Semiconductor light emitting device with an aluminum containing layer formed thereon
View Patent ↗According to one embodiment, a semiconductor light emitting device includes an n-type semiconductor layer, a p-type semiconductor layer, a well layer, a barrier layer, an Al-containing layer, and an intermediate layer. The p-type semiconductor layer is provided on a side of [0001] direction of the n-type semiconductor layer. The well layer, the barrier layer, the Al-containing layer and the intermediate layer are disposed between the n-type semiconductor layer and the p-type semiconductor layer subsequently. The Al-containing layer has a larger band gap energy than the barrier layer, a smaller lattice constant than the n-type semiconductor layer, and a composition of Al x1 Ga 1-x1-y1 In y1 N. The intermediate layer has a larger band gap energy than the well layer, and has a first portion and a second portion provided between the first portion and the p-type semiconductor layer. A band gap energy of the first portion is smaller than that of the second portion.
1. A semiconductor light emitting device comprising:
an n-type semiconductor layer including a nitride semiconductor;
a p-type semiconductor layer provided on a side of [0001] direction of the n-type semiconductor layer and including a nitride semiconductor;
a first well layer provided between the n-type semiconductor layer and the p-type semiconductor layer, the first well layer having a band gap energy smaller than a band gap energy of the n-type semiconductor layer and smaller than a band gap energy of the p-type semiconductor layer, and including a nitride semiconductor;
a first barrier layer provided between the first well layer and the n-type semiconductor layer, in contact with the first well layer, the first barrier layer having a band gap energy larger than the band gap energy of the first well layer, and including a nitride semiconductor;
an Al-containing layer provided between the first well layer and the p-type semiconductor layer, in contact with the first well layer, the Al-containing layer having a band gap energy larger than the band gap energy of the first barrier layer, having a lattice constant smaller than a lattice constant of the n-type semiconductor layer, and having a composition of Al x1 Ga 1-x1-y1 In y1 N (where 0<x1<1 and 0≦y1<1); and
an intermediate layer provided between the Al-containing layer and the p-type semiconductor layer, in contact with the Al-containing layer, having a band gap energy larger than the band gap energy of the first well layer, and including a nitride semiconductor, the intermediate layer having a first portion and a second portion provided between the first portion and the p-type semiconductor layer, a band gap energy of the first portion being smaller than a band gap energy of the second portion.
2. The device according to claim 1 , wherein the band gap energy of the first portion is smaller than or equal to the band gap energy of the p-type semiconductor layer.
3. The device according to claim 1 , wherein the band gap energy of the intermediate layer increases along a direction from the Al-containing layer toward the p-type semiconductor layer.
4. The device according to claim 1 , wherein an In composition ratio of the intermediate layer decreases along a direction from the Al-containing layer toward the p-type semiconductor layer.
5. The device according to claim 1 , wherein a thickness of the intermediate layer is not less than 5 nanometers and not more than 100 nanometers.
6. The device according to claim 1 , wherein an In composition ratio of the first portion is higher than 0 and lower than an In composition ratio of the first well layer.
7. The device according to claim 1 , wherein the intermediate layer does not include Al.
8. The device according to claim 1 , wherein the first portion does not include Al.
9. The device according to claim 1 , wherein an Al composition ratio of the Al-containing layer is not less than 0.001 and not more than 0.03.
10. The device according to claim 1 , wherein a thickness of the Al-containing layer is not less than 1 nanometer and not more than 50 nanometers.
11. The device according to claim 1 , wherein the Al-containing layer does not include In.
12. The device according to claim 1 , wherein the Al-containing layer includes:
a first layer in contact with the first well layer; and
a second layer in contact with the first layer between the first layer and the intermediate layer and having a different band gap energy from a band gap energy of the first layer.
13. The device according to claim 12 , wherein the band gap energy of the second layer is larger than the band gap energy of the first layer.
14. The device according to claim 12 , wherein the band gap energy of the second layer is smaller than the band gap energy of the first layer.
15. The device according to claim 1 , wherein a wavelength of light emitted from the first well layer is not less than 330 nanometers and not more than 580 nanometers.
16. The device according to claim 1 , wherein a thickness of the first well layer is not less than 1 nanometer and mot more than 10 nanometers.
17. The device according to claim 1 , wherein a thickness of the first barrier layer is not less than 3 nanometers.
18. The device according to claim 1 , wherein an In composition ratio of the first barrier layer is not higher than an In composition ratio of the first well layer.
19. The device according to claim 1 , wherein an In composition ratio of the first barrier layer is not lower than 0.005.
20. The device according to claim 1 , further comprising:
a second well layer provided between the first barrier layer and the n-type semiconductor layer, in contact with the first barrier layer, the second well layer having a band gap energy smaller than the band gap energy of the first barrier layer, smaller than the band gap energy of the Al-containing layer, and smaller than the band gap energy of the intermediate layer, and the second well layer including a nitride semiconductor; and
a second barrier layer provided between the second well layer and the n-type semiconductor layer, in contact with the second well layer, the second barrier layer having a band gap energy larger than the band gap energy of the second well layer and smaller than the band gap energy of the Al-containing layer, and the second barrier layer including a nitride semiconductor.
21. The device according to claim 1 , wherein an In composition ratio in the intermediate layer decreases continuously along a direction from the Al-containing layer toward the p-type semiconductor layer.
22. The device according to claim 1 , wherein an In composition ratio in the intermediate layer decreases in a stepwise along a direction from the Al-containing layer toward the p-type semiconductor layer.
23. The device according to claim 1 , wherein the intermediate layer includes an undoped InGaN.