JP3285079B2 - Semiconductor laser - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a semiconductor laser for communication and information processing.

[0002]

2. Description of the Related Art Conventionally, this type of semiconductor laser is disclosed in, for example, Electronics Letters, No. 32, August 1996.
Vol. 17, No. 1582-1583 (ELECTRONICS LE
TTERS, VOL. 32, NO. 17, pp. 1582-1583, AUGUST, 1996)
As described above, an InGaAsP-based strained MQW laser that can be manufactured at low cost and operates stably with a low operating current has been used. In such a semiconductor laser, it is important to reduce leakage current flowing in a region other than the active layer.

FIG. 19 is a cross-sectional view of a conventional semiconductor laser. An n-type cladding layer 192 made of n-type InP grown on a semiconductor substrate 191 made of n-type InP and an InAs
In this structure, an active layer 193 composed of a multiple quantum well (MQW) composed of a P well and an InGaP barrier and a p-type cladding layer 194 composed of p-type InP are buried with a buried layer 195 composed of p-type InP. At the interface where the n-type cladding layer 192 and the buried layer 195 are in contact, In
A Ppn junction 196 is formed. Further, it has a p-electrode 197 and an n-electrode 198 made of metal. Since the embedding structure is simple, the production is easy and the cost is low. Further, since the band gap of the active layer 193 is smaller than the band gap of InP, the rising voltage of the active layer 193 region is smaller than the rising voltage of the InPpn junction 196. Therefore, the current mainly flows through the active layer 193 and oscillates.

[0004]

However, the above-described structure has a problem that a large amount of leakage current flows through portions other than the active layer.

An object of the present invention is to provide a semiconductor laser which is easy to manufacture and has a small operating current with a small leakage current.

[0006]

According to the present invention, there is provided a semiconductor laser comprising: a 3-5 cladding layer made of a group 3-5 semiconductor;
A stripe-shaped active layer made of a group 5 semiconductor, a 3-5 clad layer, and a 2-6 clad layer made of a layered group 2-6 semiconductor on the active layer;
The conduction type of the cladding layer is different, and the band gap of the 2-6 cladding layer is equal to or larger than the band gap of the 3-5 cladding layer.

[0007] A pn junction through a stripe-shaped active layer and a 2-6 / 3-5 pn heterojunction formed by a 3-5 cladding layer and a 2-6 cladding layer exist in parallel. Since the band gap of the 2-6 cladding layer is much larger than that of the active layer, the rising voltage of the 2-6 / 3-5pn heterojunction is higher than the rising voltage of the pn junction via the active layer. Therefore, current concentrates on the active layer, and the leakage current decreases. Further, since the active layer is surrounded by the 3-5 cladding layer and the 2-6 cladding layer both in the vertical and horizontal directions, light and carriers are confined in the active layer.

[0008]

Embodiments of the present invention will now be described with reference to the drawings.

FIG. 1 is a sectional view showing a first embodiment of the present invention, FIG. 2 is a band structure diagram thereof, and FIG. 3 is an electrical characteristic diagram. In FIG. 1, an n-type semiconductor substrate 11 has an n-type
A 3-5 cladding layer 12 made of a Group 5 semiconductor, a striped active layer 13 made of a Group 3-5 semiconductor, and a p-type 2-6
It has a 2-6 cladding layer 14 made of a group III semiconductor, a p electrode 15 and an n electrode 16 made of a metal. The sides of the active layer 13 are in contact with the 3-5 cladding layer 12 and the 2-6 cladding layer 14 to form a 2-6 / 3-5 pn heterojunction 17. The semiconductor layer is formed by a metal organic chemical vapor deposition (MOVPE) method or a molecular beam crystal growth (MBE) method. The active layer 13 is processed into a stripe shape by a selective crystal growth method or an etching method. The p electrode 15 and the n electrode 16 can be formed by vacuum evaporation.

When a positive voltage is applied to the p-electrode 15 and a negative voltage is applied to the n-electrode 16, electrons injected from the 3-5 cladding layer 12 and holes injected from the 2-6 cladding layer 14 become active layers 1
The light is recombined at 3 to emit light, and laser oscillation occurs. The 2-6 cladding layer 14 has a large band gap because it uses a Group 2-6 semiconductor. Therefore, 2-6 of the active layer 13
As shown in FIG. 2A, the / 3-5 pn heterojunction 17 has a large diffusion potential, and a discontinuous value at the valence band edge 21 and a discontinuous value at the conduction band edge 22 are also large. As a result, the electrical characteristics have a higher rising voltage as shown by the IV curve 31 in FIG. In contrast, the band structure in the active layer 13 is shown in FIG.
As shown in (b), since the band gap of the active layer 13 is narrow, the electrical characteristics have a low rising voltage as shown by the IV curve 32 in FIG. 2-6 / 3-5pn heterojunction 1
7 is much higher than the active layer 13, so that when a voltage is applied between the p-electrode 15 and the n-electrode 16,
Current flows only through the active layer 13 and hardly flows through the 2-6 / 3-5 pn heterojunction 17. Therefore, the leakage current during laser oscillation is small, and the oscillation threshold current is small.

The desired band gap of the p-type 2-6 cladding layer 14 may be equal to or larger than the band gap of the n-type 3-5 cladding layer 12.
The effect is remarkable when the band gap difference is 0.1 eV or more, but the band gap of the group 2-6 compound semiconductor containing no Hg is 0.2 eV or more larger than the band gap of the group 3-5 semiconductor compound having the same lattice length. Since it is large, an effect can be obtained by using a group 2-6 compound semiconductor containing no Hg for the p-type cladding layer.

