding portions is perpendicular to a line segment connecting a center and a vertex of a hexagon whose component sides are defined by A axes of said GaN based semiconductor layers,
• wherein a side surface of said protruding portions is inclined so that a taper angle of said side surface is greater than 90 degrees and smaller than or equal 150 degrees, and
• wherein the top and side surfaces of said protruding portions and flat portions, where no protruding portions are formed, on the surface of said substrate are continuously covered by said GaN-based semiconductor layers.