Semiconductor laser element, inspection method and inspection device

Abstract

To provide a semiconductor laser element and the like capable of suppressing end face breakage.SOLUTION: A semiconductor laser element 14 comprises a semiconductor layer. The semiconductor layer has: a waveguide WG formed in an in-layer direction of the semiconductor layer; and a window region formed on a front-side end face of the waveguide WG. The semiconductor laser element 14 has such current-laser beam output characteristics that, at an operation temperature of 25°C±3°C, laser beam output becomes a maximum value at a first drive current value and becomes equal to or less than 20% of the maximum value at a second drive current value larger than the first drive current value. The semiconductor laser element 14 is not broken at the second drive current value I2.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present disclosure relates to a semiconductor laser device, an inspection method, and an inspection apparatus. [Background technology]

[0002] Conventionally, semiconductor laser elements are known as small-sized, high-output light sources. In order to ensure the reliability of such semiconductor laser elements, screening is performed (see, for example, Patent Document 1). In the screening method for semiconductor laser elements disclosed in Patent Document 1, the current value flowing through the semiconductor laser element is made larger than the current value at which the optical output of the semiconductor laser element is saturated, thereby shortening the time required for screening. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 10-303496 Summary of the Invention [Problem to be solved by the invention]

[0004] In the screening method for semiconductor laser elements disclosed in Patent Document 1, in order to reduce COD (catastrophic optical damage) destruction of the facets of the semiconductor laser elements during screening, screening of the semiconductor laser elements is performed at an ambient temperature higher than room temperature, thereby lowering the laser light output of the semiconductor laser elements compared to that at room temperature. However, the time required for screening increases due to the low laser drive current. Thus, destruction of the facets of the semiconductor laser elements is a problem not only during normal use but also during screening.

[0005] The present disclosure has been made to solve such problems, and has an object to provide a semiconductor laser element etc. that can suppress damage to the end face. [Means for solving the problem]

[0006] In order to achieve the above-mentioned object, a semiconductor laser element according to the present disclosure comprises a semiconductor layer, the semiconductor layer having a waveguide formed in an in-layer direction of the semiconductor layer and a window region formed on a front end face of the waveguide, the semiconductor laser element having a current-laser light output characteristic in which, at an operating temperature of 25°C±3°C, a laser light output reaches a maximum value at a first drive current value, and at a second drive current value greater than the first drive current value, the laser light output is 20% or less of the maximum value, and is not destroyed at the second drive current value.

[0007] In the semiconductor laser device according to the present disclosure, the laser light output may be 100 mW or less at the second driving current value.

[0008] In the semiconductor laser device according to the present disclosure, the laser light output may be 50 mW or less at the second driving current value.

[0009] In the semiconductor laser device according to the present disclosure, laser oscillation may stop at the second drive current value.

[0010] In the semiconductor laser element according to the present disclosure, after driving at the second driving current value, a laser light output during a second driving at the first driving current value may be 95% or more of the maximum value.

[0011] In addition, in the semiconductor laser element according to the present disclosure, after driving at the second driving current value, the laser light output during a second driving at the first driving current value may be equal to or greater than twice the absolute maximum rated light output.

[0012] In the semiconductor laser element according to the present disclosure, the driving at the first driving current value and the second driving current value may be pulse driving of 0.1 μs or more and 1 μs or less.

[0013] In the semiconductor laser device according to the present disclosure, the cavity length of the semiconductor laser device may be 300 μm or less.

[0014] In the semiconductor laser device according to the present disclosure, the oscillation wavelength of the semiconductor laser device may be not less than 780 nm and not more than 860 nm.

[0015] Further, in the semiconductor laser element according to the present disclosure, there is provided a substrate on which the semiconductor layers are stacked and which contains GaAs, the semiconductor layers having an n-type cladding layer containing n-type AlGaInP, an n-side optical guide layer, an active layer having a quantum well structure, a p-side optical guide layer, and a p-type cladding layer containing p-type AlGaInP, which are sequentially formed on the substrate, the quantum well structure being sandwiched between the p-side optical guide layer and the n-side optical guide layer and being formed of a plurality of well layers and a plurality of barrier layers containing AlGaAs, the p-side optical guide layer and the n-side optical guide layer being formed of Al y Ga z In (1-y-z) P(0≦y≦0.1, 0≦z≦0.9, 0.3≦y+z≦0.7).

[0016] In the semiconductor laser device according to the present disclosure, the plurality of well layers may include GaAs, InGaAs, or GaAsP.

[0017] In addition, in the semiconductor laser element according to the present disclosure, the window region may contain a window-region-forming impurity, and a distance from a lower end of the active layer, which is a boundary between the n-side light guiding layer and the active layer, to a diffusion end of the window-region-forming impurity in the window region on the substrate side may be 0.5 μm or more.

[0018] In the semiconductor laser element according to the present disclosure, the window region may include a region in which a portion of the quantum well structure is disordered, and a difference in energy band gap between the disordered region and another portion of the quantum well structure may be 30 meV or more.

[0019] In the semiconductor laser element according to the present disclosure, a peak wavelength of a spectrum obtained from the window region by a photoluminescence method or a cathodoluminescence method may be shorter than an oscillation wavelength of the semiconductor laser element by 30 nm or more.

[0020] In the semiconductor laser device according to the present disclosure, the peak concentration of the window region forming impurity in the portion of the active layer located in the window region is 7×10 18 / cm 3 More than 1×10 19 / cm 3 It may be the following.

[0021] In order to achieve the above-mentioned object, an inspection method according to the present disclosure is an inspection method for determining pass / fail of a semiconductor laser element to be inspected, the semiconductor laser element comprising a semiconductor layer, the semiconductor layer having a waveguide formed in an in-layer direction of the semiconductor layer and a window region formed on a front end face of the waveguide, the inspection method including the steps of: measuring characteristics of the semiconductor laser element to be inspected; after the measuring step, passing a current through the semiconductor laser element to be inspected at a second driving current value that is higher than a first driving current value at which a laser light output of the semiconductor laser element to be inspected is maximized and at which the laser light output is 20% or less of the maximum value; after the current passing step, re-measuring the characteristics of the semiconductor laser element to be inspected; and determining pass / fail of the semiconductor laser element to be inspected by comparing the characteristics of the semiconductor laser element acquired in the measuring step with the characteristics of the semiconductor laser element acquired in the re-measuring step.

[0022] In the inspection method according to the present disclosure, the second drive current value may be determined for each of the semiconductor laser devices to be inspected, based on the characteristics acquired in the measuring step.

[0023] Furthermore, in the inspection method according to the present disclosure, in the measuring step, a current value supplied to the inspected semiconductor laser element when the laser light output is a first output is a first inspection current value Ia, in the re-measuring step, a current value supplied to the inspected semiconductor laser element when the laser light output is the first output is a second inspection current value Ib, and in the judging step, the inspected semiconductor laser element may be judged to be a pass if (Ib-Ia) / Ib≦0.1 is satisfied.

[0024] Furthermore, in the inspection method according to the present disclosure, in the measuring step, when a current value supplied to the inspected semiconductor laser element is a third inspection current value, a laser light output is a second output; in the re-measuring step, when a current value supplied to the inspected semiconductor laser element is the third inspection current value, a laser light output is a third output; and in the judging step, the inspected semiconductor laser element may be judged as a pass if the third output is 93% or more of the second output.

[0025] In the inspection method according to the present disclosure, in the energizing step, a current having a pulse width of 0.1 μs or more and 1 μs or less and a pulse duty ratio of 0.1% or more and 50% or less may be applied.

[0026] In the inspection method according to the present disclosure, the current application time in the current application step does not have to exceed 20 seconds.

[0027] In the inspection method according to the present disclosure, the semiconductor laser element to be inspected may have an oscillation wavelength of 780 nm or more and 860 nm or less.

[0028] In the inspection method according to the present disclosure, the semiconductor laser element to be inspected comprises a substrate containing GaAs and a semiconductor layer laminated on the substrate, the semiconductor layer having an n-type cladding layer containing n-type AlGaInP, an n-side optical guide layer, an active layer having a quantum well structure, a p-side optical guide layer, and a p-type cladding layer containing p-type AlGaInP, which are sequentially formed on the substrate, the quantum well structure being sandwiched between the p-side optical guide layer and the n-side optical guide layer and having a plurality of well layers and a plurality of barrier layers containing AlGaAs, the n-side optical guide layer and the p-side optical guide layer being Al y Ga z In (1-y-z) P(0≦y≦0.1, 0≦z≦0.9, 0.3≦y+z≦0.7).

[0029] In the inspection method according to the present disclosure, the plurality of well layers may include GaAs, InGaAs, or GaAsP.