The longitudinal direction of the active layer 13 is the 3-5 cladding layer 1.
Light and carriers are confined in the vertical direction between the cladding layers 2 and 2-6. The lateral direction of the active layer 13 is surrounded by a 2-6 cladding layer 14, and light and carriers are also confined in the lateral direction. That is, the light and carriers are confined in the vertical and horizontal directions by the 2-6 cladding layer 14, and the current is confined. Since the structure is simple, manufacturing is easy and the yield is high. In addition, since the crystal growth temperature of the group 2-6 semiconductor is lower than that of the group 3-5 semiconductor, the crystal growth of the 2-6 cladding layer 14 is easy.

In this embodiment, the semiconductor substrate and the 3-5 cladding layer are n-type and the 2-6 cladding layer is p-type. However, the semiconductor substrate and the 3-5 cladding layer are p-type and the 2-6 cladding layer is n-type. It may be a type. Although the active layer is a single-layer group III-V semiconductor, the invention is not limited to this, and a single or multiple quantum well structure composed of multiple group III-V semiconductor layers may be used. When the 3-5 cladding layer and the semiconductor substrate are made of the same material, a part of the semiconductor substrate may be used as the 3-5 cladding layer.

The materials used in this embodiment include InP, InAs, InSb, InN, G
aAs, GaP, GaSb, GaN, etc .;
As the clad layer and the active layer, there are InGaAsP mixed crystal system, AlGaAs mixed crystal system, InGaAlP mixed crystal system, and the like. ZnSe, ZnTe, Z
nS, CdSe, CdS, CdTe, BeSe, BeT
e, MgZnSSe mixed crystal system, MgZnSeTe mixed crystal system,
MgZnCdSe mixed crystal system, BeZnSeTe mixed crystal system, B
eZnCeSe mixed crystal system, ZnCdSeTe mixed crystal system, Cd
MgSSe mixed crystal system and the like.

FIG. 4 is a sectional view showing a second embodiment of the present invention. On an n-type semiconductor substrate 41, a 3-5 cladding layer 42 made of an n-type group 3-5 semiconductor, a stripe-shaped active layer 43 made of a group 3-5 semiconductor, and a 2-type semiconductor made of a p-type group 2-6 semiconductor 6 has a cladding layer 44 and a p-electrode 45 and an n-electrode 46 made of metal. The active layer 43 is formed in a stripe shape in the groove portion of the 3-5 cladding layer 42, the 3-5 cladding layer 42 and the 2-6 cladding layer 44 are in contact on both sides, and the 2-6 / 3-5 pn heterojunction 47 is formed. Are formed. The groove portion of the 3-5 cladding layer 42 can be formed by etching, and the active layer 43 can be formed by selective growth or a combination of crystal growth and etching.

The band structure and electrical characteristics of the active layer 43 and the 2-6 / 3-5 pn heterojunction 47 are the same as in the first embodiment. The electrical characteristic of the 2-6 / 3-5pn heterojunction 47 has a high rising voltage as shown by the IV curve 31 in FIG. The active layer 43 is low as shown by the IV curve 32 in FIG. When a voltage is applied between the p electrode 45 and the n electrode 46,
Current flows only through the active layer 43 and hardly flows through the 2-6 / 3-5 pn heterojunction 47.

The longitudinal direction of the active layer 43 is the 3-5 cladding layer 4.
It is sandwiched between 2 and 2-6 cladding 44, and light and carriers are vertically confined. The lateral direction of the active layer 43 is surrounded by the 3-5 cladding layer 42, and light and carriers are also confined in the lateral direction. Since the active layer 43 and the 3-5 cladding layer 42 are group 3-5 semiconductors, the difference in the refractive index is small, and the conditions under which the single transverse mode oscillation can be performed with respect to the fluctuation of the width of the active layer 43 are loose. In addition, since the surface has good flatness, the process and integration are easy.

In this embodiment, the semiconductor substrate and the 3-5 cladding layer are n-type and the 2-6 cladding layer is p-type. However, the semiconductor substrate and the 3-5 cladding layer are p-type and the 2-6 cladding layer is n-type. It may be a type. Further, although the active layer is a single-layer group III-V semiconductor, the present invention is not limited to this, and a multiple quantum well structure composed of multiple layers of group III-V semiconductor layers may be used. When the 3-5 cladding layer and the semiconductor substrate are made of the same material, a part of the semiconductor substrate may be used as the 3-5 cladding layer.

The materials used in this embodiment include InP, InAs, InSb, InN, G
aAs, GaP, GaSb, GaN, etc .;
As the clad layer and the active layer, there are InGaAsP mixed crystal system, AlGaAs mixed crystal system, InGaAlP mixed crystal system, and the like. ZnSe, ZnTe, Z
nS, CdSe, CdS, CdTe, BeSe, BeT
e, MgZnSSe mixed crystal system, MgZnSeTe mixed crystal system,
MgZnCdSe mixed crystal system, BeZnSeTe mixed crystal system, B
eZnCeSe mixed crystal system, ZnCdSeTe mixed crystal system, Cd
There is an MgSSe-based mixed crystal system and the like.

FIG. 5 is a sectional view showing a third embodiment of the present invention, and FIG. 6 is a band structure diagram thereof. On an n-type semiconductor substrate 51, a 3-5 cladding layer 52 made of an n-type 3-5 group semiconductor, a striped n-light guide layer 53 made of an n-type 3-5 group semiconductor, and a 3-5 group semiconductor A striped active layer 54, a striped p-light guide layer 55 made of a p-type group 3-5 semiconductor, a 2-6 cladding layer 56 made of a p-type group 2-6 semiconductor, a p electrode 57 made of metal, and an n electrode 2-6 / 3-5 on both sides of the active layer 54.
A pn hetero junction 59 is formed. n light guide layer 5
3. The active layer 54 and the p-light guide layer 55 can be formed by selective growth or a combination of crystal growth and etching.

