Semiconductor optical elements and semiconductor optical devices

Abstract

To provide high-power semiconductor optical elements and semiconductor optical devices with high reliability. [Solution] The semiconductor optical element EL comprises a substrate 1, a laminate 2 in which a semiconductor layer 10, an active layer 20, and a semiconductor layer 30 are stacked in order from the substrate 1 side, an output surface PL1 provided on one side of the laminate 2, a reflecting surface PL2 provided on the other side of the laminate 2 so as to face the output surface PL1, a diffraction grating GR formed on the semiconductor layer 10 or semiconductor layer 30 between the output surface PL1 and the reflecting surface PL2, and a window region W formed at least on the output surface PL1 side of the laminate 2 to reduce the absorption rate for light generated in the active layer 20, wherein the peak wavelength of the gain spectrum of the active layer 20 is λ act The reflection wavelength of the diffraction grating GR is λ b The peak wavelength of the emission spectrum in the window region W is λ W Therefore, λ act ≥λ b >λ W To satisfy the relationship.

Description

[Technical Field]

[0001] This invention relates to semiconductor optical elements and semiconductor optical devices. [Background technology]

[0002] Broad-area laser diodes (BA-LDs) are semiconductor lasers with an expanded emission area in the lateral direction and are used as various light sources requiring high power. For example, broad-area laser diodes are used as excitation sources for solid-state lasers, fiber lasers, etc. In order to improve or stabilize the excitation efficiency, it is desirable that the oscillation wavelength fluctuation of such broad-area laser diodes used as excitation sources be kept to 2-3 nm or less.

[0003] One method for controlling the oscillation wavelength fluctuation is to use a periodic diffraction grating. Examples of periodic diffraction gratings include distributed Bragg reflectors (DBRs) and distributed feedback (DFBs). Much of the research on semiconductor lasers using such periodic diffraction gratings has been conducted with relatively low-power semiconductor lasers for communication applications, but in recent years, it has also been applied to high-power broad-area semiconductor lasers. Patent Document 1 below describes the wavelength λ at which the optical gain is maximized. g and feedback wavelength λ B The relationship is λ B >λ g By doing so, a laser has been disclosed that reduces the risk of end-face optical damage (COD) and improves reliability.

[0004] In the case of high-power broad-area semiconductor lasers, strict wavelength control is not necessarily required as in the case of semiconductor lasers for communication applications. In high-power broad-area semiconductor lasers, multiple longitudinal modes are allowed within the range of the central wavelength, but the longitudinal modes are defined in a wide dynamic range from low power to high power, and high reliability is required even at high power, which is different from semiconductor lasers for communication applications.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] By the way, in recent years, further increase in output power has been demanded for semiconductor lasers for excitation light sources. For example, semiconductor lasers capable of laser output of 10 W or more are demanded. Since such high-power semiconductor lasers are likely to cause COD, it is necessary to improve the reliability by improving COD resistance and the like.

[0007] The present invention has been made in view of the above circumstances, and an object thereof is to provide a high-power semiconductor optical element and a semiconductor optical device having high reliability.

Means for Solving the Problems

[0008] In order to solve the above problems, a semiconductor optical element (EL) according to a first aspect of the present invention includes a substrate (1), and a laminate (2) in which a first conductivity type semiconductor layer (10), an active layer (20), and a second conductivity type semiconductor layer (30) are laminated in this order from the substrate side, an emission surface (PL1) provided on one side surface of the laminate, a reflection surface (PL2) provided on the other side surface of the laminate so as to face the emission surface, a diffraction grating (GR) formed in the first conductivity type semiconductor layer or the second conductivity type semiconductor layer between the emission surface and the reflection surface, and a window region (W) formed at least on the emission surface side of the laminate and having a low absorption rate for light generated in the active layer. The peak wavelength of the gain spectrum of the active layer is λ act The reflection wavelength of the diffraction grating is λ b The peak wavelength of the emission spectrum of the window region is λ W If we set them as such, λ act ≧λ b >λ W satisfies the relationship.

