JP2006228959A - Surface-emitting semiconductor laser - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a surface-emitting semiconductor laser which has low element resistance and is suitable for high-speed modulation. <P>SOLUTION: The laser is provided with a lower DBR (distributed bragg reflector) mirror layer 11 and an upper DBR mirror layer 15 with an active layer 13 sandwiched. The laser also has a current constriction layer 15C in one part of layers forming the DBR mirror layer 15. The vicinity of the current constriction layer 15C has an impurity concentration lower than an average concentration of the DBR mirror layer 15. In this way, in the vicinity of the layer 15C having the low impurity concentration, a current flowing in a direction perpendicular to a laminated direction can be made to flow in a region having a high electric conductivity, e.g. a region having less electric resistance. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a surface emitting semiconductor laser having a current confining layer, and more particularly to a surface emitting semiconductor laser in which a current confining layer is provided in a multilayer reflector.

  Unlike a conventional Fabry-Perot resonator type semiconductor laser, a surface emitting semiconductor laser emits light in a direction orthogonal to a substrate, and a large number of elements are arranged in a two-dimensional array on the same substrate. In recent years, it has attracted attention in the field of data communication.

  Here, a basic structure and operation of a general surface emitting semiconductor laser will be briefly described. A surface emitting semiconductor laser includes a laser structure portion in which a pair of multilayer mirrors is formed on a semiconductor substrate, and an active layer serving as a light emitting region is provided between the pair of reflectors. One multilayer reflector is provided with a current confinement layer in order to increase the current injection efficiency into the active layer and lower the threshold current. Further, an n-side electrode is provided on the lower surface side, a p-side electrode is provided on the upper surface side, and an opening for emitting laser light is provided on the p-side electrode. In this surface emitting semiconductor laser, the current confined by the current confinement layer provided in one multilayer reflector is injected into the active layer, and the light emitted from the active layer is provided as a laser beam on the p-side electrode. It is emitted from the opening.

  By the way, the surface-emitting semiconductor laser described above has many advantages such as a smaller threshold current and a longer element life compared to the Fabry-Perot resonator type, but has a high element resistance, so that impedance mismatching is not caused. As a result, there is a problem that high-speed modulation originally required for data communication becomes difficult. Therefore, a method has been proposed in which a high concentration of impurities is added to the compound semiconductor layer excluding the active layer and the region in the vicinity thereof so that light absorption does not occur in the active layer and the element resistance is reduced. (Patent Document 1).

JP 2001-332812 A

  However, although this method can reduce the device resistance compared to the case where no impurity is added, the region where the doping concentration is relatively low is still widespread. It is difficult to reduce the element resistance to the extent that mismatch does not become a problem.

  The present invention has been made in view of such problems, and an object thereof is to provide a surface-emitting type semiconductor laser having a low element resistance and suitable for high-speed modulation.

  The surface-emitting type semiconductor laser of the present invention comprises a pair of multilayer reflectors with an active layer in between and a current confinement layer in a part of the layers constituting the multilayer reflector, In the vicinity, the impurity concentration is lower than the average concentration of the multilayer mirror.

  In the surface emitting semiconductor laser of the present invention, the vicinity of the current confinement layer has an impurity concentration lower than the average concentration of the multilayer reflector. As a result, the current flowing in the direction perpendicular to the stacking direction in the vicinity of the current confinement layer having a low impurity concentration is less affected by impurity scattering than the current flowing in another region having a relatively high impurity concentration. Since the mobility is increased, the vicinity of the current confinement layer having a low impurity concentration can be a region having a high electrical conductivity, that is, a region having a low electrical resistance. However, the electrical conductivity σ is an index representing the ease of carrier flow in an electric field, and is represented by σ = neμ where n is the carrier density, e is the carrier charge, and μ is the mobility. Therefore, it is necessary to set the carrier density so that the rate of increase in mobility is larger than the rate of decrease in carrier density (impurity concentration).