The band structure near the active layer 54 is as shown in FIG. 6, in which carriers are confined in the active layer 54 between the n light guide layer 53 and the p light guide layer 55. Light is 3-
The active layer 54, the n light guide layer 53, and the p light guide layer 55 are confined by the 5 clad layer 52 and the 2-6 clad layer 56. n light guide layer 53 and p light guide layer 55
By changing the refractive index and the layer thickness of the active layer 54, the light confinement ratio in the active layer 54 can be changed. As a result, desired characteristics such as a low threshold current and a high output can be obtained. Active layer 54
Rise voltage is 2-6 / 3-5 pn hetero junction 5
9, and the leakage current is very small.

In this embodiment, the semiconductor substrate and the 3-5 cladding layer 52 are of the n-type, and the 2-6 cladding layer 56 is of the p-type. The 2-6 cladding layer 56 may be an n-type, the lower side of the active layer 54 may be an n-type light guide layer, and the upper side may be a p-type light guide layer. Further, although the active layer 54 is a single-layer group III-V semiconductor, the present invention is not limited to this. For example, a multiple quantum well structure including a multilayer group III-V semiconductor layer may be used. Further, the light guide layer is a single-layer group 3-5 semiconductor, but is not limited to this.
A multilayer or a mixed crystal of a Group 3-5 semiconductor having a continuously changed composition may be used. When the 3-5 cladding layer and the semiconductor substrate are made of the same material, a part of the semiconductor substrate may be used as the 3-5 cladding layer.

FIG. 7 is a sectional view showing a fourth embodiment of the present invention. The layer structure is the same as in the third embodiment. 3
-5 has a groove in a part of the cladding layer 52, and on the groove,
It has a striped n light guide layer 53, an active layer 54 and a p light guide layer 55. This structure can be formed by a combination of etching, crystal growth, and selective growth.

The vertical light confinement of the active layer 54 can be adjusted by changing the refractive index and the layer thickness of the n light guide layer 53 and the p light guide layer 55. The lateral direction of the active layer 54 is surrounded by the 3-5 cladding layer 52, and since the difference in the refractive index is small, the condition under which the single transverse mode oscillation can be performed with respect to the fluctuation of the lateral width of the active layer 54 is loose. In addition, since the surface has good flatness, the process and integration are easy.

FIG. 8 is a sectional view showing a fifth embodiment of the present invention, and FIG. 9 is a band structure diagram thereof. On an n-type semiconductor substrate 81, a 3-5 cladding layer 82 made of an n-type 3-5 group semiconductor and an n-light guide layer 8 made of an n-type 3-5 group semiconductor
An active layer 84 made of a group 3, 3-5 semiconductor, a p-light guide layer 85 made of a p-type group 3-5 semiconductor, a 2-6 cladding layer 8
6. It has a p-electrode 88 and an n-electrode 89 made of metal.
At the interface where the 3-5 cladding layer 82 and the 2-6 cladding layer 86 are in contact, a 2-6 / 3-5 pn heterojunction 87 is formed. The 2-6 cladding layer 86 is made of p-type ZnCdSe
Mixed ZnCdSe layer 86a and p-type ZnSeTe
And a ZnSeTe layer 86b made of a mixed crystal.
The ZnCdSe layer 86a is in contact with the 3-5 cladding layer 82, contains only one group 6 element (Se), and has a ZnSeT
The e layer 86b contains two kinds of elements of the sixth group (Se, Te).

Since the ZnSeTe mixed crystal can be easily doped with p-type at a high concentration, the ZnSeTe layer 86b is a material suitable for the 2-6 cladding layer 86. However, if a ZnSeTe mixed crystal is to be grown directly on the 3-5 cladding layer 82, a mixed crystal having a desired composition cannot be obtained because the manner in which Se and Te adhere to the Group 3-5 semiconductor is greatly different. . On the other hand, since the adhesion coefficients of Zn and Cd, which are Group 2 elements, are almost the same, ZnCdSe mixed crystal can be easily grown on the 3-5 cladding layer 82. ZnCdSe layer 8
Since the adhesion coefficient of Se and Te is constant on 6a, the ZnSeTe layer 86b can be easily grown.

In general, the doping characteristics of a Group 2-6 semiconductor mixed crystal vary greatly depending on Group 6 elements. A mixed crystal containing a lot of Te tends to be p-type, and a mixed crystal containing a lot of S tends to be n-type. In order to control the doping concentration, it is effective to use a mixed crystal containing two or more kinds of Group 6 elements. However, if a mixed crystal containing two or more kinds of Group 6 elements is to be directly grown on a Group 3-5 semiconductor, the mixed crystal containing 3 or more kinds of Group 6 elements cannot be grown depending on the kind of Group 6 elements.
Since the adhesion coefficient to the group V semiconductor is very different, a mixed crystal having a large composition unevenness is formed on the growth start surface. On the other hand, the mixed crystal containing two or more kinds of Group 2 elements has no difference in the adhesion coefficient between Group 2 elements and Group 3-5 semiconductors.
It can be easily grown on group semiconductors. On the Group 2-6 semiconductor, there is no significant difference in the adhesion coefficient between Group 6 elements, so that a mixed crystal containing two or more Group 6 elements can be grown.