[0009] In the semiconductor optical element according to the first aspect of the present invention, the peak wavelength λ act of the gain spectrum of the active layer, the reflection wavelength λ b of the diffraction grating, and the peak wavelength λ W of the emission spectrum of the window region are configured to satisfy the relationship of λ act ≧λ b >λ W . Thus, even when the wavelength lock is locally lost, the oscillation wavelength of the semiconductor optical element becomes longer than the reflection wavelength λ b of the diffraction grating, and the risk of COD can be reduced, so it has high reliability. [[ID=…]]

[0010] [[ID=…]] A semiconductor optical element according to a second aspect of the present invention further satisfies the relationship of λ b >λ W + 30 nm in the semiconductor optical element according to the first aspect of the present invention.

[0011] A semiconductor optical element according to a third aspect of the present invention further comprises a conductive layer (5) provided on the laminate, which supplies a current injected into the second conductivity type semiconductor layer and releases heat generated in the laminate, in addition to the semiconductor optical element according to a first or second aspect of the present invention.

[0012] A semiconductor optical element according to a fourth aspect of the present invention is a semiconductor optical element according to a third aspect of the present invention, wherein the distance (A1) between one end of the conductive layer and the emission surface in the direction (X direction) in which the emission surface and the reflection surface face each other is shorter than the width (B1) of the window region in that direction.

[0013] A semiconductor optical element according to a fifth aspect of the present invention is a semiconductor optical element according to a third or fourth aspect of the present invention, wherein the window region is formed not only on the emission side of the laminate but also on the reflection side of the laminate.

[0014] A semiconductor optical element according to a sixth aspect of the present invention is a semiconductor optical element according to a fifth aspect of the present invention, wherein the distance (A2) between the other end of the conductive layer and the reflective surface in the aforementioned direction is shorter than the width (B2) of the window region formed on the reflective surface side of the laminate in the aforementioned direction.

[0015] A semiconductor optical element according to a seventh aspect of the present invention is a semiconductor optical element according to any one of the first to sixth aspects of the present invention, wherein the diffraction grating is a distributed Bragg reflector formed on the reflective surface side of the laminate.

[0016] A semiconductor optical element according to the eighth aspect of the present invention further comprises a current control layer (3) provided on the laminate and having at least the output surface side of the laminate as a current-free region (R1) where no current is injected.

[0017] A semiconductor optical device (DV) according to one aspect of the present invention comprises a thermally conductive submount (100) and a semiconductor optical element according to any one of the first to eighth aspects mounted on the submount via a thermally conductive metal junction layer. [Effects of the Invention]

[0018] The present invention has the effect of providing highly reliable, high-power semiconductor optical elements and semiconductor optical devices. [Brief explanation of the drawing]

[0019] [Figure 1] This is a cross-sectional view showing the main components of a semiconductor optical element according to a first embodiment of the present invention. [Figure 2] This is a plan view of a semiconductor optical element according to a first embodiment of the present invention. [Figure 3] This figure illustrates the relationship between the peak wavelength of the gain spectrum of the active layer, the reflection wavelength of the diffraction grating, and the peak wavelength of the emission spectrum of the window region in a semiconductor optical device according to the first embodiment of the present invention. [Figure 4] This is a plan view of a semiconductor optical element according to a second embodiment of the present invention. [Figure 5] This is a perspective view showing a semiconductor optical device according to one embodiment of the present invention. [Modes for carrying out the invention]

[0020] Hereinafter, semiconductor optical elements and semiconductor optical devices according to embodiments of the present invention will be described in detail with reference to the drawings. Note that in the drawings referred to below, the dimensions of each component have been appropriately changed as needed to facilitate understanding. Furthermore, in the following description, the positional relationships of each component will be explained with reference to the XYZ Cartesian coordinate system indicated in each figure (the position of the origin will be changed as needed).

[0021] [First Embodiment] Figure 1 is a cross-sectional view showing the main components of a semiconductor optical element according to the first embodiment of the present invention. Figure 2 is a plan view of the semiconductor optical element according to the first embodiment of the present invention. As shown in Figure 1, the semiconductor optical element EL of this embodiment comprises a substrate 1, a laminate 2, a current control layer 3, an electrode layer 4, a conductive layer 5, an electrode layer 6, an anti-reflective film 7, and an enhanced reflective film 8. In Figure 1, the XYZ orthogonal coordinate system is defined with the stacking direction of the laminate 2 as the Z axis, the emission direction of light emitted from the semiconductor optical element EL as the X axis, and the direction parallel to the interface between the substrate 1 and the laminate 2 and perpendicular to the X axis as the Y axis.

