Semiconductor light emitting device and method for manufacturing same
A semiconductor light emitting device includes a first conductive clad layer that is group III-V semiconductor mixed crystal, an active layer, and a second conductive clad layer. The second conductive clad layer has a laminated structure of at least three layers including a first layer, a second layer, and a third layer disposed in this order closer to the active layer. The second layer and the third layer are included in a striped ridge, and the second layer is positioned at a skirt of the ridge. The surface of the first layer is a flat part at both sides of the ridge. When Al compositions of the first layer, second layer, and third layer are X1, X2, and X3, respectively, the relation X2>X1, X3 is satisfied. When film thicknesses of the first layer, second layer, and third layer are D1, D2, and D3, the relation D2<D3 is satisfied.
1. A III-V semiconductor light emitting device comprising a first conductive clad layer, an active layer, and a second conductive clad layer laminated on a substrate in this order closer to the substrate, wherein
the second conductive clad layer is an AlGaInP-based semiconductor mixed crystal and has a laminated structure of at least three layers, including a first layer, a second layer, and a third layer disposed in this order closer to the active layer,
the second layer and the third layer are included in a striped ridge, and the second layer is positioned at a skirt of the ridge,
the first layer has a flat surface under both sides of the striped ridge and parallel to the active layer,
Al compositions X1, X2, and X3 of the first layer, the second layer, and the third layer, respectively, satisfy a relation:
X2>X1 and X2>X3, and
film thicknesses D1, D2, and D3 of the first layer, the second layer, and the third layer, respectively, satisfy a relation:
D2<D3.
2. The III-V semiconductor light emitting device of claim 1 ,
wherein
a side wall of the third layer is substantially perpendicular to a plane of the substrate.
3. The III-V semiconductor light emitting device of claim 1 ,
wherein
a slope of a side wall of the second layer is gentler at a lower part of the second layer than at an upper part of the second layer.
4. The III-V semiconductor light emitting device of claim 3 ,
wherein
the slope of the side wall of the second layer has a shape substantially perpendicular to a surface of the substrate at its upper part, and a shape flaring downward at its lower part.
5. The III-V semiconductor light emitting device of claim 1 ,
wherein
the third layer is a laminated film of a plurality of laminated layers having smaller Al composition than the second layer, and the D3 is a total film thickness of the plurality of laminated layers.
6. The III-V semiconductor light emitting device of claim 1 ,
wherein
the D2 is not less than 200 nm and not greater than 500 nm.
7. The III-V semiconductor light emitting device of claim 1 ,
wherein
the first layer, the second layer, and the third layer are formed of AlGaInP.
8. The III-V semiconductor light emitting device of claim 1 ,
wherein
the third layer to an upper part of the second layer are processed into a stripe shape by non-selective etching, and a lower part of the second layer is processed into a stripe shape by selective etching.
9. The III-V semiconductor light emitting device of claim 8 ,
wherein
the non-selective etching is dry etching, and the selective etching is wet etching.
10. A method for manufacturing a III-V semiconductor light emitting device, the method comprising:
forming on a substrate a first conductive clad layer, an active layer, and a second conductive clad layer, the second conductive clad layer is an AlGaInP-based semiconductor mixed crystal and has a laminated structure of at least three layers including a first layer, a second layer, and a third layer disposed in an order closer to the active layer;
processing the third layer to an upper part of the second layer into a stripe shape by non-selective etching; and
processing a lower part of the second layer into a stripe shape by selective etching,
wherein
Al compositions X1, X2, and X3 of the first layer, the second layer, and the third layer, respectively, satisfy a relation:
X2>X1 and X2>X3, and
film thicknesses D1, D2, and D3 of the first layer, the second layer, and the third layer, respectively, satisfy a relation:
D2<D3.
11. The method for manufacturing the III-V semiconductor light emitting device of claim 10 ,
wherein
a slope of a side wall of the third layer formed by the step of processing the stripe shape is substantially perpendicular to a plane of the substrate.
12. The method for manufacturing the III-V semiconductor light emitting device of claim 10 ,
wherein
a slope of a side wall of the second layer formed by the step of processing into the stripe shape is gentler at the lower part than at the upper part.
13. The III-V semiconductor light emitting device of claim 12 ,
wherein
the slope of the side wall of the second layer has a shape substantially perpendicular to a surface of the substrate at its upper part, and a tapered shape spreading downward at its lower part.
14. The method for manufacturing the III-V semiconductor light emitting device of claim 10 ,
wherein
the D2 is not less than 200 nm and not greater than 500 nm.
15. The method for manufacturing the III-V light emitting device of claim 10 ,
wherein
the first layer and the second layer are both formed of AlGaInP, the X1 is not greater than 0.35, and the X2 is not less than 0.55.
16. The method for manufacturing the III-V semiconductor light emitting device of claim 10 ,
wherein
the non-selective etching is dry etching, and the selective etching is wet etching.
17. The III-V semiconductor light emitting device of claim 1 , wherein the X1 is not greater than or equal to 0.35, and the X2 is not less than 0.55.
18. The III-V semiconductor light emitting device of claim 1 , wherein a sidewall of the striped ridge is covered by a current blocking layer, and the current blocking layer is in direct contact with the flat surface of the first layer.
19. The III-V semiconductor light emitting device of claim 1 , wherein the first conductive clad layer is an AlGaInP-based semiconductor mixed-crystal.
20. The III-V semiconductor light emitting device of claim 1 , wherein all the Al compositions X1, X2, and X3 are greater than 0.
21. The method for manufacturing the III-V light emitting device of claim 10 , wherein all the Al compositions X1, X2, and X3 are greater than 0.
22. A III-V semiconductor light emitting device comprising a first conductive clad layer, an active layer, and a second conductive clad layer laminated on a substrate in this order closer to the substrate, wherein
the second conductive clad layer has a laminated structure of at least three layers, including a first layer, a second layer, and a third layer disposed in this order closer to the active layer,
the second layer and the third layer are included in a striped ridge, and the second layer is positioned at a skirt of the ridge,
the first layer has a flat surface under both sides of the striped ridge and parallel to the active layer,
Al compositions X1, X2, and X3 of the first layer, the second layer, and the third layer, respectively, satisfy a relation:
X2>X1 and X2>X3,
all the Al compositions X1, X2, and X3 are greater than 0, and
film thicknesses D1, D2, and D3 of the first layer, the second layer, and the third layer, respectively, satisfy a relation:
D2<D3.
23. A method for manufacturing a III-V semiconductor light emitting device, the method comprising:
forming on a substrate a first conductive clad layer, an active layer, and a second conductive clad layer, the second conductive clad layer has a laminated structure of at least three layers including a first layer, a second layer, and a third layer disposed in an order closer to the active layer;
processing the third layer to an upper part of the second layer into a stripe shape by non-selective etching; and
processing a lower part of the second layer into a stripe shape by selective etching,
wherein
Al compositions X1, X2, and X3 of the first layer, the second layer, and the third layer, respectively, satisfy a relation:
X2>X1 and X2>X3,
all the Al compositions X1, X2, and X3 are greater than 0, and
film thicknesses D1, D2, and D3 of the first layer, the second layer, and the third layer, respectively, satisfy a relation:
D2<D3.