[0030] In addition, in order to achieve the above-mentioned object, the inspection apparatus according to the present disclosure is an inspection apparatus for performing an inspection method, and includes a temperature-controlled inspection stage for fixing the semiconductor laser element to be inspected, an inspection probe for supplying current to the semiconductor laser element to be inspected, and a light-receiving element for measuring the laser light output of the semiconductor laser element to be inspected. Effect of the Invention

[0031] According to the present disclosure, it is possible to provide a semiconductor laser element or the like capable of suppressing damage to the end face. [Brief description of the drawings]

[0032] [Figure 1] FIG. 1 is a perspective view illustrating a schematic appearance of a semiconductor laser device according to a first embodiment. [Diagram 2] FIG. 2 is a first cross-sectional view illustrating a schematic configuration of the semiconductor laser device according to the first embodiment. [Diagram 3] FIG. 3 is a second cross-sectional view illustrating the configuration of the semiconductor laser device according to the first embodiment. [Figure 4]FIG. 4 is a partially enlarged view of FIG. [Diagram 5] FIG. 5 is a graph showing an example of current-laser light output characteristics of the semiconductor laser device according to the first embodiment. [Figure 6] FIG. 6 is a schematic cross-sectional view of a substrate illustrating an overview of a semiconductor layer formation process of the semiconductor laser device according to the first embodiment. [Figure 7A] FIG. 7A is a schematic cross-sectional view of a substrate and a semiconductor layer according to the first embodiment. [Figure 7B] FIG. 7B is a schematic cross-sectional view of a substrate and a semiconductor layer illustrating a first method for forming a window region according to the first embodiment. [Figure 7C] FIG. 7C is a schematic cross-sectional view of a substrate and a semiconductor layer illustrating a second method for forming a window region according to the first embodiment. [Figure 8] FIG. 8 is a graph showing the relationship between the distance from the active layer to the Zn diffusion end in the window region and the photoluminescence wavelength from the window region according to the first embodiment. [Figure 9] FIG. 9 is a scanning electron microscope photograph showing the window region according to the first embodiment. [Figure 10] FIG. 10 is a graph showing the results of an accelerated test of a semiconductor laser device in which the distance from the lower end of the active layer to the Zn diffusion end in the window region according to the first embodiment is about 0.8 μm. [Figure 11] FIG. 11 is a graph showing the results of an accelerated test of a semiconductor laser device in which the distance from the lower end of the active layer to the Zn diffusion end in the window region according to the first embodiment is about 0.4 μm. [Figure 12] FIG. 12 is a schematic cross-sectional view of a substrate illustrating an overview of a waveguide forming step according to the first embodiment. [Figure 13] FIG. 13 is a schematic cross-sectional view of a substrate illustrating an overview of a first protective film forming step according to the first embodiment. [Figure 14] FIG. 14 is a perspective view showing the configuration of the semiconductor laser device according to the first embodiment. As shown in FIG. [Figure 15] FIG. 15 is a schematic top view showing a schematic configuration of the inspection device according to the first embodiment. [Figure 16] FIG. 16 is a schematic front view showing a schematic configuration of the inspection device according to the first embodiment. [Figure 17] FIG. 17 is a flowchart showing a method for inspecting a semiconductor laser device according to the first embodiment. [Figure 18] FIG. 18 is a graph showing an example of the measurement result of the first inspection current value in step S10 according to the first embodiment. [Figure 19] FIG. 19 is a graph showing current-laser light output characteristics when a CW current is supplied to the inspected semiconductor laser device according to the first embodiment. [Figure 20] FIG. 20 is a graph showing a first example of measurement results of the second inspection current value Ib in step S30 according to the first embodiment. [Figure 21] FIG. 21 is a graph showing a second example of measurement results of the second inspection current value Ib in step S30 according to the first embodiment. [Figure 22A] FIG. 22A is a graph showing current-laser light output characteristics of the inspected semiconductor laser device according to the first embodiment. [Figure 22B] FIG. 22B is an enlarged view of a portion of the graph in FIG. 22A. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0033] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. Note that each of the embodiments described below shows a specific example of the present disclosure. Therefore, the numerical values, shapes, materials, components, the arrangement and connection of the components, as well as the steps (processes) and the order of the steps shown in the following embodiments are merely examples and are not intended to limit the present disclosure. Therefore, among the components in the following embodiments, components that are not described in the independent claims showing the highest concept of the present disclosure will be described as optional components.

[0034] In addition, each figure is a schematic diagram and is not necessarily precisely illustrated. Therefore, the scales and the like are not necessarily the same in each figure. In each figure, the same reference numerals are given to substantially the same configurations, and duplicated explanations are omitted or simplified.

[0035] (Embodiment 1) A semiconductor laser element, an inspection method, and an inspection device according to a first embodiment will be described.

[0036] [1-1. Semiconductor laser element] First, the semiconductor laser device according to the present embodiment will be described with reference to FIGS. 1 to 4. FIG.

[0037] FIG. 1 is a perspective view showing a schematic appearance of a semiconductor laser device 14 according to this embodiment. FIG. 2 is a first cross-sectional view showing a schematic configuration of the semiconductor laser device 14 according to this embodiment. FIG. 2 shows an enlarged view of the waveguide WG and its vicinity in the II-II cross section of FIG. 1. FIG. 3 is a second cross-sectional view showing a schematic configuration of the semiconductor laser device 14 according to this embodiment. FIG. 3 shows a III-III cross section of FIG. 1. FIG. 4 is a partial enlarged view of FIG. 3. FIG. 4 shows an enlarged view of the portion enclosed by the dashed line frame IV in FIG. 3.

[0038] As shown in FIG. 2, the semiconductor laser element 14 is an element including a chip-shaped substrate 24 and a semiconductor layer 100 including an active layer 40 arranged on a first surface P1 of the chip-shaped substrate 24. The chip-shaped substrate 24 is a substrate on which the semiconductor layer 100 of the semiconductor laser element 14 is laminated. In this embodiment, the chip-shaped substrate 24 is a substrate including GaAs, more specifically, an n-GaAs substrate whose surface orientation is inclined 10 degrees from the (100) surface toward the (011) surface direction. The surface orientation of the first surface P1 is a (100) surface that is inclined 10 degrees toward the (011) surface direction and is off by 10 degrees. The semiconductor layer 100 has a first semiconductor layer 30 including a first conductive type layer, an active layer 40, and a second semiconductor layer 50 including a second conductive type layer, which are laminated in this order from the chip-shaped substrate 24 side.

[0039] As shown in FIG. 3, the semiconductor laser element 14 has a p-side lower electrode 151 and a p-side upper electrode 152 arranged on the semiconductor layer 100, and an n-side electrode 160 arranged on the surface of the chip-shaped substrate 24 on which the semiconductor layer 100 is not arranged.

[0040] Moreover, the semiconductor layer 100 of the semiconductor laser element 14 has a waveguide WG formed in an in-layer direction of the semiconductor layer 100. In other words, the waveguide WG is formed along a direction parallel to the major surface of the semiconductor layer 100. In this embodiment, the waveguide WG using a ridge structure is formed in the semiconductor layer 100. The waveguide WG extends in a first direction as shown in FIG. 1.

[0041] 3, both end faces in the first direction of the semiconductor laser element 14 are cleaved end faces 121. The two cleaved end faces 121 function as cavity faces of the semiconductor laser element 14, and second protective films 132F and 132R functioning as reflectance control films are formed on the two cleaved end faces 121. The second protective films 132F and 132R not only function as reflectance control films on the front side (the end face side from which the laser light is mainly emitted) and rear side of the cavity, respectively, but also have a function of protecting the cleaved end face 121.

[0042] 3 and 4, the semiconductor layer 100 has window regions 80 formed on both ends of the waveguide WG. In this embodiment, the window regions 80 that suppress light absorption in the active layer 40 are formed near each of the two cleavage end faces 121 that function as resonator faces.

[0043] Each component of the semiconductor laser device 14 will now be described.

[0044] The chip-shaped substrate 24 is a substrate cut into chips, and the semiconductor layer 100 is laminated on the chip-shaped substrate 24. There is no particular limitation on the configuration of the chip-shaped substrate 24. In the present embodiment, the chip-shaped substrate 24 is an n-GaAs substrate as described above.

[0045] The first semiconductor layer 30 is a semiconductor layer including a first conductive type layer. The configuration of the first semiconductor layer 30 is not particularly limited. In this embodiment, as shown in FIG. 2, the first semiconductor layer 30 includes an n-type buffer layer 31, an n-type cladding layer 32, and an n-side light guide layer 33. The n-type buffer layer 31 is an n-GaAs layer having a thickness of 0.4 μm. The n-type cladding layer 32 is an n-(Al 0.16 Ga 0.84 ) 0.5 In 0.5 The n-side optical guide layer 33 is a GaP layer having a thickness of 0.09 μm. 0.5 In 0.5 This is the P layer.

[0046] The active layer 40 is a layer that forms the light emitting portion of the semiconductor laser element 14. The configuration of the active layer 40 is not particularly limited. In the present embodiment, the active layer 40 has a quantum well structure. The quantum well structure is sandwiched between a p-side light guide layer 51 and an n-side light guide layer 33, which will be described later, and is formed of a plurality of well layers and a plurality of barrier layers containing AlGaAs. The active layer 40 is, for example, an AlGaAs layer having a thickness of 0.03 μm from the n-side light guide layer 33 side. 0.59 Ga 0.41 The As barrier layer, the GaAs well layer with a thickness of 0.0065 μm, and the Al well layer with a thickness of 0.004 μm 0.59 Ga 0.41 The As barrier layer, the GaAs well layer with a thickness of 0.0065 μm, and the Al well layer with a thickness of 0.021 μm 0.59 Ga 0.41 The active layer 40 is a multiple quantum well active layer including an As barrier layer. The active layer 40 may include well layers other than GaAs well layers, and may include InGaAs well layers or GaAsP well layers.

