JP2006054426A - Self-oscillation semiconductor laser device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a semiconductor laser device which has a low element resistance, a low thermal resistance, a low passage resistance, and a small operating current; and is capable of self oscillation. <P>SOLUTION: The self-oscillation semiconductor laser device comprises 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 block layer so formed on the second-conductivity-type first clad layer as to sandwich the both ridge side surfaces, and a second-conductivity-type third clad layer formed on the ridge of the second-conductivity-type second clad layer and the current block layer in the vicinity of the ridge, all formed on the substrate and the cross section of the ridge perpendicular to the longitudinal direction of the stripe of the ridge structure is a trapezoid satisfying the following relation; 0.05<h/[(a+b)/2]<0.5 (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). <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a semiconductor laser device having a structure suitable as a semiconductor laser capable of oscillating in a fundamental transverse mode, and in particular, the element resistance, thermal resistance, passage resistance, and operating current are all low, and self-oscillation is possible. The present invention relates to a semiconductor laser device.

  As a light source for reading an optical disk, a self-excited oscillation type semiconductor laser (wavelength multimode) that is resistant to return light noise from the optical disk is suitable. As the self-excited oscillation type semiconductor laser, an inner stripe type laser using a semiconductor current blocking layer as shown in FIGS. 5A and 5B has been conventionally used. In a structure in which no light absorption layer exists, self-excited oscillation is usually achieved by forming a saturable absorption region inside the active layer. The supersaturated absorption region can be formed on both sides immediately below the ridge or groove as shown in FIGS. 5A and 5B by broadening the light distribution compared to the current injection region. In this supersaturated absorption region, carrier generation (light emission) and carrier disappearance (quenching) are repeated in a short cycle, so that the longitudinal mode becomes multi (wavelength multi mode), and low noise can be realized. In order to reduce the return light noise of this semiconductor laser device, a method of oscillating longitudinal multimode using the self-excited oscillation phenomenon of the semiconductor laser has been developed. For example, Japanese Patent Laid-Open No. 63-202083 ) For details.

  Recently, a visible (usually 630-690 nm band) laser using an AlGaInP system has been put into practical use as a light source for information processing, in place of the conventional AlGaAs (wavelength near 780 nm), in order to improve the recording density centered on digital video discs. Being started. An example of a conventional semiconductor laser diode (LD) using an AlGaInP-based semiconductor material has a structure schematically shown in FIG.

  In FIG. 6, 601 is an n-type GaAs substrate, 602 is a clad layer made of n-type AlGaInP formed on the substrate 601, 603 is an active layer made of AlGaInP, 604 is a clad layer made of p-type AlGaInP, and 605 is an n-type. A current blocking (block) layer 606 made of GaAs is a contact layer. Here, the mixed crystal ratio is set so that the energy gap of the AlGaInP active layer 603 is smaller than the energy gap of the AlGaInP cladding layers 602 and 604, and a double heterostructure is formed. The current blocking layer 605 is provided for the purpose of so-called current confinement in order to obtain a current density necessary for laser oscillation. The current blocking layer 605 is formed by selectively etching the layer 604 to form a ridge and then selectively growing it using an amorphous film such as SiNx.

  In a conventional AlGaAs-based (wavelength near 780 nm) laser, low noise is realized by a CSP structure, a V-SIS structure, a SAS structure, and the like. For example, in Non-Patent Document 1 (Toshiba Review No. 40, No. 7, paragraphs 576 to 578), a current injection stripe is formed in the active layer by current confinement, and a saturable absorber region is generated on both sides of the stripe in the active layer. I am doing so. As a result, laser oscillation is repeatedly started and stopped, that is, self-excited oscillation is caused by the vibration of the refractive index of the light emitting portion due to the interaction of light and carriers in the active layer.

  However, if the method of forming a saturable absorber in the active layer is applied to a visible (usually 630 to 690 nm band) laser using a conventional AlGaInP system as shown in FIG. 6, the p-clad layer region immediately below the current blocking layer It is difficult to realize self-oscillation stably up to a high temperature region because the function of the saturable absorber is reduced due to excessive carrier injection due to an increase in current spread in the non-patent document 2 (Heisei 20). This is reported in the 6th Autumn Meeting of the Japan Society of Applied Physics (20p-S-15) and Non-Patent Document 3 (2007 Spring Applied Physics Related Joint Proceedings 28a-ZG-9). Therefore, as shown in FIG. 7, an AlGaInP-based self-pulsation laser having a saturable absorption layer having a band gap comparable to that of oscillation light outside the active layer is disclosed in Patent Document 2 (Japanese Patent Laid-Open No. 7-263794) and the like. Non-Patent Document 4 (H. Adachi, et al., Self-sustained pulsation in 650 nm-band AlGaInP visible laser diode with highly doped suturable absorbing layer, IEEE Photon. Technol. Lett. 7, p1406 (1995) ), Self-oscillation has been confirmed to a high temperature of 60 ° C. However, in the method of inserting the saturable absorption layer, a steep transition of the optical output is observed at the rising edge of oscillation as shown in FIG. For this reason, when automatic power control (APC) is used in a low output region when the laser output is controlled to be constant by being incorporated in an optical disk drive device, the APC circuit oscillates and power control becomes impossible. Problems can occur. In addition, by adopting a supersaturated absorption layer, the oscillation threshold current may be significantly increased due to loss in the supersaturated absorption region, the band gap of the supersaturated absorption layer may be changed, and the supersaturated absorption layer. Since the distance greatly depends on the distance between the active layer and the active layer, reproducibility, uniformity and the like are strictly required, so that the yield tends to be lowered.

  In order to solve a large practical problem of a visible light (usually 630 to 690 nm) self-excited oscillation type laser using an AlGaInP system having a supersaturated absorption layer, a conventional AlGaAs (wavelength of 780 nm) laser and Similarly, it is considered desirable to stably realize self-excited oscillation up to a high temperature region by a method of stably forming a saturable absorber in the active layer.