  In this specification, “in the vicinity of the current confinement layer” means a region from the first layer to several layers (generally about three layers) counted from the upper surface side and the lower surface side of the current confinement layer. Point to. However, when the current confinement layer is provided in a portion other than the end face of the multilayer reflector, the layers in contact with both sides of the current confinement layer are layers constituting the multilayer reflector, but the current confinement layer is When provided on the end face of the multilayer reflector, the layer in contact with one of the current confinement layers is a layer constituting the multilayer reflector, and the layer in contact with the other is the multilayer reflector. Different layers.

  Further, “impurities” are substances intentionally added to create desirable properties in the layers in the process of manufacturing a multilayer reflector, and for example, zinc (Zn), magnesium as p-type impurities. It is a concept including (Mg) or beryllium (Be), or silicon (Si) or selenium (Se) as an n-type impurity.

  According to the surface emitting semiconductor laser of the present invention, the vicinity of the current confinement layer has an impurity concentration lower than the average concentration of the multilayer reflector, thereby increasing the electrical conductivity and reducing the element resistance. be able to. As a result, impedance mismatch can be eliminated, and high-speed modulation is facilitated. Further, the reliability of the element can be improved.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

[First Embodiment]
FIG. 1 shows a cross-sectional structure of a surface emitting semiconductor laser 1 according to an embodiment of the present invention. FIG. 2 is an enlarged view of a part of the cross-sectional structure of the surface-emitting type semiconductor laser 1 shown in FIG. 1, and also shows the distribution of impurity concentration in that part. FIG. 3 shows a unique example in FIG.

  The surface emitting semiconductor laser 1 includes a lower DBR mirror layer 11 (multilayer reflective mirror), a lower clad layer 12, an active layer 13, an upper clad layer 14, an upper DBR mirror layer 15 (multilayer reflective) on one side of a substrate 10. Mirror) and p-type contact layer 16 are laminated in this order. Here, a part of the lower cladding layer 12, the active layer 13, the upper cladding layer 14, the upper DBR mirror layer 15, and the p-type contact layer 16 are formed up to the p-type contact layer 16 and then selectively etched from the upper surface. As a result, the mesa post 30 is obtained.

  The substrate 10, the lower DBR mirror layer 11, the lower cladding layer 12, the active layer 13, the upper cladding layer 14, the upper DBR mirror layer 15 and the p-type contact layer 16 are each composed of, for example, a GaAs (gallium arsenide) based compound semiconductor. Has been. The GaAs compound semiconductor is a compound semiconductor containing at least gallium (Ga) among the 3B group elements in the short periodic table and at least arsenic (As) among the 5B elements in the short periodic table. Say.

The substrate 10 is made of, for example, n-type GaAs. The lower DBR mirror layer 11 includes a low refractive index layer 11Ai and a high refractive index layer 11Bi (1 ≦ i ≦ x) as a set, and includes x sets. Note that the value of i becomes smaller toward the active layer 14 side. The high refractive index layer 11Bi has an Al _a Ga _1-a As (0 <0) with a thickness of λ / 4n (λ is an oscillation wavelength, n is a refractive index), and an n-type impurity concentration is 1.0 × 10 ¹⁸ / cm, for example. The low refractive index layer 11Ai is made of Al _b Ga _1-b As (0 ≦ b <0) having a thickness of λ / 4n and an n-type impurity concentration of 1.0 × 10 ¹⁸ / cm, for example. a). Here, examples of the n-type impurity include silicon (Si) and selenium (Se).

The lower cladding layer 12 is made of, for example, Al _c Ga _1-c As (0 <c <1). The active layer 13 is made of, for example, Al _d Ga _1-d As (0 <d <1). The upper cladding layer 14 is made of, for example, Al _f Ga _1-f As (0 <f <1). The lower cladding layer 12, the active layer 13, and the upper cladding layer 14 are preferably undoped, but may contain p-type or n-type impurities.

