JP2005333126A - Semiconductor light emitting device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a semiconductor light emitting device, in which an element resistance, a thermal resistance, a passing resistance and operating currents are low, and high power operation is possible. <P>SOLUTION: On a substrate, the semiconductor light emitting device has at least a first conductivity type clad layer, an active layer, a second conductivity type first clad layer, a second conductivity type second clad layer having a stripe-like ridge structure, a current blocking layer formed on the second conductivity type first clad layer so as to sandwich both the side faces of the ridge, and a second conductivity type third clad layer formed on the ridge of the second conductivity type second clad layer and on the current blocking layer near the ridge. The cross section perpendicular to the longitudinal direction of the stripe of the ridge structure is a trapezoid, which satisfies the relation of the expression of 0.05<h/[(a+b)/2]<0.5, where, h is height of the cross section, a is the upper side of the cross section, and b is the lower side of the cross section. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a semiconductor light emitting device useful as a semiconductor laser or the like, and more particularly to a semiconductor light emitting device having low element resistance and capable of high output operation.

  In recent years, laser diodes (LD) using III-V compound semiconductor materials have been actively developed as light sources for information processing equipment such as compact disks and optical disks. An example of a conventional LD using a III-V group compound semiconductor material is an LD made of an AlGaInP-based compound semiconductor having a structure schematically shown in FIG. In FIG. 4, 401 is an n-type substrate, 402 is an n-type first cladding layer, 403 is an active layer, 404 is a p-type second cladding layer, 405 is a p-type etching stop layer, and 406 is a p-type first cladding layer having a ridge structure. 3 cladding layers, 407 is an n-type current blocking layer, 408 is a p-type contact layer, 409 is a p-side electrode, and 410 is an n-side electrode.

  In the LD using the conventional AlGaInP-based semiconductor material shown in FIG. 4 (hereinafter referred to as “conventional LD”), a p-type third cladding layer 406 is sandwiched between current blocking layers 407, and a ridge of the p-type third cladding layer 406 is formed. Since it has a structure in which current is confined in a portion, generally, passage resistance, thermal resistance, and element resistance are high. Therefore, the conventional LD increases the amount of heat generated by the element when high current is injected, the light output decreases due to thermal saturation, the operating current increases when operated at a temperature higher than room temperature, and high frequency superposition is difficult to be applied. There was a problem of becoming.

  In the conventional LD, zinc is used as a p-type impurity in the p-type cladding layers 404 and 406. Since zinc has a property of easily diffusing in the AlGaInP crystal, it often occurs that zinc in the p-type cladding layer diffuses into the active layer while repeating epitaxial growth. When zinc diffuses into the active layer in this way, the crystallinity of the active layer is deteriorated and the life is shortened. On the other hand, if the zinc concentration is lowered to prevent diffusion, the operating voltage increases and laser oscillation becomes difficult.

  Further, in the conventional LD, the n-type cladding layer and the p-type cladding layer have a double hetero structure having an Al composition larger than that of the active layer in order to confine emitted light in the active layer. However, for example, when the amount of Al in the p-type cladding layer is increased in order to increase the light confinement, the carrier concentration decreases, resulting in a problem that the device resistance increases and the drive current increases. On the other hand, if the amount of Al in the p-type cladding layer is decreased in order to reduce the drive current, there is a problem that light confinement and carrier confinement become weak and the light emission efficiency deteriorates.

  In order to solve the above problems, several semiconductor light emitting devices have been developed so far. For example, Patent Document 1 (Japanese Patent Laid-Open No. 7-297483) describes a semiconductor laser having a p-type second cladding layer (ridge: current confinement portion) doped at a high concentration in order to reduce device resistance. ing. However, there is a drawback in that a p-type dopant such as zinc diffuses into the active layer during epitaxial growth or during energization, leading to deterioration of device characteristics and reliability. On the other hand, in Patent Document 2 (Japanese Patent Laid-Open No. 11-26880), in order to prevent diffusion of a p-type dopant into the active layer, a p-type second cladding layer (ridge: current confinement portion) and an active layer are provided. A semiconductor laser device is described in which a carrier diffusion suppression layer is provided therebetween. However, the carrier diffusion suppression layer described in Patent Document 2 cannot sufficiently cope with the change in the diffusion state of the p-type dopant due to the growth temperature, crystallinity, etc., and further has variations in device characteristics, which causes a problem in reliability reproducibility. was there. Further, in Patent Document 3 (Japanese Patent Laid-Open No. 11-87832), in order to prevent diffusion of the p-type dopant into the active layer, the p-type cladding layer and the active layer are interposed between the p-type cladding layer and the active layer. A semiconductor laser in which a layer having an intermediate band gap with the layer is formed is described. However, this semiconductor laser has the disadvantages that the etching process of the ridge portion is complicated and that it is difficult to form a stable ridge shape, for example, a depression is generated in the upper part of the side surface of the ridge portion.

  On the other hand, the conventional LD usually controls the fundamental transverse mode by forming a striped ridge in the [−110] direction (Non-patent Document 1: Fujii et al., Electronics Letters Vol. 23, No. 18). No., pages 938-939). This is because by selecting the ridge stripe direction in the [−110] direction, the luminous efficiency of the active layer made of the AlGaInP ordered crystal can be improved and the threshold current density can be lowered compared to the [110] direction. However, in order to perform the basic transverse mode at a higher output, it is necessary to make the ridge width narrower and the ridge height higher, and there is a problem that large Joule heat is generated in the ridge in the [−110] direction. there were.

In order to solve the above problem in the ridge formation direction, a semiconductor laser in which a stripe ridge is formed in the [110] direction has been developed so far (Patent Document 4: Japanese Patent Laid-Open No. 7-193313). However, the ridge structure described in Patent Document 4 has an inverted mesa shape, and in order to form a p-type third cladding layer having the inverted mesa shape, it is necessary to perform high temperature growth (700 to 850 ° C.) in a disordered state. . It is not preferable to grow at a high temperature in order to make the disordered state because the p-type dopant diffuses into the active layer during the growth process, the crystallinity of the active layer is deteriorated, the life is shortened, and the reliability is lowered.
Japanese Patent Laid-Open No. 7-297483 JP-A-11-26880 Japanese Patent Laid-Open No. 11-87832 JP-A-7-193313 Fujii et al., Electronics Letters Vol. 23, No. 18, pp. 938-939

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a semiconductor light-emitting device that has low element resistance, thermal resistance, passage resistance, and operating current, and is capable of high output operation. There is.

  In order to solve the above-described problems of the prior art, the present inventor has intensively studied the structure of a semiconductor device having a ridge structure, and as a result, the operating current is reduced by configuring the ridge structure to satisfy a specific condition. It has been found that a semiconductor light emitting device capable of being greatly reduced and capable of high temperature operation and capable of high output operation can be obtained, and the present invention has been completed.