  However, in the LD using the conventional AlGaInP-based semiconductor material shown in FIG. 9 (hereinafter referred to as “conventional LD”), the p-type third cladding layer 906 is sandwiched between the current blocking layers 907, and the p-type third cladding layer 906 is interposed. Since the current is confined at the ridge portion, generally, the passage resistance, thermal resistance and element resistance are high. Therefore, in the conventional LD, the amount of heat generated by the element increases at the time of high current injection, the temperature of the active layer rises, and the self-excited oscillation hardly occurs. There were problems such as difficulty.

  In the conventional LD, zinc is used as a p-type impurity in the p-type cladding layers 904 and 906. Since zinc has the property of easily diffusing in the AlGaInP crystal, zinc in the p-type cladding layer often diffuses into the active layer during repeated 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 laser devices have been developed so far. For example, Patent Document 3 (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 4 (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 here 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, and there is a problem in reliability reproducibility. It was. Further, in Patent Document 5 (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 5: 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 as compared with 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 having a stripe-shaped ridge formed in the [110] direction has been developed so far (Patent Document 6: Japanese Patent Laid-Open No. 7-193313). However, the ridge structure described here has an inverted mesa shape, and in order to form the inverted mesa shaped p-type third cladding layer, 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.
JP 63-202083 A JP-A-7-263794 Japanese Patent Laid-Open No. 7-297483 JP-A-11-26880 Japanese Patent Laid-Open No. 11-87832 JP-A-7-193313 TOSHIBA REVIEW 40 vol.7, 576-578 Proceedings of the 1994 Autumn Meeting of the Japan Society of Applied Physics 20p-S-15 Proceedings of Joint Lecture on Applied Physics in the Spring of 1995 28a-ZG-9 IEEE Photon. Technol. Lett. 7, p1406 (1995) 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 laser device in which all of element resistance, thermal resistance, passage resistance, and operating current are small, and capable of self-oscillation. There is.

  In order to solve the above-described problems of the prior art, the present inventor has made extensive studies on the structure of a semiconductor device having a ridge structure. By forming the body and configuring the ridge structure so as to satisfy a specific condition, heat generation in the active layer can be reduced, and stable self-oscillation characteristics can be obtained up to a high temperature region (at least 75 ° C. or more), and The present inventors have found that a semiconductor laser device capable of self-oscillation can be obtained and completed the present invention.

That is, the object of the present invention is achieved by a self-excited oscillation type semiconductor laser 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 A self-pulsation type semiconductor laser device comprising at least a second-conductivity-type third clad layer formed in the shape of a trapezoid whose transverse section perpendicular to the stripe longitudinal direction of the ridge structure 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.)
[2] The self-pulsation type semiconductor laser device according to [1], wherein the transverse section is a trapezoid whose lower base is longer than the upper base.
[3] The self-pulsation type semiconductor laser 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 self-pulsation type semiconductor laser 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 self-pulsation type semiconductor laser 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 self-pulsation type semiconductor laser device comprising at least a second conductivity type third clad layer formed on the substrate and having a maximum optical output of 5 mW or more in a single transverse mode oscillation in direct current drive at 25 ° C.
[7] The self-pulsation type semiconductor laser device according to [6], wherein the maximum light output is 10 mW or more.
[8] The self-pulsation type semiconductor laser device according to [6] or [7], wherein the optical output density is 0.3 mW / μm ² or more.
[9] 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 self-pulsation type semiconductor laser device which is composed of at least a second-conductivity-type third clad layer formed on the substrate and oscillates at a power of 5 mW or more at 70 ° C. by direct current drive.
[10] The self-pulsation semiconductor laser device according to [9], which self-oscillates at 75 ° C. with an output of 5 mW or more.
[11] The self-pulsation semiconductor laser device according to [9], which self-oscillates at 70 ° C. with an output of 10 mW or more.
[12] The self-pulsation semiconductor laser device according to [9], which self-oscillates at 75 ° C. with an output of 10 mW or more.
[13] The self-pulsation type semiconductor laser device according to [9], wherein the oscillation threshold current at 25 ° C. is 45 mA or less by direct current drive.
[14] The self-pulsation type semiconductor laser device according to any one of [1] to [13], wherein the current blocking layer is thinner than the second conductivity type second cladding layer.
[15] The self-pulsation type semiconductor laser device according to any one of [1] to [14], wherein a refractive index of the current blocking layer is smaller than a refractive index of the second conductive type second cladding layer.
[16] The self-pulsation type semiconductor laser device according to any one of [1] to [15], wherein the current blocking layer is made of one selected from the group consisting of AlGaInP, AlInP, AlGaAs, and AlGaAsP.
[17] The self-pulsation type semiconductor laser device according to [16], wherein the current blocking layer is made of AlGaAs or AlGaAsP.
[18] The self-pulsation type semiconductor laser device according to any one of [1] to [17], which has an oxidation suppression layer on the ridge structure.
[19] The self-pulsation type semiconductor laser device according to [18], wherein the oxidation suppression layer is made of a material having a larger band gap than the material of the active layer.
[20] The self-pulsation type semiconductor laser device according to [18] or [19], wherein both the second conductivity type second cladding layer and the oxidation suppression layer are made of AlGaInP.
[21] The self-oscillation type semiconductor according to any one of [1] to [20], 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. Laser device.
[22] The self-oscillation type semiconductor according to any one of [1] to [21], 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. Laser device.
[23] The self-excited oscillation semiconductor according to any one of [1] to [22], wherein the resistivity of the second conductivity type third cladding layer is smaller than the resistivity of the second conductivity type second cladding layer. Laser device.
[24] The self-pulsation type semiconductor laser device according to any one of [1] to [23], wherein the second conductivity type third cladding layer is made of AlGaAs or AlGaAsP.
[25] The self-pulsation type semiconductor laser device according to any one of [1] to [24], wherein a surface protective layer is provided on the current blocking layer.
[26] The self-pulsation type semiconductor laser device according to [25], wherein the surface protective layer is made of a material having a larger band gap than the material of the active layer.
[27] The self-pulsation type semiconductor laser according to any one of [1] to [26], wherein the active layer contains at least Ga and In as constituent elements, or contains at least Al and In. apparatus.
[28] The self-pulsation semiconductor laser device according to any one of [1] to [27], wherein the active layer includes a saturable absorber having a volume necessary for self-pulsation.
[29] The self-pulsation type semiconductor laser device according to any one of [1] to [28], wherein the substrate has an off-angle from a plane equivalent to the (100) plane.
[30] The self-pulsation type semiconductor laser device according to [29], wherein the off-angle direction of the substrate is within ± 30 ° from the direction orthogonal to the stripe longitudinal direction of the stripe-shaped ridge structure.
[31] The self-pulsation type semiconductor laser device according to any one of [1] to [30], wherein the resonator length is 150 μm to 450 μm.
[32] The self-pulsation type semiconductor laser device according to any one of [1] to [31], wherein the self-pulsation type semiconductor laser device is a semiconductor laser.
[33] 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 the manufacturing method of the self-pulsation type semiconductor laser device according to any one of [32].
[34] The method for manufacturing a self-pulsation type semiconductor laser device according to [33], further comprising a step of forming a surface protective layer on the current blocking layer after forming the current blocking layer.