In this embodiment, ZnCdSe is used as a mixed crystal containing one kind of group 6 element.
nSe, BeSe, CdS, BeTe, ZnTe, Mg
ZnSe, BeZnTe, BeCdS, MgZnCdS
e, MgBeZnTe, CdMgSSe and other 2-6
Mixed crystals may be used. Further, ZnSeTe was used as a mixed crystal containing two or more kinds of Group 6 elements, but is not limited thereto.
nSSe, ZnSTe, CdSSe, BeSeTe, Z
nCdSeTe, MgZnSeTe, BeZnSSe,
Another 2-6 mixed crystal such as BeCdSeTe may be used.
In this embodiment, the semiconductor substrate and the 3-5 cladding layer are n-type, and the 2-6 cladding layer is p-type. However, the present invention is not limited to this.
The cladding layer is an n-type, the lower side of the active layer is an n-light guide layer,
The upper side may be a p-light guide layer. In addition, the active layer is a single-layer group 3-5 semiconductor, but is not limited to this.
A single or multiple quantum well structure composed of a group V semiconductor layer may be used. Further, a structure without a light guide layer or a structure using a 3-5 cladding layer having a groove may be used. Also, 3
When the -5 cladding layer and the semiconductor substrate are made of the same material, a part of the semiconductor substrate may be used as the 3-5 cladding layer.

FIG. 10 is a sectional view showing a sixth embodiment,
FIG. 11 is a diagram showing the band structure. On a semiconductor substrate 101 made of an n-type group 3-5 semiconductor, a 3-5 cladding layer 102 made of an n-type group 3-5 semiconductor and a light guide layer 103
a, an active layer 10 comprising a group 3-5 semiconductor multiple quantum well
4. Light guide layer 103 made of p-type group 3-5 semiconductor
b, p-type 3 having the same composition as the 3-5 cladding layer 102
A light guide layer 103c made of a group -5 semiconductor, a potential relaxation layer 105 made of three p-type group 2-6 semiconductors, p
It has a 2-6 cladding layer 106 made of a type 2-6 group semiconductor, a p electrode 107 made of metal, and an n electrode 108. The potential relaxation layer 105 can be formed by a selective growth method or the like. In FIG. 10, a part of the 3-5 cladding layer 102 is etched at the same time so as to include a stripe shape, but a configuration without etching is also possible.

The light guide layer 103c and the 2-6 cladding layer 106 are p-type, and the conduction carriers are holes. FIG. 11 shows the position of the valence band edge 21 serving as a potential for holes. Valence band edge 2 of potential relaxation layer 105
The position of No. 1 is the light guide layer 103c and the 2-6 cladding layer 1
06, and gradually decreases from the side closer to the light guide layer 103c toward the 2-6 cladding layer 106 side. Therefore, discontinuous values of the valence band edge 21 at the interface between the light guide layer 103c and the potential relaxation layer 105, the interface between the 2-6 cladding layer 106 and the potential relaxation layer 105, and each interface in the potential relaxation layer 105. And the bending of the band at the interface is also reduced. As a result, the resistance to holes flowing from the 2-6 cladding layer 106 to the active layer 104 decreases, and the operating voltage of the semiconductor laser decreases.

Such potential relaxation layers 105 and 2
The -6 cladding layer 106 is made of, for example, p-type ZnCdSeTe
A layer structure in which the Se composition on the side close to the 2-6 cladding layer 106 in the mixed crystal system is increased may be used. In addition, p-type MgZ
A layer structure in which the Mg composition is increased on the side close to the 2-6 cladding layer 106 in the nSSe mixed crystal system may be used. Also, B
eZnSeTe, MgZnSeTe, MgZnCdSe
Other group 2-6 mixed crystal systems may be used.

In this embodiment, the potential relaxation layer is 3
Although the structure is a layer, the present invention is not limited to this, and a structure having one layer, four or more layers, or a structure in which the composition is continuously changed may be used. Further, although the potential relaxation layer and the 2-6 cladding layer are p-type, they are not limited to this and may be n-type.

In this embodiment, the potential relaxation layer is formed of 2
Although a Group 6 semiconductor is used, the present invention is not limited thereto, and a Group 3-5 semiconductor may be used. For example, in an AlGaAs mixed crystal system,
By increasing the composition, the valence band edge can be made deep and the conduction band edge can be made shallow. Further, even in an AlGaInP-based mixed crystal, the valence band edge can be made deep and the conduction band edge can be made shallow by increasing the Al composition. Similarly, a GaInAsP-based mixed crystal can be used. When the 3-5 cladding layer and the semiconductor substrate are made of the same material, a part of the semiconductor substrate may be used as the 3-5 cladding layer.

FIG. 12 is a sectional view showing a seventh embodiment,
FIG. 13 is a diagram showing the band structure. A 3-5 cladding layer 122 made of an n-type group 3-5 semiconductor and a light guide layer 123 on a semiconductor substrate 121 made of an n-type group 3-5 semiconductor.
a, an active layer 124 made of a group 3-5 semiconductor;
An optical guide layer 123b made of a Group 5 semiconductor, a potential relaxation layer 125 made of a p-type 2-6 semiconductor, and a p-type 2-6
It has a 2-6 cladding layer 126 made of group semiconductor, a p electrode 127 and an n electrode 128 made of metal. The potential relaxation layer 125 can be easily formed by crystal growth. 3
At the interface where the −5 cladding layer 122 and the potential relaxation layer 125 are in contact, the 2-6 / 3-5 pn heterojunction 12
9 are formed.

