Semiconductor laser element

Abstract

The invention provides a semiconductor laser element with improved service life. This semiconductor laser element is provided with: a first semiconductor layer which is a group III-V compound semiconductor layer containing at least As as a group V element; a second semiconductor layer on the first conductive side, which is a group III-V compound semiconductor layer containing at least P as a group V element, and which is disposed on the first semiconductor layer; a second conductive-side third semiconductor layer disposed on the second semiconductor layer; an active layer disposed between the second semiconductor layer and the third semiconductor layer; a window structure formed across the third semiconductor layer, the active layer, the second semiconductor layer, and the first semiconductor layer; a defect layer having a group III element of the first semiconductor layer and a group III element of the second semiconductor layer between the first semiconductor layer and the second semiconductor layer and including a defect in a region formed in the window structure; and an end surface that includes a defect layer that does not overlap the near-field pattern of the laser light on the end surface, or that overlaps only at the edge of the near-field pattern on the end surface, and that emits the laser light.

Description

Technical Field

[0001] This disclosure relates to semiconductor laser devices. Background Technology

[0002] Semiconductor laser elements that emit red or infrared lasers sometimes have a window structure formed at the laser emission end face to improve their resistance to COD (Catastrophic Optical Damage). A semiconductor laser element with a window structure is disclosed in Patent Document 1.

[0003] Patent Document 1: Japanese Patent Application Publication No. 2024-010144

[0004] Even with a windowed structure, semiconductor laser elements can sometimes experience sudden malfunctions due to COD generated during the element's operation. Summary of the Invention

[0005] The purpose of this disclosure is to provide a semiconductor laser element that reduces sudden failures caused by COD.

[0006] The semiconductor laser element of the present disclosure has the following features:

[0007] The first semiconductor layer is a III-V compound semiconductor layer containing at least As as a group V element;

[0008] The second semiconductor layer on the first conductive side, which is disposed on the first semiconductor layer, is a III-V compound semiconductor layer containing at least P of a group V element.

[0009] A third semiconductor layer on the second conductive side is disposed on the second semiconductor layer;

[0010] An active layer is disposed between the second semiconductor layer and the third semiconductor layer;

[0011] A window structure is formed covering the third semiconductor layer, the active layer, the second semiconductor layer, and the first semiconductor layer;

[0012] A defect layer, which in the region where the window structure is formed, has a group III element of the first semiconductor layer and a group III element of the second semiconductor layer between the first semiconductor layer and the second semiconductor layer and contains defects;

[0013] An end face, which includes the defect layer, emits laser light, wherein,

[0014] The defect layer does not overlap with the near-field pattern of the laser on the end face, or overlaps only at the edge of the near-field pattern on the end face.

[0015] The semiconductor laser element of this disclosure embodiment has:

[0016] The first semiconductor layer is a III-V compound semiconductor layer containing at least As as a group V element;

[0017] The second semiconductor layer on the first conductive side, which is disposed on the first semiconductor layer, is a III-V compound semiconductor layer containing at least P of a group V element.

[0018] A third semiconductor layer on the second conductive side is disposed on the second semiconductor layer;

[0019] An active layer is disposed between the second semiconductor layer and the third semiconductor layer;

[0020] A window structure is formed covering the third semiconductor layer, the active layer, the second semiconductor layer, and the first semiconductor layer;

[0021] A defect layer, which in the region where the window structure is formed, has a group III element of the first semiconductor layer and a group III element of the second semiconductor layer between the first semiconductor layer and the second semiconductor layer and contains defects;

[0022] An end face, which includes the defect layer, emits laser light, wherein,

[0023] In the far-field pattern of the laser emitted from the semiconductor laser element, when the value of the extension angle from the first semiconductor layer toward the active layer is set as x (°) and the value of the thickness of the second semiconductor layer is set as y (μm), the following equation (1) is satisfied.

[0024] y≥2.31×10 -5 x 2 -5.37×10 -2 x+4.44...(1)

[0025] Invention Effects

[0026] According to one aspect of this disclosure, it is possible to provide a semiconductor laser element with improved lifespan. Attached Figure Description

[0027] Figure 1 This is a cross-sectional view of the semiconductor laser element according to Embodiment 1.

[0028] Figure 2 This is an enlarged view of the area near the interface between the first semiconductor layer and the second semiconductor layer in the window structure of the semiconductor laser element according to Embodiment 1.

[0029] Figure 3This is a STEM image representing an example of the area near a defect layer.

[0030] Figure 4 This is a cross-sectional view of the semiconductor laser element according to Embodiment 2.

[0031] Figure 5 This is an enlarged view of the area near the interface between the first semiconductor layer and the second semiconductor layer in the window structure of the semiconductor laser element in Embodiment 2.

[0032] Figure 6 This is a cross-sectional view of a semiconductor laser element according to a modified example of Embodiment 2.

[0033] Figure 7 This is a cross-sectional view of the semiconductor laser element according to Embodiment 3.

[0034] Figure 8 This is a graph showing the failure rate of the semiconductor laser element in Embodiment 1 and Embodiment 2.

[0035] Figure 9 This is a graph representing the failure rate of the semiconductor laser element in Comparative Example 1.

[0036] Figure 10 It is a graph showing the relationship between the thickness of the defect layer and FFPy.

[0037] Explanation of reference numerals in the attached figures

[0038] 1: First semiconductor layer

[0039] 11: Substrate

[0040] 15: First bandgap easing layer (first BDR layer)

[0041] 2: Second semiconductor layer

[0042] 21: n-side coating layer

[0043] 22: n-side optical guide layer

[0044] 25: Second band discontinuity mitigation layer (second BDR layer)

[0045] 3: Third semiconductor layer

[0046] 31: p-side coating layer

[0047] 32: p-side optical guide layer

[0048] 4: Active layer

[0049] 5: Fourth semiconductor layer

[0050] 6: Window Structure

[0051] 7: Defect layer

[0052] 8: High-reflectivity coating

[0053] 9: Anti-reflective coating

[0054] 100, 200, 300, 400: Semiconductor laser elements

[0055] E1, E2: End face

[0056] G: Diffraction grating

[0057] PS: Phase shift structure Detailed Implementation

[0058] The embodiments of the present invention will now be described in detail. However, the embodiments shown below exemplify semiconductor laser elements for embodying the technical concept of the present invention, and the present invention is not limited to the semiconductor laser elements shown below.

[0059] In this specification, the stacking direction of the semiconductor layers is referred to as the thickness direction. Additionally, the optical axis direction of the optical waveguide is referred to as the longitudinal direction. The direction perpendicular to both the thickness direction and the longitudinal direction is referred to as the transverse direction.