That is, the object of the present invention is achieved by a semiconductor light emitting device having the following configuration.
[1] A substrate, a first conductivity type cladding layer comprising at least one layer formed on the substrate, an active layer formed on the first conductivity type cladding layer, and an active layer formed on the active layer A second conductivity type first cladding layer; a second conductivity type second cladding layer having a striped ridge structure formed on the second conductivity type first cladding layer; and the second conductivity type second cladding layer. A current blocking layer formed on the second conductivity type first cladding layer so as to sandwich both side surfaces of the ridge, and on the ridge of the second conductivity type second cladding layer and on the current blocking layer in the vicinity of the ridge And a second light emitting type third cladding layer formed on the semiconductor ridge structure, wherein the cross section perpendicular to the stripe longitudinal direction of the ridge structure is a trapezoid satisfying the following formula.
0.05 <h / [(a + b) / 2] <0.5
(In the above equation, h is the height of the cross section, a is the upper base of the cross section, and b is the lower base of the cross section.)
[2] The semiconductor light-emitting device according to [1], wherein the cross section is a trapezoid whose lower base is longer than the upper base.
[3] The semiconductor light emitting device according to [1] or [2], wherein the cross section is a trapezoid having an upper base of 0.4 μm to 4 μm.
[4] The semiconductor light-emitting device according to any one of [1] to [3], wherein the cross section is a trapezoid having a height of 0.2 μm to 1.5 μm.
[5] The semiconductor light emitting device according to any one of [1] to [4], wherein a shape of the cross section is asymmetrical.
[6] A substrate, a first conductivity type cladding layer comprising at least one layer formed on the substrate, an active layer formed on the first conductivity type cladding layer, and formed on the active layer A second conductivity type first cladding layer; a second conductivity type second cladding layer having a striped ridge structure formed on the second conductivity type first cladding layer; and the second conductivity type second cladding layer. A current blocking layer formed on the second conductivity type first cladding layer so as to sandwich both side surfaces of the ridge, and on the ridge of the second conductivity type second cladding layer and on the current blocking layer in the vicinity of the ridge A semiconductor light emitting device comprising at least a second conductivity type third clad layer formed on the substrate and having a maximum light output of 80 mW or more in a single transverse mode oscillation in pulse driving at 25 ° C.
[7] The semiconductor light emitting device according to [6], wherein the maximum light output is 200 mW or more.
[8] The semiconductor light emitting device according to [6] or [7], wherein the light output density is 4 mW / μm ² or more.
[9] The semiconductor light emitting device according to any one of [1] to [8], wherein the current blocking layer is thinner than the second conductivity type second cladding layer.
[10] The semiconductor light emitting device according to any one of [1] to [9], wherein a refractive index of the current blocking layer is smaller than a refractive index of the second conductivity type second cladding layer.
[11] The semiconductor light-emitting device according to any one of [1] to [10], wherein the current blocking layer is configured of one kind selected from the group consisting of AlGaInP, AlInP, AlGaAs, and AlGaAsP.
[12] The semiconductor light emitting device according to [11], wherein the current blocking layer is made of AlGaAs or AlGaAsP.
[13] The semiconductor light-emitting device according to any one of [1] to [12], which includes an oxidation suppression layer on the ridge structure.
[14] The semiconductor light-emitting device according to [13], wherein the oxidation suppression layer is made of a material having a larger band gap than the material of the active layer.
[15] The semiconductor light-emitting device according to [13] or [14], wherein the second conductivity type second cladding layer and the oxidation suppression layer are both made of AlGaInP.
[16] The semiconductor light emitting device according to any one of [1] to [15], wherein a refractive index of the second conductive type third cladding layer is smaller than a refractive index of the second conductive type second cladding layer.
[17] The semiconductor light emitting device according to any one of [1] to [16], wherein a constituent element of the second conductivity type third cladding layer is different from a constituent element of the second conductivity type second cladding layer.
[18] The semiconductor light emitting device according to any one of [1] to [17], wherein a resistivity of the second conductivity type third cladding layer is smaller than a resistivity of the second conductivity type second cladding layer.
[19] The semiconductor light emitting device according to any one of [1] to [18], wherein the second conductivity type third cladding layer is made of AlGaAs or AlGaAsP.
[20] The semiconductor light-emitting device according to any one of [1] to [19], which has a surface protective layer on the current blocking layer.
[21] The semiconductor light-emitting device according to [20], wherein the surface protective layer is made of a material having a larger band gap than the material of the active layer.
[22] The semiconductor light emitting device according to any one of [1] to [21], wherein the active layer contains at least Ga and In as constituent elements, or contains at least Al and In.
[23] The semiconductor light emitting device according to any one of [1] to [22], wherein the substrate has an off-angle from a plane equivalent to the (100) plane.
[24] The semiconductor light-emitting device according to [23], wherein an off-angle direction of the substrate is within ± 30 ° from a direction orthogonal to a stripe longitudinal direction of the stripe-shaped ridge structure.
[25] The semiconductor light-emitting device according to any one of [1] to [24], wherein the semiconductor light-emitting device is a semiconductor laser device.
[26] A substrate, a first conductivity type cladding layer comprising at least one layer formed on the substrate, an active layer formed on the first conductivity type cladding layer, and formed on the active layer A laminate comprising at least a second conductivity type first cladding layer and a second conductivity type second cladding layer formed on the second conductivity type first cladding layer is prepared, and A stripe-shaped protective film is formed on the second-conductivity-type second clad layer, and the second-conductivity-type second clad layer is partially etched to form the second-conductivity-type second clad layer in a stripe-shaped ridge structure. Forming a current blocking layer so as to sandwich both side surfaces of the ridge of the second conductivity type second cladding layer, removing the protective layer, and on the ridge of the second conductivity type second cladding layer A second conductivity type second electrode on the current blocking layer near the ridge; Comprising the step of forming a cladding layer, [1] to a method of manufacturing a semiconductor light emitting device according to any one of [25].
[27] The method for manufacturing a semiconductor light-emitting device according to [26], further including a step of forming a surface protective layer on the current blocking layer after the formation of the current blocking layer.

  In the semiconductor light emitting device of the present invention, a current blocking layer having a real guide structure is formed on both sides of a second conductive second cladding layer having a ridge structure whose cross-sectional structure is designed so as to satisfy a specific condition, and further a ridge structure A second conductive third cladding layer for confining light. With this configuration, according to the present invention, it is possible to provide a semiconductor light-emitting device capable of high output operation with less element resistance, passage resistance and thermal resistance.

The semiconductor light emitting device of the present invention will be specifically described with reference to the drawings.
In the present specification, a numerical range represented by using “to” means a range including numerical values described before and after “to” as a lower limit value and an upper limit value.

  FIG. 1 is a schematic cross-sectional view of a semiconductor light emitting device having a configuration from a substrate of the present invention to a second conductivity type third cladding layer. As shown in FIG. 1, the semiconductor light emitting device of the present invention is formed on a substrate 101 on a first conductivity type cladding layer 102, an active layer 106 formed on the first conductivity type cladding layer 102, and an active layer 106. The second conductivity type first cladding layer 107, the second conductivity type second cladding layer 108 having a striped ridge structure formed on the second conductivity type first cladding layer 107, and the second conductivity type first cladding. A current blocking layer 109 formed on both sides of the ridge structure on the cladding layer 107, and a second conductivity type third layer formed on the second conductivity type second cladding layer 108 and the current blocking layer 109. The clad layer 110 is comprised at least.

  FIG. 2 is a schematic cross-sectional view of a semiconductor laser according to a preferred embodiment of the present invention. 2 includes a substrate 201, a buffer layer 202 formed on the substrate 201, a first conductivity type first cladding layer 203 formed on the buffer layer, and a first conductivity type first. A first conductivity type second cladding layer 204 formed on the cladding layer 203, an active layer 205 formed on the first conductivity type second cladding layer 204, and a second conductivity type formed on the active layer 205. A first cladding layer 206; an etching stop layer 207 formed on the second conductivity type first cladding layer; and a second conductivity type second cladding layer having a ridge structure on a stripe formed on the etching stop layer 207. 208, a current blocking layer 209 formed on both sides of the second conductivity type second cladding layer having a ridge structure on the etching stop layer 207, and a second conductivity type second An oxidation suppression layer 210 formed on the ridge structure of the ladder layer 208, a surface protective layer (cap layer) 211 formed on the current blocking layer 209, and a second conductivity type formed on the surface protective layer 211. From the third cladding layer 212, the contact layer 213 formed on the second conductivity type third cladding layer 212, and the p-side electrode 214 and the n-side electrode 215 formed on the contact layer 213 side and the substrate 201 side, respectively. It is configured.

  In this specification, the expression “B layer formed on the A layer” means that the B layer is formed so that the bottom surface of the B layer is in contact with the top surface of the A layer, and one or more on the top surface of the A layer. It includes both of the case where a layer is formed and a B layer is formed on the layer. Further, the above expression also includes the case where the upper surface of the A layer and the bottom surface of the B layer are in partial contact and one or more layers exist between the A layer and the B layer in other portions. Specific embodiments are apparent from the following description of each layer and specific examples.

In FIGS. 1 and 2, the conductivity and material of the substrates 101 and 201 are not particularly limited as long as a double heterostructure crystal can be grown thereon. Preferably, it is a conductive semiconductor substrate. Specifically, a crystal substrate such as GaAs, InP, GaP, ZnSe, ZnO, Si, and Al ₂ O ₃ suitable for crystal thin film growth on the substrate, particularly a crystal substrate having a zinc blende type structure is used. preferable. In this case, the substrate crystal growth surface is preferably a low-order surface or a crystallographically equivalent surface, and the (100) surface is most preferable.

  In the present specification, the (100) plane does not necessarily have to be a strictly (100) plane, and includes a plane equivalent to the (100) plane, that is, a plane having an off-angle of about 30 ° at the maximum. To do. The upper limit of the off-angle size is preferably 30 ° or less, and more preferably 14 ° or less. The lower limit of the off-angle size is preferably 0.5 ° or more, more preferably 2 ° or more, further preferably 6 ° or more, and most preferably 10 ° or more.

  The off-angle direction of the substrates 101 and 201 is preferably within ± 30 ° from the direction perpendicular to the direction in which the stripes constituting the ridge structure of the second conductivity type second cladding layers 108 and 208 described later extend. The direction within ± 7 ° is more preferable, and the direction within ± 2 ° is most preferable. The direction of the stripe of the ridge structure is preferably [0-11] or an equivalent direction when the plane orientation of the substrates 101 and 201 is (100), and the off-angle direction is the [011] direction or equivalent. A direction within ± 30 ° from the direction is preferable, a direction within ± 7 ° is more preferable, and a direction within ± 2 ° is most preferable.

  In this specification, the [01-1] direction refers to a [11] plane between a (100) plane and a [01-1] plane in general III-V and II-VI semiconductors. The [01-1] direction is defined so that the [-1] plane is a plane on which a group V or group VI element appears, respectively.

Further, the substrates 101 and 201 may be hexagonal type substrates, and for example, a substrate made of Al ₂ O ₃ , 6H—SiC, or the like may be used.

  As shown in FIG. 2, it is preferable to form a buffer layer 202 having a thickness of about 0.2 to 2 μm on the substrate 201 in order to prevent normal substrate defects from being brought into the epitaxial growth layer. As the material of the buffer layer, the same material as that of the substrate is usually used. For example, GaAs, GaP, InP, GaN, GaInP, GaInAs, GaInN, ZnSe, ZnSSe, ZnO or the like of the first conductivity type is preferable.

A compound semiconductor layer including active layers 106 and 205 is formed on the substrates 101 and 201. The compound semiconductor layer includes layers having a refractive index lower than that of the active layer above and below the active layers 106 and 205, of which the substrate-side layer is a first conductivity type cladding layer (preferably an n-type cladding layer) and the other epitaxial layer. The layers on the side function as a second conductivity type cladding layer (preferably a p-type cladding layer). The magnitude relationship between these refractive indexes can be adjusted by appropriately selecting the material composition of each layer according to a method known to those skilled in the art. For example, the active layer and the cladding layer have a refractive index changed by changing an Al composition such as Al _x Ga _1-x As, (Al _x Ga _1-x ) _y In _1-y P, Al _x Ga _1-x N, etc. Can be adjusted.