  In the self-pulsation type semiconductor laser 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 to satisfy a specific condition. Further, a second conductivity type third cladding layer for confining light is provided on the ridge structure. With this configuration, according to the present invention, it is possible to provide a self-excited oscillation type semiconductor laser device that has a small element resistance, passage resistance, thermal resistance, and operating current, and is capable of stable self-excited oscillation up to a high temperature region.

  The self-excited oscillation type semiconductor laser device of the present invention will be specifically described with reference to the drawings. The description of the constituent elements described below may be made based on typical embodiments of the present invention, but the present invention is not limited to such embodiments. 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 showing the structure from the substrate to the second conductivity type third cladding layer of the self-pulsation type semiconductor laser device of the present invention. As shown in FIG. 1, a self-excited oscillation type semiconductor laser device of the present invention includes a first conductive clad layer 102 on a substrate 101, an active layer 106 formed on the first conductive clad layer 102, A second conductivity type first cladding layer 107 formed on the active layer 106; a second conductivity type second cladding layer 108 having a striped ridge structure formed on the second conductivity type first cladding layer 107; A current blocking layer 109 formed on both sides of the ridge structure on the second conductivity type first cladding layer 107, and on the second conductivity type second cladding layer 108 and the current blocking layer 109. And a second conductivity type third cladding layer 110.

  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 self-pulsation type semiconductor laser 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 may be a single bulk active layer, but in order to shorten the wavelength and reduce the threshold value, a multiple layer composed of a quantum well layer and a barrier layer and / or a confinement layer sandwiching the quantum well layer is used. A quantum well (MQW) structure is more preferable. In order to form a saturable absorber having a volume necessary for self-oscillation in the active layer, it is effective to increase the number of wells compared to a single mode laser that does not normally oscillate. Further, in this case, in order to improve the high temperature operation, it is effective to apply a compressive or tensile strain to the quantum well layer. In addition, when tensile strain is applied, oscillation in the TM mode is facilitated, but the characteristics can be improved while the band gap is increased, which is effective in improving the performance of a laser in a short wavelength region.

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.
In addition, it is preferable from a viewpoint of a COD level improvement that the active layer in the both ends of an optical waveguide has a band gap transparent with respect to the light generated in the active layer in the current injection region in the center of the optical waveguide.

When the active layer is made of GaInP or AlGaInP, a single-layer bulk active layer may be used, but the quantum well layer and the quantum well layer are sandwiched in order to shorten the wavelength (630 nm to 665 nm) and reduce the threshold value. A multiple quantum well (MQW) structure composed of a barrier layer and / or a confinement layer is more preferable. Furthermore, in this case, in order to improve the high temperature operation, compressed into the quantum well layer _{(Ga x In 1-x P} , x <0.52) or pulling _{(Ga x In 1-x P} , x> 0.52) It is effective that the distortion is added. When tensile strain is applied, oscillation in the TM mode is facilitated. However, since the characteristics can be improved while the band gap is increased, it is effective for improving the performance of a laser having a shorter wavelength region of 630 to 650 nm.

  In order to form a saturable absorber of the volume necessary for self-oscillation in the active layer, the total thickness of the active layer, that is, the total thickness of each quantum well active layer in the case of multiple quantum wells, is self-oscillation. From the viewpoint of securing the volume of the supersaturated absorption region necessary for the above, the lower limit is preferably 5 nm or more, more preferably 10 nm or more, further preferably 15 nm or more, and most preferably 25 nm. From the viewpoint of suppressing COD at the end face, the upper limit is preferably 200 nm or less, more preferably 15 nm or less, still more preferably 100 nm or less, and most preferably 50 nm or less.

For the same reason, in order to realize a practical self-pulsation laser, the thickness of each active layer is preferably 2 nm or more, more preferably 3 nm or more, further preferably 4 nm or more, and more preferably 5 nm or more as the lower limit. Most preferred. From the viewpoint of suppressing COD at the end face, the upper limit is preferably 20 nm or less, more preferably 15 nm or less, further preferably 9 nm or less, and most preferably 7 nm or less.
It is preferable that the total thickness of the active layer (the total thickness of all quantum well layers in the active layer) is thicker than a certain extent in the range in which the self-excited oscillation is likely to occur and the range in which the self-excited oscillation can be sustained (temperature / light output). Specifically, the lower limit of the active layer total thickness is preferably 25 nm or more, more preferably 30 nm or more, and further preferably 35 nm or more. On the other hand, the upper limit of the total thickness of the active layer is preferably not more than the thickness at which the quantum effect functions when the active layer is not distorted. That is, the upper limit of the active layer total thickness is preferably 100 nm or less, more preferably 80 nm or less, and further preferably 70 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 active layer total thickness is preferably 80 nm or less, more preferably 60 nm or less, and further preferably 50 nm or less.

  A preferable number of quantum wells is 4 to 10, preferably 4 to 9, more preferably 7 to 9, and further preferably 7 to 8 when the oscillation wavelength of a 600 nm band red laser at room temperature (25 ° C.) is 630 to 670 nm. , Most preferably 8. On the other hand, when the oscillation wavelength near room temperature is 670 to 700 nm, it is 3 to 9, preferably 5 to 8, more preferably 6 to 8, still more preferably 6 to 7, and most preferably 7. It is. 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.