[0060] (Implementation Method 1)

[0061] <Semiconductor Laser Components 100>

[0062] First, use Figure 1 and Figure 2 The semiconductor laser element 100 of Embodiment 1 is described below. The semiconductor laser element 100 of this disclosure includes: a first semiconductor layer 1 comprising a group III-V material (As); a second semiconductor layer 2 disposed on the first semiconductor layer 1 with a first conductive side comprising a group III-V material (P); a third semiconductor layer 3 disposed on the second conductive side of the second semiconductor layer 2; an active layer 4 disposed between the second semiconductor layer 2 and the third semiconductor layer 3; and a window structure 6 disposed throughout the third semiconductor layer 3, the active layer 4, the second semiconductor layer 2, and the first semiconductor layer 1. In the region where the window structure 6 is formed, the semiconductor laser element 100 of this disclosure has a defect layer 7 and an end face E1 between the first semiconductor layer 1 and the second semiconductor layer 2. The defect layer 7 comprises a group III material of the first semiconductor layer 1 and a group III material of the second semiconductor layer 2 and contains defects. The end face E1 contains the defect layer 7 and emits laser light. The defect layer 7 does not overlap with the near-field pattern of the laser light at the end face E1, or overlaps only at the edge of the near-field pattern at the end face E1.

[0063] This enables the provision of semiconductor laser elements with improved lifespan.

[0064] Semiconductors used in semiconductor laser elements that emit red or infrared lasers include III-V compound semiconductors with group V elements As or P. Lattice matching in III-V compound semiconductors with group V elements As and P can be achieved by adjusting the composition ratio of group III elements. For example, AlGaInP, with an In composition ratio of approximately 0.5, exhibits lattice matching. However, when impurities diffuse to form the window structure 6, interdiffusion of In (indium), Al (aluminum), and Ga (gallium) also occurs between As (arsenic) and P (phosphorus) compound semiconductors. As a result, the composition ratio of group III elements near the interface of the As and P compounds that are lattice-matched with GaAs changes, resulting in lattice mismatch with GaAs exceeding the critical film thickness, thus creating crystal defects. These defects gain laser energy through overlap with the laser beam and extend towards the active layer 4 during driving. As the defect extends, the overlap ratio with the laser beam also increases, making it easier to absorb the laser. It is believed that the defect generates heat due to laser absorption, producing COD (Chemical Oxygen Demand).

[0065] Therefore, minimizing the overlap between defects and the laser helps improve the COD level, resulting in semiconductor laser elements with reduced sudden failures caused by COD.

[0066] use Figure 1 and Figure 2 The structure of the semiconductor laser element 100 will be described. Figure 1 This is a cross-sectional view of the semiconductor laser element 100 according to Embodiment 1. Figure 1 It is a cross-sectional view along the direction of the resonator (i.e., longitudinal direction). Figure 2 This is an enlarged view of the area near the interface between the first semiconductor layer 1 and the second semiconductor layer 2 in the window structure 6 of the semiconductor laser element 100 of Embodiment 1.

[0067] (First semiconductor layer 1)

[0068] The first semiconductor layer 1 comprises one or more As-containing group III-V semiconductor layers. The first semiconductor layer 1 may be, for example, GaAs, AlGaAs, InGaAs, AlInAs, or AlGaInAs. As is not an impurity but is part of the composition of the semiconductor layers constituting the first semiconductor layer 1. The first semiconductor layer 1 may be a semiconductor layer having a first conductive side having one or more layers containing impurities of a first conductivity type. The first conductivity type may be n-type. Impurities of the first conductivity type may be, for example, Si (silicon), C (carbon), Ge (germanium), Sn (tin), or Te (tellurium). The thickness of the first semiconductor layer 1 may be, for example, 0.01 μm or more and 0.1 μm or less.

[0069] (Second semiconductor layer 2)

[0070] The second semiconductor layer 2 is a group III-V semiconductor layer containing phosphorus (P) formed on the first semiconductor layer 1. The second semiconductor layer 2 is a semiconductor layer having a first conductive side of one or more layers containing impurities of a first conductivity type. The impurities of the first conductivity type can be, for example, Si, C, Ge, Sn, or Te. The second semiconductor layer 2 can be, for example, InGaP, AlGaInP, or AlInP. P is not an impurity but is part of the composition of the semiconductor layer constituting the second semiconductor layer 2.

[0071] The second semiconductor layer 2 includes at least a cladding layer that encapsulates light into the active layer 4. The thickness of the second semiconductor layer 2 is, for example, 1 μm or more and 4 μm or less. As a result, the active layer 4 can be moved away from the defect layer 7, thereby reducing the overlap between the near-field pattern at the end face E1 of the emitted laser and the defect layer 7.

[0072] (Third semiconductor layer 3)

[0073] The third semiconductor layer 3 is a semiconductor layer disposed above the second semiconductor layer 2. The third semiconductor layer 3 is a semiconductor layer having a second conductive side of one or more layers containing impurities of a second conductivity type different from the first conductivity type. The impurities of the second conductivity type can be, for example, Mg (magnesium), Zn (zinc), or C. The third semiconductor layer 3 is, for example, a III-V group semiconductor containing P or As. The third semiconductor layer 3 can be, for example, GaP, InGaP, AlInP, or AlGaInP.

[0074] The third semiconductor layer 3 includes at least a cladding layer that encapsulates light into the active layer 4. The thickness of the third semiconductor layer 3 is, for example, 0.5 μm or more and 2 μm or less.

[0075] (Active layer 4)

[0076] An active layer 4 is disposed between the second semiconductor layer 2 and the third semiconductor layer 3. The active layer 4 has a quantum well structure, which can be a single quantum well structure with one well layer and multiple barrier layers, or a multi-quantum well structure with multiple well layers and multiple barrier layers. The well layers can be, for example, InGaP, AlGaInP, InGaAsP, AlGaInAsP, or AlInAsP. The barrier layers can also be, for example, InGaP, AlGaInP, InGaAsP, AlGaInAsP, or AlInAsP. Furthermore, the semiconductor laser element can have one or more light-emitting points. In the case of multiple light-emitting points, light of the same color is emitted from each light-emitting point. That is, the semiconductor laser element emits only red light or only infrared light.

[0077] (Window construction 6)

[0078] The window structure 6 is disposed over the third semiconductor layer 3, the active layer 4, the second semiconductor layer 2, and the first semiconductor layer 1. The window structure 6 is disposed on the end face E1 and the region near the end face E1. The window structure 6 has a bandgap energy greater than the energy corresponding to the wavelength of the laser emitted from the end face E1. The window structure 6 is formed, for example, by diffusion of Zn or interdiffusion of group III elements via holes.

[0079] (Defect layer 7)

[0080] The defect layer 7 contains defects. The defect layer 7 is formed within the window structure 6 and disposed between the first semiconductor layer 1 and the second semiconductor layer 2. The defect layer 7 contains group III materials of the first semiconductor layer 1 and the second semiconductor layer 2. The origin of the defect is the interface between the first semiconductor layer 1 and the second semiconductor layer 2. The defect layer 7 can be formed due to the formation of the window structure 6. That is, it is believed that during the formation of the window structure 6, defects may occur due to the interdiffusion of group III elements contained in the first semiconductor layer 1 and the second semiconductor layer 2. Typically, semiconductor layers containing As and P can achieve lattice matching by setting the In composition ratio to approximately 0.5, resulting in almost no defects. However, in the semiconductor laser element 100 of Embodiment 1, during the formation of the window structure 6, elements such as Zn or group III elements interdiffusion via holes occur. At this time, Ga, Al, and In also diffuse, changing the composition of the first semiconductor layer 1 and the second semiconductor layer 2, resulting in a lattice mismatch. In a state of lattice mismatch, strain caused by the difference in lattice constants generates defects at the interface between the first semiconductor layer 1 and the second semiconductor layer 2. These defects include at least line defects (i.e., dislocations).