The upper DBR mirror layer 15 includes a low refractive index layer 15Aj and a high refractive index layer 15Bj (1 ≦ j ≦ y) as a set, and includes y sets. Note that the value of j becomes smaller toward the active layer 14 side. The high refractive index layer 15Bj has, for example, Al _g Ga _1-g As (0 <0) with a thickness of λ / 4n (λ is an oscillation wavelength, n is a refractive index) and a p-type impurity concentration of 1.0 × 10 ¹⁸ / cm. The low refractive index layer 11Aj is made of Al _h Ga _1-h As (0 ≦ h <) having a thickness of λ / 4n and a p-type impurity concentration of 1.0 × 10 ¹⁸ / cm, for example. g). Here, examples of the p-type impurity include zinc (Zn), magnesium (Mg), and beryllium (Be).

However, in the upper DBR mirror layer 15, a current confinement layer 15 </ b> C is formed instead of the low refractive index layer 15 </ b> Aj at a portion of the low refractive index layer 15 </ b> Aj that is j sets apart from the active layer 13 side. The current confinement layer 15C includes a current injection region 15C-1 provided in the central region and a current confinement region 15C-2 provided in a portion surrounding the current injection region 15C-1. The current injection region 15C-1 is made of, for example, AlAs having a p-type impurity concentration of 1.0 × 10 ¹⁸ / cm, and the current confinement region 15C-2 is made of, for example, Al ₂ O ₃ .

By the way, in the present embodiment, in the upper DBR mirror layer 15, the impurity concentration in the vicinity of the current confinement layer 15C is set lower than the impurity concentration in other regions, for example, 1.0 × 10 ¹⁷ / cm ³ or less. . Note that the vicinity of the current confinement layer 15C refers to a region from the first layer to several layers (approximately three layers) from the upper and lower surfaces of the current confinement layer 15C, that is, the current confinement layer. It refers to a pair of several layers sandwiching 15C. However, the number of layers having a low impurity concentration on the upper surface side need not be the same as the number of layers having a low impurity concentration on the lower surface side. In addition, the composition and impurity concentration of the lower impurity concentration layer on the upper surface side need not be the same as the composition and impurity concentration of the lower impurity concentration layer on the lower surface side.

In addition, the low concentration as exemplified above is realized by stopping the supply of impurities in the process of manufacturing the current confinement layer 15C and its neighboring layers, but in reality, impurities in other layers are diffused. Therefore, the concentration often becomes approximately 1.0 × 10 ¹⁶ / cm ³ or more and 1.0 × 10 ¹⁷ / cm ³ or less.

  In FIG. 2, when the current confinement layer 15C is provided in the portion of the j-th low refractive index layer 15Aj counted from the active layer 13 side, the impurity concentrations of the layers in contact with both surfaces of the current confinement layer are the other. The impurity concentration distribution when the concentration is lower than the impurity concentration in the region is illustrated. At this time, in the upper DBR mirror layer 15, the low impurity concentration layers are the high refractive index layers 15Bj-1 and 15Bj.

  Further, when the current confinement layer 15C is provided at the low refractive index layer 15A1, which is the end face of the upper DBR mirror layer 15, the result is as shown in FIG. At this time, in the upper DBR mirror layer 15, the layer having a low impurity concentration includes a layer that is not a layer constituting the upper DBR mirror layer 15 as in the case of FIG. 2. Specifically, the high refractive index layer 15B1 and the upper cladding layer 14 are formed.

  The p-type contact layer 16 is made of, for example, p-type GaAs, and has, for example, a circular opening 16A in a region facing the current injection region 15C-1.

  The insulating layer 17 is formed so as to cover the entire mesa post 30 excluding the opening 16A and the peripheral edge of the opening 16A in the p-type contact layer 16, and is made of polyimide, for example. The p-side electrode 18 is formed so as to cover the peripheral edge of the opening 16 </ b> A and the insulating layer 17. The p-side electrode 18 is formed by, for example, laminating a titanium (Ti) layer, a platinum (Pt) layer, and a gold (Au) layer in this order from the p-side contact layer 16 side, and is electrically connected to the p-type contact layer 16. It is connected to the. An n-type contact layer 19 and an n-side electrode 20 are formed in this order on the back surface of the substrate 10. Here, the n-type contact layer 19 is made of, for example, n-type GaAs. The n-side electrode 20 has a structure in which, for example, an alloy layer of gold (Au) and germanium (Ge), a nickel (Ni) layer, and a gold (Au) layer are sequentially stacked from the substrate 10 side. And is electrically connected to the n-type contact layer 19.