  The optical confinement layer is effective from the viewpoint of increasing confinement efficiency in the quantum well layer and preventing contamination (diffusion) of impurities such as Zn into the quantum well layer. By appropriately selecting the thickness of the confinement layer, it is possible to reduce the laser oscillation threshold current and improve the lifetime. Specifically, the thickness of the confinement layer is preferably 0.01 μm or more, more preferably 0.02 μm or more, and more preferably 0.04 μm or more as a lower limit from the viewpoint of securing the volume of the supersaturated absorption region necessary for self-excited oscillation. Is more preferable, and 0.06 μm or more is most preferable. From the viewpoint of suppressing COD at the end face, the upper limit is preferably 0.5 μm or less, more preferably 0.3 μm or less, further preferably 0.15 μm or less, and most preferably 0.1 μm or less.

  The thickness of the optical confinement layer is preferably 50 nm or more, more preferably 60 nm or more as the lower limit when the oscillation wavelength of the 600 nm band red laser at room temperature is 630 to 670 nm. As an upper limit, 200 nm or less is preferable and 100 nm or less is more preferable. On the other hand, when the oscillation wavelength near room temperature is 670 to 700 nm, the lower limit is preferably 40 nm or more, and more preferably 50 nm or more. As an upper limit, 150 nm or less is preferable and 100 nm or less is more preferable. When the number of quantum wells is 6, 50 to 150 nm is preferable, when the number of quantum wells is 7, 40 to 130 nm is preferable, and when the number of quantum wells is 8, 25 to 90 nm is preferable.

The carrier concentration in the active layer is not particularly limited, but the quantum well layer and the barrier layer are not doped in particular, and are not doped (in this case, slightly (usually 1 × 10 ¹⁷ cm ⁻³ or less) 1 or the second conductivity type) is more preferable from the viewpoint of improving and stabilizing the performance of the device. Further, it is preferable that the optical confinement layer is also undoped at least in a portion close to the quantum well layer.

  A second conductivity type cladding layer is formed on the active layers 106 and 205. In the present invention, 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. More preferably. 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, it is preferable not to absorb light from the active layer 205 by appropriately selecting the material and thickness from the viewpoint of reducing the operating current. When making an etching stop layer function as a supersaturated absorption layer, you may absorb the light from an active layer.

  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 realizing the total thickness of the mold 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 stripe longitudinal direction is a forward mesa shape, the passage resistance is likely to increase as compared with the case of the reverse mesa shape.
In the self-excited oscillation type semiconductor laser 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 less than 1.5 μm, more preferably less than 0.7 μm, and further preferably less than 0.6 μm. Preferably, it is less than 0.55 μm. The lower limit of the height of the ridge is preferably 0.1 μm or more, more preferably 0.2 μm or more, still more preferably 0.3 μm or more, and most preferably 0.35 μm or more. preferable. 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 off-angles and stripes are formed in a direction perpendicular to the off-angle direction, the shape of the cross section of the ridge structure is generally asymmetrical, but the self-oscillation type of the present invention In the semiconductor laser device, the second conductivity type third cladding layers 110 and 212 as light confinement layers are separately formed on the ridge (second conductivity type second cladding layers 108 and 208), thereby increasing the height of the ridge. Can be lowered. Thereby, the self-excited oscillation type semiconductor laser 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. In addition, the material and thickness of the oxidation suppression layer 210 are preferably selected so that the material is transparent to the light generated in the active layer 205. 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 for the current blocking layers 109 and 209, for example, SiNx, 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 the lower refractive index than the second conductivity type second cladding layers 108 and 208 and the lattice matching with the GaAs substrate, AlGaAs, AlAs, AlGaAsP, AlGaInP, or AlInP is used as a current blocking layer made of a semiconductor. Is preferred. Since AlGaInP or AlInP has a lower thermal conductivity than AlGaAs or AlGaAsP, the temperature of the active layer tends to increase. For this reason, it is preferable to select AlGaAs, AlAs, or AlGaAsP for stable self-oscillation up to a high temperature. 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 set 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 of 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) of the current blocking layer at the flat portion beside the ridge is preferably h + 0.2 μm or less, preferably h or less, based on the height (h) of the ridge. Is more preferable, and h-0.05 μm or less is most preferable. 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 formed 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. The thickness is more preferably 0.2 μm or more, further preferably 0.3 μm or more, and most preferably 0.4 μm or more. In addition, the upper limit of the thickness of the second conductivity type third cladding layers 110 and 212 is preferably 2 μm or less, more preferably 1.5 μm or less, and further preferably 1 μm or less. Most preferably, it is 8 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 0.07 or less, and even more preferably 0.05 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 0.003 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 0.89 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 smaller band gap than the active layer. Specifically, the contact layer 213 is a III-containing material that does not contain Al such as GaAs, GaAsP, GaInAs, GaInP, and GaInN. 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 designing the semiconductor laser 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 increased, the supersaturated absorption region in the active layer is increased, and self-excited oscillation is likely to occur. For this reason, the vertical spread angle is set to be relatively large. However, if the vertical divergence angle is too large, the optical damage (COD) level of the emission end face and the light receiving efficiency at the detector of the optical system will be reduced. Conversely, if it is too small, the supersaturated absorption region will be reduced. Therefore, self-excited oscillation is less likely to occur. Therefore, the lower limit of the vertical spread angle is preferably 24 ° or more, more preferably 27 ° or more, further preferably 29 ° or more, and most preferably 32 ° or more. On the other hand, the upper limit of the vertical spread angle is preferably 42 ° or less, more preferably 40 ° or less, still more preferably 38 ° or more, and most preferably 36 ° or less.

  After determining the vertical divergence angle, the structural parameters that largely control the possibility of self-excited oscillation 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 “stripes”). 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. Further, when the active layers 106 and 205 have a quantum well structure, they are formed at the tops of the current blocking layer and the active layer, that is, the layers closest to the current blocking layer (light confinement layer, barrier layer, or quantum well). The distance to the layer) is dp.

