Semiconductor laser element, manufacturing method thereof, optical disk apparatus and optical transmission system
First Claim
1. A semiconductor laser element comprising:
- a semiconductor substrate of first conductivity type;
a lower cladding layer of first conductivity type, an active layer, a first upper cladding layer of second conductivity type, and a second upper cladding layer of second conductivity type, which are stacked in this order on the semiconductor substrate;
a third upper cladding layer of second conductivity type and a contact layer of second conductivity type, which are formed directly or via a semiconductor layer of second conductivity type on the second upper cladding layer and constitute a stripe-shaped ridge structure; and
an electrode layer, wherein a second-conductivity-type doping concentration of the second upper cladding layer is lower than second-conductivity-type doping concentrations of the first upper cladding layer and the third upper cladding layer and is not higher than 1×
1017 cm−
3;
a sum total of a layer thickness of the first upper cladding layer and a layer thickness of the second upper cladding layer is 0.3 m-1.5 μ
m, inclusive, and the electrode layer forms an ohmic junction with the contact layer, and the electrode layer forms a Schottky junction with at least part of the second upper cladding layer located beside the ridge structure when the electrode layer is directly formed on the second upper cladding layer, and when the electrode layer is formed on the second upper cladding layer via the semiconductor layer of second conductivity type, the electrode layer forms a Schottky junction with at least part of the semiconductor layer of second conductivity type located beside the ridge structure.
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Abstract
A semiconductor laser element has a lower cladding layer of first conductivity type, an active layer, a first upper cladding layer of second conductivity type, and a second upper cladding layer of second conductivity type, which are stacked in this order on a semiconductor substrate of first conductivity type. The laser element further has a third upper cladding layer of second conductivity type and a contact layer of second conductivity type, which constitute a stripe-shaped ridge structure. A second-conductivity-type doping concentration of the second upper cladding layer is lower than those of the first and third upper cladding layers and is not higher than 1×1017 cm−3. A sum total of layer thicknesses of the first and second upper cladding layers is 0.3-1.5 μm, inclusive. An electrode layer forms an ohmic junction with the contact layer, and a Schottky junction with the second upper cladding layer.
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Citations
58 Claims
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1. A semiconductor laser element comprising:
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a semiconductor substrate of first conductivity type;
a lower cladding layer of first conductivity type, an active layer, a first upper cladding layer of second conductivity type, and a second upper cladding layer of second conductivity type, which are stacked in this order on the semiconductor substrate;
a third upper cladding layer of second conductivity type and a contact layer of second conductivity type, which are formed directly or via a semiconductor layer of second conductivity type on the second upper cladding layer and constitute a stripe-shaped ridge structure; and
an electrode layer, wherein a second-conductivity-type doping concentration of the second upper cladding layer is lower than second-conductivity-type doping concentrations of the first upper cladding layer and the third upper cladding layer and is not higher than 1×
1017 cm−
3;
a sum total of a layer thickness of the first upper cladding layer and a layer thickness of the second upper cladding layer is 0.3 m-1.5 μ
m, inclusive, andthe electrode layer forms an ohmic junction with the contact layer, and the electrode layer forms a Schottky junction with at least part of the second upper cladding layer located beside the ridge structure when the electrode layer is directly formed on the second upper cladding layer, and when the electrode layer is formed on the second upper cladding layer via the semiconductor layer of second conductivity type, the electrode layer forms a Schottky junction with at least part of the semiconductor layer of second conductivity type located beside the ridge structure. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23)
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24. An optical disk apparatus having a semiconductor laser element as a light emitting device, said semiconductor laser element comprising:
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a semiconductor substrate of first conductivity type;
a lower cladding layer of first conductivity type, an active layer, a first upper cladding layer of second conductivity type, and a second upper cladding layer of second conductivity type, which are stacked in this order on the semiconductor substrate;
a third upper cladding layer of second conductivity type and a contact layer of second conductivity type, which are formed directly or via a semiconductor layer of second conductivity type on the second upper cladding layer and constitute a stripe-shaped ridge structure; and
an electrode layer, wherein a second-conductivity-type doping concentration of the second upper cladding layer is lower than second-conductivity-type doping concentrations of the first upper cladding layer and the third upper cladding layer and is not higher than 1×
1017 cm−
3;
a sum total of a layer thickness of the first upper cladding layer and a layer thickness of the second upper cladding layer is 0.3 μ
m-1.5 μ
m, inclusive, andthe electrode layer forms an ohmic junction with the contact layer, and the electrode layer forms a Schottky junction with at least part of the second upper cladding layer located beside the ridge structure when the electrode layer is directly formed on the second upper cladding layer, and when the electrode layer is formed on the second upper cladding layer via the semiconductor layer of second conductivity type, the electrode layer forms a Schottky junction with at least part of the semiconductor layer of second conductivity type located beside the ridge structure.