Valence band edge 2 of potential relaxation layer 125
The position of 1 is the light guide layer 123b and the 2-6 clad layer 12
6 is an intermediate value of 2 and 2-6 / 3-5 pn heterojunction 1
The band structure of 29 is as shown in FIG. 13A, and the band structure near the active layer 124 is as shown in FIG.
In the 2-6 / 3-5pn heterojunction 129, since the potential relaxation layer 125 is made of a Group 2-6 semiconductor, the band gap is large and the rise voltage is high. In the vicinity of the active layer 124, the interface between the light guide layer 123b and the potential relaxation layer 125, and the potential relaxation layers 125 and 2-
The bending of the band at the interface of the six cladding layers 126 is reduced, and the resistance to holes is reduced. As a result, the operating voltage of the semiconductor laser decreases.

Such potential relaxation layers 125 and 2
The -6 cladding layer 126 is made of, for example, p-type ZnCdSeTe.
It is sufficient to use a mixed crystal system in which the Se composition in the potential relaxation layer 125 is reduced and the Se composition in the 2-6 cladding layer 126 is increased. Similarly, p-type MgZnSSe,
BeZnSeTe, MgZnSeTe, MgZnCdS
Another group 2-6 mixed crystal system such as e may be used.

In this embodiment, the potential relaxation layer is 1
Although the structure is a layer, the invention is not limited to this, and a multilayer structure or a structure in which the composition changes continuously may be used. Further, although the potential relaxation layer and the 2-6 cladding layer are p-type, they are not limited to this and may be n-type. When the 3-5 cladding layer and the semiconductor substrate are made of the same material, a part of the semiconductor substrate may be used as the 3-5 cladding layer.

FIG. 14 is a sectional view showing the eighth embodiment. Semiconductor substrate 14 made of an n-type group 3-5 semiconductor
1, an n-type 3-5 cladding layer 142 made of a group 3-5 semiconductor, a light guide layer 143a, an active layer 144 made of a group 3-5 semiconductor multiple quantum well, and a light guide made of a p-type group 3-5 semiconductor The light guide layer 143c made of a p-type group 3-5 semiconductor and having the same composition as the layers 143b and the 3-5 cladding layer 142, an insulator film 145, and a mesa stripe 2-6 made of a p-type group 2-6 semiconductor. It has a clad layer 146, a p-electrode 148 and an n-electrode 149 made of metal. At the interface between the 3-5 cladding layer 142 and the 2-6 cladding layer 146, a 2-6 / 3-5pn heterojunction 147 is formed. The 2-6 cladding layer 146 can be formed by a selective growth method or the like using the insulator film 145 as a mask. Insulator film 1
For 46, SiO ₂ or Si ₂ N ₃ may be used. 2-
By forming the 6-cladding layer 146 in a mesa stripe shape, the area of the 2-6 / 3-5 pn heterojunction 147 was reduced, the capacity was reduced, and high-speed operation became possible.

In this embodiment, the 3-5 cladding layer is n-type and the 2-6 cladding layer is p-type. However, the 3-5 cladding layer may be p-type and the 2-6 cladding layer may be n-type. Although the active layer has a multiple quantum well structure and the light guide layer is provided, the present invention is not limited to this, and another structure such as a double hetero structure or a single quantum well structure may be used. When the 3-5 cladding layer and the semiconductor substrate are made of the same material, a part of the semiconductor substrate may be used as the 3-5 cladding layer.

FIG. 15 is a sectional view showing the ninth embodiment. Semiconductor substrate 15 made of n-type group 3-5 semiconductor
1, a 3-5 cladding layer 152 made of an n-type group 3-5 semiconductor, a light guide layer 153a, an active layer 154 made of a group 3-5 semiconductor, a light guide layer 153b made of a p-type group 3-5 semiconductor, An optical guide layer 153c made of a p-type group 3-5 semiconductor and having the same composition as the 3-5 clad layer 152, an insulator film 155, a 2-6 clad layer 156 made of a p-type group 2-6 semiconductor, and made of metal p electrode 158, n electrode 15
9 The interface between the 3-5 cladding layer 152 and the 2-6 cladding layer 156 has a 2-6 / 3-5 pn heterojunction 1
57 are formed. 2-6 cladding layer 156 is MB
It can be formed by E method or the like. Si is used for the insulator film 155.
O ₂ or Si ₂ N ₃ may be used. By inserting the insulator film 155, the 2-6 / 3-5pn heterojunction 15
7, the area is reduced, the capacity is reduced, and high-speed operation is possible. Also, the leakage current flowing through the 2-6 / 3-5pn heterojunction 157 is reduced. Further, since the shape is flat, the process is easy and the yield is high. In addition, since the contact area between the 2-6 cladding layer 156 and the p-electrode 158 is large, there is an advantage that the electrode resistance is reduced.

In this embodiment, the 3-5 cladding layer is n-type and the 2-6 cladding layer is p-type. However, the 3-5 cladding layer may be p-type and the 2-6 cladding layer may be n-type. Further, although the active layer is a single-layer group 3-5 semiconductor and the light guide layer is provided, the present invention is not limited to this, and another structure such as a single or multiple quantum well structure may be used. When the 3-5 cladding layer and the semiconductor substrate are made of the same material, a part of the semiconductor substrate may be used as the 3-5 cladding layer.

FIG. 16 is a sectional view showing a tenth embodiment. It has a 2-6 cladding layer 161 made of a p-type 2-6 group semiconductor, a contact layer 162 made of a high-concentration p-type 2-6 group semiconductor, and a p electrode 163 made of metal. For other configurations, any of the above embodiments is possible. The contact layer 162 can be formed by an MBE method or the like. The impurity concentration of the contact layer 162 is set to 10 ¹⁸ cm ⁻³
By setting the base, ohmic electrode characteristics can be obtained.

In the p-type contact layer, ZnTe: N,
BeTe: N, ZnTe: P, ZnSeTe: N, Be
Group 2-6 semiconductors such as Se: N and CdSeTe: N,
These superlattice structures may be used.