[0047] With such an active layer 40, the oscillation wavelength of the semiconductor laser element 14 is 780 nm or more and 860 nm or less. In such a semiconductor laser element 14, the energy of the laser light is higher than that of a semiconductor laser element having an oscillation wavelength in the 1.3 μm band, for example, and therefore end face damage is more likely to occur. However, in the semiconductor laser element 14 according to this embodiment, the end face damage can be suppressed by the characteristic configuration of the window region 80, the cavity length, each optical guide layer, etc., which will be described later.

[0048] The second semiconductor layer 50 is a semiconductor layer including a second conductive type layer having a different conductive type from the first conductive type layer. The configuration of the second semiconductor layer 50 is not particularly limited. In this embodiment, as shown in FIG. 2, the second semiconductor layer 50 includes a p-side light guide layer 51, a p-type first cladding layer 52, a p-type second cladding layer 53, a p-type third cladding layer 54, a p-type intermediate layer 55, and a p-type contact layer 56.

[0049] The p-side optical guide layer 51 is a Ga 0.5 In 0.5 This is the P layer.

[0050] The p-type first cladding layer 52 is a p-(Al 0.30 Ga 0.70 ) 0.5 In 0.5 The p-type second cladding layer 53 is a p-(Al 0.60 Ga 0.40 ) 0.5 In 0.5 The p-type third cladding layer 54 is a p-(Al 0.30 Ga 0.70 ) 0.5 In 0.5 It is a P layer. Each of the p-type first cladding layer 52, the p-type second cladding layer 53, and the p-type third cladding layer 54 is an example of a p-type cladding layer according to the present embodiment.

[0051] The p-type intermediate layer 55 is a p-(Al 0.1 Ga 0.9 ) 0.5 In 0.5 The p-type intermediate layer 55 has a lower Al composition than the p-type third cladding layer 54. The p-type contact layer 56 is a p-GaAs layer having a thickness of 0.23 μm.

[0052] The first protective film 131 is formed on a part of the upper part and the side surface of the ridge forming the waveguide WG, the groove TR, and the flat parts on both sides, as shown in Fig. 2. At the upper part of the ridge, the first protective film 131 has an opening that exposes the upper part of the ridge, and as shown in Fig. 4, the vicinity of the cleavage end face 121 including the window region 80 is covered with the first protective film 131. The first protective film 131 is not particularly limited as long as it is a dielectric film, and SiO2, SiN, TiO2, ZrO2, Al2O3, Nb2O5, Ta2O5, etc. can be used. In this embodiment, the first protective film 131 is a SiN film with a thickness of about 180 nm.

[0053] 2 to 4 is a patterned metal film, and in this embodiment, includes a Ti film with a thickness of about 50 nm, a Pt film with a thickness of about 150 nm, and an Au film with a thickness of about 50 nm, which are laminated in this order from the semiconductor layer 100 side. The p-side lower electrode 151 is connected to the p-type contact layer 56 in the opening of the first protective film 131.

[0054] In this embodiment, the p-side upper electrode 152 shown in FIG. 3 is an Au film having a thickness of 2.0 μm or more and 5.0 μm or less.

[0055] In this embodiment, the n-side electrode 160 shown in FIG. 3 includes, stacked in this order from the chip-shaped substrate 24 side, an AuGe film with a thickness of 90 nm, a Ni film with a thickness of 20 nm, an Au film with a thickness of 50 nm, a Ti film with a thickness of 100 nm, a Pt film with a thickness of 50 nm, a Ti film with a thickness of 50 nm, a Pt film with a thickness of 100 nm, and an Au film with a thickness of 500 nm.

[0056] The configuration and method of forming the second protective films 132F and 132R are not particularly limited. In this embodiment, the second protective film 132F used on the front side is a dielectric multilayer film formed by laminating a combination of an Al2O3 film having a thickness of 50 nm and a Ta2O5 film having a thickness of 55 nm from the cleavage end face 121 side once or multiple times. The second protective film 132R used on the rear side is a dielectric multilayer film formed by laminating a combination of an Al2O3 film having a thickness of 50 nm and a Ta2O5 film having a thickness of 55 nm from the cleavage end face 121 side once or multiple times. A Al2O3 film, thickness λ / 8n S SiO2 film, thickness λ / 4n TAfter stacking the Ta2O5 films in order, a thickness of λ / 4n S SiO2 film and thickness λ / 4n T The dielectric multilayer film is a laminate of a Ta2O5 film and a Ta2O5 film. A , n T , n S respectively indicate the refractive indexes of the Al2O3 film, the Ta2O5 film, and the SiO2 film for light of wavelength λ. In this embodiment, λ is about 860 nm, and after a 65 nm thick Al2O3 film, a 74 nm thick SiO2 film, and a 102 nm thick Ta2O5 film are laminated in this order from the cleaved facet 121 side, a 147 nm thick SiO2 film and a 102 nm thick Ta2O5 film are laminated multiple times in combination.

[0057] The window region 80 is formed by diffusing impurities for forming a window region, such as Zn. The window region 80 is a region in which the energy band gap of the active layer 40 is expanded by diffusing the impurities for forming a window region in the vicinity of the cavity face of the semiconductor laser element 14. The window region 80 is formed by disordering the quantum well structure of the active layer 40. That is, a part of the quantum well structure in the vicinity of the cavity face is a disordered region. In this embodiment, the window region length (the length of the window region 80 in the first direction) is different between the front side and the rear side of the cavity. For example, the window region length on the front side is about 10 μm, and the window region length on the rear side is about 7 μm. In this way, the window region length is larger on the front side where the light density is high. This can reduce the end face damage of the semiconductor laser element 14.

[0058] 4, the window region 80 is formed so as to terminate in the n-type cladding layer 32. In this embodiment, the distance Dz from the active layer lower end 40a, which is the boundary between the n-side light guiding layer 33 and the active layer 40, to the Zn diffusion end 80a is 0.8 μm. Here, the boundary between the active layer 40 and the p-side light guiding layer 51 is defined as the active layer upper end 40b.

[0059] The window region forming impurity concentration of the portion of the active layer 40 located in the window region 80 is, for example, 5×10 19 / cm 3 It may be less than 7 x 10 18 / cm 3 More than 1×10 19 / cm 3 The average window region-forming impurity concentration of the portions of the first p-type cladding layer 52, the second p-type cladding layer 53, and the third p-type cladding layer 54 located in the window region 80 may be preferably 6 times or less, and more preferably 3 times or less, of the average window region-forming impurity concentration of the portions other than the window regions.

[0060] As described above, in this embodiment, the semiconductor laser element 14 includes a substrate including GaAs on which the semiconductor layer 100 is stacked. The semiconductor layer 100 also includes an n-type cladding layer 32 including n-type AlGaInP, an n-side light guide layer 33, an active layer 40 having a quantum well structure, a p-side light guide layer 51, and a p-type cladding layer including p-type AlGaInP, which are sequentially formed on the chip-shaped substrate 24. The window region 80 includes a region in which a part of the quantum well structure is disordered.

[0061] As described later, in this embodiment, the saturation optical output is reduced by shortening the cavity in the semiconductor laser element 14. However, shortening the cavity in this way may increase the operating voltage of the semiconductor laser element 14. In order to reduce the operating voltage, a method of reducing the operating voltage by reducing the Al composition of the p-type cladding layers (the first p-type cladding layer 52, the second p-type cladding layer 53, and the third p-type cladding layer 54) and the n-type cladding layer is conceivable. However, when the Al composition of each cladding layer is reduced, the light confinement effect of each cladding layer is reduced and the amount of light seeping out to the p-type cladding layer side is increased, so that the optical loss is increased. Furthermore, by reducing the Al composition of each cladding layer, the diffusion speed of Zn is reduced, so that the time required to form the window region 80 having a desired energy band gap is increased. Accordingly, the concentration of Zn diffusing into the active layer 40 is increased, and the optical loss in the active layer 40 is increased.

[0062] Therefore, in this embodiment, a p-side light guide layer 51 and an n-side light guide layer 33 made of AlGaInP are inserted between the active layer 40 and the p-type cladding layer and between the active layer 40 and the n-type cladding layer, respectively. This provides a light confinement effect, so that light loss can be suppressed without increasing the thickness of the barrier layer of the active layer 40. Note that, in order to reliably obtain the light confinement effect of each light guide layer, the Al composition of each light guide layer may be lower than the Al composition of each cladding layer. Furthermore, by using AlGaInP, which has a higher Zn diffusion rate than AlGaAs, for each light guide layer, the concentration of Zn diffusing into the active layer 40 can be suppressed, so that light loss in the window region 80 can be reduced.

[0063] More specifically, the p-side optical guide layer 51 and the n-side optical guide layer 33 are made of Al y Ga z In (1-y-z) P(0≦y≦0.1, 0≦z≦0.9, 0.3≦y+z≦0.7).

[0064] In the semiconductor laser device 14, by using the p-side light guiding layer 51 and the n-side light guiding layer 33 in this manner, it is possible to reduce the optical loss in the window region 80 as described above.

[0065] In this embodiment, the window regions are formed on both the front and rear sides of the resonator, but it is also possible to form a window region only on the front side, without forming a window region on the rear side. In this case, since no window region is formed on the rear side, it is easy to ensure the length of the region of the waveguide WG where the window region 80 is not formed when the resonator length is shortened.

