Nitride semiconductor light-emitting device

A nitride semiconductor light-emitting device which is formed by stacking nitride semiconductor crystals in a +c-axis direction, each nitride semiconductor crystal containing Al and having a polar or semipolar surface either serving as a growth face, the device comprising an active layer, a first composition-graded layer and a second composition-graded layer, wherein:

• the active layer is interposed between the first and second composition-graded layers;
• and
• each one of the first and second composition-graded layers is composition-graded so that an Al composition value thereof is rendered smaller as each one of the first and second composition-graded layers comes close to a side where a sum of spontaneous polarization and piezoelectric polarization is negative;
• the first composition-graded layer has a first interface between the active layer and the first composition-graded layer and a second interface away from the first interface, and the first interface has a larger Al composition value than the second interface;
• and
• the second composition-graded layer has a third interface between the active layer and the second composition-graded layer and a fourth interface away from the third interface and the fourth interface has a smaller Al composition value than the third interface.