[0022] Substrate 1 is a first-conductivity semiconductor substrate. The laminate 2 is provided on substrate 1 and consists of a semiconductor layer 10 (first-conductivity semiconductor layer), an active layer 20, and a semiconductor layer 30 (second-conductivity semiconductor layer), which are stacked in order from the substrate 1 side. One side of the laminate 2 (the +X side) is the emission surface PL1 to which light generated in the active layer 20 is emitted, and the other side of the laminate 2 (the -X side) is the reflection surface PL2 to which light generated in the active layer 20 is reflected.

[0023] The semiconductor layer 10 of the laminate 2 consists of a buffer layer 11, a first cladding layer 12, a diffraction grating layer 13, a second cladding layer 14, and a waveguide layer 15, stacked in that order from the substrate 1 side. The active layer 20 of the laminate 2 generates light of a predetermined wavelength when an electric current is injected. The semiconductor layer 30 of the laminate 2 consists of a waveguide layer 31 and a cladding layer 32, stacked in that order from the active layer 20 side.

[0024] As shown in Figure 1, a diffraction grating GR forming a DFB is formed in the diffraction grating layer 13. The diffraction grating GR is formed along the X direction on the +X side (output surface PL1 side) of the diffraction grating layer 13 and, together with the reflecting surface PL2, constitutes a resonator. The length of the diffraction grating GR in the X direction is set considering the output of the semiconductor optical element EL, etc. As shown in Figure 2, the length of the diffraction grating GR in the Y direction is set to be slightly shorter than the length of the semiconductor optical element EL in the Y direction.

[0025] Here, the length L of the diffraction grating GR in the X direction can be freely set so that the product (κL) of the coupling coefficient κ of the diffraction grating GR and the length L of the diffraction grating GR is a required value. For example, if the distance in the Z direction between the diffraction grating layer 13 and the active layer 20 is short, the length L of the diffraction grating GR in the X direction can be shortened, and conversely, if the distance between the diffraction grating layer 13 and the active layer 20 is long, the length L of the diffraction grating GR in the X direction can be lengthened to adjust the above product (κL). It is preferable that the order of the diffraction grating GR be second order or lower with respect to the oscillation wavelength.

[0026] The diffraction grating GR is located within the current injection region R0 (details will be described later) with respect to the X direction. Alternatively, the diffraction grating GR may be located within the non-current injection region R1 (details will be described later) with respect to the X direction. By forming the diffraction grating GR in the non-current injection region R1, the reliability of the semiconductor optical element EL can be further improved. The diffraction grating GR may be formed in the semiconductor layer 30 of the laminate 2, rather than in the semiconductor layer 10.

[0027] The current control layer 3 controls the current injected into the laminate 2. Specifically, the current control layer 3 consists of a block layer 41 and a contact layer 42 stacked in order from the semiconductor layer 30 side. The block layer 41 is provided with a region 41a that allows current supplied via the contact layer 42 to pass through, and a region 41b that blocks it. The block layer 41 uses region 41b to define the +X side (output surface PL1 side) and the -X side (reflection surface PL2 side) of the laminate 2 as a current-free injection region R1 where no current is injected, and region 41b to define the area between the current-free injection region R1 as a current-injection region R0 where current is injected.

[0028] Window regions W are formed on the +X side (emission surface PL1 side) and the -X side (reflection surface PL2 side) of the laminate 2 and the current control layer 3. The window regions W are provided to reduce the absorption rate of the light generated in the active layer 20. The window regions W are regions designed to have a larger energy bandgap than the regions other than the window regions W (non-window regions). The window regions W are arranged, for example, in the current non-injection region R1 when viewed in plan view (see FIG. 2). The shape of the window region W when viewed in plan view can be an arbitrary shape. For example, the shape of the window region W when viewed in plan view may be a shape corresponding to the shape of the current non-injection region R1 when viewed in plan view. Note that the window region W on the -X side (reflection surface PL2 side) of the laminate 2 and the current control layer 3 can be omitted.

[0029] The electrode layer 4 is the electrode layer on the p side of the semiconductor optical element EL and is formed on the contact layer 42 of the current control layer 3. The electrode layer 4 is, for example, a Ti / Au laminated film. The conductive layer 5 is a metal layer for supplying the current injected into the semiconductor layer 30 of the laminate 2 through the current injection region R0 of the electrode layer 4 and the current control layer 3 and for releasing the heat generated in the laminate 2, and is formed on the electrode layer 4. The conductive layer 5 is formed, for example, by gold plating having a thickness of 1 μm or more. The electrode layer 6 is the electrode layer on the n side of the semiconductor optical element EL and is formed on the back surface (-Z side surface) of the substrate 1. The electrode layer 6 is, for example, a Ni / Ge / Au laminated film.