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25. An optical transmission system having a semiconductor laser element as a light source, said semiconductor laser element comprising:
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a semiconductor substrate of first conductivity type;
a lower cladding layer of first conductivity type, an active layer, a first upper cladding layer of second conductivity type, and a second upper cladding layer of second conductivity type, which are stacked in this order on the semiconductor substrate;
a third upper cladding layer of second conductivity type and a contact layer of second conductivity type, which are formed directly or via a semiconductor layer of second conductivity type on the second upper cladding layer and constitute a stripe-shaped ridge structure; and
an electrode layer, wherein a second-conductivity-type doping concentration of the second upper cladding layer is lower than second-conductivity-type doping concentrations of the first upper cladding layer and the third upper cladding layer and is not higher than 1×
1017 cm−
3;
a sum total of a layer thickness of the first upper cladding layer and a layer thickness of the second upper cladding layer is 0.3 μ
m-1.5 μ
m, inclusive, andthe electrode layer forms an ohmic junction with the contact layer, and the electrode layer forms a Schottky junction with at least part of the second upper cladding layer located beside the ridge structure when the electrode layer is directly formed on the second upper cladding layer, and when the electrode layer is formed on the second upper cladding layer via the semiconductor layer of second conductivity type, the electrode layer forms a Schottky junction with at least part of the semiconductor layer of second conductivity type located beside the ridge structure.
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26. A semiconductor laser element comprising:
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a substrate of first conductivity type, an active layer formed on the substrate of first conductivity type and a stack of semiconductor layers of second conductivity type formed on the active layer, wherein the stack of semiconductor layers of second conductivity type comprises at least a low-concentration semiconductor layer having a doping concentration of not higher than 1×
1017 cm−
3 and a high-concentration semiconductor layer having a doping concentration of not lower than 1×
1018 cm−
3,an electrode is formed on the stack of semiconductor layers of second conductivity type, a low concentration-side compound layer is formed at an interface between the electrode and the low-concentration semiconductor layer, said low concentration-side compound layer being comprised of at least one of constituent elements of the electrode and at least one of constituent elements of the low-concentration semiconductor layer, and a high concentration-side compound layer is formed at an interface between the electrode and the high-concentration semiconductor layer, said high concentration-side compound layer being comprised of at least one of the constituent elements of the electrode and at least one of constituent elements of the high-concentration semiconductor layer. - View Dependent Claims (27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45)
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46. A semiconductor laser element manufacturing method, comprising the steps of:
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forming an active layer on a substrate of first conductivity type;
forming on the active layer a stack of semiconductor layers of second conductivity type that includes at least a low-concentration semiconductor layer having a doping concentration of not higher than 1×
1017 cm−
3 and a high-concentration semiconductor layer having a doping concentration of not lower than 1×
1018 cm−
3;
forming an electrode on the stack of semiconductor layers of second conductivity type; and
forming a compound layer at an interface between the electrode and the stack of semiconductor layers of second conductivity type by carrying out heat treatment after formation of the electrode. - View Dependent Claims (47, 48, 49, 50, 51, 52, 53, 54, 55, 56)
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57. An optical disk apparatus having a semiconductor laser element as a light emitting device, said semiconductor laser element comprising:
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a substrate of first conductivity type, an active layer formed on the substrate of first conductivity type and a stack of semiconductor layers of second conductivity type formed on the active layer, wherein the stack of semiconductor layers of second conductivity type comprises at least a low-concentration semiconductor layer having a doping concentration of not higher than 1×
1017 cm−
3 and a high-concentration semiconductor layer having a doping concentration of not lower than 1×
1018 cm−
3,an electrode is formed on the stack of semiconductor layers of second conductivity type, a low concentration-side compound layer is formed at an interface between the electrode and the low-concentration semiconductor layer, said low concentration-side compound layer being comprised of at least one of constituent elements of the electrode and at least one of constituent elements of the low-concentration semiconductor layer, and a high concentration-side compound layer is formed at an interface between the electrode and the high-concentration semiconductor layer, said high concentration-side compound layer being comprised of at least one of the constituent elements of the electrode and at least one of constituent elements of the high-concentration semiconductor layer.
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58. An optical transmission system having a semiconductor laser element as a light source, said semiconductor laser element comprising:
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a substrate of first conductivity type, an active layer formed on the substrate of first conductivity type and a stack of semiconductor layers of second conductivity type formed on the active layer, wherein the stack of semiconductor layers of second conductivity type comprises at least a low-concentration semiconductor layer having a doping concentration of not higher than 1×
1017 cm−
3 and a high-concentration semiconductor layer having a doping concentration of not lower than 1×
1018 cm−
3,an electrode is formed on the stack of semiconductor layers of second conductivity type, a low concentration-side compound layer is formed at an interface between the electrode and the low-concentration semiconductor layer, said low concentration-side compound layer being comprised of at least one of constituent elements of the electrode and at least one of constituent elements of the low-concentration semiconductor layer, and a high concentration-side compound layer is formed at an interface between the electrode and the high-concentration semiconductor layer, said high concentration-side compound layer being comprised of at least one of the constituent elements of the electrode and at least one of constituent elements of the high-concentration semiconductor layer.
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Specification