[0081] The defect layer 7 is, for example, a layer comprising Ga, Al, and In. The thickness of the defect layer can be, for example, 0.01 μm or more and 1.5 μm or less. The thickness of the defect layer is measured in the direction from the interface between the first semiconductor layer 1 and the second semiconductor layer 2 toward the active layer. Figure 1In the cross-sectional observation shown, the defects contained in the defect layer extend from the interface between the first semiconductor layer 1 and the second semiconductor layer 2 toward the active layer. The defects can be observed using a scanning transmission electron microscope (STEM). In this specification, the thickness of the defect layer 7 corresponds to the distance between the position of the closest point to the active layer among the defect tips within the defect layer 7 and the interface between the first semiconductor layer 1 and the second semiconductor layer 2. As a specific method for measuring the thickness of the defect layer 7, a STEM image of the region containing the defect layer is obtained. A measurement region is selected from the obtained STEM image, and within this measurement region, the defect extending from the interface between the first semiconductor layer 1 and the second semiconductor layer 2 that extends closest to the active layer 4 is identified. This defect is referred to as the measurement target defect. The distance between the tip of the measurement target defect and the interface is defined as the thickness of the defect layer 7. STEM images are taken at a magnification of 10,000 to 60,000x, with the interface substantially horizontal. The measurement region is selected to include the measurement target defect, and its horizontal dimension is, for example, set to 3 μm.

[0082] Figure 3 This is a bright-field image of a STEM image representing an example near defect layer 7. From Figure 3 It can be seen that the defect extends towards the active layer 4 from the interface between the first semiconductor layer 1 and the second semiconductor layer 2, i.e., the interface between the As-based III-V semiconductor and the P-based III-V semiconductor. In this example, the thickness h of the defect layer is approximately 0.6 μm.

[0083] The defect layer 7 is formed by forming the window structure 6 as described above. Therefore, if there is no diffusion of Zn or interdiffusion of Group III elements via holes up to the vicinity of the interface between the first semiconductor layer 1 and the second semiconductor layer 2, the lattice matching of these layers is maintained, and thus the defect layer 7 is not generated. However, in this embodiment, the semiconductor laser element has a defect layer 7 formed along with the formation of the window structure 6. This is to improve the COD level by allowing Zn to diffuse or allowing Group III elements to interdiffusion via holes to reach the area including the vicinity of the aforementioned interface. Furthermore, as described later, the near-field pattern can be expanded while the far-field pattern can be reduced.

[0084] (Near-field pattern)

[0085] The near-field pattern (NFP) reflects the shape of the laser propagating in the optical waveguide. Within the waveguide, the core is sandwiched between cladding layers, thus most of the laser is encapsulated within the core. However, in the portion with window structure 6, the encapsulation of the laser is weaker. The NFP is larger in the portion with window structure 6 compared to the waveguide without it. In particular, the NFP is largest at the end face E1.

[0086] In the semiconductor laser element 100 of Embodiment 1, the defect layer 7 does not overlap with the near-field pattern of the laser at the end face E1, or overlaps only at the edge of the NFP at the end face E1. Therefore, the defect has difficulty receiving laser light energy. Consequently, the defect is less likely to extend toward the active layer 4, and the COD level of the semiconductor laser element 100 is improved. Furthermore, to confirm the overlap between the NFP and the defect layer 7, in Figure 1 In a cross-sectional view of the region containing the core of the optical waveguide shown, the edge can be determined based on the line profile shape in the thickness direction of the NFP.

[0087] In this specification, the edge of an NFP refers to the region outside the beam point defined by the beam diameter of the NFP. The beam diameter is defined by D4σ. D4σ is the sum of the values ​​of 1 / e when the beam profile is an ideal Gaussian. 2 The defined beam diameter is consistent. Furthermore, it is sufficient to know the overlap between defect layer 7 and the edge of the NFP, and to what extent they overlap; therefore, only the line profile in the thickness direction of the NFP needs to be considered.

[0088] The NFP can be measured without directly observing the shape at end face E1. As described later, after the laser beam exits from end face E1, the NFP changes into a far-field pattern (FFP) due to diffraction. The FFP is related to the Fourier transform of the NFP. Therefore, by performing an inverse Fourier transform on the FFP using a convex lens, the shape of the NFP can be reproduced at a location far from end face E1. The size of the reproduced NFP image is observed, and the distance from the lens to the image and the rear focal length of the lens are known. Therefore, the size of the NFP at end face E1 can be determined using the definition of lateral magnification. Since the size of the semiconductor laser element 100 and the position of the defect layer 7 on end face E1 are also known, it is possible to evaluate whether and to what extent the NFP overlaps with the defect layer 7. For example, an image of the NFP can be obtained using a collimating photometer optical system M-Scope type C manufactured by Synos ​​Corporation.

[0089] The defect layer 7 can overlap only at the edge of the NFP on the end face E1. In this case, the defect layer 7 preferably overlaps with the NFP only within a range where the area of ​​the NFP from the end of the NFP is less than 0.025%. In other words, this allows the defect layer 7 to not overlap with the NFP within a range of 49.975% (=50-0.025%) of the area from the center of the NFP, and the defect layer 7 to overlap with the NFP on the outer side of the central region. The area of ​​the NFP is a proportion when the area estimated according to the line profile in the thickness direction of the NFP is set to 100%. The end of the NFP represents the location where the value shown by the line profile is substantially zero. At the edge of the NFP, the area of ​​the NFP is relatively small. Therefore, the overlap range between the edge of the NFP and the defect layer 7 becomes smaller, which can improve the COD grade. This evaluation, as described above, can be performed by acquiring an image of the NFP and overlaying it onto the defect layer using a collimated light measurement optics system M-Scope type C.

[0090] (Far field pattern)

[0091] The far-field pattern (FFP) is the diffraction pattern of the NFP. An FFP is typically represented by the lateral spread angle (FFPx) and the thickness spread angle (FFPy). These spread angles are determined based on the half-value full width (in other words, the half-value full angle).

[0092] As mentioned earlier, FFPs are diffraction patterns of NFPs, and they are in a corresponding relationship. When the NFP in the thickness direction is small (i.e., when the light containment is strong), the angle of the FFP in the thickness direction becomes larger. On the other hand, when the NFP in the thickness direction is large (i.e., when the light containment is weak), the angle of the FFP in the thickness direction becomes smaller.

[0093] Light encapsulation in the thickness direction of a semiconductor laser element is achieved through a stacked structure of semiconductor layers, assuming that the single-mode condition is approximately satisfied in the thickness direction. Therefore, the inventors believe that if it is assumed that the FFP can be approximated by a Gaussian, then the FFP can be used instead of the NFP to derive a structure that keeps the defect layer 7 away from the NFP. To verify this assumption, the following experiments and simulations were conducted.