  As shown in FIG. 1, when the first conductivity type cladding layer is one layer, the first conductivity type cladding layer 102 can be formed of a material having a refractive index smaller than that of the active layer 106. The refractive index of the first conductivity type cladding layer 102 is larger than the refractive index of the second conductivity type first cladding layer, the second conductivity type second cladding layer, and the second conductivity type third cladding layer described later. preferable. The first conductivity type cladding layer 102 is formed of a general III-V group or II-VI group semiconductor such as AlGaInP, AlInP, AlGaAs, AlGaAsP, AlGaInAs, GaInAsP, AlGaInN, BeMgZnSe, MgZnSSe, CdZnSeTe, etc. It can be formed using materials.

The lower limit of the carrier concentration of the first conductivity type cladding layer 102 is preferably 1 × 10 ¹⁶ cm ⁻³ or more, more preferably 5 × 10 ¹⁶ cm ⁻³ or more, and 1 × 10 ¹⁷ cm ^−3. The above is most preferable. On the other hand, the upper limit of the carrier concentration is preferably 5 × 10 ¹⁹ cm ⁻³ or less, more preferably 5 × 10 ¹⁸ cm ⁻³ or less, and most preferably 2 × 10 ¹⁸ cm ⁻³ or less. .

  The thickness of the first conductivity type cladding layer 102 is preferably about 0.5 to 4 μm, more preferably about 1 to 3 μm, when it is composed of a single layer.

The first conductivity type cladding layer may be composed of a plurality of layers having different carrier concentrations, compositions, etc., as shown in the preferred embodiment of FIG. When the first conductivity type cladding layer is formed of a plurality of layers having different carrier concentrations, the carrier concentration of the first conductivity type second cladding layer 204 on the active layer 205 side is the first conductivity type first on the substrate 201 side. It is preferable to make it lower than the carrier concentration of the clad layer 203. The carrier concentration of the first conductivity type first cladding layer 203 on the substrate 201 side is preferably in the range of 1 × 10 ^{16 to} 3 × 10 ¹⁸ cm ⁻³ , and is 5 × 10 ¹⁶ to 2 × 10 ¹⁸ cm ^−3. Is preferred. In addition, the thickness of the first conductivity type second cladding layer 204 on the active layer 205 side is preferably smaller than the thickness of the first conductivity type first cladding layer 203. The lower limit of the thickness of the first conductivity type second cladding layer 204 is preferably 0.01 μm or more, more preferably 0.03 μm or more, and the upper limit is preferably 1 μm or less, 0.7 μm. The following is more preferable. As an example of the case where the first conductivity type cladding layer is formed of a plurality of layers having different compositions, for example, the first conductivity type first cladding layer 203 made of AlGaAs or AlGaAsP on the substrate 201 side, and the layer An example may be exemplified by the first conductive type second cladding layer 204 made of AlGaInP or AlInP on the active layer 205 side.

  The structure of the active layers 106 and 205 constituting the semiconductor light emitting device of the present invention is not particularly limited. In the example of FIG. 1, the active layer 106 has a multiple quantum well (MQW) structure. Specifically, this multi-quantum well structure sequentially includes an optical confinement layer (non-doped) 103, a quantum well layer (non-doped) 104, a barrier layer (non-doped) 105, a quantum well layer (non-doped) 104, and a confinement layer (non-doped) 103. It has a laminated structure. The active layer is thus a multi-quantum layer having three or more quantum well layers and a barrier layer sandwiched between them, and an optical confinement layer stacked on the uppermost quantum well layer and the lowermost quantum well layer. In addition to the well structure (MQW), for example, a single quantum well structure (SQW) composed of a quantum well layer and an optical confinement layer sandwiching the quantum well layer from above and below, or a double quantum well structure (DQW) Good. When the active layer has a quantum well structure, a shorter wavelength (630 nm to 660 nm) and a lower threshold can be achieved as compared with a single-layer bulk active layer.

Examples of the material of the active layers 106 and 205 include GaInP, AlGaInP, GaInAs, AlGaInAs, GaInAsP, and AlGaInN. In particular, in the case of a material containing Ga and In or Al and In as constituent elements, a natural superlattice is easily formed, so that the effect of suppressing the natural superlattice by using an off-substrate is increased.
Note that the active layers at both ends of the optical waveguide preferably have a band gap that is transparent to light generated in the active layer in the current injection region at the center of the optical waveguide.
In order to realize a practical high-power laser, the lower limit of the total active layer thickness is preferably 2 nm or more, more preferably 25 nm or more, further preferably 30 nm or more, and most preferably 35 nm or more. On the other hand, the upper limit of the total thickness of the active layer is preferably set to be equal to or less than a thickness at which a high COD level is realized and the quantum effect functions when the active layer is not strained. That is, the upper limit of the active layer total thickness is preferably 50 nm or less, more preferably 40 nm or less, and further preferably 35 nm or less. Moreover, when the active layer is distorted, it is preferable to set the thickness not to exceed the critical film thickness. That is, the upper limit of the total active layer thickness is preferably 40 nm or less, more preferably 30 nm or less, and even more preferably 25 nm or less.
The preferable number of quantum wells is 1 to 5, preferably 1 to 4, more preferably 2 to 3, most preferably 3 when the oscillation wavelength of a 600 nm band red laser at room temperature (25 ° C.) is 630 to 670 nm. On the other hand, when the oscillation wavelength near room temperature is 670 to 700 nm, it is 1 to 5, preferably 1 to 4, more preferably 2 to 3, and most preferably 2. The thickness of the quantum well is preferably 3 to 7 nm and more preferably 4 to 6 nm when the oscillation wavelength near room temperature (25 ° C.) is 630 to 670 nm. On the other hand, when the oscillation wavelength near room temperature (25 ° C.) is 670 to 700 nm, 6 to 10 nm is preferable, and 7 to 9 nm is more preferable.

  A second conductivity type cladding layer is formed on the active layers 106 and 205. When the etching stop layer is formed, at least three second conductivity type cladding layers are formed. In the following description, the second conductivity type first clad layers 107 and 206, the second conductivity type second clad layers 108 and 208, and the second conductivity type third clad layers 110 and 212 are sequentially arranged from the side closer to the active layer 106. The preferred embodiment will be described as an example. When the etching stop layer is not formed, at least two second conductivity type cladding layers are formed.

  The second conductivity type first cladding layers 107 and 206 can be formed of a material having a refractive index lower than that of the active layers 106 and 205 in order to confine light in the active layer. For example, the second conductivity type first cladding layers 107 and 206 may be formed of a general III-V group such as a second conductivity type AlGaInP, AlInP, AlGaAs, AlGaAsP, AlGaInAs, GaInAsP, AlGaInN, BeMgZnSe, MgZnSSe, CdZnSeTe, and the like. A group VI semiconductor can be used. When the second-conductivity-type first cladding layers 107 and 206 are composed of a group III-V compound semiconductor containing Al, Al, such as GaAs, GaAsP, GaInAs, GaInP, and GaInN, is formed on the substantially entire surface that can be grown. Covering with an III-V group compound semiconductor not included is preferable because surface oxidation can be prevented.

The lower limit of the carrier concentration of the second conductivity type first cladding layers 107 and 206 is preferably 2 × 10 ¹⁷ cm ⁻³ or more, more preferably 3 × 10 ¹⁷ cm ⁻³ , and more preferably 5 × 10 ^17. Most preferably, it is cm ⁻³ . The upper limit of the carrier concentration is preferably 5 × 10 ¹⁸ cm ⁻³ , more preferably 4 × 10 ¹⁸ cm ⁻³ , and most preferably 2 × 10 ¹⁸ cm ⁻³ .

 If the thickness of the second conductivity type first cladding layers 107 and 206 becomes too thin, the optical confinement becomes too strong, making it difficult to oscillate a single transverse mode up to a high output, and a current blocking layer 109 described later. , 209 is likely to occur. On the other hand, if it becomes too thick, the current spreads in the lateral direction too much in the second conductivity type first cladding layers 107 and 206, and the threshold current and the operating current increase. Considering these, the lower limit of the thickness of the second conductivity type first cladding layers 107 and 206 is preferably 0.03 μm or more, more preferably 0.05 μm or more, and 0.07 μm or more. Most preferred. The upper limit is preferably 0.5 μm or less, more preferably 0.3 μm or less, and most preferably 0.2 μm or less.

  The refractive indexes of the second conductivity type first cladding layers 107 and 206 may be smaller than the refractive index of the first conductivity type cladding layer 102. In this way, it is possible to control the light distribution (near-field image) so that light effectively oozes from the active layer to the light guide layer side. In addition, since optical waveguide loss from the active region (portion where the active layer exists) to the zinc diffusion region can be reduced, it is possible to achieve improvement in laser characteristics and reliability in high output operation.

  As shown in FIG. 2, an etching stop layer 207 is formed on the second conductivity type first cladding layer 206 in order to prevent erosion of the second conductivity type first cladding layer 206 by the etching reagent during the etching process. be able to. When the etching stop layer 207 is provided, at least when the second conductivity type second cladding layer 208 having the ridge structure is regrown, it is possible to easily prevent the generation of a high resistance layer that increases the passage resistance at the regrowth interface. Will be able to.

The material of the etching stop layer 207 is not particularly limited as long as it is resistant to the etching reagent during the etching process, that is, is not eroded. The material of the etching stop layer 207 may have an anti-oxidation function in addition to the anti-erosion function. _{Specifically, Al X Ga 1-x As} (0 ≦ x ≦ 1), ln y Ga ly P (0 ≦ y ≦ 1), (Al u Ga 1-u) v InP (0 <u ≦ 1, 0 <v ≦ 1), In p Al q Ga r n (0 ≦ p ≦ 1,0 ≦ q ≦ 1,0 ≦ r ≦ 1), In l Al m Ga n As (0 ≦ l ≦ 1,0 ≦ m ≦ 1,0 ≦ n ≦ 1) , In s Ga 1-s As t P 1-t (0 ≦ s ≦ 1,0 ≦ t ≦ 1) , and the like.

