Optical semiconductor device and method of manufacturing optical semiconductor device
An optical semiconductor device includes a substrate; and an active layer disposed on the substrate, wherein the active layer includes a first barrier layer containing GaAs, a quantum dot layer, which is disposed on the first barrier layer, which includes a quantum dot containing InAs, which includes a side barrier layer which covers at least a part of the quantum dot and a side surface of the quantum dot, and having an elongation strain inherent therein, and a second barrier layer disposed on the quantum dot layer.
1. An optical semiconductor device comprising:
a substrate; and
an active layer disposed on the substrate,
wherein the active layer includes a first barrier layer containing GaAs, a quantum dot layer, which is disposed on the first barrier layer, which includes a quantum dot containing InAs, which includes a side barrier layer which covers at least a part of the quantum dot and a side surface of the quantum dot, and having an elongation strain inherent therein, and a second barrier layer disposed on the quantum dot layer,
wherein the quantum dot layer is doped to become a p-type.
2. The optical semiconductor device according to claim 1 , wherein an absolute value of the difference in lattice constant between the first barrier layer and the side barrier layer is larger than or equal to an absolute value of the difference in lattice constant between the first barrier layer and the quantum dot.
3. The optical semiconductor device according to claim 1 , wherein the side barrier layer further comprises a group V element.
4. The optical semiconductor device according to claim 1 , wherein the side barrier layer comprises at least one material selected from the group consisting of BAs, BGaAs, BInAs, BGaInAs, BGaP, BGaAsP, BAsSb, BGaAsSb, BInAsSb, BGaInAsSb, BGaPSb, and BGaAsPSb.
5. The optical semiconductor device according to claim 1 , wherein the side barrier layer comprises B.sub.xGa.sub.1-xAs (where 0.46.ltoreq.x.ltoreq.1).
6. The optical semiconductor device according to claim 1 , wherein the side barrier layer has a lattice constant of 5.25 .ANG. or less.
7. The optical semiconductor device according to claim 1 , wherein the side barrier layer has a thickness smaller than or equal to the height of the quantum dot.
8. The optical semiconductor device according to claim 1 , wherein a plurality of the quantum dot layers are disposed between the first barrier layer and the second barrier layer and the quantum dot layers are laminated such that the quantum dots are in contact with each other vertically.
9. The optical semiconductor device according to claim 1 , wherein the first barrier layer, the quantum dot layer, and the second barrier layer are laminated repeatedly in the active layer.
10. A method of manufacturing an optical semiconductor device comprising:
forming a first barrier layer containing GaAs on a substrate;
forming a quantum dot having a compressive strain inherent therein on the first barrier layer;
forming a side barrier layer, which has a band gap larger than the band gap of the quantum dot, which has an elongation strain inherent therein, and which contains B, so as to cover at least a part of a side surface of the quantum dot; and
forming a second barrier layer on the quantum dot and the side barrier layer,
wherein the quantum dot is doped to become a p-type.
11. The method of manufacturing an optical semiconductor device according to claim 10 , wherein an absolute value of the amount of elongation strain inherent in the side barrier layer is larger than or equal to an absolute value of the amount of compressive strain inherent in the quantum dot.
12. The method of manufacturing an optical semiconductor device according to claim 10 , wherein
before the forming of the second barrier layer,
a quantum dot layer including coupled quantum dots is formed by repeating the forming of the quantum dot and the forming of the side barrier layer a plurality of times.
13. The method of manufacturing an optical semiconductor device according to claim 12 , wherein
the forming of the first barrier layer, the forming of the quantum dot layer including coupled quantum dots, and the forming of the second barrier layer are repeated a plurality of times.
14. The method of manufacturing an optical semiconductor device according to claim 10 , wherein
the forming of the quantum dot, the forming of the side barrier layer, and the forming of the second barrier layer are repeated a plurality of times.
15. The method of manufacturing an optical semiconductor device according to claim 10 , wherein
the upper portion of the quantum dot is substantially flattened after the side barrier layer is formed.