Patent ID: 7235821

Claim:
An optical device comprising: an active layer made of a Group III-V semiconductor compound and having a quantum well of a bandgap grading structure in which conduction band energy and valence band energy change linearly with a slope with the content change of predetermined components while an energy bandgap between the conduction band energy and the valence band energy is maintained at a predetermined value; and two barrier layers, one of which is positioned on an upper surface of the active layer and the other is positioned on a lower surface of the active layer, and which are made of a Group III-V semiconductor compound and have higher conduction band energy and lower valence band energy than the active layer, wherein the active layer is made of Ga 1-x In x N y As 1-y where 0<x<x1 and 0<y<1 and wherein the predetermined components are In and N.