[0030] Here, the conductive layer 5 is formed such that the distance A1 between one end portion in the X direction and the emission surface PLl is shorter than the width B1 in the X direction of the window region W formed on the +X side (emission surface PL1 side) (A1 < B1). Similarly, the conductive layer 5 is formed such that the distance A2 between the other end portion in the X direction and the reflection surface PL2 is shorter than the width B2 in the X direction of the window region W formed on the -X side (reflection surface PL2 side) (A2 < B2). This is to efficiently release the heat generated in the laminate 2 and prevent COD caused by heat, thereby improving the reliability of the semiconductor optical element EL.

[0031] COD is caused by positive feedback in which the light (laser light) amplified by the semiconductor optical element EL is absorbed to generate heat, and the heat generation increases the light absorption rate, thereby causing further light absorption. The heat generation due to light absorption occurs in the region other than the window region W (non-window region), and becomes significantly smaller in the window region W. Therefore, if the conductive layer 5 is formed such that (A1 < B1) and (A2 < B2), the entire non-window region where heat generation occurs in the X direction is covered by the conductive layer 5, and the heat generated in the laminate 2 is efficiently released by the conductive layer 5. As a result, COD is prevented.

[0032] The antireflection film 7 is a so-called AR (Anti Reflective) coat and is formed on the emission surface PL1 which is one side surface of the laminate 2. The high reflection film 8 is a so-called HR (High Reflection) coat and is formed on the reflection surface PL2 which is the other side surface of the laminate 2. The reflectance of the antireflection film 7 and the high reflection film 8 can be freely selected according to the design of the semiconductor optical element EL. For example, a single layer film such as Al2O3, AlN, Si, SiO2, TiO2, or a multilayer film formed by combining two or more of these can be used to achieve a low reflectance of about 0.1%. Also, by laminating a plurality of pairs of two of these, a high reflectance close to 100% can be achieved.

[0033] In addition, the semiconductor layer 10, the active layer 20, and the semiconductor layer 30 of the laminate 2, as well as the block layer 41 and the contact layer 42 of the current control layer 3, can be formed by, for example, the metal organic chemical vapor deposition (MOCVD) method. At this time, as raw materials, necessary raw materials selected from trimethylgallium (TMG), trimethylaluminum (TMA), trimethylindium (TMI), arsine gas (AsH3), halomethanes such as carbon bromide (CBr4) or carbon chloride (CCl4), diethylzinc (DEZ), monosilane (SiH4), etc. may be appropriately used according to the materials constituting each layer.

[0034] A semiconductor optical element (EL) is, for example, a semiconductor laser element that has a light emission width of 75 μm or more in the Y direction, a resonator length of 3 mm or more, and is capable of outputting laser light with an output of 10 W or more. Such a semiconductor optical element (EL) can also be called a broad-area semiconductor laser. In this embodiment, for the sake of ease of understanding, the case in which the first conductivity type is n-type and the second conductivity type is p-type will be explained as an example.

[0035] Here, the peak wavelength of the gain spectrum of the active layer 20 is λ act The reflection wavelength of the diffraction grating GR is λ b The peak wavelength of the emission spectrum in the window region W is λ W The semiconductor optical element EL of this embodiment is λ act ≥λ b >λ W It is structured to satisfy the following relationship.

[0036] Figure 3 is a diagram illustrating the relationship between the peak wavelength of the gain spectrum of the active layer, the reflection wavelength of the diffraction grating, and the peak wavelength of the emission spectrum of the window region in a semiconductor optical device according to the first embodiment of the present invention. The graph in Figure 3 has wavelength on the horizontal axis and gain (optical gain) on the vertical axis. In the graph in Figure 3, the dashed curve shows an example of the gain spectrum of the active layer 20 during free operation (when wavelength is not locked), and the solid curve shows an example of the gain spectrum of the active layer 20 during locked operation (when wavelength is locked). The horizontal axis (wavelength) in Figure 3 represents the peak wavelength λ at which the gain of the gain spectrum of the active layer 20 is maximum during free operation. act This is shown as a deviation from the original.