[0094] A windowed semiconductor laser element with multiple n-side cladding layers of 0.9 μm thickness and an FFPy range of approximately 55°–70° was fabricated, and the relationship between failure rate and FFPy was investigated. A tendency for failure rate to decrease was observed as FFPy increased. According to the results, the failure rate decreased significantly when FFPy exceeded approximately 60°. Furthermore, the failure rate decreased with a current density of 3826 A / cm². 2The failure rate is expressed as the number of laser diode elements that suddenly fail within 200 hours when the current is input to the laser diode element ÷ the number of laser diode elements tested × 100 (%). However, under this condition, 200 hours is equivalent to 1000 hours in a normal test. That is, the failure rate measurement is a measurement under accelerated test conditions. In addition, the thickness of the defect layer was measured for these semiconductor laser elements, and the relationship between the failure rate and the thickness was investigated. The results showed that the larger the thickness of the defect layer, the greater the tendency for the failure rate to increase. The threshold thickness of the defect layer at which the failure rate begins to increase is about 0.3 μm. Furthermore, based on these results, a graph was plotted with FFPy (°) as the horizontal axis (i.e., the x-axis) and the thickness of the defect layer (μm) as the vertical axis (i.e., the y-axis). If the results are fitted with a linear function, they can be approximated by y = -0.04x + 2.94. The results are shown in... Figure 10 .

[0095] Assuming the FFP is Gaussian, the NFP of the reproduced FFPy was simulated. In other words, the NFP was simulated based on the measured FFPy. Next, the overlap between the NFP and the defect layer was investigated. If the angle of the FFPy (°), the thickness of the defect layer (μm), and the percentage of light overlapping the defect layer (%) are grouped and represented in brackets, the values ​​are (45.7°, 1.107μm, 67.09%), (49.7°, 0.947μm, 38.54%), (52.3°, 0.843μm, 19.88%), (56.1°, 0.691μm, 4.67%), (58.3%, 0.603μm, 1.62%), (62.9°, 0.419μm, 0.14%), and (66.9°, 0.259μm, 0.01%). The thickness of the defect layer is determined by... Figure 10 The approximation y = -0.04x + 2.94 is obtained. The proportion of light overlapping with the defect layer represents the proportion of the overlapping light with the defect layer relative to the total area of ​​the simulated NFP line profile.

[0096] Three data points with FFPy values ​​of 58.3°, 62.9°, and 66.9° were plotted relative to the thickness of the defect layer and the proportion of light overlapping with the defect layer. The three data points were selected such that they encompassed a presumed threshold of 60° and values ​​before and after it within the range of FFPy they defined. For the plotted data points, an exponential function with Napier's constant e as the base was fitted. y = 4 × 10⁻⁶ -4 ×e 13.865x x (μm) is the thickness of the defect layer, and y (%) is the proportion of light overlapping with the defect layer. If the aforementioned thickness threshold of 0.3 μm is substituted into x in this approximation, it can be estimated that the overlap between the NFP and the defect layer is approximately 0.025%.

[0097] Plot the distance from the center of the NFP to where the area becomes 49.975 (=50-0.025) (%) (in other words, the distance when the overlap between defect layer 7 and NFP becomes 0.025% of NFP). On the NFP, determine the specific location by ensuring that the area of ​​the NFP between the center of the NFP and the specific location becomes 49.975% (=50-0.025) of the total area of ​​the NFP. The specific location also refers to the position of the edge of the overlapping area when the area of ​​the overlapping region between the defect layer and NFP becomes 0.025% of the total area of ​​NFP.

[0098] For each semiconductor laser element, the distance between the center of the NFP and a specific location is measured. The distance is plotted as FFPy (°) on the horizontal axis (x-axis) and the measured distance (μm) on the vertical axis (y-axis). If the obtained curve is approximated using a quadratic function, the approximate formula is y = 2.31 × 10⁻⁶. -5 x 2 -0.0137x+1.5082.

[0099] The two approximations are y = -0.04x + 2.94 and y = 2.31 × 10 -5 x 2 The sum of -0.0137x + 1.5082 refers to the sum of the "thickness of the defect layer" and the "distance between the center of the NFP and a specific location (i.e., the distance between the center of the NFP and the edge of the overlapping region when the area of ​​the overlapping region of the defect layer and the NFP is 0.025% of the total area of ​​the NFP)". Therefore, their sum is an approximation of the thickness of the preferred second semiconductor layer 2, which is expressed as equation (1) below.

[0100] Based on the above research, the following equation (1) is obtained. That is, in the FFP of the laser emitted from the semiconductor laser element 100, when the value of the spread angle (°) in the direction from the first semiconductor layer 1 toward the active layer 4 (i.e., the thickness direction) is set as x, and the value of the thickness (μm) of the second semiconductor layer 2 is set as y, the following equation (1) is preferably satisfied.

[0101] y≥2.31×10 -5 x 2 -5.37×10 -2 x+4.44...(1)

[0102] When the thickness (y) of the second semiconductor layer 2 is equal to the value shown on the right side of Equation (1), the overlap area between the NFP and the defect layer is 0.025%. By making the thickness (y) of the second semiconductor layer 2 greater than the value shown on the right side of Equation (1), the overlap between the NFP and the defect can be reduced. As can be seen from Equation (1), the thickness of the second semiconductor layer 2 is preferably different depending on the spread angle of the FFP in the thickness direction. FFPy (i.e., x in Equation (1)) can be 45° or more and 70° or less, or 50° or more and 60° or less. For example, when x is 50°, y is 1.81 μm or more. In addition, when x is 60°, y is 1.30 μm or more.

[0103] If the thickness of the second semiconductor layer 2 is too large, the resistivity increases, and the forward voltage (Vf) when driving the semiconductor laser element rises. Therefore, the thickness can be appropriately set in a way that prevents Vf from rising excessively. The thickness of the second semiconductor layer 2 can, for example, be 4 μm or less. The thickness of the second semiconductor layer 2 is preferably 2 μm or less. This further reduces the rise in Vf.

[0104] The thickness of the second semiconductor layer 2 can satisfy equation (1) and be 4 μm or less. Specifically, the thickness of the second semiconductor layer 2 can be 1 μm or more and 4 μm or less, preferably 1 μm or more and 2 μm or less. As a result, the overlap between the defect layer 7 and the NFP can be reduced, thereby improving the COD level and obtaining a semiconductor laser element 100 with reduced burst failures caused by COD. Furthermore, the rise in Vf when driving the semiconductor laser element can be reduced.

[0105] (Distance between active layer 4 and defective layer 7)

[0106] The distance from the active layer 4 to the defect layer 7 is 0.5 μm or more and 3 μm or less, preferably 2 μm or more and 2.5 μm or less. This reduces the overlap between the defect layer 7 and the NFP, thereby improving the COD level and resulting in a semiconductor laser element 100 that reduces sudden failures caused by COD.

[0107] (Relationship between the thickness of the second semiconductor layer 2 and the defect layer 7)

[0108] The thickness of the second semiconductor layer 2 is more than twice and less than four times the thickness of the defect layer 7. Compared with the thickness of the defect layer 7, the thickness of the second semiconductor layer 2 is sufficiently large, thereby reducing the overlap between the defect layer 7 and the NFP. Furthermore, when the defects contained in the defect layer 7 extend obliquely, the length of the defects is evaluated in terms of the length in the thickness direction.