[0066] The current-laser light output characteristics of the semiconductor laser device 14 having such a structure will be described with reference to Fig. 5. Fig. 5 is a graph showing an example of the current-laser light output characteristics of the semiconductor laser device 14 according to the present embodiment.

[0067] Fig. 5 shows the current-laser light output characteristics when a current with a pulse width of 0.8 μs and a pulse duty ratio of 24% is supplied to the semiconductor laser element 14 held on a stage whose stage temperature is controlled to 25°C ± 3°C. The horizontal axis of Fig. 5 shows the current value [mA] supplied to the semiconductor laser element 14, and the vertical axis shows the laser light output [mW] of the semiconductor laser element 14. When the current value supplied to the semiconductor laser element 14 is about 400 mA, the maximum laser light output Pmax is about 400 mW, and thereafter, as the current value supplied is increased, the laser light output gradually decreases, and at a current value of about 550 mA, it decreases to about 0 mW.

[0068] The semiconductor laser element 14 has a current-laser light output characteristic in which, at an operating temperature of 25°C±3°C, the laser light output is 20% or less of the maximum value Pmax at a second drive current value I2 that is greater than the first drive current value I1 at which the laser light output is the maximum value Pmax, and the semiconductor laser element 14 can be made not to be destroyed at the second drive current value I2.

[0069] Furthermore, by setting the operating temperature of the semiconductor laser element 14 to 25° C.±3° C., the semiconductor laser element 14 can be made to be less likely to be destroyed even with a large laser current than when current is applied at a higher temperature.

[0070] In addition, in this embodiment, a semiconductor laser element without any internal defects and without degradation can be realized. This allows a high-output semiconductor laser element in which the maximum laser light output Pmax of the semiconductor laser element 14 is 200 mW or more. Also, a high-output semiconductor laser element in which the maximum laser light output Pmax of the semiconductor laser element 14 is 300 mW or more can be realized.

[0071] In addition, a semiconductor laser element can be realized in which the laser light output reaches a maximum value Pmax at the first drive current value I1, and after drive at the second drive current value I2, the laser light output during the second drive at the first drive current value I1 is 95% or more of the maximum value Pmax.

[0072] It is also possible to realize a semiconductor laser element in which the laser light output during the second drive at the first drive current value I1 is at least twice the absolute maximum rated light output, where the absolute maximum rated light output means the maximum light output allowed for normal use of each semiconductor laser element.

[0073] [1-2. Manufacturing method of semiconductor laser element] Next, a method for manufacturing the semiconductor laser device according to the present embodiment will be described. In the present embodiment, each step of the method for manufacturing the semiconductor laser device described above will be described as an example of the semiconductor laser device.

[0074] [1-2-1. Semiconductor layer formation process] The semiconductor layer forming process according to this embodiment will be described with reference to the drawings. Fig. 6 is a schematic cross-sectional view of a substrate 20 illustrating an overview of the semiconductor layer forming process of the semiconductor laser element according to this embodiment.

[0075] 6, first, a substrate 20 having a first surface P1 and a second surface P2 is prepared, and a semiconductor layer 100 including an active layer 40 is formed on the first surface P1 of the substrate 20. Each layer constituting the semiconductor layer 100 is laminated by, for example, metal-organic chemical vapor deposition (MOCVD). In this embodiment, as the semiconductor layer 100, a first semiconductor layer 30 including a first conductive type layer, the active layer 40, and a second semiconductor layer 50 including a second conductive type layer are formed in this order from the substrate 20 side.

[0076] Next, in this embodiment, a so-called window region is formed in a region near the resonator facet of the semiconductor laser element. Hereinafter, a method for forming the window region will be described with reference to Figs. 7A to 7C. Fig. 7A is a schematic cross-sectional view of substrate 20 and semiconductor layer 100 according to this embodiment. Figs. 7B and 7C are schematic cross-sectional views of substrate 20 and semiconductor layer 100 illustrating a method for forming window region 80 according to this embodiment. Figs. 7A to 7C show cross sections of substrate 20 and semiconductor layer 100 taken along a first direction.

[0077] For example, as shown in FIG. 7B, the window region 80 may be formed by thermally diffusing Zn on the p-type contact layer included in the second semiconductor layer 50. Specifically, a ZnO film serving as a diffusion source, and a SiN film or a SiO film for suppressing evaporation of Zn are sequentially formed above the p-type contact layer, and Zn is diffused near the resonator facet of the semiconductor laser element by heat treatment, thereby expanding the energy band gap of the active layer 40. This makes it possible to form the window region 80 in which light absorption in the active layer 40 is suppressed. According to this method for forming a window region, the peak concentration of Zn in the portion of the active layer 40 located in the window region 80 is 5×10 19 / cm 3 It is about the following.

[0078] 7C, a window region 80 may be formed by thermally diffusing Zn through a layer 50d made of p-type GaInP or p-type AlGaInP directly on the p-type contact layer. In this case, the layer 50d is removed after the window region 80 is formed. According to this method of forming a window region, the peak concentration of Zn in the portion of the active layer 40 located in the window region 80 is about 1×10 19 / cm 3 It is about the following.

[0079] By forming such a window region 80, deterioration in the vicinity of the cavity facet of the semiconductor laser element 14 can be suppressed. Here, a more effective configuration of the window region 80 will be described with reference to Figs. 8 to 11. Fig. 8 is a graph showing the relationship between the distance Dz from the active layer lower end 40a to the Zn diffusion end 80a of the window region 80 according to this embodiment and the photoluminescence (PL) wavelength from the window region 80. Fig. 9 is a scanning electron microscope photograph showing the window region 80 according to this embodiment. Figs. 10 and 11 are graphs showing the results of accelerated tests of semiconductor laser elements when the distances from the active layer lower end 40a to the Zn diffusion end in the window region 80 according to this embodiment are about 0.8 µm and about 0.4 µm, respectively. In the graphs shown in Figs. 10 and 11, the horizontal axis indicates the duration of the accelerated test, and the vertical axis indicates the rate of change of the current flowing through the semiconductor laser element. 10 and 11 were performed on a plurality of semiconductor laser elements having a cavity length of 280 μm under conditions of a temperature of 110° C. and an input power of 70 mW. Note that the current input to the semiconductor laser elements was CW (continuous wave).

[0080] As shown in Fig. 8, there is a correlation between the distance Dz from the active layer lower end 40a to the Zn diffusion end 80a and the PL wavelength. The distance Dz can be measured using a scanning microscope photograph, for example, as shown in Fig. 9. The whitish region below the active layer 40 in Fig. 9 indicates the Zn diffusion region.

[0081] As shown in FIG. 8, when the distance Dz is small, the PL wavelength becomes longer, the optical absorption in the window region 80 increases, and the effect of the window region 80 in suppressing the deterioration of the cavity facet is reduced. For example, in the example shown in FIG. 10, the PL wavelength of the window region 80 is about 740 nm, which is sufficiently short compared to the oscillation wavelength 830 nm of the semiconductor laser element, so the effect of the window region 80 in suppressing the deterioration of the cavity facet is obtained. On the other hand, in the example shown in FIG. 11, the PL wavelength of the window region 80 is about 805 nm, which is not sufficiently short compared to the oscillation wavelength 830 nm of the semiconductor laser element, so a change in the amount of current is observed in the accelerated test, and deterioration occurs. In other words, in the example shown in FIG. 11, the effect of the window region 80 in suppressing the deterioration of the cavity facet is not obtained.

[0082] From these test results, it was found that a sufficient degradation suppression effect can be obtained if the peak wavelength of the spectrum obtained by the photoluminescence method from the window region 80 is shorter than the oscillation wavelength of the semiconductor laser element by 30 nm or more.

[0083] In the above, the peak wavelength of the spectrum in the window region 80 is obtained by the photoluminescence method, but it may be obtained by other methods. For example, the peak wavelength of the spectrum may be obtained by the cathode luminescence method.

[0084] In addition, the window region 80 may include a region in which part of the quantum well structure is disordered, and the difference in the energy band gap between the disordered region and the remaining part of the quantum well structure that is not disordered may be 30 meV or more. This has been found to provide a sufficient effect of suppressing degradation.

[0085] Furthermore, the distance Dz from the lower end 40a of the active layer to the diffusion end 80a of the window region forming impurity Zn in the window region 80 on the chip-shaped substrate 24 side may be 0.5 μm or more. This allows the PL wavelength in the window region 80 to be sufficiently short, thereby suppressing deterioration of the cavity facets.

[0086] [1-2-2. Waveguide formation process] Next, the waveguide forming step will be described with reference to the drawings. Fig. 12 is a schematic cross-sectional view of the substrate 20 illustrating an overview of the waveguide forming step according to this embodiment.

[0087] As shown in Fig. 12, a plurality of pairs of trenches TR are formed in the second semiconductor layer 50 formed on the substrate 20 in a direction perpendicular to the plane of the paper in Fig. 12, thereby forming a waveguide WG using a ridge formed between the pair of trenches TR. In this manner, a plurality of waveguides WG extending in the first direction are formed in the semiconductor layer 100. The width of the waveguide WG is, for example, about 3 µm.