In this embodiment, the 2-6 cladding layer and the contact layer 162 are p-type, but may be n-type. n
Type contact layers include ZnSe: Cl, BeSe: C
1, ZnSe: Ga, ZnCdSe: Cl, MgBeS
A group 2-6 semiconductor such as e: Cl, ZnS: Cl, and CdS: Cl, or a superlattice structure thereof may be used.

Next, an eleventh embodiment will be described with reference to the sectional view of FIG.

The 3-5 cladding layer 1 is formed on the semiconductor substrate 11.
2. By lattice-matching each layer of the active layer 13 and the 2-6 cladding layer 14, defects at each interface are reduced, and leakage current is reduced. In addition, stress on the active layer 13 is eliminated, the life of the device is prolonged, and the yield is improved. When the semiconductor substrate 11 is InP, the 3-5 cladding layer 12 is InP, the active layer 13 is InGaAsP, and the 2-6 cladding layer 14 is ZnCdSeTe, MgZnSeTe,
A mixed crystal system such as MgZnCdSe and CdMgSSe may be used.

When the semiconductor substrate 11 is made of GaAs, 3
-5 cladding layer 12 is made of AlGaAs and active layer 13 is made of Al
2-6 cladding layer 14 made of GaAs or InGaAs
Include ZnSSe, MgZnSSe, ZnBeSeTe,
A mixed crystal system such as MgZnSTe may be used. GaAs
In the semiconductor substrate 11, the 3-5 cladding layer 12 is formed of AlGaI.
The same applies when nP and the active layer 13 are made of AlGaInP.
A -6 mixed crystal system can be used. GaSb or InAs
Is a semiconductor substrate 11, and the 3-5 cladding layer 12 and the active layer 13 are made of InGaAsSb, InAsPSb, AlGaAs.
When using any of sSb, ZnCdSeTe,
A mixed crystal system such as CdSSeTe and MgZnSeTe may be used.

[0048]

【Example】

 Embodiment 1 A first embodiment of the present invention will be described with reference to FIG. Half
Using a p-type InP substrate as the conductive substrate 171,
Layer 172 is p-type InP (p = 5 × 10¹⁷cm ^-3,thickness
1 μm), and the light guide layer 173a is formed of InGaAsP (p =
1 × 10¹⁷cm ^-3, A thickness of 0.1 μm)
InGaAs / InGaAsP multiple quantum well, light guide
The layer 173b is formed of InGaAsP (n = 1 × 10¹⁷cm^-3,
The thickness of the light guide layer 173c is n-type InP.
(N = 5 × 10¹⁷cm^-3, Thickness 0.2μm) and organic
After crystal growth by metal vapor phase epitaxy, photolithography
Light guide layer 173 by luffy and dry etching
a, 173b, 173c and the active layer 174 are etched.
Striped shape. I by molecular beam epitaxy
n-type CdSSe lattice-matched to nP (n = 5 × 10¹⁷c
m^-32-6 clad layer 175 made of
After growing, the n-electrode 176 and the p-electrode
It was formed by an empty deposition method. 3-5 cladding 172 and 2-
At the interface where the 6 cladding layer 175 is in contact, 2-6 / 3-5
A pn heterojunction 178 is formed.

FIG. 18 is a band structure diagram of the semiconductor laser of this embodiment. 2-6 / 3-5pn heterojunction 1
Reference numeral 78 denotes a 2-6 cladding layer 1 as shown in FIG.
The band gap at 75 is large, and the band discontinuity at the interface is large. Therefore, the rising voltage is large. The band structure near the active layer 174 is as shown in FIG. 18B, and the rising voltage is determined by the band gap of the active layer 174, and is smaller than that of the 2-6 / 3-5pn heterojunction 178. As a result, the leakage current is reduced, and 30
The threshold current at a resonator length of 0 μm and a stripe width of 2 μm was 2 mA.

In this embodiment, the active layer portion is processed into a stripe shape by etching, but the stripe shape of the active layer portion may be formed by selective growth.

Further, as the 2-6 cladding layer, n-type CdS
Although Se was used, the present invention is not limited to this, and n-type ZnCdSSe lattice-matched to InP may be used. Also, ZnCdS
eTe, ZnMgSeTe, ZnCdMgSe, CdM
A mixed crystal of 2-6 such as gSSe may be used.

In the above embodiment, the semiconductor substrate and the 3-5 cladding layer are p-type, and the 2-6 cladding layer is n-type.
The cladding layer may be p-type.

Although an InGaAsP system lattice-matched to InP was used as the group III-V semiconductor, an InAlAsP system or a combination thereof, or an AGaAs lattice-matched to GaAs was used.
An lGaAsP-based, GaInNAs-based, AlGaInP-based, or a combination thereof may be used.

Embodiment 2 Next, a second embodiment of the present invention will be described with reference to FIG. Using an n-type InP substrate as the semiconductor substrate 101,
5 cladding layer 102 is formed of n-type InP (n = 5 × 10 ¹⁷ cm).
^-3 , thickness 1 μm), and the light guide layer 103a is made of InGaAs.
P (n = 1 × 10 ¹⁷ cm ⁻³ , thickness 0.1 μm), the active layer 104 is formed of InGaAs / InGaAsP multiple quantum well,
The light guide layer 103b is formed of InGaAsP (p = 1 × 10 ^17).
cm ⁻³ , thickness 0.1 μm), and the light guide layer 103c is made of p-type InP (p = 5 × 10 ¹⁷ cm ⁻³ , thickness 0.1 μm). P-type ZnSe _0.54 Te _0.46 , p-type by molecular beam epitaxy
Type Zn _0.82 Cd _0.18 Se _0.69 Te _0.31 , p-type Zn _0.65 C
d _0.35 Se _0.85 Te _{0.15 A} potential relaxation layer 105 composed of three layers is grown, and the light guide layers 103a, 103b, 103 are formed by photolithography and dry etching.
c, The active layer 104 and a part of the 3-5 cladding layer 102 were etched to form a stripe shape having a width of 2 μm.
A 2-6 cladding layer 106 made of p-type ZnCdSe (p = 5 × 10 ¹⁷ cm ⁻³ , 2 μm) lattice-matched to InP is grown by molecular beam epitaxy, and a p electrode 107 and an n electrode 108 made of Au are grown. Was formed by a vacuum evaporation method.