[0037] As shown in Figure 3, the gain spectrum of the active layer 20 has a peak wavelength λ act The gain is maximized at the peak wavelength λ act The gain gradually decreases as you move away from the point. Here, the gain spectrum of the active layer 20 is the peak wavelength λ act On the shorter wavelength side, the peak wavelength λ actThe gain decreases gradually as you move away from the target. On the other hand, the gain spectrum of the active layer 20 is as follows: peak wavelength λ act On the longer wavelength side, the peak wavelength λ act The gain decreases sharply as you move away from the peak wavelength λ. act This is because the longer wavelength range is defined by the band gap of the semiconductor constituting the active layer 20.

[0038] The semiconductor optical element EL can oscillate as a laser at a wavelength where the gain spectrum of the active layer 20 is greater than or equal to the oscillation threshold gain. During free operation, the semiconductor optical element EL will, for example, as shown in Figure 3, have a peak wavelength λ at which the gain of the gain spectrum of the active layer 20 is greater than or equal to the oscillation threshold gain GT1. act It can generate laser oscillation.

[0039] In this embodiment, the semiconductor optical element EL has a diffraction grating GR formed on it, and as shown in Figure 3, the oscillation threshold gain is equal to the reflection wavelength λ of the diffraction grating GR. b The oscillation threshold gain drops sharply to GT2. In other words, the semiconductor optical element EL reduces losses by feeding back light of wavelengths within the range in which gain can be obtained by the diffraction grating GR to the active layer 20, and the reflection wavelength λ of the diffraction grating GR b The gain is designed to outweigh the losses. That is, the semiconductor optical element EL, during lock operation, is designed to have a reflection wavelength λ of the diffraction grating GR. b It is designed to wavelength-lock and generate laser oscillation.

[0040] Here, focusing on the temperature rise when the semiconductor optical element EL is driven by a laser, the peak wavelength λ of the gain spectrum of the active layer 20 act This fluctuates significantly due to the synergistic effect of band gap variations and carrier distribution variations. On the other hand, the reflection wavelength λ of the diffraction grating GR b This is caused by a change in the diffraction grating spacing due to temperature changes, and although it varies depending on the material and configuration, the peak wavelength λ of the gain spectrum of the active layer 20 act This is small compared to the fluctuations of other factors. As the operating temperature rises, the risk of wavelength locking increases, so it is necessary to maintain a stable operating temperature.

[0041] In particular, in broad-area semiconductor lasers, the light density is not constant in both the vertical (X) and horizontal (Y) directions within the current injection region, and therefore the amount of heat generated within the area is also not constant. This increases the risk of wavelength locking being lost in certain areas of the laser. This phenomenon becomes more pronounced as the output power increases.

[0042] In this embodiment, λ act ≥λ b It is configured to satisfy the following relationship: Even if the wavelength lock is locally released, the oscillation wavelength of the semiconductor optical element EL will be the reflection wavelength λ of the diffraction grating GR. b This is to reduce the risk of COD by using longer wavelengths.

[0043] Furthermore, λ act <λ b If the system is configured to satisfy the following relationship, then when the wavelength lock is locally released, the oscillation wavelength of the semiconductor optical element EL will be, for example, the peak wavelength λ of the gain spectrum of the active layer 20. act Thus, the oscillation wavelength of the semiconductor photoelement EL is the peak wavelength λ of the emission spectrum in the window region W. W As it gets closer, the risk of COD increases and reliability decreases.

[0044] Furthermore, in this embodiment, λ b >λ W It is configured to satisfy the following relationship: the reflection wavelength λ of the diffraction grating GR. b COD caused by wavelength-locked laser light is prevented. Here, the window region W is formed by mixing the active layer 20 with the surrounding material, so the peak wavelength λ of the emission spectrum of the window region W W Also, the peak wavelength λ of the gain spectrum of the active layer 20 act It can be assumed that it has a similar temperature dependence. As the operating temperature rises, the peak wavelength λ of the emission spectrum in the window region W changes. W and the reflection wavelength λ of the diffraction grating GR bConsidering that the difference between them narrows, and that the light transmittance of the material has a trailing edge that reflects wavelength dispersion, at room temperature, λ b >λ W It is preferable to satisfy the relationship of +30nm.