  If the vertical spread angle is made too narrow, the second conductivity type first cladding layer is made too thin, or the stripe width is made too wide, self-excited oscillation may not be achieved. Conversely, if the vertical divergence angle is made too thick, the second conductivity type first cladding layer is made too thick, or the stripe width is made too narrow, self-oscillation occurs, but the operating current becomes too large. Degrading the laser characteristics. Further, in order to stably maintain the self-excited oscillation even at a high temperature, it is preferable that dp can be set as small as possible. The reason is that the smaller the dp, the smaller the current leakage in the lateral direction on both sides of the ridge, and it becomes possible to form a saturable absorption region in the active layer sufficient for self-excited oscillation even at high temperatures. For this reason, in order to achieve self-excited oscillation, it is necessary to place the above dp and W within an appropriate range with good controllability. That is, about dp, 0.003-0.5 micrometer is preferable, 0.04-0.25 micrometer is more preferable, 0.05-0.19 micrometer is further more preferable, 0.06-0.15 micrometer is especially preferable. About W, 1-4 micrometers are preferable, 1.2-3.5 micrometers is more preferable, 1.6-2.9 micrometers is more preferable, 1.9-2.5 micrometers is especially preferable.

  However, if the purpose of use (where the divergence angle is set, etc.) and the material system (refractive index, resistivity, etc.) are different, the optimum range also shifts slightly. It should also be noted that this optimum range affects each of the above structural parameters.

As an optical design guideline for the stripe width (opening width) W1 and the thickness dp of the cladding layer on both sides of the ridge to satisfy the self-excited oscillation condition, the lateral effective refractive index step in the active layer is set to 2 to 7 × 10 ^{−. About 3} , leaching rate to both sides of ridge Γact. It is necessary to set out to about 10 to 40%.
Further, since the volume of the saturable absorber is determined by the cross section × resonator length, the resonator length also needs to be optimized. As for the length of the resonator length, the lower limit is preferably 150 μm or more, more preferably 200 μm or more, further preferably 250 μm or more, and most preferably 270 μm or more. About an upper limit, 600 micrometers or less are preferable, 500 micrometers or less are more preferable, 450 micrometers or less are more preferable, and 370 micrometers or less are the most preferable.

The method for manufacturing the self-pulsation type semiconductor laser 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 self-pulsation type semiconductor laser 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 of manufacturing the self-excited oscillation type semiconductor laser device of the present invention, first, a step of forming a first conductivity type first cladding layer on a substrate, and a step of forming an active layer on the first conductivity type cladding layer, Forming a second conductivity type first cladding layer on the active layer, and 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 on both sides of the second conductivity type second cladding layer on the second conductivity type first cladding layer; and a ridge of the second conductivity type second cladding layer And a step of forming a second conductivity type third cladding layer on the substrate and at least a part of the current blocking layer. 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 SiNx films, SiO ₂ films, SiON films, Al ₂ O ₃ films, ZnO films, SiC films, 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 self-excited oscillation type semiconductor laser device of the present invention is used as a semiconductor laser, information processing light sources (usually AlGaAs system (wavelength near 780 nm), AlGaInP system (wavelength 600 nm band), InGaN system (wavelength near 400 nm) are used. )), A communication signal light source (usually 1.3 μm band or 1.5 μm band having InGaAsP or InGaAs as an active layer) laser, and various other devices such as a communication semiconductor laser device. In the semiconductor laser of the present invention, the maximum light output in the single transverse mode when driven at 25 ° C. with a direct current is preferably 5 mW or more, more preferably 7 mW or more, and 10 mW or more. Is more preferable. Further, the optical power density is preferably 4 mW / μm ² or more, more preferably 6 mW / [mu] m ² or more, further preferably 8 mW / [mu] m ² or more. Furthermore, 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 typical semiconductor laser of the present invention oscillates at 75 ° C. with an output of 5 mW or more. If a specific example is shown in relation to temperature, a typical semiconductor laser of the present invention self-oscillates at an output of 5 mW at, for example, 70 ° C, and self-oscillates at an output of 5 mW at 75 ° C. If it is 70 ° C., it will self-oscillate with an output of 10 mW and if it is 75 ° C., it will self-oscillate with an output of 10 mW. Further, the oscillation threshold current at 25 ° C. with direct current (DC) drive is, for example, 45 mA or less, preferably 40 mA or less, and more preferably 35 mA 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 self-pulsation type semiconductor laser 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 (1.2 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 A multi-well (MQW, N) with 6 wells consisting of 5 nm Ga _0.5 In _0.5 P strained quantum well layer (non-doped) 322 and 5 nm thick (Al _0.5 Ga _0.5 ) _0.5 In _0.5 P barrier layer (non-doped) 323 = 6) p-type first cladding layer made of active layer 303 and 0.08 μm thick p-type (Al _0.7 Ga _0.3 ) _0.5 In _0.5 P (p = 1 × 10 ¹⁸ cm ⁻³ , refractive index 3.2454) 304, 5 nm thick p-type Ga _0.5 P-type etching stop layer 305 made of In _0.5 P (p = 1 × 10 ¹⁸ cm ⁻³ ), (Al _0.7 Ga _0.3 ) _0.5 In _0.5 P (Zn-doped: p = 1 × 10 ¹⁸ cm) having a thickness of 0.5 μm ^-3 , refractive index 3.2454), p-type second cladding layer 306 having a thickness of 0.01 μm and p-type (Al _0.2 Ga _0.8 ) _0.5 In _0.5 P (p = 1 × 10 ¹⁸ cm ⁻³ ). A p-type oxidation suppression layer 307 was sequentially laminated to form a double heterostructure (FIG. 3A). Next, after a SiNx protective film having a thickness of 100 nm is deposited on the surface of the double hetero substrate by plasma CVD, a stripe whose longitudinal direction is the [01-1] direction (direction perpendicular to the off direction of the substrate) is formed by photolithography. A large number of SiNx protective films 351 having a shape were formed (FIG. 3B).