  The surface emitting semiconductor laser 1 having such a configuration can be manufactured, for example, as follows.

4A to 4C show the manufacturing method in the order of steps. For example, in order to manufacture a GaAs (gallium arsenic) based surface emitting semiconductor laser 1, a compound semiconductor layer on the substrate 10 is formed by, for example, MOCVD (Metal Organic Chemical Vapor Deposition) method. Form. At this time, for example, trimethylaluminum (TMA), trimethylgallium (TMG), trimethylindium (TMIn), or arsine (AsH ₃ ) is used as a raw material for the III-V group compound semiconductor. , H ₂ Se, and dimethyl zinc (DMZ), for example, is used as the acceptor impurity material.

  Specifically, first, as shown in FIG. 4A, on the substrate 10, the lower DBR mirror layer 11, the lower cladding layer 12, the active layer 13, the upper cladding layer 14, the upper DBR mirror layer 15 and p. The side contact layer 16 is laminated in this order.

However, when the layers near the current confinement layer 15C in the upper DBR mirror layer 15 are stacked, the supply of impurities is stopped. As a result, the layers in the vicinity of the current confinement layer 15C can be undoped, but in reality, the impurity concentration of these layers is approximately 1.0 × 10 ¹⁶ / cm ³ due to diffusion of impurities from adjacent layers. It is often in the range of 1.0 × 10 ¹⁷ / cm ³ or less.

  Next, as shown in FIG. 4B, for example, a mask layer (not shown) is formed on the p-side contact layer 16, and the reactive ion etching (RIE) method is used to form p. The side contact layer 16, the upper DBR mirror layer 15, the upper cladding layer 14, the active layer 13 and a part of the lower cladding layer 12 are selectively removed, and a part of the p-side contact layer 16 is etched to form an opening 16A. Form. Thereby, the mesa post 30 having the opening 16A at the top is formed.

  Next, as shown in FIG. 4C, an oxidation process is performed at a high temperature in a water vapor atmosphere, and Al in a layer made of AlAs that becomes the current confinement layer 15C is selected from the outside of the mesa post 30. Oxidizes. As a result, the current injection region 15C-1 is formed in the center region of the layer, and the current confinement region 15C-2 is formed in the other regions. As a result, the current injection region 15C-1 and the current confinement region 15C- A current confinement layer 15C made of 2 is formed.

  Next, as shown in FIG. 1, the insulating layer 17 is laminated on the mesa post 30 and the peripheral substrate of the mesa post 30 by, for example, a CVD (Chemical Vapor Deposition) method. Thereafter, a part of the top of the mesa post 30 in the insulating layer 17 is selectively removed by etching to expose the upper DBR mirror layer 15 in the opening 16A, and the outer edge of the opening 16A in the p-side contact layer 16 Expose the part.

  Subsequently, for example, Ti, Pt, and Au are sequentially laminated on the mesa post 30 and the peripheral substrate of the mesa post 30 by, for example, a vacuum deposition method, to form the p-side electrode 18. Thereafter, the p-type cladding layer 15 is exposed in the opening 16A by lift-off or selective etching. When the p-type cladding layer 15 is exposed by lift-off, a photoresist film is formed in the opening 16A in advance before forming the p-side electrode 18, and then the p-side electrode 18 is removed together with the photoresist film. To do.

  Next, the back surface of the substrate 11 is appropriately polished to adjust the thickness of the substrate, and then the n-side contact layer 19 is formed on the surface. Subsequently, for example, an n-side electrode 20 is formed by laminating an alloy layer of gold and germanium (Ge), a Ni layer, and an Au layer in this order. In this way, the surface emitting semiconductor laser element 1 is manufactured.

