Nitride semiconductor light emitting device
View Patent ↗A nitride semiconductor light emitting device has high internal quantum efficiency but low operating voltage. The nitride semiconductor light emitting device includes an n-nitride semiconductor layer; an active layer of multi-quantum well structure formed on the n-nitride semiconductor layer, and having a plurality of quantum well layers and a plurality of quantum barrier layers; and a p-nitride semiconductor layer formed on the active layer. One of the quantum well layers adjacent to the n-nitride semiconductor layer has an energy band gap greater than that of another one of the quantum well layers adjacent to the p-nitride semiconductor layer.
1. A nitride semiconductor light emitting device comprising:
an n-nitride semiconductor layer;
an active layer of multi-quantum well structure formed on the n-nitride semiconductor layer, and having three or more quantum well layers and a plurality of quantum barrier layers; and
a p-nitride semiconductor layer formed on the active layer,
wherein one of the three or more quantum well layers adjacent to the n-nitride semiconductor layer has an energy band gap greater than those of another one of the three or more quantum well layers adjacent to the p-nitride semiconductor layer, and one of the three or more of quantum well layers proximate to the n-nitride semiconductor layer has a smaller thickness than another one of the three or more quantum well layers less proximate to the n-nitride semiconductor layer.
2. The nitride semiconductor light emitting device according to claim 1 , wherein one of the three or more quantum well layers adjacent to the n-nitride semiconductor layer has an In content lower than that of another one of the quantum well layers adjacent to the p-nitride semiconductor layer.
3. The nitride semiconductor light emitting device according to claim 1 , wherein the three or more quantum well layers and the quantum barrier layers alternate with each other, the three or more quantum well layers having a composition of In x Ga 1-y N, where 0≦x≦1, and the quantum barrier layers having a composition of In y Ga 1-y N, where 0≦y<1, x>y.
4. The nitride semiconductor light emitting device according to claim 1 , wherein the three or more quantum well layers have a composition of InGaN, and the quantum barrier layers have a composition of GaN excluding In.
5. The nitride semiconductor light emitting device according to claim 1 , wherein the three or more quantum well layers have a energy band gap increasing with increase of proximity to the n-nitride semiconductor layer.
6. The nitride semiconductor light emitting device according to claim 1 , wherein the three or more quantum well layers have an In content decreasing with increase of proximity to the n-nitride semiconductor layer.
7. The nitride semiconductor light emitting device according to claim 1 , wherein each of the three or more quantum well layers has a thickness ranging from 10 Å to 100 Å.