A Group III nitride compound semiconductor includes a multiple layer structure having an emission layer between an n-type cladding layer and a p-type cladding layer. The n-type cladding layer may be below the emission layer, having been formed on another n-type layer which was formed over a buffer Layer and a sapphire substrate. The emission layer has a thickness which is wider than the diffusion length of holes within the emission layer. The n-type cladding layer is doped with a donor impurity and has a lattice constant Substantially equal to a lattice constant of the emission layer. The p-type cladding layer is doped with an acceptor impurity and has a forbidden band sufficiently wider than the forbidden band of the emission layer in ordor to confine electrons injected into the emission layer.