  Next, wet etching was performed up to the surface of the etching stop layer 305 using the stripe-shaped SiNx protective film 351 so that the stripe width at the bottom of the ridge was 2.2 μm. At this time, the width of the upper part of the ridge is 1.4 μm, the ridge shape is asymmetrical, and the total 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.

An n-type Al _0.9 Ga _0.1 As current blocking layer having a thickness of 0.4 μm is formed on the portion removed by etching for ridge formation using the stripe-shaped SiNx protective film 351 by selective growth using MOCVD. (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 SiNx 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 the thickness is again increased by MOCVD. 0.5 μm thick p-type Al _0.8 Ga _0.2 As third cladding layer (p = 1 × 10 ¹⁸ cm ⁻³ , refractive index 3.2267) 310, 0.05 μm thick p-type Al _0.35 Ga _0.65 As intermediate band A gap layer (p = 1.5 × 10 ¹⁸ cm ⁻³ ) 311 and a p-type GaAs contact layer (p = 7 × 10 ¹⁸ cm ⁻³ ) 311 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). At this time, the resonator length was 300 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 with an HCl / III group molar ratio of 0.2, particularly HCl, in order to suppress the deposition of poly on the SiNx protective film. / TMA was introduced so that the molar ratio was 0.22.

The manufactured semiconductor laser device was continuously energized (CW) at 25 ° C. to measure current-light output characteristics and current-voltage characteristics.
As shown in Table 1 below, the semiconductor laser device of this example oscillates in longitudinal multimode as shown in FIG. 4A, and the visibility indicating the coherence with the return light is 0.25. It has been found that low noise operation is possible without a high frequency superposition circuit. The oscillation wavelength was 656 nm on average, the threshold current was 27 mA, the operating current at 5 mW output was 31 mA, and the low threshold and low operating current were excellent. Further, the vertical divergence angle of the semiconductor laser of the present invention is an average of 37.5 °, the horizontal divergence angle is 10.6 °, and the device resistance is suppressed to about 10Ω even though the p-side cladding layer is made thick. I was able to.
Thus, the semiconductor laser device of this embodiment can reduce the heat generation of the element because of its low passage resistance, and can realize a stable self-oscillation operation even at a high temperature of 75 ° C. or higher.

(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 0.5 μm), and current-light output and current-voltage obtained by direct current drive. Characteristics were measured. The threshold current is as high as 60 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 0.5 μm), the thickness of the p-type second cladding layer is set to 1 μm in order to compensate for the thickness, and the rest is performed by the same method as in the first embodiment. A device was fabricated, and current-light output characteristics and current-voltage characteristics were measured. The obtained semiconductor laser device did not oscillate.
The cause is considered to be that the width of the upper portion of the ridge is considerably narrowed to 0.2 μm and the element resistance is considerably high (20Ω or more) due to the side etching under the stripe-like SiNx protective film. .

(Example 2)
The p-type third cladding layer 310 was automatically formed in the same manner as in Example 1 except that the thickness 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. An excited oscillation type semiconductor laser device was manufactured.
Although the initial characteristics were almost the same as those of Example 1, the element resistance was 15Ω, which was a little higher than that of Example 1, and self-oscillation at 70 ° C. was not obtained. The reason is, the _{(Al 0.75 Ga 0.25) 0.5 In} 0.5 that P resistivity and thermal resistance greater than the resistivity and the thermal resistance of the p-type Al _0.8 Ga _0.2 As, the heat generation of the element, that increase the temperature of the active layer This is probably because

(Example 3)
In this example, the self-pulsation type semiconductor laser 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 GaAs having a thickness of 0.5 μm is formed by MOCVD. (N = 1 × 10 ¹⁸ cm ⁻³ ) (not shown), n-type Ga _0.5 In _0.5 P (n = 1 × 10 ¹⁸ cm ⁻³ ) (not shown) with a thickness of 0.1 μm, thickness 1 .6 μm n-type (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 optical confinement layer ( The number of wells consisting of (non-doped) 321, Ga _0.5 In _0.5 P strained quantum well layer (non-doped) 322 having a thickness of 5 nm, and (Al _0.5 Ga _0.5 ) _0.5 In _0.5 P barrier layer (non-doped) 323 having a thickness of 4.8 nm is 8 A multiple quantum well (MQW, N = 8) active layer 303 with a thickness of 0. P-type first clad layer 304 made of 1 μm p-type (Al _0.7 Ga _0.3 ) _0.5 In _0.5 P (p = 1 × 10 ¹⁸ cm ⁻³ , refractive index 3.2454), p-type Ga _0.5 In 5 nm thick _A p-type etching stop layer 305 made of _0.5 P (p = 1 × 10 ¹⁸ cm ⁻³ ), (Al _0.7 Ga _0.3 ) _0.5 In _0.5 P (Zn-doped: p = 1 × 10 ¹⁸ cm ^{− with} a thickness of 0.5 μm. ³ , p-type second cladding layer 306 having a refractive index of 3.2454), 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. A double heterostructure was formed by sequentially laminating the type oxidation inhibiting layers 307 (FIG. 3A). Next, after a SiNx protective film having a thickness of 100 nm is deposited on the surface of the double hetero substrate by plasma CVD, a stripe whose longitudinal direction is the [01? 1] direction (direction perpendicular to the off direction of the substrate) is formed by photolithography. A large number of SiNx protective films 351 having a shape were formed (FIG. 3B).

  Next, wet etching was performed up to the surface of the etching stop layer 305 by using this stripe-shaped SiNx protective film 351 so that the stripe width at the bottom of the ridge was 2.6 μm. At this time, the width of the upper portion of the ridge is 1.7 μm, the shape of the ridge is asymmetrical, and the total of the two base angles is 100 ° (one base angle is 60 ° and the other base angle is 40 °). 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.