[0088] The method of forming the waveguide WG is not particularly limited. In this embodiment, in order to form a ridge, a mask is formed with SiO2 or the like using a photolithography technique. Then, the groove TR is formed, that is, the ridge is formed, by non-selective etching such as dry etching. At this time, the dry etching is performed on the p-type contact layer, the p-type intermediate layer, the p-type third cladding layer, and the p-type second cladding layer, and the p-type second cladding layer is removed partway without being completely removed.

[0089] Next, a protective film such as SiO2 is formed over the entire upper surface of the semiconductor layer 100 on which the ridge is formed.

[0090] Next, the SiO2 protective film is removed only from the bottom of the trench TR by dry etching, while the sidewalls and top of the ridge are still covered with the protective film.

[0091] Next, the p-type second cladding layer is completely removed by selective etching such as wet etching. As a result, the p-type first cladding layer is exposed at the bottom of the groove TR. In this manner, the waveguide WG can be formed in the semiconductor layer 100.

[0092] The dry etching technique that can be employed in this embodiment may be anisotropic plasma etching, such as a method using inductively coupled plasma (hereinafter referred to as ICP) or electron cyclotron resonance (hereinafter referred to as ECR) plasma.

[0093] As the etching gas, a mixed gas of SiCl4 and Ar is used, but chlorine gas, boron trichloride gas, or the like may be used instead of SiCl4.

[0094] In this embodiment, the dry etching technique is an ICP method, and a mixed gas of SiCl4 and Ar is used as the etching gas. The etching conditions can be, but are not limited to, a volume content of SiCl4 in the mixed gas of 5 to 12%, a temperature of the lower electrode on which the semiconductor substrate is placed is 150°C to 200°C, a pressure in the chamber is 0.1 Pa to 1 Pa, a bias power of the lower electrode is 50 W to 150 W, and an ICP power is 200 W to 300 W.

[0095] [1-2-3. First protective film formation process] Next, the first protective film forming step will be described with reference to FIG.

[0096] Fig. 13 is a schematic cross-sectional view of the substrate 20 illustrating an overview of the first protective film formation step according to the present embodiment. Fig. 13 is an enlarged view illustrating the first protective film formation step inside the dashed frame XIII illustrated in Fig. 12. As illustrated in Fig. 13, the first protective film 131 is formed on the semiconductor layer 100 except for a part of the upper part of the ridge. The part of the upper part of the ridge where the first protective film 131 is not formed becomes a region to be connected to a p-side lower electrode to be formed later.

[0097] There is no particular limitation on the method for forming the first protective film 131. In this embodiment, the first protective film 131 made of SiN is formed to a thickness of about 180 nm on a part of the top and side surfaces of the ridge, the trench TR, and the flat portions on both sides.

[0098] [1-2-4. Electrode formation process] Next, the electrode formation step will be described. The electrodes formed in this step are a p-side electrode, an n-side electrode, etc. for supplying power to the semiconductor laser device manufactured by the manufacturing method according to the present embodiment.

[0099] The p-side lower electrode 151 is formed on the upper part of the semiconductor layer 100 including the upper part of the ridge and the trench TR. In addition, a p-side upper electrode 152 is formed on the p-side lower electrode 151. The p-side lower electrode 151 is connected to the second semiconductor layer 50 through an opening in the first protective film 131 provided on the ridge.

[0100] There is no particular limitation on the configuration and formation method of the p-side lower electrode 151 and the p-side upper electrode 152. In this embodiment, a resist mask is formed by photolithography, and after pretreatment by wet etching, a Ti film with a thickness of about 50 nm, a Pt film with a thickness of about 150 nm, and an Au film with a thickness of about 50 nm are sequentially formed by deposition.

[0101] Next, a pattern for the p-side upper electrode 152 is formed using a resist mask by photolithography, and an Au film having a thickness of 2.0 μm to 5.0 μm is formed by electrolytic plating. Next, the resist is removed by lift-off to form the patterned p-side upper electrode 152.

[0102] Next, the substrate 20 is polished until the thickness from the second surface P2 of the substrate 20 to the p-side upper electrode 152 is about 100 μm (polishing process is not shown). Then, a resist mask is formed on the second surface P2 by photolithography, and after pretreatment by wet etching, an AuGe film, a Ni film, an Au film, a Ti film, a Pt film, a Ti film, a Pt film, and an Au film are sequentially formed by deposition. Then, the resist is removed by lift-off to form a patterned n-side electrode 160.

[0103] Through the above steps, the substrate 20 on which the semiconductor layer 100 is laminated is formed.

[0104] [1-2-5. Cleavage process] Next, the cleavage step will be described with reference to the drawings. In this step, the substrate 20 on which the semiconductor layer 100 formed by the above-mentioned step is laminated is cleaved at a plane corresponding to the cavity facet of the semiconductor laser element. That is, as shown in FIG. 3, the substrate 20 is cleaved so that the window region 80 is disposed at the cavity end facet. In this embodiment, the cleavage is performed so that the cavity length of the semiconductor laser element 14 is 300 μm or less. This makes it possible to form a bar-shaped substrate on which the semiconductor layer 100 is formed.

[0105] Here, by setting the cavity length of the semiconductor laser element 14 to 300 μm or less, the proportion of the region of the waveguide WG other than the window region 80 can be reduced, thereby reducing the saturated optical output. Therefore, it is possible to suppress damage to the end face of the semiconductor laser element 14. In this embodiment, the cavity length is 280 μm.

[0106] [1-2-6. Second protective film formation process] Next, the second protective film forming process will be described. In this process, a second protective film is formed on the cleaved facet 121 formed in the above cleavage process by ECR chemical vapor deposition or the like. The configuration and forming method of the second protective films 132F and 132R are not particularly limited.

[0107] The light reflectance of the second protective film is about 30% for the second protective film 132F on the front side, and 90% or more for the second protective film on the rear side. Furthermore, the bar-shaped substrate formed in the above process is divided into chips to form the semiconductor laser element 14 according to this embodiment.

[0108] [1-3. Inspection method for semiconductor laser element] Next, a method for inspecting the semiconductor laser device 14 according to the present embodiment will be described.

[0109] [1-3-1. Inspection equipment] First, the state of the semiconductor laser element 14 during inspection will be described with reference to Fig. 14. Fig. 14 is a perspective view showing the configuration of a semiconductor laser device 106 according to this embodiment. As shown in Fig. 14, the semiconductor laser device 106 includes the semiconductor laser element 14 and a submount 104. In the semiconductor laser device 106, the semiconductor laser element 14 is mounted on the submount. In this manner, the semiconductor laser element 14 is inspected as the semiconductor laser device 106 in a state where it is mounted on the submount 104.

[0110] The material for forming the submount 104 is not particularly limited as long as it has good heat dissipation properties, and may be Si, SiC, AlN, CuW, or the like. In this embodiment, the material is Si. The semiconductor laser element 14 is mounted on the submount 104 with the junction up by, for example, AuSn solder.

[0111] Next, an inspection device used in the inspection method for the semiconductor laser element 14 according to the present embodiment will be described with reference to Figs. 15 and 16. Figs. 15 and 16 are schematic top and front views, respectively, showing a schematic configuration of an inspection device 200 according to the present embodiment. Note that Figs. 15 and 16 also show a semiconductor laser device 106 including the semiconductor laser element 14 together with the inspection device 200. The semiconductor laser element 14 is an example of a semiconductor laser element to be inspected in the inspection method according to the present embodiment. Also, in Fig. 16, the light receiving element 120 of the inspection device 200 is omitted from illustration.

[0112] As shown in FIGS. 15 and 16, an inspection device 200 according to this embodiment includes an inspection stage 111, an inspection probe 107 that supplies a current to the semiconductor laser device under inspection, and a light receiving element 120.

[0113] The inspection apparatus 200 according to the present embodiment may use, as the semiconductor element to be inspected, for example, the semiconductor laser element 14 alone, or the semiconductor laser element 14 mounted on the submount 104. In the following, an example will be described in which the semiconductor laser element 14 mounted on the submount 104 (i.e., the semiconductor laser device 106) is used as the semiconductor element to be inspected.

[0114] 16, the inspection stage 111 includes a metal stage 108, a temperature measuring element 109, and a temperature control element 110. The temperature of the inspection stage 111 is controlled, and the semiconductor laser device to be inspected is fixed to the inspection stage 111. As shown in FIG.

[0115] The metal stage 108 is a stage formed of a material with high thermal conductivity. For example, Cu or the like can be used as a material for forming the metal stage 108. The metal stage 108 also has a function of fixing the semiconductor laser element to be inspected. The configuration for fixing the semiconductor laser element to be inspected is not particularly limited. For example, the metal stage 108 may have a through hole in the surface on which the semiconductor laser element to be inspected is placed, and the semiconductor laser element to be inspected may be adsorbed by suctioning the through hole.

[0116] The temperature measuring element 109 is an element that measures the temperature of the inspection stage 111. The configuration of the temperature measuring element 109 is not particularly limited. In this embodiment, the temperature measuring element 109 is configured as a resistance temperature detector using Pt or the like. This makes it possible to measure the temperature of the inspection stage 111 with high accuracy. Also, in this embodiment, the temperature measuring element 109 is inserted into a hole formed in the metal stage 108.

