A method of producing a light-emitting semiconductor device of a group III nitride compound includes forming an N-layer of an N-type conduction, the N-layer comprising gallium nitride, forming a high carrier concentration N+-layer satisfying the formula (Alx3Ga1-x3)y3In1-y3N, wherein 0≦x3≦1, 0≦y3≦1 and 0≦x3+y3≦1, on the N-layer, forming an emission layer of a group III nitride compound semiconductor satisfying the formula, Alx1Gay1In1-x1-y1N, where 0≦x1≦1, 0≦y1≦1 and 0≦x1+y1≦1 on the high carrier concentration layer N+layer, doping Si and Zn into the emission layer, forming a P-layer of a P-type conduction, on the emission layer, the P-layer including aluminum gallium nitride satisfying the formula Alx2Ga1-x2N, wherein 0≦x2≦1, and forming a contact layer of a P-type conduction, on the P-type layer, the contact layer including gallium nitride.