FIG. 11 is a band structure diagram at this time.
By sandwiching the potential relaxation layer 105 between the light guide layer 103c and the 2-6 cladding layer 106, the interface between the light guide layer 103c and the potential relaxation layer 105,
The discontinuous value of the valence band edge 21 at the interface between the six cladding layer 106 and the potential relaxation layer 105 and at each interface in the potential relaxation layer 105 is reduced, and the bending of the band at the interface is also reduced. Thereby, the 2-6 cladding layer 1
The resistance to holes flowing from the semiconductor layer 06 to the active layer 104 decreases, and the operating voltage of the semiconductor laser decreases. The operation voltage was reduced from 1.5 V to 1.3 V by introducing the potential relaxation layer 105. Along with this, the leakage current also decreases,
The threshold voltage was reduced from 2 mA to 1.8 mA.

In this embodiment, p-type ZnSe_0.54Te_0.46,
p-type Zn_0.82Cd_0.18Se_0.69Te _0.31, P-type Zn_0.65
Cd_0.35Se_0.85Te_0.15Potential relaxation consisting of three layers
Although the sum layer was used, the present invention is not limited to this.
May be a structure in which the structure or composition changes continuously. Also,
As a material for the potential relaxation layer, a material for the light guide layer
Corresponding to ZnMgSeTe, ZnMgSSe, ZnCdS
Others such as Se, CdMgSSe, ZnCdMgSe
A material system may be used, and the material is not limited to a group 2-6 semiconductor.
It may be composed of a Group 3-5 semiconductor. Also, the potential
The relaxation layer and the 2-6 cladding layer are p-type, but are not limited to this.
Instead, it may be an n-type.

[0057]

As described above, according to the present invention,
A semiconductor laser which is easy to manufacture and has a small threshold current can be obtained. This is because a group 2-6 semiconductor having a large band gap and a low growth temperature is used for one clad layer.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing a first embodiment of the present invention.

FIG. 2 is a band structure diagram according to the first embodiment of the present invention.

FIG. 3 is an electrical characteristic diagram of the first embodiment of the present invention.

FIG. 4 is a sectional view showing a second embodiment of the present invention.

FIG. 5 is a sectional view showing a third embodiment of the present invention.

FIG. 6 is a band structure diagram according to a third embodiment of the present invention.

FIG. 7 is a sectional view showing a fourth embodiment of the present invention.

FIG. 8 is a sectional view showing a fifth embodiment of the present invention.

FIG. 9 is a band structure diagram according to a fifth embodiment of the present invention.

FIG. 10 is a sectional view showing a sixth embodiment of the present invention.

FIG. 11 is a band structure diagram according to a sixth embodiment of the present invention.

FIG. 12 is a sectional view showing a seventh embodiment of the present invention.

FIG. 13 is a band structure diagram according to a seventh embodiment of the present invention.

FIG. 14 is a sectional view showing an eighth embodiment of the present invention.

FIG. 15 is a sectional view showing a ninth embodiment of the present invention.

FIG. 16 is a sectional view showing a tenth embodiment of the present invention.

FIG. 17 is a sectional view showing a first embodiment of the present invention.

FIG. 18 is a band structure diagram of the first embodiment of the present invention.

FIG. 19 is a sectional view showing a conventional example.

[Explanation of symbols]

 Reference Signs List 11 semiconductor substrate 12 3-5 cladding layer 13 active layer 14 2-6 cladding layer 15 p electrode 16 n electrode 17 2-6 / 3-5 pn heterojunction 21 valence band edge 22 conduction band edge 31 IV curve 32 I −V curve 41 semiconductor substrate 42 3-5 cladding layer 43 active layer 44 2-6 cladding layer 45 p electrode 46 n electrode 47 2-6 / 3-5 pn heterojunction 51 semiconductor substrate 52 3-5 cladding layer 53 n light guide Layer 54 active layer 55 p light guide layer 56 2-6 clad layer 57 p electrode 58 n electrode 59 2-6 / 3-5 pn heterojunction 81 semiconductor substrate 82 3-5 clad layer 83 n light guide layer 84 active layer 85 p Light guide layer 86 2-6 cladding layer 86a ZnCdSe layer 86b ZnSeTe layer 87 2-6 / 3-5pn heterojunction 88 p electrode 89 Electrode 101 semiconductor substrate 102 3-5 cladding layer 103a, b, c light guide layer 104 active layer 105 potential relaxation layer 106 2-6 cladding layer 107 p electrode 108 n electrode 121 semiconductor substrate 122 3-5 cladding layer 123a, b light Guide layer 124 Active layer 125 Potential alleviation layer 126 2-6 cladding layer 127 P electrode 128 N electrode 129 2-6 / 3-3 pn heterojunction 141 Semiconductor substrate 142 3-5 Clad layer 143 a, b, c Optical guide layer 144 Active Layer 145 Insulator film 146 2-6 Clad layer 147 2-6 / 3-5 pn heterojunction 148 P electrode 149 N electrode 151 Semiconductor substrate 152 3-5 Clad layer 153 a, b, c Light guide layer 154 Active layer 155 Insulator Film 156 2-6 Cladding layer 157 2-6 3-5pn heterojunction 158 p electrode 159 n electrode 161 2-6 cladding layer 162 contact layer 163 p electrode 171 semiconductor substrate 172 3-5 cladding layer 173a, b, c light guide layer 174 active layer 175 2-6 cladding layer 176 N electrode 177 P electrode 178 2-6 / 3-5 pn heterojunction