[0045] Next, we will describe in more detail the configuration of the semiconductor optical element EL shown in Figure 1. The details of the substrate 1, the laminate 2, and the current control layer 3 will be described in order below.

[0046] <Circuit board 1> The substrate 1 includes a compound semiconductor and a dopant. Examples of compound semiconductors include III-V compound semiconductors such as GaAs and InP. Examples of dopants include elements such as Si, Ge, Sn, S, Se, and Te. These can be used individually or in combination of two or more. The thickness of the substrate 1 is not particularly limited, but is, for example, about 250 to 450 μm.

[0047] <Laminate 2> The laminate 2 comprises, for example, a semiconductor layer 10, an active layer 20, and a semiconductor layer 30, as described above. The laminate 2 includes a compound semiconductor. Examples of compound semiconductors include GaAs, AlGaAs, InGaAs, InGaAlAs, InP, GaInP, AlInP, AlGaInP, and InGaAsP.

[0048] Semiconductor layer 10 The semiconductor layer 10 includes, for example, as described above, a buffer layer 11, a first cladding layer 12, a diffraction grating layer 13, a second cladding layer 14, and a waveguide layer 15. The buffer layer 11 is a layer provided between the substrate 1 to form a high-quality semiconductor layer 10. The first cladding layer 12 is a layer for confining the light generated in the active layer 20. The diffraction grating layer 13 is a layer in which a diffraction grating GR is formed. As the diffraction grating layer 13, for example, a superlattice structure in which different kinds of semiconductor compounds are alternately laminated can be used. The second cladding layer 14 is a layer for confining the light generated in the active layer 20 together with the first cladding layer 12. The waveguide layer 15 is a layer in which the light generated in the active layer 20 propagates together with the active layer 20. Hereinafter, a GaAs-AlGaAs-based laser will be described as an example.

[0049] The semiconductor layer 10 contains a compound semiconductor and a dopant. The compound semiconductor may be the same as or different from the compound semiconductor contained in the substrate 1. For example, when the semiconductor layer 10 contains AlGaAs as the compound semiconductor, if the composition of Al is x and the composition ratio of Al to Ga is x:(1 - x). In this case, for the waveguide layer 15 of the semiconductor layer 10, it is desirable that the composition x of Al is, for example, 0 < x ≦ 0.3.

[0050] As the dopant, the same dopant as that in the substrate 1 can be used. For example, the doping concentration of the waveguide layer 15 is 16 ~1×10 17 cm -3 in the range of concentration, and it is more desirable that it is in the range of concentration of 2×10 16 ~5×10 16 cm -3

[0051] The thicknesses of the first cladding layer 12, the second cladding layer 14, and the waveguide layer 15 are not particularly limited, but for example, it is preferable that they are about 1 μm. The doping concentration and thickness of the waveguide layer 15 are designed in consideration of the balance between the resistance value of the semiconductor optical element EL and the decrease in the light emission efficiency due to free carrier absorption.

[0052] 《Active layer 20》 The active layer 20 has a band gap smaller than that of the semiconductor layers 10 and 30, and is a layer that generates light by current injection. The active layer 20 contains a compound semiconductor. The compound semiconductor is appropriately selected according to the wavelength of light emitted from the semiconductor photoelement EL. Examples of compound semiconductors include InGaAs, GaAs, InGaAlAs, AlGaInP, and InGaAsP.

[0053] The active layer 20 may be composed of a laminate including, for example, a quantum well layer between two barrier layers. The two barrier layers on either side of the quantum well layer are layers containing a compound semiconductor having a band gap larger than the band gap of the quantum well layer. The barrier layers may further contain dopants. The barrier layers can consist of a layer with a constant doping concentration, a graded layer in which the doping concentration changes as it moves away from the quantum well layer, or a laminate of these. Alternatively, the barrier layers can consist of a layer in which the elemental composition of the compound semiconductor is constant, a graded layer in which the elemental composition of the compound semiconductor changes along the direction away from the quantum well layer, or a laminate of these.

[0054] The thickness of the active layer 20 is not particularly limited, but is, for example, about 3 to 70 nm. The active layer 20 may also be a multi-quantum well structure in which quantum well layers and barrier layers are alternately stacked over multiple layers.

