Nitride based semiconductor device

A nitride based semiconductor device comprising an n-type nitride semiconductor layer, a p-type nitride semiconductor layer, and an active layer formed between the p-type nitride semiconductor layer and n-type nitride semiconductor layer and having a quantum well layer and a quantum barrier layer,

• wherein the device includes an electron emitting layer formed of at least two repeats of first nitride semiconductor layers and second nitride semiconductor layers having different compositions, disposed between the n-type nitride semiconductor layer and the active layer,
• the first nitride semiconductor layers have an energy band gap greater than that of the quantum well layer, smaller than that of the quantum barrier layer, and decreasing closer to the active layer, and
• the second nitride semiconductor layers have an energy band gap at least higher than that of the adjacent first nitride semiconductor layer(s) and have a thickness such that electrons accumulated in the first nitride semiconductor layer can be tunneled toward the active layer.