 The thickness of the etching stop 207 is generally selected so that the band gap is larger than the material of the active layer 205, and the upper limit thereof is preferably 20 nm or less, more preferably 10 nm or less, and 6 nm or less. Is more preferable. The lower limit is preferably 1 nm or more, more preferably 1.5 nm or more, and further preferably 2 nm or more.

 The conductivity type of the etching stop layer 207 is not particularly limited when it is removed by etching, but is preferably the second conductivity type. The etching stop layer 207 is preferably lattice-matched as much as possible to the substrate 201. Furthermore, from the viewpoint of reducing operating current, it is preferable not to absorb light from the active layer 205 by appropriately selecting the material and thickness.

  A semiconductor layer having a striped ridge structure is formed on the second conductivity type first cladding layer 107 or the etching stop layer 207. The semiconductor layer having this ridge structure includes at least the second conductivity type second cladding layers 108 and 208, and may include other semiconductor layers such as the oxidation suppression layer 210. Second conductivity type third cladding layers 110 and 212 for optical confinement are separately formed on the ridge, and the desired cladding layer thickness is set to the thickness of the second conductivity type second cladding layers 108 and 208 and the second conductivity type. By making it possible to realize the total thickness of the third cladding layers 110 and 212, the thickness of the second conductivity type second cladding layers 108 and 208 can be reduced, that is, the height of the ridge can be reduced. As a result, the passage resistance can be lowered, the influence of ridge asymmetry can be reduced, and a high kink level can be achieved.

The height of the ridge (the thickness of the second conductivity type second cladding layers 108 and 208) is preferably low from the viewpoint of reducing the passage resistance as much as possible, but if the height of the ridge is too low, the current When the blocking layers 109 and 209 are formed, overgrowth on the selective growth mask easily occurs. When Al is contained in the ridge portion, particularly the second conductivity type second cladding layers 108 and 208, the resistivity is likely to increase, and when Al and In are contained, the resistivity is further increased. This increase in resistivity becomes more significant in the p-type. Further, when the shape of the ridge cross section perpendicular to the longitudinal direction of the stripe of the ridge is a forward mesa shape, the passage resistance is likely to increase as compared with the case of the reverse mesa shape.
In the semiconductor light emitting device of the present invention, the ridge has a trapezoidal cross section that satisfies the following formula.
0.05 <h / [(a + b) / 2] <0.5
In the above formula, h is the height of the cross section, a is the upper base of the cross section, and b is the lower base of the cross section. The range of h / [(a + b) / 2] is preferably 0.07 to 0.45, more preferably 0.1 to 0.35, and 0.12 to 0.3. Is more preferable, and 0.15-0.25 is most preferable.
When it is necessary to form the forward mesa direction as in the AlGaInP system, if the ridge portion is formed by wet etching, the sum of both bottom angles of the trapezoid of the ridge cross section is usually reduced (specifically, 130 °). And the like), the passage resistance is likely to increase. From these viewpoints, the upper limit of the height of the ridge (cross section height) is preferably 1.5 μm or less, more preferably 1.0 μm or less, and further preferably 0.8 μm or less. Preferably, it is 0.55 μm or less. The lower limit of the height of the ridge is preferably 0.1 μm or more, more preferably 0.2 μm or more, further preferably 0.3 μm or more, and 0.35 μm or more. Most preferred. By setting the height of the ridge within the above range, the total of both base angles of the trapezoid can be adjusted to a range of 130 to 140 °, preferably 135 to 140 °.

  When oscillating in a single transverse mode, the upper limit of the width of the bottom of the ridge (the length of the lower base of the trapezoid) of the second conductivity type second cladding layers 108 and 208 is preferably 5.0 μm or less. It is more preferably 4.0 μm or less, further preferably 3.5 μm or less, and most preferably 3.0 μm or less. Further, the lower limit of the width of the ridge bottom is preferably 0.5 μm or more, more preferably 1.0 μm or more, further preferably 1.3 μm or more, and most preferably 1.5 μm or more. preferable. When the current blocking layers 109 and 209 have a lower refractive index than the second conductivity type second cladding layers 108 and 208, that is, in the case of an actual refractive index waveguide structure (real guide structure), the current blocking layers 109 and 209 are Compared to the structure that absorbs light generated in the active layers 106 and 205 (loss guide structure), the width of the bottom of the ridge needs to be narrowed. In the forward mesa shape, increasing the height of the ridge is significant. This will increase the passage resistance. From such a viewpoint, in the case of the real refractive index waveguide structure, the upper limit of the width of the ridge bottom is preferably 4.0 μm or less, more preferably 3.5 μm or less, and 3.0 μm or less. Is more preferable, and most preferably 2.8 μm or less. Further, the lower limit of the width of the ridge bottom is preferably 0.5 μm or more, more preferably 1.0 μm or more, further preferably 1.3 μm or more, and most preferably 1.5 μm or more. . When the width of the bottom of the ridge is Wa and the width of the top of the ridge is Wb, the upper limit of the average value (Wa + Wb) / 2 is preferably 4.5 μm or less, more preferably 4 μm or less in the actual refractive index waveguide structure. More preferably, it is 5 μm or less. The lower limit is preferably 1.8 μm or more, more preferably 2 μm or more, and further preferably 2.2 μm or more.

  When the substrates 101 and 201 have an off-angle and stripes are formed in a direction orthogonal to the off-angle direction, the shape of the cross section of the ridge structure is generally asymmetrical, but in the semiconductor light emitting device of the present invention, The height of the ridge can be reduced by separately forming the second conductivity type third cladding layers 110 and 212 as light confinement layers on the ridge (second conductivity type second cladding layers 108 and 208). it can. Thereby, the semiconductor light emitting device of the present invention can reduce the influence of the ridge asymmetry even when it has an off-angle, and as a result, a high kink level can be achieved.

  When the ridge shape is asymmetrical, the lower limit of | (one base angle) − (the other base angle) |, which is the absolute value of the difference between one base angle and the other base angle, is preferably 2 ° or more. 11 ° or more, more preferably 15 ° or more. The upper limit is preferably 35 ° or less, more preferably 30 ° or less, and most preferably 25 ° or less.

  For the same reason, when a wurtzite substrate is used, the extending direction of the stripe region of the ridge structure is preferably [11-20] or [1-100] on the (0001) plane, for example. In HVPE (Hydride Vapor Phase Epitaxy), either direction is acceptable, but in MOVPE, the [11-20] direction is more preferable.

  The materials of the second conductivity type second cladding layers 108 and 208 are the same as those of the second conductivity type first cladding layers 107 and 206 described above, but the second conductivity type AlGaInP, AlInP, AlGaAs, AlGaAsP, AlGaInAs, GaInAsP, AlGaInN, Common III-V group and II-VI group semiconductors such as BeMgZnSe, MgZnSSe, and CdZnSeTe can be used. However, from the viewpoint of making the second conductivity type second cladding layers 108 and 208 transparent to the light emitted from the active layers 106 and 205, a group III-V composed of at least three elements, II- It is preferably a group VI semiconductor, more preferably containing Al, more preferably containing Al and In, and most preferably AlGaInP or AlInP.

The lower limit of the carrier concentration in the ridge (second conductive second cladding layer 108, 208) is preferably 1 × 10 ¹⁷ cm ⁻³ or more, more preferably 3 × 10 ¹⁷ cm ⁻³ or more. It is most preferable that it is × 10 ¹⁷ cm ⁻³ or more. The upper limit of the carrier concentration is preferably 2 × 10 ¹⁹ cm ⁻³ or less, more preferably 5 × 10 ¹⁸ cm ⁻³ or less, and most preferably 3 × 10 ¹⁸ cm ⁻³ or less. .

  Both side surfaces of the ridge structure of the second conductivity type second cladding layers 108 and 208 having the ridge structure are sandwiched between current blocking layers 109 and 209. At this time, the side surfaces of the ridge structure of the second conductivity type second cladding layers 108 and 208 may not be entirely sandwiched between the current blocking layers 109 and 209 from the upper end to the lower end. The gap may be sandwiched between the current blocking layers 109 and 209. Since the current flows through the second conductivity type second cladding layers 108 and 208 while being confined by the current blocking layers 109 and 209, the passing resistance of the element is equal to the resistance of the second conductivity type second cladding layers 108 and 208. It depends heavily. The effect of reducing the passage resistance of the present invention obtained by adjusting the thickness and width of the second conductivity type second cladding layers 108 and 109 having the ridge structure of the present invention is particularly the second conductivity type second cladding layer. This is remarkable when the conductivity types 108 and 208 are p-type. This is because the p-type has lower mobility and higher resistivity than the n-type, and the dopant of the p-type is more easily diffused (for example, zinc (Zn) for the p-type and silicon for the n-type). (Si) is used as a dopant, but the p-type is more easily diffused) and the p-type is more susceptible to the absorption of light emitted from the active layer. This is because it is not appropriate to raise the carrier concentration of the second cladding layer of the die and lower the passage resistance because it causes deterioration of the laser device characteristics and reliability.

  Although not shown, an etching stop layer may be formed between the second conductivity type second cladding layers 108 and 208 and the second conductivity type third cladding layers 109 and 209. By forming the etching stop layer, the controllability of the ridge shape of the second conductivity type second cladding layers 108 and 208, particularly the width of the bottom of the ridge can be improved.