[0109] (Fourth semiconductor layer 5)

[0110] The fourth semiconductor layer 5 is a contact layer. The fourth semiconductor layer 5 is connected to the electrode. The fourth semiconductor layer 5 can be, for example, GaAs, AlGaAs, or GaP.

[0111] (Horizontal mode)

[0112] The semiconductor laser element 100 of Embodiment 1 can achieve multimode oscillation. This increases the power of the laser. The mode number of the transverse mode can be controlled by the transverse width of the optical waveguide.

[0113] (Anti-reflective coating 9)

[0114] An anti-reflective coating 9 can also be provided on the end face E1. This allows for efficient laser extraction. The anti-reflective coating 9 is a dielectric multilayer film, for example, it can be a multilayer film containing at least two layers selected from SiO2, Al2O3, and Ta2O5. The reflectivity of the anti-reflective coating 9 at the laser wavelength can be, for example, more than 5% and less than 15%.

[0115] (High-reflectivity coating 8)

[0116] To achieve efficient resonance, a high-reflectivity coating 8 can be disposed on the end face E2, opposite to the end face E1 from which the emitted laser light is emitted. This enables efficient light resonance. The high-reflectivity coating 8 is a dielectric multilayer film, for example, a multilayer film comprising at least two layers selected from SiO2, Ta2O3, and Al2O3. The reflectivity of the high-reflectivity coating 8 at the wavelength of the laser light can, for example, be 90% or more and 100% or less.

[0117] (A variation of Implementation Method 1)

[0118] As described above, NFP is associated with FFP. Therefore, even without determining NFP, the required thickness of the second semiconductor layer 2 can be determined based on the spread angle of the FFP in the thickness direction. Therefore, the semiconductor laser element can also have the structure of the following modified example.

[0119] Semiconductor laser elements have:

[0120] A first semiconductor layer 1 comprising a group III-V semiconductor, As;

[0121] A second semiconductor layer 2 comprising a first conductive side of a group III-V containing P, disposed on top of a first semiconductor layer 1;

[0122] A third semiconductor layer 3 disposed on the second conductive side above the second semiconductor layer 2;

[0123] An active layer 4 is disposed between the second semiconductor layer 2 and the third semiconductor layer 3;

[0124] A window structure 6 is configured to extend across the third semiconductor layer 3, the active layer 4, the second semiconductor layer 2, and the first semiconductor layer 1;

[0125] In the region where the windowed structure 6 is formed, there is a group III material of the first semiconductor layer 1 and a group III material of the second semiconductor layer 2 between the first semiconductor layer 1 and the second semiconductor layer 2, and a defect layer 7 containing defects.

[0126] The end face E1, which contains the defect layer 7 and emits laser light, wherein...

[0127] In the far-field pattern of the laser emitted from the semiconductor laser element, when the value of the extension angle from the first semiconductor layer 1 towards the active layer 4 is set as x (°) and the value of the thickness of the second semiconductor layer 2 is set as y (μm), y ≥ 2.31 × 10⁻⁶. -5 x 2 -5.37×10 -2 x+4.44.

[0128] As a result, the COD level is improved, leading to semiconductor laser elements that reduce sudden failures caused by COD.

[0129] (Implementation Method 2)

[0130] Figure 4 and Figure 5 This illustrates a semiconductor laser element 200 according to Embodiment 2. The semiconductor laser element 200 of Embodiment 2 differs from the semiconductor laser element 100 of Embodiment 1 in the following aspects: Specifically, the first semiconductor layer 1 includes a substrate 11 and a first band discontinuity mitigation layer 15 (first BDR layer 15), and the second semiconductor layer 2 includes a second band discontinuity mitigation layer 25 (second BDR layer 25), an n-side cladding layer 21, and an n-side photoconductor layer 22. Furthermore, the third semiconductor layer 3 includes a p-side photoconductor layer 32 and a p-side cladding layer 31. These aspects differ from the semiconductor laser element 100 of Embodiment 1. Therefore, light can be efficiently sealed in the thickness direction, and laser oscillation can be performed efficiently.

[0131] use Figure 4 and Figure 5 The structure of the semiconductor laser element 200 according to Embodiment 2 will be described below. Hereinafter, only the changes compared to Embodiment 1 will be described. Figure 4 This is a cross-sectional view of the semiconductor laser element 200 according to Embodiment 2. Figure 4 It is a cross-sectional view along the direction of the resonator (i.e., longitudinal direction). Figure 5 This is an enlarged view of the area near the interface between the first semiconductor layer 1 and the second semiconductor layer 2 in the window structure 6 of the semiconductor laser element 200 of Embodiment 2.

[0132] (Substrate 11)

[0133] The first semiconductor layer 1 includes a substrate 11. The substrate 11 is the growth substrate for each semiconductor layer. The substrate 11 may be a GaAs substrate. The thickness of the substrate 11 may be, for example, 300 μm or more and 1000 μm or less.

[0134] (First BDR Layer 15)

[0135] The first semiconductor layer 1 includes a first BDR layer 15. The first BDR layer 15 is disposed on the substrate 11. The first BDR layer 15 is a layer that mitigates the discontinuities in the valence band and / or conduction band generated at the heterojunction of the semiconductor. The first BDR layer 15 may be, for example, AlGaAs or AlGaInAs. The thickness of the first BDR layer 15 may be, for example, 0.01 μm or more and 0.1 μm or less.

[0136] (Second BDR Layer 25)

[0137] The second semiconductor layer 2 includes a second BDR layer 25. The second BDR layer 25 may be, for example, AlInP or AlGaInP. The thickness of the second BDR layer 25 may be, for example, 0.01 μm or more and 0.1 μm or less. In Embodiment 2, the interface between the first BDR layer 15 and the second BDR layer 25 is the interface between an As-based III-V semiconductor layer and a P-based III-V semiconductor layer.

[0138] (n-side cladding layer 21)

[0139] The second semiconductor layer 2 includes an n-side cladding layer 21. The n-side cladding layer 21 can be, for example, AlInP or AlGaInP. The thickness of the n-side cladding layer 21 can be, for example, 0.4 μm or more and 4 μm or less. The second BDR layer 25 is thinner than the n-side cladding layer 21. Because the second BDR layer 25 is thinner, defects are located not only in the second BDR layer 25 but also in the n-side cladding layer 21. That is, the defect layer extends to a portion of the n-side cladding layer 21.

[0140] (n-side optical guide layer 22)

[0141] The second semiconductor layer 2 includes an n-side photoconductor layer 22. The n-side photoconductor layer 22 may be, for example, AlInP or AlGaInP. The thickness of the n-side photoconductor layer 22 may be, for example, greater than 0.02 μm and less than 0.3 μm.

[0142] (p-side optical guide layer 32)

[0143] The third semiconductor layer 3 includes a p-side photoconductor layer 32. The p-side photoconductor layer 32 may be, for example, AlInP or AlGaInP. The thickness of the p-side photoconductor layer 32 may be, for example, greater than 0.02 μm and less than 0.3 μm.

[0144] (p-side cladding layer 31)

[0145] The third semiconductor layer 3 includes a p-side cladding layer 31. The p-side cladding layer 31 can be, for example, AlInP or AlGaInP. The thickness of the p-side cladding layer 31 can be, for example, greater than 0.4 μm and less than 4 μm.