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-63-205979 (JP, A) JP-A-8-8482 (JP, A) JP-A-8-250809 (JP, A) JP-A-62 84581 (JP, A) JP-A-1-313981 (JP, A) JP-A-4-186686 (JP, A) JP-A-7-106685 (JP, A) JP-A-9-92926 (JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) H01S 5/00-5/50

Claims (14)

(57) [Claims] 1. A 3-5 cladding layer having a stripe-shaped groove made of a group 3-5 semiconductor, a striped active layer made of a group 3-5 semiconductor on a groove of the 3-5 clad layer,
A 3-6 cladding layer comprising a layered group 2-6 semiconductor on the 3-5 cladding layer and the active layer, wherein the 3-5 cladding layer and the 2-6 cladding layer have different conduction types. And a band gap of the 2-6 cladding layer is equal to or larger than a band gap of the 3-5 cladding layer. 2. A striped light guide layer made of a Group 3-5 semiconductor having a larger band gap than the active layer is provided between the active layer and the 2-6 cladding layer, and the conduction type of the light guide layer is 2. The semiconductor laser according to claim 1, wherein the value is equal to said 2-6 cladding layer. 3. The 2-6 cladding layer is composed of two or more Group 2-6 semiconductor mixed crystals, and the layer in contact with the 3-5 cladding layer is 1 layer.
Consisting of more than one kind of group 2 element and one kind of group 6 element,
3. The semiconductor according to claim 1, wherein at least one of the layers not in contact with the 3-5 cladding layer is composed of at least one kind of Group 2 element and two kinds of Group 6 element. laser. 4. A stripe-like potential relaxation layer comprising a single-layer or multi-layer group 3-5 semiconductor or a group 2-6 semiconductor is provided between the light guide layer and the 2-6 cladding layer. The conduction type of the relaxation layer is equal to the conduction type of the 2-6 cladding layer, and the potential for conduction carriers is an intermediate value between the 2-6 cladding layer and the light guide layer. Semiconductor laser. 5. Between the light guide layer and the 2-6 cladding layer,
And between the 3-5 cladding layer and the 2-6 cladding layer, a potential relaxation layer composed of a group 2-6 semiconductor having a single layer or a multilayer structure, and the conduction type of the potential relaxation layer is 2 or less.
3. The semiconductor laser according to claim 2, wherein the conductivity type is equal to the conductivity type of the -6 cladding layer, and the potential for carriers is an intermediate value between the 2-6 cladding layer and the light guide layer. 6. The semiconductor laser according to claim 1, wherein the 2-6 cladding layer has a mesa stripe shape. 7. The semiconductor laser according to claim 1, wherein an insulating layer is provided in a part or all between the 3-5 cladding layer and the 2-6 cladding layer. 8. A contact layer comprising a 2-6 clad layer and a contact layer made of a group 2-6 semiconductor having the same conductivity type and a high impurity concentration as the 2-6 clad layer.
8. The semiconductor laser according to claim 7. 9. The semiconductor device according to claim 1, wherein a lattice length of the group 3-5 semiconductor forming the 3-5 cladding layer is equal to a lattice length of the group 2-6 semiconductor forming the 2-6 cladding layer. 2. The semiconductor laser according to claim 1. 10. A three-dimensional semiconductor comprising a group 3-5 semiconductor.
A clad layer 5, a striped active layer made of a group 3-5 semiconductor on the 3-5 clad layer, and a layered 2-6 semiconductor formed on the 3-5 clad layer and the active layer.
6 clad layer, wherein the 3-5 clad layer and the 2 clad layer
The conduction type of the cladding layer is different from that of the active layer, and the band gap of the cladding layer is equal to or larger than the band gap of the cladding layer. A light guide layer formed of a group III-V semiconductor having a band gap larger than that of the active layer between the light guide layer and the cladding layer; the conduction type of the light guide layer is equal to that of the 2-6 cladding layer; A potential relaxation layer composed of a single-layer or multi-layer group 2-6 semiconductor, between the guide layer and the 2-6 cladding layer and between the 3-5 cladding layer and the 2-6 cladding layer; A semiconductor laser, wherein the conduction type of the potential relaxation layer is equal to the conduction type of the 2-6 cladding layer, and the potential for carriers is an intermediate value between the 2-6 cladding layer and the light guide layer. 11. The semiconductor laser according to claim 10, wherein the 2-6 cladding layer has a mesa stripe shape. 12. The semiconductor laser according to claim 10, wherein an insulating layer is provided partially or entirely between the 3-5 cladding layer and the 2-6 cladding layer. 13. The semiconductor device according to claim 1, further comprising a contact layer made of a Group 2-6 semiconductor having the same conductivity type and a high impurity concentration as the 2-6 cladding layer, on the 2-6 cladding layer.
13. The semiconductor laser according to any one of 0 to 12. 14. The semiconductor device according to claim 10, wherein a lattice length of the group 3-5 semiconductor forming the 3-5 cladding layer is equal to a lattice length of the group 2-6 semiconductor forming the 2-6 cladding layer. 2. The semiconductor laser according to claim 1.