  Further, as shown in FIG. 2, a second conductivity type oxidation suppression layer 210 can be formed on the second conductivity type second cladding layer 208. When the second conductivity type second cladding layer 208 is made of a III-V group compound semiconductor containing Al, the Al composition of the oxidation suppression layer 210 is smaller than the Al composition of the second conductivity type second cladding layer 208. Is preferred. By forming the oxidation suppression layer 210 on the second conductivity type second cladding layer 208, when the second conductivity type third cladding layer 212 is regrown at least on the ridge, the passage resistance is increased at the regrowth interface. Such a high resistance layer can be easily prevented. The material of the oxidation suppression layer 210 is not particularly limited as long as it is difficult to oxidize or is a material that can be easily cleaned even when oxidized. Specific examples include a III-V group compound semiconductor layer having a low content of easily oxidizable elements such as Al. When Al is contained, the Al content is preferably 0.3 or less, more preferably 0.25 or less, and most preferably 0.15 or less. For example, AlGaInP or GaInP is preferable. Further, it is preferable that the material is transparent to the light generated in the active layer 205 by selecting the material and thickness of the oxidation suppression layer 210. In particular, in the case of the actual refractive index guide, it is preferable to adopt such a form as compared with the case of the loss guide. The material of the oxidation suppression layer 210 is generally selected from materials having a larger band gap than the material of the active layer 205. However, even if the material has a small band gap, the thickness of the oxidation suppression layer 210 is preferably 30 nm or less, preferably If it is 20 nm or less, more preferably 10 nm or less, light absorption can be substantially ignored to some extent, so that it can be used.

  The current blocking layers 109 and 209 are formed on the second conductivity type first cladding layer 107 or the etching stop layer 207 and are formed so as to sandwich both side surfaces of the second conductivity type second cladding layers 108 and 208. The current blocking layers 109 and 209 have a function of constricting so that current flows through the ridges of the second conductivity type second cladding layers 108 and 208. The material of the current blocking layers 109 and 209 may be a semiconductor or a dielectric. Since the semiconductor and the dielectric each have advantages and disadvantages as described below, it is preferable that the material of the current blocking layer is appropriately determined in consideration of these advantages and disadvantages.

  When a semiconductor is used as the material for the current blocking layers 109 and 209, the heat conductivity is higher than that of the dielectric film, so that the heat dissipation is good, the cleaving property is good, and the flattening is easy to assemble in a junction-down manner. There is an advantage that the contact resistance can be easily lowered because the contact layer is easily formed on the entire surface. However, when using a high Al composition compound such as AlGaAs or AlInP in order to make the semiconductor have a low refractive index, there is a drawback that measures such as surface oxidation are necessary.

When a dielectric is used as the material of the current blocking layers 109 and 209, for example, SiN _x , SiO ₂ , Al ₂ O ₃ , AlN, or the like can be used. When a dielectric is used, a current blocking layer having a low refractive index and excellent insulating properties can be obtained. However, it has disadvantages such as poor heat dissipation due to low thermal conductivity, poor cleavage, and difficulty in assembling with junction down because it is difficult to flatten.

  In consideration of a lower refractive index than the second conductivity type second cladding layers 108 and 208 and lattice matching with the GaAs substrate, it is preferable to use AlGaAs, AlGaAsP, AlGaInP, or AlInP as a current blocking layer made of a semiconductor. . AlGaInP or AlInP has poor thermal conductivity compared to AlGaAs or AlGaAsP, changes in refractive index due to the formation of a natural superlattice, and unstable In composition in selective growth (ridge sidewall and bottom surface). If it is possible to prevent poly deposition on the protective film (selective growth with addition of HCl), it is preferable to select AlGaAs or AlGaAsP. However, in the case of AlGaAs or AlGaAsP, since AlAs and AlP exhibit deliquescence, the upper limit of the Al composition is preferably 0.97 or less, more preferably 0.95 or less, and most preferably 0.93 or less. Since it is necessary to make the refractive index lower than that of the second conductivity type second cladding layers 108 and 208, the lower limit of the Al composition is preferably 0.3 or more, more preferably 0.35 or more, and most preferably 0.4 or more. preferable.

  The refractive indexes of the current blocking layers 109 and 209 are made lower than the refractive indexes of the second conductivity type second cladding layers 108 and 208 sandwiched between the current blocking layers 109 and 209 (actual refractive index waveguide structure). By controlling the refractive index in this way, the operating current can be reduced as compared with the conventional loss guide structure. The lower limit of the refractive index difference between the current blocking layers 109 and 209 and the second conductivity type second cladding layers 108 and 208 is 0.001 or more when the current blocking layers 109 and 209 are formed of a compound semiconductor. Is more preferable, 0.003 or more is more preferable, and 0.007 or more is most preferable. The upper limit of the refractive index difference is preferably 1.0 or less, more preferably 0.5 or less, and most preferably 0.1 or less. When the current blocking layers 109 and 209 are made of a dielectric, the lower limit is preferably 0.1 or more, more preferably 0.3 or more, and 0.7 or more. Most preferred. The upper limit of the refractive index difference is preferably 3.0 or less, more preferably 2.5 or less, and most preferably 1.8 or less.

The conductivity type of the current blocking layers 109 and 209 may be either the first conductivity type or high resistance (undoped or doped with impurities (O, Cr, Fe, etc.) forming a deep order), or a combination of the two. Alternatively, it may be formed of a plurality of layers having different conductivity types or compositions. For example, a current blocking layer formed in the order of the second conductive type or high resistance semiconductor layer and the first conductive type semiconductor layer from the side close to the active layers 106 and 205 can be preferably used. From the viewpoint of the current blocking function, the conductivity type of the current blocking layers 109 and 209 is preferably the first conductivity type. When the current blocking layers 109 and 209 are of the first conductivity type, there is a problem that if the carrier concentration is too low, the current easily leaks, while if it is too high, the loss due to light absorption increases. From these viewpoints, the lower limit of the carrier concentration of the current blocking layer is preferably 1 × 10 ¹⁶ cm ⁻³ or more, more preferably 1 × 10 ¹⁷ cm ⁻³ or more, and 3 × 10 ¹⁷ cm ^−3. The above is most preferable. The upper limit of the carrier concentration is preferably 2 × 10 ¹⁹ cm ⁻³ or less, more preferably 5 × 10 ¹⁸ cm ⁻³ or less, and most preferably 3 × 10 ¹⁸ cm ⁻³ or less. .

  If the thickness of the current blocking layers 109 and 209 made of a semiconductor is too thin, there is a problem that current leaks. On the other hand, if the thickness is too large, the selective growth protective film overgrows and it is difficult to remove the protective film on both sides of the ridge. There is a problem of becoming. From such a viewpoint, the lower limit of the thickness at the ridge side flat portion of the current blocking layers 109 and 209 made of a semiconductor is preferably 0.03 μm or more, more preferably 0.1 μm or more, and most preferably 0.2 μm or more. In addition, the upper limit of the thickness (d) at the ridge side flat portion of the current blocking layer is preferably h + 0.2 μm or less, and preferably h or less, based on the height (h) of the ridge. More preferably, it is most preferably h-0.05 μm or less. When the thickness of the current blocking layer on both sides of the ridge is larger than the thickness of the flat portion, 0.8 <d / h <2 is preferable, 0.9 <d / h <1.5 is more preferable, More preferably, 1 <d / h <1.3.

  As described above, the material of the current blocking layers 109 and 209 is preferably formed of AlGaAs from the viewpoint of overgrowth in the selective growth protective film. That is, when the current blocking layers 109 and 209 are formed of AlGaInP or AlInP, there are a problem that overgrowth is likely to occur in the selective growth protective film and a problem that the composition differs between the ridge side and the flat portion. In contrast, when the current blocking layers 109 and 209 are formed of AlGaAs, overgrowth is relatively difficult to occur, and the composition is uniform between the ridge side and the flat portion. For this reason, the current blocking layers 109 and 209 are preferably formed of AlGaAs.

  The current blocking layers 109 and 209 are made of two or more layers having different refractive indexes, carrier concentrations, or conductivity types in order to control the light distribution (particularly the lateral light distribution) or improve the current blocking function. It may be formed.

  Further, as shown in FIG. 2, a surface protective layer 211 may be formed on the current blocking layer 209. By forming the surface protective layer 211, the surface oxidation of the current blocking layer 209 can be suppressed, and the current blocking layer can be prevented from being damaged or etched when the protective film for selective growth is removed. In addition, the surface of the current blocking layer can be prevented from being roughened at the temperature rising stage during regrowth, and the surface morphology and crystallinity of the regrowth layer can be improved. When the current blocking layer 209 is transparent to the light generated in the active layer 205, the surface protective layer 211 is also transparent to the light generated in the active layer 205, that is, more than the material of the active layer 205. It is preferable to be made of a material having a large band gap. In the case where the current blocking layer is a dielectric, and in particular an actual refractive index guide, it is preferable to adopt such a form as compared with the loss guide. However, even if the material has a small band gap, if the thickness is 30 nm or less, preferably 20 nm or less, more preferably 10 nm or less, light absorption can be substantially ignored to some extent. 211 material. The Al composition of the surface protective layer 211 is preferably smaller than the Al composition of the current blocking layer 209. Various materials can be used as the material of the surface protective layer 211, but the surface morphology and crystallinity of the regrowth due to the surface roughness of the underlayer due to the V group element substitution at the temperature rising stage during the regrowth can be prevented. Therefore, it is preferable to use the same material system as that of the upper surface of the ridge, that is, the second conductivity type second cladding layers 108 and 208 or the antioxidant layer 210, and among them, AlGaInP or GaInP is preferable. The conductivity type of the surface protective layer 211 is not particularly limited, but the current blocking function can be improved by using the second conductivity type.