[0146] (Third BDR layer)

[0147] In embodiment 2, the semiconductor laser element 200 may also have a third BDR layer disposed on the third semiconductor layer 3. The third BDR layer may be, for example, AlInP or AlGaInP. The thickness of the third BDR layer may be, for example, 0.01 μm or more and 0.1 μm or less.

[0148] (Inclination of the laser's optical axis at the end face)

[0149] During the formation of window structure 6, the refractive index distribution near the interface between the first semiconductor layer 1 and the second semiconductor layer 2, and near the upper surface of the third semiconductor layer 3, tends to change more readily than before the formation of window structure 6 due to the diffusion of Zn or the disordering of the semiconductor layers caused by the interdiffusion of group III elements via holes. The refractive index distribution after the formation of window structure 6 becomes asymmetric about the core of the optical waveguide compared to the refractive index distribution before its formation. This asymmetry in the refractive index distribution affects the emission angle of the laser emitted from end face E1. Specifically, the optical axis of the laser is tilted towards the thickness direction relative to the normal of end face E1.

[0150] The impact of refractive index asymmetry can be reduced by increasing the thickness of each cladding layer. This is because the regions of refractive index asymmetry (i.e., near the interface between the first semiconductor layer 1 and the second semiconductor layer 2, and near the upper surface of the third semiconductor layer 3) are far from the core, making it difficult for light to perceive the refractive index in these regions. Therefore, light is less affected by the regions of refractive index asymmetry, and the tilt of the optical axis is improved. In Embodiment 2, to sufficiently ensure the distances from the core to the interface between the first semiconductor layer 1 and the second semiconductor layer 2, and from the core to the upper surface of the third semiconductor layer 3, the thickness of the n-side cladding layer 21 can be 1.3 μm or more and 4 μm or less, and the thickness of the p-side cladding layer 31 can be 1.3 μm or more and 4 μm or less. In this way, even if the interface between the first semiconductor layer 1 and the second semiconductor layer 2 and the upper surface of the third semiconductor layer 3 are far from the core to form the window structure 6, thereby causing the refractive index distribution in the thickness direction to be asymmetrical, its impact can be reduced, and the angle at which the optical axis of the laser is tilted in the thickness direction relative to the normal of the end face E1 can be decreased. Furthermore, the thicknesses of the n-side cladding layer 21 and the p-side cladding layer 31 are preferably 2 μm or less, and more preferably 1.5 μm or less. This reduces the tilt of the optical axis and decreases the increase in resistance caused by the thickened semiconductor layer, thus reducing the increase in Vf.

[0151] The absolute value of the angle between the laser's optical axis and the normal to the end face E1 in the thickness direction can be 0.01° or more and 0.95° or less, preferably 0.01° or more and 0.6° or less, and more preferably 0.01° or more and 0.3° or less. This improves the tilt of the laser's optical axis, facilitating its combination with optical elements disposed downstream of the semiconductor laser element's optical axis. For example, it facilitates laser coupling with a lens. Furthermore, it facilitates adjustment of the incident angle toward the reflector.

[0152] (Modified example)

[0153] A modified example of the semiconductor laser element 200 according to Embodiment 2 will be described below. Hereinafter, only the changes relative to Embodiment 2 will be described. Figure 6 This is a cross-sectional view of a modified semiconductor laser element 300. Figure 6 This is a cross-sectional view along the resonator direction (i.e., longitudinal direction). The difference between the modified semiconductor laser element 300 and the semiconductor laser element 200 of Embodiment 2 is that it has a window structure 6 not only on the end face E1 side but also on the end face E2 side. In any window structure 6, a window structure 6 is formed near the interface between the first BDR layer 15 and the second BDR layer 25. Figure 5 Defect layer 7, as shown in the example.

[0154] The semiconductor laser element 300 in Modified Example 2 also reduces sudden failures caused by COD by increasing the COD level, just like the semiconductor laser element 200 in Embodiment 2.

[0155] (Implementation Method 3)

[0156] The semiconductor laser element 400 of Embodiment 3 differs from the semiconductor laser element 200 of Embodiment 2 in the following aspects: Specifically, unlike the semiconductor laser element 200 of Embodiment 2, the semiconductor laser element 400 is a single-mode laser and has a diffraction grating in the second semiconductor layer 2 or the third semiconductor layer 3. In Embodiment 3, the semiconductor laser element 400 can also be a distributed feedback type laser element or a distributed Bragg reflection type laser element. Thus, a laser with a narrow spectral linewidth and wavelength selected by the diffraction grating is obtained.

[0157] use Figure 7 The structure of the semiconductor laser element 400 in Embodiment 3 will be described. Hereinafter, only the changes compared to Embodiment 2 will be described. Figure 7 This is a cross-sectional view of the semiconductor laser element 400 according to Embodiment 3. Figure 7 It is the cross section in the direction of the resonator (i.e., longitudinal direction).

[0158] (Diffraction grating)

[0159] like Figure 7 As shown, the semiconductor laser element 400 has a diffraction grating G at least in the portion where the window structure 6 is not provided. The diffraction grating G is disposed in the second semiconductor layer 2 or the third semiconductor layer 3. Figure 7 In the second semiconductor layer 2, a diffraction grating G is disposed on the n-side cladding layer 21, and multiple protrusions of the n-side photoconductor layer 22 are alternately arranged in the resonator direction to form a periodic structure. If the period of the diffraction grating G is set to Λ, the oscillation wavelength in vacuum is set to λ, and the equivalent refractive index of the stacked structure with the diffraction grating is set to n... eq Then the oscillation wavelength is λ = 2 × n eq ×Λ. The period Λ of the diffraction grating can be, for example, greater than 100 nm and less than 500 nm. The diffraction grating G can have a phase-shifting structure PS. The phase-shifting structure PS can be a 1 / 4 wavelength phase-shifting structure. Thus, longitudinal single-mode oscillation can be achieved.

[0160] [Example]

[0161] The present invention will be specifically described below through embodiments, but the present invention is not limited to these embodiments.

[0162] <Example 1>

[0163] As Example 1, multiple semiconductor laser elements corresponding to Embodiment 2 were fabricated. The semiconductor laser element of Example 1 was obtained by forming a first BDR layer, a second BDR layer, an n-side cladding layer, an n-side photoconductor layer, an active layer, a p-side photoconductor layer, and a p-side cladding layer on a GaAs substrate using MOCVD. Zn was diffused after forming the p-side cladding layer, and a window structure was formed at and near the cleaved end face. A defect layer was formed by forming the window structure. The first BDR layer was an AlGaAs layer, and the second BDR layer was an AlGaInP layer. That is, the interface between the first BDR layer and the second BDR layer was the interface between a first III-V group semiconductor layer containing As and a second III-V group semiconductor layer containing P. The total thickness of the second BDR layer, the n-side cladding layer, and the n-side photoconductor layer, i.e., the thickness of the second semiconductor layer, was set to 2 μm. For the multiple semiconductor laser elements fabricated, the amount of Zn diffusion during the fabrication of the window structure was adjusted so that the FFPy of the laser emitted from the semiconductor laser element was in the range of approximately 45° to approximately 60°.