[0117] The temperature control element 110 is an element that controls the temperature of the inspection stage 111. The temperature control element 110 is feedback-controlled so that the temperature measurement result by the temperature measurement element 109 is maintained within a predetermined range. The configuration of the temperature control element 110 is not particularly limited. In this embodiment, a Peltier element is used as the temperature control element 110. This allows the inspection stage 111 to be cooled and heated quickly, thereby enabling highly accurate temperature control. In this embodiment, the temperature of the inspection stage 111 can be maintained at 25°C±1°C (i.e., in the range of 24°C to 26°C).

[0118] The inspection probe 107 is a probe that supplies a current to the semiconductor laser element under test. The inspection probe 107 is composed of two probes, one on a high potential side and one on a low potential side, and a current is supplied from a power supply connected to the inspection probe 107. The amount of current flowing through the inspection probe 107 can be adjusted by controlling the power supply. In this embodiment, the high potential side probe is abutted against the p-side upper electrode 152 of the semiconductor laser element 14, which is the semiconductor laser element under test. The low potential side probe is abutted against the electrode 105 on the submount 104. The electrode 105 of the submount 104 is connected to the n-side electrode 160 of the semiconductor laser element 14. Such an inspection probe 107 can supply a desired current to the semiconductor laser element under test.

[0119] 15 is an element that measures the laser light output of the semiconductor laser element under test. The light receiving element 120 is disposed at a position facing the light emitting part 102 corresponding to the laser light emitting part of the semiconductor laser element 14, which is the semiconductor laser element under test, and measures the laser light output of the semiconductor laser element 14. The configuration of the light receiving element 120 is not particularly limited. For example, a thermal sensor, a photodiode, or the like can be used as the light receiving element 120.

[0120] The inspection device according to the present embodiment has the above-mentioned configuration, and can measure the relationship between the supplied current and the laser light output while controlling the temperature of the inspection stage 111, i.e., the temperature of the semiconductor laser element to be inspected, with high precision. This makes it possible to judge the quality of the semiconductor laser element to be inspected with high precision.

[0121] [1-3-2. Inspection process] Next, each step in the method for inspecting the semiconductor laser device 14 according to the present embodiment will be described with reference to Fig. 17. Fig. 17 is a flow chart showing the method for inspecting the semiconductor laser device 14 according to the present embodiment.

[0122] As shown in FIG. 17, first, the characteristics of the semiconductor laser element to be inspected are measured (S10). Specifically, a first inspection current value Ia supplied to the semiconductor laser element to be inspected when the laser light output becomes a first output Pw1 is measured. Here, the first output Pw1 is not particularly limited as long as it is a laser light output that the semiconductor laser element to be inspected can output, but may be, for example, a rated laser light output. In this embodiment, the first output Pw1 is 50 mW. Using the inspection device 200 according to this embodiment, the current flowing through the inspection probe 107 is measured when the laser light output becomes 50 mW while measuring the laser light output of the semiconductor laser element to be inspected using the light receiving element 120.

[0123] Here, an example of the measurement result in this inspection process will be described with reference to FIG. 18. FIG. 18 is a graph showing an example of the measurement result of the first inspection current value Ia in step S10 according to the present embodiment. The horizontal axis of FIG. 18 indicates the current value [mA] supplied to the semiconductor laser element under inspection, and the vertical axis indicates the laser light output [mW] of the semiconductor laser element under inspection. In addition, in the example shown in FIG. 18, a current with a pulse width of 3 μs and a pulse duty ratio of 20% is supplied to the semiconductor laser element under inspection. That is, the current is supplied intermittently. The operating temperature of the semiconductor laser element under inspection is 25° C.±1° C. That is, the temperature of the inspection stage 111 of the inspection device 200 is controlled to 25° C.±1° C. In the example shown in FIG. 18, the first inspection current value Ia is about 56 mA.

[0124] Also, in this process, a second drive current value I2 is measured which is greater than the first drive current value I1 at which the laser light output of the semiconductor laser element under test becomes the maximum value Pmax and at which the laser light output becomes 20% or less of the maximum value Pmax. The operating temperature of the semiconductor laser element under test in measuring the second drive current value I2 is 25°C±3°C. In this embodiment, the operating temperature of the semiconductor laser element under test in measuring the second drive current value I2 is 25°C±1°C.

[0125] Here, an example of the measurement result of the second drive current value I2 will be described with reference to Fig. 5 mentioned above. Fig. 5 is also a graph showing an example of the measurement result of the second drive current value I2 in step S10 according to the present embodiment. The horizontal axis of Fig. 5 indicates the current value [mA] supplied to the semiconductor laser element under test, and the vertical axis indicates the laser light output [mW] of the semiconductor laser element under test.

[0126] In the example shown in Fig. 5, a current having a pulse width of 0.8 μs and a pulse duty ratio of 24% is supplied to the semiconductor laser element to be inspected. In the example shown in Fig. 5, the maximum value Pmax is about 400 mW, and the first drive current value I1 is about 400 mA, so that the second drive current value I2 can be set to 550 mA or more, which results in a laser light output of about 80 mW or less. In this embodiment, the second drive current value I2 is determined for each semiconductor laser element to be inspected based on the characteristics obtained in this process. This makes it possible to supply a current of a current value suitable for each semiconductor laser element to be inspected.

[0127] The effect of using such a pulse current will be described with reference to Fig. 5 and Fig. 19. Fig. 19 is a graph showing the current-laser light output characteristic when a CW current is supplied to the semiconductor laser element to be inspected according to the present embodiment. The graph showing the case where a pulse current is supplied to the semiconductor laser element to be inspected shown in Fig. 5 is compared with the graph showing the case where a CW current is supplied to the semiconductor laser element to be inspected shown in Fig. 19. As shown in Figs. 5 and 19, the laser light output is lower and the supplied current value is also smaller when a CW current is supplied. This is considered to be because the amount of heat generated in the semiconductor laser element to be inspected is greater when a CW current is supplied, and the semiconductor laser element to be inspected is affected by the heat. In this way, when a pulse current is supplied to the semiconductor laser element to be inspected, a higher current value can be determined as the second drive current value I2, so that the semiconductor laser element to be inspected can be inspected with a higher laser light output and current value.

[0128] In addition, in the process of measuring the second drive current value I2 in step S10 at 25° C.±3° C., if the second drive current value I2 is measured at a higher temperature, the laser light output will be lower and the supplied current value will also be smaller, and the second drive current I2 will be determined to be smaller. In this way, when a pulse current is supplied to the semiconductor laser element to be inspected at 25° C.±3° C., a higher current value can be determined as the second drive current value I2, and inspection can be performed at a higher laser light output and current value.

[0129] In this embodiment, the measurement of the second drive current value I2 is performed for each semiconductor laser device to be inspected in this inspection process, but the measurement of the second drive current value I2 does not have to be included in this inspection process. For example, the second drive current value I2 may be measured using a standard sample semiconductor laser device to be inspected, thereby determining the second drive current value I2 in advance before this inspection process.

[0130] In addition to the condition that the laser light output is 20% or less of the maximum value Pmax, the second drive current value I2 may be determined to be a current value at which the laser light output of the semiconductor laser element to be inspected is 100 mW or less. This allows the second drive current value I2 to be made larger, making it possible to select a semiconductor laser element that can further suppress damage. Furthermore, in addition to the above-mentioned condition, the second drive current value I2 may be determined to be a current value at which the laser light output of the semiconductor laser element to be inspected is 50 mW or less, or may be determined to be a current value at which laser oscillation stops. This makes it possible to select a semiconductor laser element that can further suppress damage.

[0131] After step S10 described above, as shown in FIG. 17, a current is passed through the semiconductor laser element to be inspected at the second drive current value I2 described above (S20). In this step, the operating temperature of the semiconductor laser element to be inspected is set to 25° C.±3° C. In this embodiment, a current with a pulse width of 0.1 μs or more and 1 μs or less and a pulse duty ratio of 0.1% or more and 50% or less is passed through. Here, in step S10, a pulse current is supplied at 25° C.±3° C. to determine the second drive current value I2, so that the laser current passed through the semiconductor laser element to be inspected in step S20 can be increased, thereby shortening the time required for inspection.

[0132] In this embodiment, a current having a pulse width of 0.8 μs and a pulse duty ratio of 24% is supplied to the semiconductor laser element to be inspected at an operating temperature of 25° C.±1° C. for a current-on time of 8 seconds. The current-on time preferably does not exceed 20 seconds, for example. Here, the current-on time includes not only the period during which a pulsed current actually flows through the semiconductor laser element to be inspected, but also the current-supply pause period between pulses (i.e., the period during which no current flows through the semiconductor laser element to be inspected). The current-on process may be performed at a higher operating temperature. For example, the current-on process may be performed at an operating temperature of about 100° C. This increases the junction temperature of the semiconductor laser element to be inspected during current-on and applies a high load, thereby further shortening the current-on time. Furthermore, the current-on time is preferably 5 seconds or more and less than 20 seconds. By setting the current-on time to 5 seconds or more, a semiconductor laser element that can further suppress destruction can be selected.

[0133] After the above-mentioned step S20, the characteristics of the semiconductor laser device under test are measured again (S30) in the same manner as in the above-mentioned step S10. Here, the second inspection current value Ib supplied to the semiconductor laser device under test when the laser light output becomes the above-mentioned first output Pw1 is measured.

[0134] Next, the characteristics of the semiconductor laser device to be inspected acquired in step S10 are compared with the characteristics of the semiconductor laser device to be inspected acquired in step S30 to determine whether the semiconductor laser device to be inspected is good or bad (S40).