  Second conductivity type third cladding layers 110 and 212 are formed on the ridges of the second conductivity type second cladding layers 108 and 208 and on the current blocking layers 109 and 209 in the vicinity of the ridges. The second conductivity type third cladding layers 110 and 212 may cover all over the current blocking layers 109 and 209 or may cover only the vicinity of the ridge. The second conductivity type third cladding layers 110 and 212 are made of a material having a refractive index lower than that of the active layers 106 and 205. For example, general III-V group and II-VI group semiconductors such as second conductivity type AlGaInP, AlInP, AlGaAs, AlGaAsP, AlGaInAs, GaInAsP, AlGaInN, BeMgZnSe, MgZnSSe, and CdZnSeTe can be used.

  If the thickness of the second conductivity type third cladding layers 110 and 212 is too thin, light confinement becomes insufficient, light absorption becomes remarkable in the contact layer 213, and a threshold current and an operating current increase. On the other hand, if it is too thick, the passage resistance increases, and this increase in passage resistance becomes a serious problem in the case of a material having a high resistivity such as p-type AlGaInP. Therefore, AlGaAs or AlGaAsP is preferably used as the material of the second conductivity type third cladding layer, and the lower limit of the thickness of the second conductivity type third cladding layers 110 and 212 is preferably set to 0.1 μm or more. 0.4 μm or more, more preferably 0.8 μm or more, and most preferably 1.1 μm or more. The upper limit of the thickness of the second conductivity type third cladding layers 110 and 212 is preferably 3 μm or less, more preferably 2.5 μm or less, and further preferably 2 μm or less. Most preferably, it is 6 μm or less.

The lower limit of the carrier concentration of the second conductivity type third cladding layers 110 and 212 is preferably 1 × 10 ¹⁷ cm ⁻³ or more, more preferably 3 × 10 ¹⁷ cm ⁻³ or more, and 5 × 10. Most preferably, it is ¹⁷ cm ⁻³ or more. The upper limit of the carrier concentration is preferably 2 × 10 ¹⁹ cm ⁻³ or less, more preferably 5 × 10 ¹⁸ cm ⁻³ or less, and most preferably 3 × 10 ¹⁸ cm ⁻³ or less. .

  The refractive index of the second conductivity type third cladding layers 110 and 212 is preferably smaller than the refractive index of the second conductivity type second cladding layers 108 and 208. Thereby, light leakage to the second conductivity type contact layer side can be reduced, the threshold current can be reduced, the film thickness of the second conductivity type third cladding layer can be reduced, and the passage resistance can be reduced. In addition, the thermal resistance can be reduced. The upper limit of the refractive index difference is preferably 0.1 or less, more preferably 0.03 or less, and still more preferably 0.01 or less. Further, the lower limit of the refractive index difference is preferably 0.001 or more, more preferably 0.002 or more, and further preferably 0.004 or more. The material of the second conductivity type third cladding layers 110 and 212 is preferably AlGaAs or AlGaAsP from the viewpoint of lowering the resistivity or thermal resistance than the second conductivity type second cladding layers 108 and 208, and further the second conductivity type. From the viewpoint of lowering the refractive index than the second cladding layers 108 and 208, the lower limit of the Al composition is preferably 0.67 or more, more preferably 0.72 or more, and most preferably 0.76 or more. In order for AlAs and AlP to show deliquescence, the upper limit of the Al composition is preferably 0.97 or less, more preferably 0.93 or less, and most preferably 0.79 or less.

  On the second conductivity type third cladding layers 110 and 212, in order to reduce the contact resistance with the electrode material, a (second conductivity type) contact layer 213 having a low resistance (high carrier concentration) as shown in FIG. Is preferably formed. In particular, it is preferable to form the electrode after forming the contact layer over the entire surface of the uppermost layer (second conductivity type third cladding layer 212) on which the electrode is to be formed. The material of the contact layer 213 is usually selected from a clad layer, more preferably a material having a band gap smaller than that of the active layer. Forming with a group V compound semiconductor is preferable because surface oxidation can be prevented.

The contact layer 213 preferably has a low resistance and an appropriate carrier density in order to obtain ohmic properties with the metal electrode. The lower limit of the carrier density of the contact layer 213 is preferably 1 × 10 ¹⁸ cm ⁻³ or more, more preferably 3 × 10 ¹⁸ cm ⁻³ or more, and 5 × 10 ¹⁸ cm ⁻³ or more. Is most preferred. The upper limit of the carrier concentration is preferably 2 × 10 ²⁰ cm ⁻³ or less, more preferably 5 × 10 ¹⁹ cm ⁻³ or less, and most preferably 3 × 10 ¹⁸ cm ⁻³ or less. . The thickness of the contact layer 213 is preferably 0.1 to 10 μm, more preferably 0.2 to 7 μm, and most preferably 1 to 5 μm.

Further, an intermediate band gap layer of the second conductivity type may be formed between the second conductive third cladding layer 212 and the contact layer 213. Thereby, the passage resistance due to the hetero barrier between the second conductivity type third cladding layer 212 and the contact layer 213 can be reduced. The lower limit of the carrier density of the intermediate band gap layer is preferably 1 × 10 ¹⁷ cm ⁻³ or more, more preferably 5 × 10 ¹⁷ cm ⁻³ or more, and 1 × 10 ¹⁸ cm ⁻³ or more. Most preferred. The upper limit of the carrier density of the intermediate band gap is preferably 5 × 10 ¹⁹ cm ⁻³ or less, more preferably 1 × 10 ¹⁹ cm ⁻³ or less, and 5 × 10 ¹⁸ cm ⁻³ or less. Most preferably it is. The thickness of the intermediate band gap layer is preferably 0.01 to 0.5 μm, more preferably 0.02 to 0.3 μm, and most preferably 0.03 to 0.2 μm. preferable.

  In the structure of the semiconductor light emitting device of the present invention, first, the thickness of the active layer and the composition of the cladding layer are determined in order to obtain a desired vertical divergence angle. Usually, when the vertical divergence angle is narrowed, the light penetration from the active layer to the cladding layer is promoted, the light density at the end face is reduced, and the optical damage (COD) level of the emission end face can be improved. Therefore, when high output operation is required, the vertical divergence angle is set to be relatively narrow. However, the lower limit of the vertical divergence angle is that the oscillation threshold current increases due to the reduction of optical confinement in the active layer and There is a limitation due to suppression of deterioration of temperature characteristics due to carrier overflow, preferably 12 ° or more, more preferably 14 ° or more, and most preferably 15 ° or more. The upper limit of the vertical divergence angle is preferably 30 ° or less, more preferably 25 ° or less, and most preferably 22 ° or less.

  Next, when the vertical divergence angle is determined, the structural parameters that largely control the high output characteristics are the distance (dp) between the active layers 106 and 205 and the current blocking layers 109 and 209 and the stripe width at the bottom of the ridge (hereinafter referred to as “stripe”). Width)) (Wb). Usually, the second conductivity type first cladding layers 107 and 206 exist between the active layers 106 and 205 and the current blocking layers 109 and 209. In this case, dp is the second conductivity type first cladding layer. 107 and 206. When the active layers 106 and 205 have a quantum well structure, the distance between the active blocking layer closest to the current blocking layer and the current blocking layer is dp. About dp, 0.003-0.5 micrometer is preferable, 0.04-0.3 micrometer is more preferable, 0.05-0.25 micrometer is further more preferable, 0.06-0.2 micrometer is especially preferable. W is preferably 1 to 4 μm, more preferably 1.2 to 3.5 μm, further preferably 1.6 to 2.9 μm, and particularly preferably 1.9 to 2.7 μm.

The method for producing the semiconductor light emitting device of the present invention is not particularly limited. Any method manufactured by any method is included in the scope of the present invention as long as it satisfies the requirements of the present invention.
When manufacturing the semiconductor light emitting device of the present invention, a conventionally used method can be appropriately selected and used. The crystal growth method is not particularly limited. For crystal growth of a double heterostructure and selective growth of a ridge portion, metal organic vapor phase epitaxy (MOCVD), molecular beam epitaxy (MBE), hydride or A known growth method such as a halide vapor phase growth method (VPE method) or a liquid phase growth method (LPE method) can be appropriately selected and used.

  As a method for manufacturing a semiconductor light emitting device of the present invention, first, a step of forming a first conductivity type first cladding layer on a substrate, a step of forming an active layer on the first conductivity type cladding layer, and the active layer Forming a second conductivity type first cladding layer thereon, forming a second conductivity type second cladding layer having a striped ridge structure on the second conductivity type first cladding layer; Forming a current blocking layer so as to sandwich both side surfaces of the second conductivity type second cladding layer on the two conductivity type first cladding layer; and on the ridge of the second conductivity type second cladding layer and at least A step of forming a second conductivity type third cladding layer on a part of the current blocking layer can be exemplified. In addition, a step of forming a buffer layer on the substrate, a step of forming an etching stop layer on the second conductivity type first cladding layer, a step of forming an oxidation suppression layer on the second conductivity type second cladding layer, a current A step of forming a surface protective layer on the blocking layer and a step of forming a contact layer on the second conductivity type third cladding layer may be included.

  The specific growth conditions of each layer vary depending on the layer composition, growth method, device shape, etc., but when a III-V compound semiconductor layer is grown using the MOCVD method, the double heterostructure grows. The temperature is about 650 to 750 ° C., the V / III ratio is about 20 to 60 (in the case of AlGaAs) or about 300 to 600 (in the case of InGaAsP and AlGaInP), the NAM region and the block region are grown at a growth temperature of 600 to 700 ° C., V / III The ratio is preferably about 40 to 60 (in the case of AlGaAs) or 350 to 550 (in the case of InGaAsP or AlGaInP).