[0164] <Example 2>

[0165] As Example 2, multiple semiconductor laser elements were fabricated. The difference from the semiconductor laser element in Example 1 is that the thickness of the second semiconductor layer was set to 1 μm, and the diffusion amount of Zn during the fabrication of the window structure was adjusted to make FFPy range from about 66° to about 70°.

[0166] <Comparative Example 1>

[0167] As a comparative example 1, multiple semiconductor laser elements were fabricated. The difference from the semiconductor laser element of Example 1 is that the thickness of the second semiconductor layer was set to 1 μm, and the diffusion amount of Zn during the fabrication of the window structure was adjusted so that FFPy was in the range of about 45° to about 65.9°.

[0168] (Failure rate)

[0169] The failure rate of the semiconductor laser elements of Example 1, Example 2 and Comparative Example 1 was investigated. Figure 8 This is a graph representing the failure rates of Embodiment 1 and Embodiment 2. Figure 8 In the diagram, the black circle represents the result of Example 1, and the white circle represents the result of Example 2. Figure 9 This is a graph representing the failure rate of Comparative Example 2. Figure 8 and Figure 9 The horizontal axis represents the FFPy angle of the laser emitted from each semiconductor laser element, and the vertical axis represents the failure rate. For ease of comparison, Figure 8 and Figure 9 The horizontal and vertical axes have the same scale.

[0170] exist Figure 8 In the diagram, the curve indicated by the arrow represents a failure caused by an end-face splitting anomaly, which can be ignored. Otherwise, the failure rate of the semiconductor laser element in Example 1 is 0%. Furthermore, no failure caused by a splitting anomaly can be confirmed in the semiconductor laser element of Example 2. The maximum failure rate of the semiconductor laser element in Example 2 is approximately 20%.

[0171] exist Figure 9 In Comparative Example 1, no fault caused by a splitting anomaly was identified in the semiconductor laser element. According to... Figure 9 The failure rate of the semiconductor laser element in Comparative Example 1 was the highest, approximately 70%.

[0172] The results of Example 1 show a significant difference in failure rate compared to Comparative Example 1. Particularly within the FFPy range of 50° to 60°, even with approximately the same FFPy value, the failure rate differs. The larger the NFP in the thickness direction at the end face, the smaller the FFPy becomes due to diffraction. In other words, the smaller the FFPy, the larger the NFP in the thickness direction at the end face. Therefore, it is believed that the above results are because the thickness of the second semiconductor layer in Example 1 is 2 μm, which is larger than the thickness of the second semiconductor layer in Comparative Example 1. That is, the defect layer does not overlap with the NFP at the end face, or only overlaps with the edge of the NFP at the end face, thus presumably improving the COD level and reducing sudden failures.

[0173] The results of Example 2 also show a tendency towards a lower failure rate compared to Comparative Example 1. The thickness of the second semiconductor layer 2 in Example 2 is the same as that in Comparative Example 1, but the FFPy in Example 2 is greater than that in Comparative Example 1. As mentioned above, the smaller the FFPy, the larger the NFP at the end face; therefore, the thickness of the second semiconductor layer required in Example 2 to reduce the overlap between the NFP and the defect layer 7 at the end face is smaller. Therefore, it is speculated that even if the thickness of the second semiconductor layer is the same, Example 2 tends to have a lower failure rate than Comparative Example 1.

[0174] Furthermore, the thickness of the second semiconductor layer 2 estimated by the above formula (1) was compared with that of Example 1, Example 2, and Comparative Example 1. According to formula (1), the thickness of the second semiconductor layer preferably having FFPy (i.e., x in formula (1)) in the range of 45° to 60° is about 1.3 μm or more. The thickness of the second semiconductor layer preferably having FFPy in the range of 66° to 70° is about 0.8 μm or more. As can be seen from formula (1), the smaller the FFPy (i.e., x in formula (1)), the smaller the preferred thickness of the second semiconductor layer. Based on these results, it is speculated that the second semiconductor layer of the semiconductor laser element in Example 1 and Example 2 is formed with sufficient thickness. On the other hand, it is speculated that the thickness of the second semiconductor layer in Comparative Example 1 is insufficient.

[0175] <Example 3>

[0176] A semiconductor laser element of Example 3 was fabricated. As Example 3, a semiconductor laser element corresponding to Example 2 was fabricated. The semiconductor laser element of Example 3 was obtained by forming a first BDR layer, a second BDR layer, an n-side cladding layer, an n-side photoconductor layer, an active layer, a p-side photoconductor layer, and a p-side cladding layer on a GaAs substrate using MOCVD. After forming the p-side cladding layer, Zn was diffused, and a window structure was formed at and near the cleaved end face. A defect layer was formed by forming the window structure. The thickness of the n-side cladding layer was set to 1.9 μm, and the thickness of the p-side cladding layer was set to 1.4 μm.

[0177] <Comparative Example 2>

[0178] The semiconductor laser element of Comparative Example 2 was fabricated. The semiconductor laser element of Comparative Example 2 differs from the semiconductor laser element of Example 3 in that the thickness of both the n-side cladding layer and the p-side cladding layer is set to 1 μm.

[0179] (Inclination of the optical axis)

[0180] The tilt of the laser optical axis was investigated by driving the semiconductor laser elements of Example 3 and Comparative Example 2. In Example 3, the absolute value of the angle between the laser optical axis and the normal to the end face was 0.51°. In Comparative Example 2, the absolute value of the angle between the laser optical axis and the normal to the end face was 0.98°. Therefore, it can be confirmed that the tilt of the optical axis of the semiconductor laser element of Example 3 is improved.

[0181] This disclosure comprises the following components.

[0182] (Item 1) A semiconductor laser element, comprising:

[0183] The first semiconductor layer is a III-V compound semiconductor layer containing at least As as a group V element;

[0184] The second semiconductor layer on the first conductive side, which is disposed on the first semiconductor layer, is a III-V compound semiconductor layer containing at least P of a group V element.

[0185] A third semiconductor layer on the second conductive side is disposed on the second semiconductor layer;

[0186] An active layer is disposed between the second semiconductor layer and the third semiconductor layer;

[0187] A window structure is formed covering the third semiconductor layer, the active layer, the second semiconductor layer, and the first semiconductor layer;

[0188] A defect layer, which in the region where the window structure is formed, has a group III element of the first semiconductor layer and a group III element of the second semiconductor layer between the first semiconductor layer and the second semiconductor layer and contains defects;

[0189] An end face, which includes the defect layer, emits laser light, wherein,

[0190] The defect layer does not overlap with the near-field pattern of the laser on the end face, or overlaps only at the edge of the near-field pattern on the end face.

[0191] (Item 2) In the semiconductor laser element of Item 1, the defect layer overlaps with the near-field pattern only within a range of less than 0.025% of the area of ​​the near-field pattern from the end of the near-field pattern.

[0192] (Item 3) In the semiconductor laser element described in Item 1 or Item 2, in the far-field pattern of the laser, when the value of the extension angle from the first semiconductor layer toward the active layer is set to x (°) and the value of the thickness of the second semiconductor layer is set to y (μm), the following equation (1) is satisfied.

