Nitride semiconductor device
The invention relates to a nitride semiconductor device having electron-emitting. In the device, an n-type nitride semiconductor layer is formed over a substrate, and an active layer is formed over the n-type nitride semiconductor layer. Also, a p-type nitride semiconductor layer is formed on the active layer. The active layer is formed between the p-type nitride semiconductor layer and the n-type nitride semiconductor layer and includes a quantum well layer and a quantum barrier layer. Further, an electron-emitting layer is formed between the n-type nitride semiconductor layer and the active layer. The electron-emitting layer includes a nitride semiconductor quantum dot layer formed on the n-type nitride semiconductor layer and having a composition expressed by Al X In y Ga 1-X-y) N, where 0≦x≦1 and 0≦y≦1, and a resonance tunnel layer formed on the nitride semiconductor quantum dot layer and having energy band gap bigger than that of adjacent quantum dot layer.
1 . A nitride semiconductor device comprising:
an n-type nitride semiconductor layer;
a p-type nitride semiconductor layer;
an active layer formed between the p-type nitride semiconductor layer and the n-type nitride semiconductor layer and having a quantum well layer and a quantum barrier layer; and
an electron-emitting layer formed between the n-type nitride semiconductor layer and the active layer;
wherein the electron-emitting layer comprises:
a nitride semiconductor quantum dot layer formed on the n-type nitride semiconductor layer, and having a composition expressed by Al X In y Ga (1-X-y) N, where 0≦x≦1 and 0≦y≦1, and a resonance tunnel layer formed on the nitride semiconductor quantum dot layer, and having energy band gap bigger than that of the quantum well layer.
2 . The nitride semiconductor device according to claim 1 , wherein the nitride semiconductor quantum dot layer has a thickness ranging from 1 monolayer to 50 Å.
3 . The nitride semiconductor device according to claim 2 , wherein the nitride semiconductor quantum dot layer has a thickness of 10 to 30 Å.
4 . The nitride semiconductor device according to claim 1 , wherein the nitride semiconductor quantum dot layer has a lattice constant different from that of the n-type nitride semiconductor layer.
5 . The nitride semiconductor device according to claim 4 , wherein the nitride semiconductor quantum dot layer has a composition expressed by Al X In y Ga (1-X-y) N, where 0≦x≦1 and 0≦y≦1, and the n-type nitride semiconductor layer has a composition expressed by Al x1 In y1 Ga (1-x1-y1) N, where 0≦x 1 ≦1 and 0≦y 1 ≦1, wherein x is at least 0.3 greater than y.
6 . The nitride semiconductor device according to claim 4 , wherein the nitride semiconductor quantum dot layer has a composition expressed by In y Ga (1-y) N and the n-type nitride semiconductor layer is made of GaN, wherein y ranges from 0.3 to 1.
7 . The nitride semiconductor device according to claim 1 , wherein the resonance tunnel layer has a thickness of 0.5 to 10 nm.
8 . The nitride semiconductor device according to claim 1 , wherein the resonance tunnel layer has a composition expressed by In y2 Ga (1-y2) N, where y is 0.2 or less.
9 . The nitride semiconductor device according to claim 1 , wherein the resonance tunnel layer has a composition identical to that of the quantum barrier layer.
10 . The nitride semiconductor device according to claim 1 , wherein the resonance tunnel layer comprises an undoped layer.
11 . The nitride semiconductor device according to claim 1 , wherein the resonance tunnel layer is n-doped to a concentration of 10 20 /cm 3 or less.