[0135] Here, an example of judgment in this step will be described with reference to Figs. 20 and 21. Figs. 20 and 21 are graphs showing an example of measurement results of the second inspection current value Ib in step S30 according to this embodiment. The horizontal axis of Figs. 20 and 21 indicates the current value [mA] supplied to the semiconductor laser element under test, and the vertical axis indicates the laser light output [mW] of the semiconductor laser element under test. In the example shown in Figs. 20 and 21, a current with a pulse width of 3 μs and a pulse duty ratio of 20% is supplied to the semiconductor laser element under test, similarly to the example shown in Fig. 18. The operating temperature of the semiconductor laser element under test is 25°C±1°C.

[0136] 20, the second inspection current value Ib supplied to the semiconductor laser device to be inspected when the first output Pw1 (50 mW) is reached is about 56 mA, similar to the first inspection current value Ia. In this way, even when the current is passed in step S20, the semiconductor laser device to be inspected that does not experience any change in characteristics is determined to be a non-defective product.

[0137] On the other hand, in the example shown in Fig. 21, the second inspection current value Ib is greater than 80 mA. In other words, it is presumed that the energization in step S20 destroys the inspected semiconductor laser element, causing a change in the characteristics of the inspected semiconductor laser element. In this way, the inspected semiconductor laser element whose characteristics have changed due to the energization in step S20 is determined to be a defective product.

[0138] In this embodiment, if (Ib-Ia) / Ib≦0.1 is satisfied between the first inspection current value Ia and the second inspection current value Ib, the inspected semiconductor laser element is judged to be a pass / fail product, and otherwise the inspected semiconductor laser element is judged to be a defective product.

[0139] By the inspection method as described above, it is possible to select a semiconductor laser element having a current-laser light output characteristic in which the laser light output is a maximum value Pmax at a first drive current value I1 at an operating temperature of 25°C±3°C, and the laser light output is 20% or less of the maximum value Pmax at a second drive current value I2 greater than the first drive current value I1, and which is not destroyed at the second drive current value I2. Here, it is considered that the destruction of the semiconductor laser element when energized at the second drive current value I2 occurs mainly due to defects present inside the laser element. Therefore, by the inspection method according to the present embodiment, it is possible to select a semiconductor laser element that has no defects inside the laser element and does not deteriorate. The maximum value Pmax of the laser light output of the semiconductor laser element may be 200 mW or more. This makes it possible to realize a semiconductor laser element with a high output. Also, the maximum value Pmax of the laser light output of the semiconductor laser element may be 300 mW or more. This makes it possible to realize a semiconductor laser element with an even higher output.

[0140] The inspection method according to the present embodiment is not limited to the above-mentioned configuration. For example, in steps S10 and S30, instead of measuring the first inspection current value Ia and the second inspection current value Ib supplied to the semiconductor laser device to be inspected when the first output Pw1 is obtained, the maximum value Pmax of the laser light output may be measured. Regarding such a measurement example, FIG. 22A is a graph showing the current-laser light output characteristic of the semiconductor laser device to be inspected according to the present embodiment. FIG. 22B is a partially enlarged view of the graph of FIG. 22A. FIG. 22B is an enlarged view of the dashed frame in FIG. 22A. The solid lines in FIG. 22A and FIG. 22B show the first measurement result, and the dashed lines show the second measurement result.

[0141] 22A and 22B, a first measurement of the current-laser light output characteristics may be performed in step S10, and after energization in step S20, a second measurement of the current-laser light output characteristics may be performed in step S30. If the laser light output reaches a maximum value Pmax at the first drive current value I1 in the first measurement, and if the laser light output during the second drive at the first drive current value I1 after drive at the second drive current value I2 in step S20 is 95% or more of the maximum value Pmax, the inspected semiconductor laser element may be determined to be a non-defective product.

[0142] Also, if the laser light output during the second drive at the first drive current value I1 is more than twice the absolute maximum rated light output, the inspected semiconductor laser element may be determined to be a non-defective product. Note that the absolute maximum rated light output here means the maximum light output allowed for normal use of each semiconductor laser element.

[0143] These inspection methods also make it possible to select semiconductor laser elements that are free from internal degradation.

[0144] Also, in steps S10 and S30, instead of measuring the first inspection current value Ia and the second inspection current value Ib supplied to the semiconductor laser element to be inspected when the first output Pw1 is obtained, the laser light output when the current value supplied to the semiconductor laser element to be inspected is the third inspection current value I3 may be measured. Specifically, in step S10, when the current value supplied to the semiconductor laser element to be inspected is the third inspection current value I3, the laser light output is the second output Pw2. Also, in step S30, when the current value supplied to the semiconductor laser element to be inspected is the third inspection current value I3, the laser light output is the third output P3. Here, in step S40, the semiconductor laser element to be inspected may be determined to be a non-defective product when the third output P3 is 93% or more of the second output Pw2.

[0145] This inspection method also makes it possible to select semiconductor laser elements that are free from internal degradation.

[0146] (Embodiment 2) A semiconductor laser device according to embodiment 2 will be described. The semiconductor laser device according to this embodiment differs from the semiconductor laser device 14 according to embodiment 1 mainly in the configuration of the active layer 40. The semiconductor laser device according to this embodiment will be described below, focusing on the differences from the semiconductor laser device 14 according to embodiment 1.

[0147] In the semiconductor laser device according to the present embodiment, the active layer 40 is made of In x Ga 1-x The well layer includes GaAs (0.01≦x≦0.1). In order to realize an oscillation wavelength of 830 nm using such a well layer, the well layer needs to be relatively thick. That is, the thickness of the GaAs-based material, in which the diffusion rate of the impurity Zn for forming the window region is slow, increases. Therefore, the time required to form the window region 80 having the desired energy band gap increases. Accordingly, the concentration of Zn diffusing into the active layer 40 increases, and the optical loss in the active layer 40 increases. Therefore, in this embodiment as well, as in the first embodiment, the effect of using AlGaInP, in which the diffusion rate of Zn is high, for each optical guide layer is large.

[0148] An example of the configuration of each layer of the semiconductor layer 100 according to this embodiment will be described below.

[0149] In this embodiment, as shown in Fig. 2, the first semiconductor layer 30 includes an n-type buffer layer 31, an n-type cladding layer 32, and an n-side light guide layer 33. The n-type buffer layer 31 is an n-GaAs layer having a thickness of 0.4 µm. The n-type cladding layer 32 is an n-(Al 0.17 Ga 0.83 ) 0.5 In 0.5 The n-side optical guide layer 33 is a GaP layer having a thickness of 0.09 μm. 0.5 In 0.5 It's P.

[0150] The active layer 40 is formed by a 0.024 μm thick Al 0.59 Ga 0.41 As barrier layer and 0.0055μm thick In0.03 Ga 0.97 As well layer and Al layer with a thickness of 0.004 μm 0.59 Ga 0.41 As barrier layer and 0.0055μm thick In 0.03 Ga 0.97 As well layer and Al layer with a thickness of 0.021 μm 0.59 Ga 0.41 and an As barrier layer.

[0151] The second semiconductor layer 50 includes a p-side optical guide layer 51, a p-type first cladding layer 52, a p-type second cladding layer 53, a p-type third cladding layer 54, a p-type intermediate layer 55, and a p-type contact layer 56. The p-side optical guide layer 51 is a Ga 0.5 In 0.5 The p-type first cladding layer 52 is a p-(Al 0.30 Ga 0.70 ) 0.5 In 0.5 The p-type second cladding layer 53 is a p-(Al 0.60 Ga 0.40 ) 0.5 In 0.5 The p-type third cladding layer 54 is a p-(Al 0.30 Ga 0.70 ) 0.5 In 0.5 The p-type intermediate layer 55 is a p-(Al 0.1 Ga 0.9 ) 0.5 In 0.5 The Al composition of the p-type intermediate layer 55 is lower than that of the p-type third cladding layer 54. The p-type contact layer 56 is a p-GaAs layer having a thickness of 0.23 μm.

[0152] The semiconductor laser device having the above-mentioned configuration can also provide the same effects as those of the semiconductor laser device 14 according to the first embodiment.

[0153] (Embodiment 3) A semiconductor laser device according to embodiment 3 will be described. The semiconductor laser device according to this embodiment differs from the semiconductor laser device 14 according to embodiment 1 mainly in the configuration of the active layer 40. The semiconductor laser device according to this embodiment will be described below, focusing on the differences from the semiconductor laser device 14 according to embodiment 1.

[0154] In the semiconductor laser devices according to the first and second embodiments, the oscillation mode is the TE mode, but in the semiconductor laser device according to this embodiment, the oscillation mode is the TM mode. Therefore, it is necessary to increase the thickness of the well layer in the active layer 40. Accordingly, the thickness of the GaAs-based material in which the diffusion speed of the impurity Zn for forming the window region is slow increases. Therefore, the time required to form the window region 80 having the desired energy band gap increases. Accordingly, the concentration of Zn diffusing into the active layer 40 increases, and the optical loss in the active layer 40 increases. Therefore, in this embodiment, as in the first embodiment, the effect of using AlGaInP, in which the diffusion speed of Zn is high, for each optical guide layer is large.

[0155] An example of the configuration of each layer of the semiconductor layer 100 according to this embodiment will be described below.