  In particular, when a current blocking layer formed by selective growth using a protective film contains Al, such as AlGaAs or AlGaInP, a small amount of HCl gas is introduced during growth to prevent poly deposition on the mask. Is very preferable. When the Al composition is higher, or the mask width or mask area ratio is larger, the other growth conditions are constant, so that poly deposition is prevented and selective growth is performed only on the exposed surface of the semiconductor (selective mode). The amount of HCl introduced necessary for this increases. On the other hand, when the introduction amount of HCl gas is too large, the growth of the AlGaAs layer does not occur, and conversely, the semiconductor layer is etched (etching mode), but when other growth conditions are made constant as the Al composition becomes higher, The amount of HCl introduced necessary to enter the etching mode increases. For this reason, the optimum amount of HCl introduced greatly depends on the number of moles of the group III raw material containing Al such as trimethylaluminum. Specifically, the lower limit of the ratio of the number of moles of HCl supplied to the number of moles of Group III raw material containing Al (HCl / Group III) is preferably 0.01 or more, and 0.05 or more. Is more preferable and 0.1 or more is most preferable. The upper limit is preferably 50 or less, more preferably 10 or less, and most preferably 5 or less. However, when the compound semiconductor layer containing In is selectively grown (particularly, HCl is introduced), composition control tends to be difficult.

When performing ridge formation or selective growth, a protective film can be used. The protective film is preferably a dielectric, and is specifically selected from the group consisting of SiN _x film, SiO 2 film, SiON film, Al 2 O 3 film, ZnO film, SiC film and amorphous Si. The protective film is used when the ridge portion is formed by selective regrowth using MOCVD or the like as a mask.

  When the semiconductor light emitting device of the present invention is used as a semiconductor laser, information processing light sources (usually AlGaAs (wavelength near 780 nm), AlGaInP (wavelength 600 nm band), InGaN (wavelength near 400 nm)), communication Signal light source (usually 1.3 μm band and 1.5 μm band with InGaAsP or InGaAs active layer) laser, fiber excitation light source (InGaAs strained quantum well active layer / near 980 nm using GaAs substrate, InGaAsP strained well active layer Examples of such devices include a semiconductor laser device for communication such as a laser using a / InP substrate). When the semiconductor laser of the present invention is driven with a high-speed pulse, the output in the single transverse mode is preferably 80 mW or more, more preferably 100 mW or more, and further preferably 120 mW or more, It is especially preferable that it is 160 mW or more. Further, the semiconductor laser of the present invention preferably has a low passage resistance when driven, preferably 8Ω or less, more preferably 7Ω or less, and most preferably 6Ω or less.

  The semiconductor laser of the present invention is effective in that a laser having a nearly circular shape as a communication laser increases the coupling efficiency with a fiber. In addition, a far-field image having a single peak can be used as a laser suitable for a wide range of applications such as information processing and optical communication. Furthermore, the structure of the present invention can be applied to a light emitting diode (LED) such as an edge emitting type in addition to the semiconductor laser.

  Hereinafter, the present invention will be described in more detail with reference to specific examples. The materials, reagents, ratios, operations, and the like shown in the following examples can be appropriately changed without departing from the spirit of the present invention. Therefore, the scope of the present invention is not limited to the specific examples shown below.

(Example 1)
In this example, the semiconductor light emitting device shown in FIG. 3 was manufactured. On an n-type GaAs (n = 1 × 10 ¹⁸ cm ⁻³ ) substrate 301 having a thickness of 350 μm and 10 ° off from the (100) plane in the [011] direction, an n-type (2.0 μm thick) is formed by MOCVD. Al _0.7 Ga _0.3 ) _0.5 In _0.5 P (n = 8 × 10 ¹⁷ cm ⁻³ , refractive index 3.2454) cladding layer 302, (Al _0.5 Ga _0.5 ) _0.5 In _0.5 P light confinement layer (non-doped) 321, thickness 5 nm Ga _0.5 In _0.5 P strained quantum well layer (non-doped) 322, 5 nm thick (Al _0.5 Ga _0.5 ) _0.5 In _0.5 P barrier layer (non-doped) 323, 5 nm thick Ga _0.5 In _0.5 P strained quantum well layer (non-doped) 324, a thickness of _{5nm (Al 0.5 Ga 0.5) 0.5} in 0.5 P barrier layer (non-doped) 325, Ga _0.5 in _0.5 P strained quantum well layer having a thickness of 5 nm (non-doped) 326 and (Al _0.5 Ga _0.5 In _0.5 P light confining layer (non-doped) 327 sequentially stacked formed by a triple quantum well (TQW) active layer 303, thickness 0.15μm p-type _{(Al 0.7 Ga 0.3) 0.5 In} 0.5 P (p = 1 × 10 P-type first cladding layer 304 made of ¹⁸ cm ⁻³ and refractive index 3.2454), p-type etching stop layer made of p-type Ga _0.5 In _0.5 P (p = 1 × 10 ¹⁸ cm ⁻³ ) having a thickness of 5 nm. 305, p-type second cladding layer 306 made of (Al _0.7 Ga _0.3 ) _{0.5 In 0.5} P (Zn dope: p = 1 × 10 ¹⁸ cm ⁻³ , refractive index 3.2454) having a thickness of 0.5 μm, A p-type oxidation inhibiting layer 307 made of p-type (Al _0.2 Ga _0.8 ) _0.5 In _0.5 P (p = 1 × 10 ¹⁸ cm ⁻³ ) having a thickness of 0.01 μm was sequentially laminated to form a double heterostructure ( FIG. 3 (a)). Next, after depositing a SiN _x protective film having a thickness of 100 nm on the surface of the double hetero substrate by plasma CVD, the [01-1] direction (direction orthogonal to the off direction of the substrate) is defined as the longitudinal direction by photolithography. A large number of stripe-shaped SiN _x protective films 351 were formed (FIG. 3B).

Next, wet etching was performed up to the surface of the etching stop layer 305 using the stripe-shaped SiN _x protective film 351 so that the stripe width at the bottom of the ridge was 2.5 μm. At this time, the width of the top of the ridge is 1.7 μm, the ridge shape is asymmetrical, and the sum of the two base angles is 105 ° (one base angle is 62 ° and the other base angle is 43 °). It was. (FIG. 3C). At this time, a hydrochloric acid-based mixed solution or a sulfuric acid-based mixed solution was used as an etching solution for wet etching.

In the portion removed by etching for ridge formation using the stripe-shaped SiN _x protective film 351, n-type Al _0.9 Ga _0.1 As current with a thickness of 0.4 μm is blocked by selective growth using the MOCVD method. Layer (n = 2 × 10 ¹⁸ cm ⁻³ , refractive index 3.1590) 308 and 0.01 μm thick n-type (Al _0.7 Ga _0.3 ) _0.5 In _0.5 P surface protective layer (n = 1 × 10 ¹⁸ cm ^{− 3} ) 309 was formed (FIG. 3D). Thereafter, the striped SiN _x protective film 351 is removed by wet etching using a buffered hydrofluoric acid solution or dry etching using a gas such as SF ₆ or CF ₄ (FIG. 3E), and again by MOCVD. P-type Al _0.78 Ga _0.22 As third cladding layer (p = 1 × 10 ¹⁸ cm ⁻³ , refractive index 3.2407) 310 having a thickness of 0.8 μm, p-type Al _0.35 Ga _0.65 As having a thickness of 0.05 μm A band gap layer (p = 1.5 × 10 ¹⁸ cm ⁻³ ) 311 and a p-type GaAs contact layer (p = 7 × 10 ¹⁸ cm ⁻³ ) 312 having a thickness of 3.5 μm were grown.

  Thereafter, a p-side electrode 313 was deposited and the substrate was thinned to 100 μm, and then an n-side electrode 314 was deposited and alloyed (FIG. 3 (f)). The wafer thus produced was cleaved and cut into a chip bar so as to form a laser light emitting end face (primary cleavage). The resonator length at this time was 1000 μm. The front end face was asymmetrically coated with a low reflection film and the rear end face was asymmetrically coated, and then separated into chips by secondary cleavage. The separated chips were assembled by junction down to obtain a semiconductor laser device.

In the MOCVD method, trimethylgallium (TMG), trimethylindium (TMI), and trimethylaluminum (TMA) were used as group III materials, arsine and phosphine as group V materials, and hydrogen as a carrier gas. Further, dimethyl zinc (DMZ) was used as the p-type dopant, and disilane was used as the n-type dopant. Further, during the growth of the n-type Al _0.9 Ga _0.1 As layer (undoped) 308, HCl gas is used in an HCl / III group molar ratio of 0.2, particularly in order to suppress the deposition of poly on the SiN _x protective film. The molar ratio of HCl / TMA was introduced to be 0.22.

The manufactured semiconductor laser device was continuously energized (CW) at 25 ° C., and current-light output and current-voltage characteristics obtained by high-speed pulse measurement (pulse width: 100 nsec, duty: 50%) were measured.
The results are shown in FIG. In the semiconductor laser device fabricated according to this example, in high-speed pulse measurement, the optical output increased with an increase in operating current, no kinks occurred up to 200 mW, and high output characteristics were obtained. The semiconductor laser device of this example showed excellent characteristics such as an oscillation wavelength of 667 nm on average, a threshold current of 37 mA, and a slope efficiency of 0.95 mW / mA on average. Further, the semiconductor laser of the present invention has an average vertical divergence angle of 19 ° and a horizontal divergence angle of 8 °, and the device resistance can be suppressed to a small value of about 5.5Ω even though the p-side cladding layer is made thick. did it.
As described above, since the semiconductor laser device of this example has a small passage resistance, it can reduce the heat generation of the element, and can stably operate for a long time at a high temperature and a high output (for example, 70 ° C., CW 70 mW). It becomes possible.