An n-type Al _0.85 Ga _0.15 As current blocking layer having a thickness of 0.4 μm is formed on the portion removed by etching for ridge formation using the stripe-shaped SiNx protective film 351 by selective growth using the MOCVD method. (N = 2 × 10 ¹⁸ cm ⁻³ , refractive index 3.1924) 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 SiNx 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 the thickness is again increased by MOCVD. 0.5 μm thick p-type Al _0.78 Ga _0.22 As third cladding layer (p = 1 × 10 ¹⁸ cm ⁻³ , refractive index 3.2407) 310, 0.05 μm thick p-type Al _0.35 Ga _0.65 As intermediate band A gap layer (p = 1.5 × 10 ¹⁸ cm ⁻³ ) 311 and a p-type GaAs contact layer (p = 7 × 10 ¹⁸ cm ⁻³ ) 311 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 1114 was deposited and alloyed (FIG. 3F). The wafer thus produced was cleaved and cut into a chip bar so as to form a laser light emitting end face (primary cleavage). At this time, the resonator length was 300 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, when the n-type Al _0.9 Ga _0.1 As layer 308 was grown, a small amount of HCl gas was introduced to suppress the deposition of poly on the SiNx protective film.

The current is generated by continuously energizing (CW) the manufactured semiconductor laser device. Optical output characteristics and current? Voltage characteristics were measured.
As shown in FIG. 10, the semiconductor laser device of this example oscillates in longitudinal multimode even at 75 ° C. and 10 mW (peak wavelength 676.3 nm), and the visibility indicating the coherence with the return light is 0.34. It has been found that low noise operation is possible without high frequency superposition circuit up to high temperature (75 ° C. or higher) and high output (10 mW or higher).

Example 4
In this example, a plurality of self-excited oscillation type semiconductor laser devices having different active layer total thicknesses were manufactured as shown in FIG. 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 GaAs having a thickness of 0.5 μm is formed by MOCVD. (N = 1 × 10 ¹⁸ cm ⁻³ ) (not shown), n-type Ga _0.5 In _0.5 P (n = 1 × 10 ¹⁸ cm ⁻³ ) (not shown) with a thickness of 0.1 μm, thickness 1 .2 μm n-type (Al _0.7 Ga _0.3 ) _0.5 In _0.5 P (n = 8 × 10 ¹⁷ cm ⁻³ ) cladding layer 302, (Al _0.5 Ga _0.5 ) _0.5 In _0.5 P optical confinement layer (non-doped) 321, Ga _0.5 In _0.5 P strain 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 multi-well (MQW) active layer 303, 0.1 μm thick p type _{(Al 0.7 Ga 0.3) 0.5 In} 0.5 P (p = 1 × 10 18 c P-type first cladding layer 304 made of ^-3) and a thickness of 5 nm p-type _{Ga 0.5 In 0.5 P (p =} 1 × 10 18 cm -3) p -type etching stop layer 305 made of, a thickness of 0.5μm P-type second cladding layer 306 made of (Al _0.7 Ga _0.3 ) _0.5 In _0.5 P (Zn-doped: p = 1 × 10 ¹⁸ cm ⁻³ ), 0.01 μm thick p-type (Al _0.2 Ga _0.8 ) _0.5 In _A p-type oxidation suppression layer 307 made of _0.5 P (p = 1 × 10 ¹⁸ cm ⁻³ ) was sequentially stacked to form a double heterostructure (FIG. 3A). Next, after a SiNx protective film having a thickness of 100 nm is deposited on the surface of the double hetero substrate by plasma CVD, a stripe whose longitudinal direction is the [01? 1] direction (direction perpendicular to the off direction of the substrate) is formed by photolithography. A large number of SiNx protective films 351 having a shape were formed (FIG. 3B).

  Next, wet etching was performed up to the surface of the etching stop layer 1305 by using the striped SiNx protective film 351 so that the stripe width at the bottom of the ridge was 2.6 μm. At this time, the width of the upper portion of the ridge was 1.7 μm. (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.

An n-type Al _x Ga _1-x As current having a thickness of 0.4 μm is formed on the portion removed by etching for ridge formation using the stripe-shaped SiNx protective film 351 by selective growth using the MOCVD method. Blocking layer (x = 0.85 to 0.9, n = 2 × 10 ¹⁸ cm ⁻³ ) 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 SiNx 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 the thickness is again increased by MOCVD. 0.5 μm thick p-type Al _0.78 Ga _0.22 As third cladding layer (p = 1 × 10 ¹⁸ cm ⁻³ ) 310, 0.05 μm thick p-type Al _0.35 Ga _0.65 As intermediate band gap layer (p = 1) 0.5 × 10 ¹⁸ cm ⁻³ ) 311 and a 3.5 μm thick p-type GaAs contact layer (p = 7 × 10 ¹⁸ cm ⁻³ ) 312 was 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). At this time, the resonator length was 300 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 Al _x Ga _1-x As current blocking layer (x = 0.85 to 0.9, n = 2 × 10 ¹⁸ cm ⁻³ ) 308, the deposition of poly on the SiNx protective film is suppressed. For this purpose, HCl gas was introduced.

  The current is generated by continuously energizing (CW) the manufactured semiconductor laser device. Optical output characteristics and current? As a result of measuring the voltage characteristics, the self-excited oscillation range (temperature / light output) does not depend much on the number of well layers, and the active layer total thickness (the total thickness of all quantum well layers in the active layer) It turned out to be strongly dependent. As shown in FIG. 11, self-oscillation at 25 ° C. and 5 mW was possible when the total active layer thickness was 25 nm or more, and self-oscillation at 70 ° C. and 5 mW was possible when the thickness was 30 nm or more. Furthermore, self-oscillation at 75 ° C. and 10 mW was possible at 35 nm or more. Therefore, the lower limit of the total active layer thickness is preferably 25 nm or more, more preferably 30 nm or more, and further preferably 35 nm or more. When the active layer is distorted as in this embodiment, it is preferable to set the thickness not to exceed the critical film thickness. That is, the upper limit of the active layer total thickness is preferably 80 nm or less, more preferably 60 nm or less, and further preferably 50 nm or less. On the other hand, the upper limit of the total thickness of the active layer is preferably not more than the thickness at which the quantum effect functions when the active layer is not distorted. That is, the upper limit of the active layer total thickness is preferably 100 nm or less, more preferably 80 nm or less, and further preferably 70 nm or less.