[0193] y≥2.31×10 -5 x 2 -5.37×10 -2 x+4.44...(1)

[0194] (Item 4) A semiconductor laser element having:

[0195] The first semiconductor layer is a III-V compound semiconductor layer containing at least As as a group V element;

[0196] The second semiconductor layer on the first conductive side, which is disposed on the first semiconductor layer, is a III-V compound semiconductor layer containing at least P of a group V element.

[0197] A third semiconductor layer on the second conductive side is disposed on the second semiconductor layer;

[0198] An active layer is disposed between the second semiconductor layer and the third semiconductor layer;

[0199] A window structure is formed covering the third semiconductor layer, the active layer, the second semiconductor layer, and the first semiconductor layer;

[0200] A defect layer, which in the region where the window structure is formed, has a group III element of the first semiconductor layer and a group III element of the second semiconductor layer between the first semiconductor layer and the second semiconductor layer and contains defects;

[0201] An end face, which includes the defect layer, emits laser light, wherein,

[0202] In the far-field pattern of the laser emitted from the semiconductor laser element, when the value of the extension angle from the first semiconductor layer toward the active layer is set as x (°) and the value of the thickness of the second semiconductor layer is set as y (μm), the following equation (1) is satisfied.

[0203] y≥2.31×10 -5 x 2 -5.37×10 -2 x+4.44...(1)

[0204] (Item 5) In any one of items 1 to 4, the thickness of the second semiconductor layer is 1 μm or more and 3.5 μm or less.

[0205] (Item 6) In any one of items 1 to 5, the distance from the active layer to the defect layer is 0.5 μm or more and 3 μm or less.

[0206] (Item 7) In any one of items 1 to 6, the thickness of the second semiconductor layer is more than 3 times and less than 10 times the thickness of the defect layer.

[0207] (Item 8) In any one of items 1 to 7, the second semiconductor layer includes at least an n-side cladding layer, and the third semiconductor layer includes at least a p-side cladding layer.

[0208] (Item 9) In the semiconductor laser element described in Item 8, the thickness of the n-side cladding layer is 1.3 μm or more and 4 μm or less, and the thickness of the p-side cladding layer is 1.3 μm or more and 4 μm or less.

[0209] (Item 10) In any one of items 1 to 9, the first semiconductor layer includes a substrate and a band discontinuity mitigation layer disposed on the substrate, the substrate being a GaAs substrate, the band discontinuity mitigation layer including an AlGaAs layer, the second semiconductor layer being an AlInP layer or an AlGaInP layer, and the defect layer including Al, In, and Ga.

[0210] (Item 11) In any one of items 1 to 10, the thickness of the defect layer is 0.01 μm or more and 1.5 μm or less.

[0211] (Item 12) In any one of items 1 to 11, the window structure is distributed with Zn.

[0212] (Item 13) In any one of items 1 to 12, the semiconductor laser element is capable of multimode oscillation.

Claims

1. A semiconductor laser element having: a first semiconductor layer which is a III-V compound semiconductor layer containing at least As as a Group V element; a second semiconductor layer on the first semiconductor layer, which is a III-V compound semiconductor layer containing at least P as a Group V element on a first conductive side; a third semiconductor layer on the second semiconductor layer on a second conductive side; an active layer between the second semiconductor layer and the third semiconductor layer; a window structure formed throughout the third semiconductor layer, the active layer, the second semiconductor layer, and the first semiconductor layer; a defect layer containing defects in a region where the window structure is formed, having a Group III element of the first semiconductor layer and a Group III element of the second semiconductor layer between the first semiconductor layer and the second semiconductor layer, the defect layer being included in an end face from which laser light is emitted, the semiconductor laser element characterized in that the defect layer does not overlap a near-field pattern of the laser light at the end face, or overlaps only an edge of the near-field pattern at the end face.

2. The semiconductor laser element according to claim 1, characterized in that the defect layer overlaps the near-field pattern only in a range where an area of the near-field pattern is 0.025% or less from an end of the near-field pattern.

3. The semiconductor laser element according to claim 1 or 2, characterized in that, in a far-field pattern of the laser light, when a value of a spread angle in a direction from the first semiconductor layer toward the active layer is set as x (°) and a value of a thickness of the second semiconductor layer is set as y (μm), the following expression (1) is satisfied.

4. A semiconductor laser element having: a first semiconductor layer which is a III-V compound semiconductor layer containing at least As as a Group V element; a second semiconductor layer on the first semiconductor layer, which is a III-V compound semiconductor layer containing at least P as a Group V element on a first conductive side; a third semiconductor layer on the second semiconductor layer on a second conductive side; an active layer between the second semiconductor layer and the third semiconductor layer; a window structure formed throughout the third semiconductor layer, the active layer, the second semiconductor layer, and the first semiconductor layer; a defect layer containing defects in a region where the window structure is formed, having a Group III element of the first semiconductor layer and a Group III element of the second semiconductor layer between the first semiconductor layer and the second semiconductor layer, the defect layer being included in an end face from which laser light is emitted, the semiconductor laser element characterized in that, in a far-field pattern of the laser light emitted from the semiconductor laser element, when a value of a spread angle in a direction from the first semiconductor layer toward the active layer is set as x (°) and a value of a thickness of the second semiconductor layer is set as y (μm), the following expression (1) is satisfied.

5. The semiconductor laser element according to any one of claims 1, 2, or 4, characterized in that ​ ​ ​ ​ ​ ​ ​ ​ y ≥ 2.31 x 10 -5 x 2 -5.37 x 10 -2 x + 4.44... (1). ​ ​ ​ ​ ​ ​ ​ ​ ​ y ≥ 2.31 x 10 -5 x 2 -5.37 x 10 -2 x + 4.44... (1). ​ The second semiconductor layer has a thickness of 1 μm or more and 3.5 μm or less.

6. The semiconductor laser element according to any one of claims 1, 2, or 4, wherein The distance from the active layer to the defect layer is 0.5 μm or more and 3 μm or less.

7. The semiconductor laser element according to any one of claims 1, 2, or 4, wherein The second semiconductor layer has a thickness of 3 times or more and 10 times or less of the thickness of the defect layer.

8. The semiconductor laser element according to any one of claims 1, 2, or 4, wherein The second semiconductor layer includes at least an n-side cladding layer, The third semiconductor layer includes at least a p-side cladding layer.

9. The semiconductor laser element according to claim 8, wherein The n-side cladding layer has a thickness of 1.3 μm or more and 4 μm or less, The p-side cladding layer has a thickness of 1.3 μm or more and 4 μm or less.

10. The semiconductor laser element according to any one of claims 1, 2, or 4, wherein The first semiconductor layer includes a substrate and a band discontinuity relaxation layer disposed on the substrate, The substrate is a GaAs substrate, The band discontinuity relaxation layer includes an AlGaAs layer, The second semiconductor layer is an AlInP layer or an AlGaInP layer, The defect layer includes Al, In, and Ga.

11. The semiconductor laser element according to any one of claims 1, 2, or 4, wherein The defect layer has a thickness of 0.01 μm or more and 1.5 μm or less.

12. The semiconductor laser element according to any one of claims 1, 2, or 4, wherein The window structure has Zn distributed therein.

13. The semiconductor laser element according to any one of claims 1, 2, or 4, wherein The semiconductor laser element is capable of realizing a multi-mode oscillation.

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