Nitride semiconductor device with superlattice active layer including barrier layers with different energy band gaps

A nitride semiconductor device comprising:

• a p-type nitride semiconductor layer;
• an n-type nitride semiconductor layer;
• and
• an active layer disposed between the p-type and n-type nitride layers and comprising a plurality of quantum barrier layers and quantum well layers deposited alternately on each other,
• wherein the active layer has a superlattice structure where the quantum barrier layer has a thickness for enabling a carrier injected from the p-type and n-type nitride semiconductor layers to be tunneled therethrough,
• at least one of the quantum barrier layers has an energy band gap greater than that of the p-type nitride semiconductor layer,
• the plurality of quantum barrier layers have different energy band gaps in order for the energy band gaps to increase with proximity to the p-type nitride semiconductor layer,
• each energy band gap of the quantum barrier layers is greater than respective energy band gaps of the quantum well layers, and
• the quantum barrier having an energy band gap greater than that of the p-type nitride semiconductor is disposed between two of the quantum well layers.