[0055] Semiconductor layer 30 The semiconductor layer 30 includes, for example, a waveguide layer 31 and a cladding layer 32, as described above. The waveguide layer 31, together with the active layer 20, is a layer through which light generated in the active layer 20 propagates. The cladding layer 32 is a layer for confining the light generated in the active layer 20. In other words, the light generated in the active layer 20 propagates through the waveguide layer 31, the waveguide layer 15 of the semiconductor layer 10, and the active layer 20 while being confined by the cladding layer 32 and the second cladding layer 14 and first cladding layer 12 of the semiconductor layer 10.

[0056] The semiconductor layer 30 includes a compound semiconductor and a dopant. The compound semiconductor may be the same as or different from the compound semiconductor included in the substrate 1 or the semiconductor layer 10. For example, when the semiconductor layer 30 includes AlGaAs as the compound semiconductor, it is desirable that the waveguide layer 31 of the semiconductor layer 30 has, for example, 0 < x ≤ 0.3. Examples of the dopant include elements such as C. The doping concentration of the waveguide layer 31 may be the same as or different from the doping concentration of the waveguide layer 15 in the semiconductor layer 10. For example, the doping concentration of the waveguide layer 31 is in the range of 1×10 16 ~1×10 17 cm -3 is desirable, and more preferably in the range of 2×10 16 ~5×10 16 cm -3 of the range.

[0057] The thickness of the waveguide layer 31 may be the same as or different from the thickness of the waveguide layer 15 in the semiconductor layer 10. The thickness of the cladding layer 32 may be the same as or different from the thickness of the first cladding layer 12 in the semiconductor layer 10. The thicknesses of the waveguide layer 31 and the cladding layer 32 are not particularly limited, but for example, it is preferably about 1 μm.

[0058] 〈Current control layer 3〉 The current control layer 3 includes, for example, as described above, a blocking layer 41 and a contact layer 42. The blocking layer 41 causes current to be injected into the current injection region R0 and prevents current from being injected into the current non-injection region R1. The contact layer 42 makes the contact with the electrode layer 4 an ohmic contact.

[0059] The block layer 41 and the contact layer 42 contain a compound semiconductor and a dopant. The compound semiconductor may be the same as or different from the compound semiconductor contained in the substrate 1, semiconductor layer 10, or semiconductor layer 30. Here, the dopant in region 41a of the block layer 41 can be the same as the dopant used in semiconductor layer 30, and the dopant in region 41b of the block layer 41 can be the same as the dopant in the substrate 1 or the dopant used in semiconductor layer 10. This is because region 41b of the block layer 41 needs to block the current. The dopant in the contact layer 42 can be the same as the dopant used in semiconductor layer 30.

[0060] In this embodiment, the semiconductor optical element EL was described using the example where the current control layer 3 is a so-called SAS (Self-Aligned Structure), but the current control layer 3 is not limited to a so-called SAS. The current control layer 3 may be a so-called ridge structure or a so-called electrode stripe structure.

[0061] As described above, in this embodiment, a diffraction grating GR is formed on the semiconductor layer 10 or the semiconductor layer 30 between the output surface PL1 and the reflecting surface PL2 of the laminate 2, which is made up of a laminate 10, an active layer 20, and a semiconductor layer 30. Furthermore, a window region W is formed at least on the output surface PL1 side of the laminate 2 to reduce the absorption rate of light generated by the active layer 20. The peak wavelength λ of the gain spectrum of the active layer 20 act , the reflection wavelength λ of the diffraction grating GR b , the peak wavelength λ of the emission spectrum in the window region W W is, λ act ≥λ b >λ W It is configured to satisfy the following relationship. As a result, the semiconductor optical element EL of this embodiment has high reliability because it can reduce the risk of COD.

[0062] [Second Embodiment] Figure 4 is a plan view of a semiconductor optical element according to a second embodiment of the present invention. In Figure 6, components similar to those shown in Figure 2 are denoted by the same reference numerals. The semiconductor optical element EL of this embodiment has basically the same configuration as the semiconductor optical element EL shown in the first embodiment. However, the semiconductor optical element EL of this embodiment differs from the semiconductor optical element EL shown in the first embodiment in the configuration of the diffraction grating GR.

