The present invention provides another active layer structure provided in a light emission device for emitting a light with a predetermined wavelength. The active layer structure comprises a multiple quantum well structure and at least a second well layer. The multiple quantum well structure comprises alternating laminations of first well layers showing electroluminescence and potential barrier layers. The first well layers have a first set of energy band gaps which are uniform and correspond to the predetermined wavelength. An energy band gap is defined as a difference between a ground level of electrons in conduction band and a ground level of holes in valence band. The second well layer is provided within any of the potential barrier layers so that the second well layer is separated by the potential barrier layers from the first well layers. The second well layer has a second energy band gap in a range which is above the first set of energy band gaps and below a set of forbidden band widths of the potential barrier layers. The range of the second energy band gaps is defined so that the second well layer exits carrier accumulations and no electroluminescence to thereby ensure that carriers accumulated in the second well layer are injected into the first well layers when the first well layers are deficient in carriers for the electro-luminescence.