  According to the present invention, it is possible to provide a semiconductor laser device capable of self-oscillation up to a high temperature with all of element resistance, passage resistance, thermal resistance and operating current being small. Since this self-excited oscillation type semiconductor laser device is resistant to return light noise from the optical disk, a high-frequency superposition circuit is not required for the read optical disk reading device, and the number of parts and the cost can be reduced. Further, even when a light source with low coherence is required, such as for distance measurement, it can be suitably used.

It is a schematic sectional drawing of the semiconductor laser 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 in Examples 1-4 of this invention. It is a graph which shows the oscillation spectrum (a) and visibility (b) of the semiconductor laser produced in Example 1 of this invention. It is a schematic explanatory drawing of the semiconductor laser using the conventional AlGaInP type semiconductor material. It is a schematic explanatory drawing of the semiconductor laser using the conventional AlGaInP type semiconductor material. It is a schematic explanatory drawing of the semiconductor laser using the conventional AlGaInP type semiconductor material. It is a graph which shows the electric current-light output characteristic of the semiconductor laser using the conventional AlGaInP type semiconductor material. It is a schematic explanatory drawing of the semiconductor laser using the conventional AlGaInP type semiconductor material. It is a graph which shows the oscillation spectrum (a) and visibility (b) of the semiconductor laser produced in Example 3 of this invention. It is a figure which shows the achievement status of the self-oscillation of each semiconductor laser produced in Example 4 of this invention.

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 Multiple quantum well ( MQW) active layer 304 p-type first cladding layer 305 p-type TCHING STOP layer 306 p-type second cladding layer 307 p-type oxidation suppression layer 308 n-type current blocking layer 309 n-type surface protection layer 310 p-type third cladding layer 311 p-type intermediate band gap layer 312 p-type GaAs contact layer 313 p side Electrode 314 n-type electrode 321 optical confinement layer 322 strained quantum well layer 323 barrier layer 351 SiNx protective film 501 substrate 502 n-type cladding layer 503 active layer 504 p-type first cladding layer 505 p-type second cladding layer 506 n-type current blocking Layer 507 p-type contact layer 508 p-side electrode 509 n-side electrode 511 substrate 512 n-type cladding layer 513 active layer 514 p-type first cladding layer 515 n-type current blocking layer 516 p-type second cladding layer 517 p-type contact layer 518 p-side electrode 519 n-side electrode 601 substrate 602 n Type AlGaInP cladding layer 603 AlGaInP active layer 604 p type AlGaInP cladding layer 605 n type GaAs current blocking layer 606 p type GaAs contact layer 701 substrate 702 n type AlGaInP cladding layer 703 GaInP active layer 704 p type AlGaInP first cladding layer 705 p type GaInP supersaturated absorption layer 706 p-type AlGaInP second cladding layer 707 n-type GaAs current blocking layer 708 p-type GaAs contact layer 901 n-type substrate 902 n-type first cladding layer 903 active layer 904 p-type second cladding layer 905 p-type etching Stop layer 906 p-type third cladding layer 907 n-type current blocking layer 908 p-type contact layer 909 p-side electrode 910 n-side electrode

Claims (23)

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 self-pulsation type semiconductor laser device comprising at least a second-conductivity-type third cladding layer, 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 self-pulsation type semiconductor laser device according to claim 1, wherein the cross section is a trapezoid whose lower base is longer than the upper base. 3. The self-pulsation type semiconductor laser device according to claim 1, wherein the cross section is a trapezoid having an upper base of 0.4 μm to 4 μm. The self-pulsation type semiconductor laser device according to any one of claims 1 to 3, wherein the cross section is a trapezoid having a height of 0.2 µm to 1.5 µm. The self-pulsation type semiconductor laser device according to any one of claims 1 to 4, wherein the 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 self-pulsation type semiconductor laser device comprising at least a second conductivity type third cladding layer and having a maximum optical output of 5 mW or more in single transverse mode oscillation in direct current drive at 25 ° C. The self-pulsation type semiconductor laser device according to claim 6, wherein the optical output density is 0.3 mW / μm ² or more. 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 self-excited oscillation type semiconductor laser device which is composed of at least a second conductivity type third cladding layer and self-oscillates with an output of 5 mW or more at 70 ° C. by DC driving. 9. The self-excited oscillation type semiconductor laser device according to claim 8, wherein the oscillation threshold current at 25 [deg.] C. is 45 mA or less by direct current drive. The self-pulsation type semiconductor laser device according to any one of claims 1 to 9, wherein the current blocking layer is thinner than the second conductivity type second cladding layer. The self-pulsation type semiconductor laser device according to any one of claims 1 to 10, wherein a refractive index of the current blocking layer is smaller than a refractive index of the second conductive type second cladding layer. The self-pulsation type semiconductor laser device according to any one of claims 1 to 11, wherein the current blocking layer is made of one selected from the group consisting of AlGaInP, AlInP, AlGaAs, and AlGaAsP. The self-pulsation type semiconductor laser device according to any one of claims 1 to 12, further comprising an oxidation suppression layer on the ridge structure. The self-pulsation type semiconductor laser device according to claim 13, wherein the oxidation suppression layer is made of a material having a larger band gap than the material of the active layer. The self-pulsation type semiconductor laser 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 self-pulsation type semiconductor laser 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 self-pulsation type semiconductor laser device according to any one of claims 1 to 16, further comprising a surface protective layer on the current blocking layer. The self-pulsation type semiconductor laser device according to claim 17, wherein the surface protective layer is made of a material having a larger band gap than the material of the active layer. The self-pulsation type semiconductor laser device according to any one of claims 1 to 18, wherein the active layer includes a saturable absorber having a volume necessary for self-pulsation. The self-pulsation type semiconductor laser device according to any one of claims 1 to 19, wherein the substrate has an off-angle from a plane equivalent to a (100) plane. The self-pulsation type semiconductor laser device according to any one of claims 1 to 20, wherein a resonator length is 150m to 450m. 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, self-pulsation type semiconductor laser device manufacturing method according to any one of claims 1 to 21. The method of manufacturing a self-pulsation type semiconductor laser device according to claim 22, further comprising a step of forming a surface protective layer on the current blocking layer after the formation of the current blocking layer.

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