A barrier layer made of Al_xGa_1-xN (0x0.18) is formed in a light-emitting semiconductor device using gallium nitride compound having a multi quantum-well (MQW) structure. By controlling a composition ratio x of aluminum (Al) or thickness of the barrier layer, luminous intensity of the device is improved. An n-cladding layer made of Al_xGa_1-xN (0x0.06) is formed in a light-emitting semiconductor device using gallium nitride compound. By controlling a composition ratio x of aluminum or thickness of the n-cladding layer, luminous intensity of the device is improved. A p-type layer and an n-type layer are formed in a light-emitting semiconductor device using gallium nitride compound having a double-hetero junction structure. By controlling a ratio of a hole concentration of the p-type layer and an electron concentration of the n-type layer approximates to 1, luminous intensity of the device is improved.