[0156] In this embodiment, as shown in Fig. 2, the first semiconductor layer 30 includes an n-type buffer layer 31, an n-type cladding layer 32, and an n-side light guide layer 33. The n-type buffer layer 31 is an n-GaAs layer having a thickness of 0.4 µm. The n-type cladding layer 32 is an n-(Al 0.19 Ga 0.81 ) 0.5 In 0.5 The n-side optical guide layer 33 is a GaP layer having a thickness of 0.09 μm. 0.5 In 0.5 It's P.

[0157] The active layer 40 includes a GaAsP well layer having tensile strain, and is provided with an Al 0.59 Ga 0.41 As barrier layer and GaAs with a thickness of 0.0065 μm0.84 P 0.16 Well layer and Al with a thickness of 0.008 μm 0.59 Ga 0.41 As barrier layer and GaAs with a thickness of 0.0065 μm 0.84 P 0.16 Well layer and Al with a thickness of 0.008 μm 0.59 Ga 0.41 As barrier layer and GaAs with a thickness of 0.0065 μm 0.84 P 0.16 Well layer and Al with a thickness of 0.021 μm 0.59 Ga 0.41 The active layer 40 is a multiple quantum well active layer including an As barrier layer. By applying tensile strain to the active layer 40 in this manner, a semiconductor laser device that oscillates in the TM mode can be fabricated.

[0158] The second semiconductor layer 50 includes a p-side optical guide layer 51, a p-type first cladding layer 52, a p-type second cladding layer 53, a p-type third cladding layer 54, a p-type intermediate layer 55, and a p-type contact layer 56. The p-side optical guide layer 51 is a Ga 0.5 In 0.5 The p-type first cladding layer 52 is a p-(Al 0.30 Ga 0.70 ) 0.5 In 0.5 The p-type second cladding layer 53 is a p-(Al 0.60 Ga 0.40 ) 0.5 In 0.5 The p-type third cladding layer 54 is a p-(Al 0.30 Ga 0.70 ) 0.5 In 0.5 The p-type intermediate layer 55 is a p-(Al 0.1 Ga 0.9 ) 0.5 In 0.5 The Al composition of the p-type intermediate layer 55 is lower than that of the p-type third cladding layer 54. The p-type contact layer 56 is a p-GaAs layer having a thickness of 0.23 μm.

[0159] The semiconductor laser device having the above-mentioned configuration can also provide the same effects as those of the semiconductor laser device 14 according to the first embodiment.

[0160] (Variations, etc.) Although the semiconductor laser element and the like according to the present disclosure have been described based on the embodiments, the present disclosure is not limited to the above-described embodiments.

[0161] For example, the present disclosure also includes forms obtained by applying various modifications to the embodiments that a person skilled in the art may conceive, and forms realized by arbitrarily combining the components and functions of each embodiment within the scope that does not deviate from the spirit of the present disclosure.

[0162] For example, the inspection method according to the above embodiment can be applied to a semiconductor laser element to be inspected in any mounting state. For example, when the semiconductor laser element to be inspected is in a state as shown in FIG. 14, or in a standalone state not mounted on the submount 104, the above inspection method can be performed using the inspection device 200. Also, when the semiconductor laser element to be inspected is in a state other than those, for example, in a CAN package state in which the submount 104 is mounted on a stem, or in a frame package state, the above inspection method can be applied by configuring an inspection device suited to those states.

[0163] In addition, in the semiconductor laser devices according to the above-described embodiments and their modified examples, the waveguide is formed using a ridge structure, but the means for forming the waveguide is not limited to this, and a buried type structure or the like may also be used. [Industrial Applicability]

[0164] The semiconductor laser device and the like according to the present disclosure can be particularly used in light sources and the like that require high reliability. [Explanation of symbols]

[0165] 14 Semiconductor laser element 20 Substrate 24 Chip-shaped substrate 30 First semiconductor layer 31 n-type buffer layer 32 n-type cladding layer 33 n-side optical guide layer 40 Active layer 40a Bottom of active layer 40b Top of active layer 50 Second semiconductor layer 51 p-side optical guide layer 52 p-type first cladding layer 53 p-type second cladding layer 54 p-type third cladding layer 55 p-type intermediate layer 56 p-type contact layer 80 Window Area 80a Zn diffusion end 100 Semiconductor layer 102 Light emitting part 104 Submount 105 Electrode 106 Semiconductor laser device 107 Inspection probe 108 Metal Stage 109 Temperature measuring element 110 Temperature control element 111 Inspection Stage 120 Photodetector 121 Cleavage end face 131 First protective film 132F, 132R Second protective film 151 p side lower electrode 152 p side upper electrode 160 n-side electrode 200 Inspection Equipment Dz Distance P1 First Side P2 Second Side TR groove WG waveguide

Claims

1. A semiconductor laser element, A semiconductor layer; a substrate on which the semiconductor layer is stacked and which contains GaAs; The semiconductor layer is a waveguide formed in an in-layer direction of the semiconductor layer; a window region formed on at least a front end surface of the waveguide; the semiconductor layer has an n-type cladding layer including n-type AlGaInP, an n-side optical guide layer, an active layer having a quantum well structure, a p-side optical guide layer, and a p-type cladding layer including p-type AlGaInP, which are successively formed on the substrate; the quantum well structure is sandwiched between the p-side optical guide layer and the n-side optical guide layer, and is formed of a plurality of well layers including GaAs, InGaAs, or GaAsP, and a plurality of barrier layers including AlGaAs; The p-side optical guide layer and the n-side optical guide layer are made of Al ｙ G ｚ In （１－ｙ－ｚ） P(0≦y≦0.1, 0≦z≦0.9, 0.3≦y+z≦0.7), the window region includes a window region forming impurity, The impurity for forming the window region is diffused in the window region at least from an upper end of the active layer, which is a boundary between the p-side light guide layer and the active layer, to a lower end of the active layer, which is a boundary between the n-side light guide layer and the active layer. Semiconductor laser element.

2. The boundary between the n-side optical guide layer and the active layer is a lower end of the active layer, and the window region is The distance to the diffusion end of the window region forming impurity on the substrate side is 0.5 μm or more.

2. The semiconductor laser device according to claim 1.

3. A semiconductor laser element, A semiconductor layer; a substrate on which the semiconductor layer is stacked and which contains GaAs; The semiconductor layer is a waveguide formed in an in-layer direction of the semiconductor layer; a window region formed on at least a front end surface of the waveguide, the semiconductor layer has an n-type cladding layer including n-type AlGaInP, an n-side optical guide layer, an active layer having a quantum well structure, a p-side optical guide layer, and a p-type cladding layer including p-type AlGaInP, which are successively formed on the substrate; the quantum well structure is sandwiched between the p-side optical guide layer and the n-side optical guide layer, and is formed of a plurality of well layers including GaAs, InGaAs, or GaAsP, and a plurality of barrier layers including AlGaAs; The p-side optical guide layer and the n-side optical guide layer are made of Al ｙ G ｚ In （１－ｙ－ｚ） P(0≦y≦0.1, 0≦z≦0.9, 0.3≦y+z≦0.7), the window region includes a window region forming impurity, The boundary between the n-side optical guide layer and the active layer is a lower end of the active layer, and the window region is The distance to the diffusion end of the window region forming impurity on the substrate side is 0.5 μm or more. Semiconductor laser element.

4. The cavity length of the semiconductor laser element is 300 μm or less.

4. The semiconductor laser device according to claim 1,

5. The oscillation wavelength of the semiconductor laser element is 780 nm or more and 860 nm or less.

5. The semiconductor laser device according to claim 1.

6. The lower end of the window region is located in the n-type cladding layer.

6. The semiconductor laser device according to claim 1,

7. The window region includes a region in which a part of the quantum well structure is disordered.

7. The semiconductor laser device according to claim 1.

8. The difference between the energy band gap in the disordered region and the energy band gap in the remainder of the quantum well structure is 30 meV or more.

8. The semiconductor laser device according to claim 7.

9. The peak wavelength of the spectrum obtained by the photoluminescence method or the cathodoluminescence method from the window region is shorter than the oscillation wavelength of the semiconductor laser element by 30 nm or more.

9. The semiconductor laser device according to claim 1.

10. The peak concentration of the impurity for forming the window region in the portion of the active layer located in the window region is 7×10 １８ / cm ３ Above 1 x 10 １９ / cm ３ is less than or equal to 10. The semiconductor laser device according to claim 1.

11. The average window region forming impurity concentration of the portion of the p-type cladding layer located in the window region is 6 times or less than the average window region forming impurity concentration of the portion of the p-type cladding layer other than the window region.

11. The semiconductor laser device according to claim 1.

12. The length of the window region formed on the front end face of the waveguide in the longitudinal direction of the waveguide is greater than the length of the window region formed on the rear end face of the waveguide in the longitudinal direction of the waveguide.

12. The semiconductor laser device according to claim 1.

13. The semiconductor layer includes a p-type contact layer disposed above the p-type cladding layer.

13. The semiconductor laser device according to claim 1.

14. The semiconductor layer includes a p-type intermediate layer disposed between the p-type cladding layer and the p-type contact layer. The semiconductor laser device according to claim 13.

15. The p-type cladding layer includes a plurality of layers having different compositions.

15. The semiconductor laser device according to claim 1.

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