[0063] As shown in Figure 2, the semiconductor optical element EL of the first embodiment had a structure in which a diffraction grating GR forming a DFB (Dynamic Field Breakdown) was located within the current injection region R0 in the X direction. In contrast, the semiconductor optical element EL of this embodiment has a configuration in which the diffraction grating GR forms a DBR (Dynamic Field Breakdown) and is located outside the current injection region R0. With this configuration, current is not injected into the diffraction grating GR, preventing defects in the diffraction grating GR and heat generation due to current absorption, thereby improving reliability.

[0064] Figure 5 is a perspective view showing a semiconductor optical device according to one embodiment of the present invention. As shown in Figure 5, the semiconductor optical device DV of this embodiment comprises a thermally conductive submount 100 and a semiconductor optical element EL of either the first or second embodiment described above. In the semiconductor optical device DV, the semiconductor optical element EL is mounted on the submount 100 via a thermally conductive metal junction layer (not shown) in an inverted state (with the electrode layer 6 on the upper side and the conductive layer 5 on the lower side).

[0065] Specifically, the submount 100 has a positive electrode 101 and a negative electrode 102 on its upper surface. The semiconductor optical element EL is mounted on the positive electrode 101 such that the conductive layer 5 shown in Figure 1 is electrically conductive with the positive electrode 101. In addition, the electrode layer 6 shown in Figure 1 and the negative electrode 102 of the semiconductor optical element EL are electrically connected by a wire (not shown). Therefore, by supplying an appropriate current between the positive electrode 101 and the negative electrode 102, laser light is emitted from the emission surface PL1 of the semiconductor optical element EL mounted on the submount 100.

[0066] Furthermore, the semiconductor optical element and semiconductor optical device of the present invention are not limited to the embodiments described above, nor are they limited to the modifications described above. In other words, the present invention can be freely modified within the scope of the present invention. For example, although the above embodiments and specific configuration examples mainly describe a stacked structure of the semiconductor optical element, structures other than the stacked structure are arbitrary. [Explanation of Symbols]

[0067] 1...Substrate, 2...Laminate, 3...Current control layer, 5...Conductive layer, 10...Semiconductor layer, 20...Active layer, 30...Semiconductor layer, 100...Submount, DV...Semiconductor optical device, EL...Semiconductor optical element, GR...Diffraction grating, PL1...Emission surface, PL2...Reflection surface, R1...Current non-injection region, W...Window region

Claims

1. circuit board and A laminate comprising, in order from the substrate side, a first conductivity semiconductor layer, an active layer, and a second conductivity semiconductor layer, An ejection surface provided on one side of the laminate, A reflective surface provided on the other side of the laminate so as to face the aforementioned emission surface, Between the emission surface and the reflection surface, a diffraction grating formed in the first conductivity type semiconductor layer or the second conductivity type semiconductor layer, A window region formed at least on the output surface side of the laminate, which reduces the absorption rate of light generated in the active layer, Equipped with, The peak wavelength of the gain spectrum of the active layer is λ act , the reflection wavelength of the diffraction grating is λ b , the peak wavelength of the emission spectrum in the window region is λ W Therefore, λ act ≥λ b >λ W Satisfying the relationship, Semiconductor optical element.

2. λ b >λ W The semiconductor optical element according to claim 1, further satisfying the relationship of +30 nm.

3. The semiconductor optical element according to claim 1, further comprising a conductive layer provided on the laminate, which supplies a current injected into the second conductive semiconductor layer and releases heat generated in the laminate.

4. The semiconductor optical element according to claim 3, wherein the distance between one end of the conductive layer and the output surface in the direction in which the output surface and the reflecting surface face each other is shorter than the width of the window region in that direction.

5. The semiconductor optical element according to claim 4, wherein the window region is formed not only on the emission side of the laminate but also on the reflection side of the laminate.

6. The semiconductor optical element according to claim 5, wherein the distance between the other end of the conductive layer and the reflective surface in the aforementioned direction is shorter than the width of the window region formed on the reflective surface side of the laminate in the aforementioned direction.

7. The semiconductor optical element according to claim 1, wherein the diffraction grating is a distributed Bragg reflector formed on the reflective surface side of the laminate.

8. The semiconductor optical element according to claim 1, further comprising a current control layer provided on the laminate, wherein at least the exit surface side of the laminate is a current-free region where no current is injected.

9. A submount with thermal conductivity, A semiconductor optical element according to any one of claims 1 to 8, mounted on the submount via a thermally conductive metal bonding layer, A semiconductor optical device equipped with the following features.

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