(Comparative Example 1)
A semiconductor laser device was fabricated by the same method as in Example 1 without forming the p-type third cladding layer (thickness 1.2 μm), and current-light output and current- obtained by high-speed pulse measurement Voltage characteristics were measured. The threshold current was as high as 75 mA, and the slope efficiency was as low as 0.35 mW / mA.
It is considered that the cause of the deterioration of the laser characteristics is that the light leakage to the p-type contact layer is increased, the light loss is increased, that is, the waveguide loss is greatly increased.

(Comparative Example 2)
Without forming the p-type third cladding layer (thickness 1.2 μm), the thickness of the p-type second cladding layer is 1.7 μm to compensate for the thickness, and the width of the bottom of the ridge is 3 μm (compared to Example 1). Other than that, a semiconductor laser device was manufactured by the same method as in Example 1, and current-light output and current-voltage characteristics obtained by high-speed pulse measurement were measured. The obtained semiconductor laser device did not oscillate.
This is because the width of the upper portion of the ridge is considerably narrowed to 0.2 μm due to the side etching under the stripe-like SiN _x protective film, and the device resistance is considerably high (20Ω or more). it is conceivable that.

(Example 2)
The semiconductor was fabricated in the same manner as in Example 1 except that the p-type third cladding layer 310 was changed to (Al _0.75 Ga _0.25 ) _0.5 In _0.5 P (p = 7 × 10 ¹⁸ cm ⁻³ ) having a thickness of 0.5 μm. A light emitting device was manufactured.
The initial characteristics were almost the same as in Example 1, but the element resistance was 8Ω, which was a little higher than that in Example 1. The reason is considered to be that the resistivity of (Al _0.75 Ga _0.25 ) _0.5 In _0.5 P is larger than the resistivity of p-type Al _0.8 Ga _0.2 As.

  The semiconductor light emitting device of the present invention can be suitably used as a semiconductor laser capable of high output operation with low element resistance, passage resistance and thermal resistance. Lasers suitable as light sources for optical disc reading and writing, lasers suitable for a wide range of applications such as lasers for information processing and optical communication, information processing, optical communication, medical care, laser DDZ, etc. that require high output operation, The present invention can also be applied as a light emitting diode (LED) such as an edge emitting type.

It is a schematic sectional drawing of the semiconductor light-emitting device which has a structure from the board | substrate of this invention to the 2nd conductivity type 3rd cladding layer. 1 is a schematic cross-sectional view of a semiconductor laser according to a preferred embodiment of the present invention. It is a schematic explanatory drawing for demonstrating the state in the manufacturing process of the semiconductor laser used by the suitable Example of this invention. It is a schematic explanatory drawing of the semiconductor laser using the conventional AlGaInP type semiconductor material. It is a graph which shows the relationship between the operating current of the semiconductor laser produced in the suitable Example of this invention, and optical output.

Explanation of symbols

DESCRIPTION OF SYMBOLS 101 Substrate 102 1st conductivity type cladding layer 103 Optical confinement layer 104 Quantum well layer 105 Optical confinement layer 106 Active layer 107 2nd conductivity type 1st cladding layer 108 2nd conductivity type 2nd cladding layer 109 Current blocking layer 110 2nd conductivity Type third cladding layer 201 substrate 202 buffer layer 203 first conductivity type first cladding layer 204 second conductivity type second cladding layer 205 active layer 206 second conductivity type first cladding layer 207 etching stop layer 208 second conductivity type second 2 Cladding layer 209 Current blocking layer 210 Oxidation suppressing layer 211 Surface protective layer 212 Second conductivity type third cladding layer 213 Contact layer 214 p side electrode 215 n side electrode 301 n type GaAs substrate 302 n type cladding layer 303 Triple quantum well ( TQW) active layer 304 p-type first cladding layer 305 p-type Tsu quenching stop layer 306 p-type second cladding layer 307 p-type oxidation control layer 308 n-type Al _0.9 Ga _0.1 As current blocking layer 309 n-type _{(Al 0.7 Ga 0.3) 0.5 In} 0.5 P surface protective layer 310 p-type Al _0.78 Ga _0.22 As Third cladding layer 311 p-type Al _0.35 Ga _0.25 As intermediate band gap layer 312 p-type GaAs contact layer 313 p-side electrode 314 n-type electrode 321 (Al _0.5 Ga _0.5 ) _0.5 In _0.5 P optical confinement layer 322 Ga _0.5 In _0.5 P strained quantum well layer _{323 (Al 0.5 Ga 0.5) 0.5} In 0.5 P barrier layers 324 Ga _0.5 In _0.5 P strained quantum well layer _{325 (Al 0.5 Ga 0.5) 0.5In} 0.5 P barrier layers 326 Ga _0.5 In _0.5 P strained quantum well layer _{327 (Al 0.5 Ga 0.5) In} 0.5 P light confining layer 351 SiN _x protective film 401 n-type substrate 402 n-type First cladding layer 403 an active layer 404 p-type second cladding layer 405 p-type etching stop layer 406 p-type third cladding layer 407 n-type current blocking layer 408 p-type contact layer 409 p-side electrode 410 n-side electrode

Claims (20)

A substrate, a first conductivity type cladding layer comprising at least one layer formed on the substrate, an active layer formed on the first conductivity type cladding layer, and a second conductivity formed on the active layer A first conductivity type second cladding layer, a second conductivity type second cladding layer having a striped ridge structure formed on the second conductivity type first cladding layer, and a ridge of the second conductivity type second cladding layer. A current blocking layer formed on the second conductivity type first cladding layer so as to sandwich both side surfaces; a ridge of the second conductivity type second cladding layer; and a current blocking layer in the vicinity of the ridge. And a second light emitting type third cladding layer, wherein the ridge structure has a trapezoidal shape in which a cross section perpendicular to the longitudinal direction of the stripe satisfies the following formula.
0.05 <h / [(a + b) / 2] <0.5
(In the above equation, h is the height of the cross section, a is the upper base of the cross section, and b is the lower base of the cross section.) The semiconductor light emitting device according to claim 1, wherein the cross section is a trapezoid whose lower base is longer than the upper base. The semiconductor light emitting device according to claim 1, wherein the cross section is a trapezoid having an upper base of 0.4 μm to 4 μm. The semiconductor light-emitting device according to claim 1, wherein the cross section is a trapezoid having a height of 0.2 μm to 1.5 μm. The semiconductor light-emitting device according to claim 1, wherein a shape of the cross section is asymmetrical. A substrate, a first conductivity type cladding layer comprising at least one layer formed on the substrate, an active layer formed on the first conductivity type cladding layer, and a second conductivity formed on the active layer A first conductivity type second cladding layer, a second conductivity type second cladding layer having a striped ridge structure formed on the second conductivity type first cladding layer, and a ridge of the second conductivity type second cladding layer. A current blocking layer formed on the second conductivity type first cladding layer so as to sandwich both side surfaces; a ridge of the second conductivity type second cladding layer; and a current blocking layer in the vicinity of the ridge. A semiconductor light emitting device comprising at least a second conductivity type third cladding layer and having a maximum light output of 80 mW or more in single transverse mode oscillation in pulse driving at 25 ° C. The semiconductor light-emitting device according to claim 6, wherein the light output density is 4 mW / μm ² or more. The semiconductor light-emitting device according to claim 1, wherein the current blocking layer is thinner than the second conductivity type second cladding layer. The semiconductor light-emitting device according to claim 1, wherein a refractive index of the current blocking layer is smaller than a refractive index of the second conductivity type second cladding layer. 10. The semiconductor light emitting device according to claim 1, wherein the current blocking layer is made of one selected from the group consisting of AlGaInP, AlInP, AlGaAs, and AlGaAsP. The semiconductor light-emitting device according to claim 1, further comprising an oxidation suppression layer on the ridge structure. The semiconductor light emitting device according to claim 11, wherein the oxidation suppression layer is made of a material having a larger band gap than the material of the active layer. The semiconductor light emitting device according to claim 1, wherein a refractive index of the second conductive type third cladding layer is smaller than a refractive index of the second conductive type second cladding layer. The semiconductor light emitting device according to claim 1, wherein a resistivity of the second conductivity type third cladding layer is smaller than a resistivity of the second conductivity type second cladding layer. The semiconductor light-emitting device according to claim 1, further comprising a surface protective layer on the current blocking layer. The semiconductor light emitting device according to claim 15, wherein the surface protective layer is made of a material having a larger band gap than the material of the active layer. The semiconductor light-emitting device according to claim 1, wherein the substrate has an off-angle from a plane equivalent to the (100) plane. The semiconductor light-emitting device according to claim 1, wherein the semiconductor light-emitting device is a semiconductor laser device. A substrate, a first conductivity type cladding layer comprising at least one layer formed on the substrate, an active layer formed on the first conductivity type cladding layer, and a second conductivity formed on the active layer A laminate composed of at least a first type cladding layer and a second conductivity type second cladding layer formed on the second conductivity type first cladding layer is prepared, and the second conductivity type of the laminate is prepared. A stripe protective film is formed on the second cladding layer, and the second conductivity type second cladding layer is partially etched to form the second conductivity type second cladding layer into a stripe ridge structure. Forming a current blocking layer so as to sandwich both sides of the ridge of the second conductivity type second cladding layer, removing the protective layer, and on the ridge of the second conductivity type second cladding layer and in the vicinity of the ridge; A second conductivity type third clad is formed on the current blocking layer. Includes forming a layer, a method of manufacturing a semiconductor light emitting device according to any one of claims 1 to 18. The method of manufacturing a semiconductor light emitting device according to claim 19, further comprising forming a surface protective layer on the current blocking layer after forming the current blocking layer.

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