  In this surface-emitting type semiconductor laser 1, when a predetermined voltage is applied between the n-side electrode 20 and the p-side electrode 18, current is injected into the active layer 13 through the current injection region 15C-1 in the current confinement layer 15C. As a result, light emission is caused by recombination of electrons and holes. This light is reflected by the pair of the lower DBR mirror layer 11 and the upper DBR mirror layer 15 and causes laser oscillation at a wavelength at which the phase change when it reciprocates once in the element is an integral multiple of 2π. Is emitted.

  By the way, in a general surface emitting semiconductor laser, as described above, a high concentration of impurities is added to the compound semiconductor layer excluding the active layer and the vicinity thereof so that light absorption does not occur in the active layer. In addition, the element resistance is reduced. This is an attempt to decrease the element resistance by increasing the carrier density n (impurity concentration) by paying attention to the fact that the electric conductivity σ is expressed by σ = neμ. However, in such a configuration, although it is possible to reduce the element resistance as compared with the case where no impurity is added, since the region where the doping concentration is relatively low still covers a wide range, the impedance during high-speed modulation is still large. It is difficult to reduce the element resistance to the extent that mismatch does not become a problem.

On the other hand, in the surface emitting semiconductor laser 1 according to the present embodiment, the impurity concentration in the vicinity of the current confinement layer 15C is reduced to, for example, 1.0 × 10 ¹⁷ / cm ³ or less. This is not to lower the element resistance by increasing the carrier density n (impurity concentration) as in the above example, but to decrease the element resistance by increasing the mobility μ.

  More specifically, when the impurity concentration in the vicinity of the current confinement layer 15C is reduced to a predetermined concentration, the rate of increase in mobility becomes larger than the rate of decrease in impurity concentration, and as a result, the electrical conductivity σ (= Neμ) increases. In this manner, in the vicinity of the current confinement layer 15C having a low impurity concentration, a current flowing in a direction perpendicular to the stacking direction can be passed in a region having a high electrical conductivity, that is, a region having a low electrical resistance. .

  Thus, according to the surface-emitting type semiconductor laser 1 of the present invention, the electric conductivity is increased because the vicinity of the current confinement layer 15C has an impurity concentration lower than the average concentration of the upper DBR mirror layer 15. Thus, the element resistance can be reduced. As a result, impedance mismatch can be eliminated, and high-speed modulation is facilitated. In addition, the reliability of the element can be improved.

[Second Embodiment]
Next, a surface emitting semiconductor laser 2 according to a second embodiment of the present invention will be described. In the present embodiment, not only the vicinity of the current confinement layer 15C but also the current confinement layer 15C in the upper DBR mirror layer 15 is lower in concentration than the impurity concentration in other regions, for example, 1.0 × 10 ¹⁷ / cm ^3. The following concentration is different from the first embodiment.

FIG. 7 shows the state of the current injection region of the surface emitting semiconductor laser according to the first comparative example. FIG. 8 shows the state of the current injection region 15C-1 of the surface emitting semiconductor laser 2 according to the second embodiment. In the surface emitting semiconductor laser according to the first comparative example, the impurity concentration of the current confinement layer and the vicinity thereof is set to a high concentration (for example, 1.0 × 10 ¹⁸ / cm ³ ), and the current confinement layer is made of AlAs. This is different from the surface emitting semiconductor laser 2 according to the second embodiment in that it is configured as described above.

  In the surface emitting semiconductor laser, one of the factors affecting the NFP (Near Field Pattern) of the laser light is the shape of the current injection region in the current confinement layer. A concentric luminance distribution having a peak at the center portion of the light spot is an ideal NFP, but when oxidation is performed on AlAs doped with a high concentration of impurities, FIG. 7 illustrates a first comparative example. As described above, since a rhombus current injection region is formed in the central portion of the opening 116A in accordance with the crystal orientation, the luminance distribution has peaks at the four corners of the rhombus, and NFP is not ideal. In addition, since the current concentrates on the four corners of the rhombus, the deterioration rate of the element increases. Therefore, the lifetime of the element is shortened, and the reliability of the element is lowered. Therefore, conventionally, AlGaAs obtained by adding Ga to AlAs is oxidized to form a current confinement layer having a disk-shaped current injection region. However, when Ga is added, the diameter of the current injection region does not become constant in the plane and has a distribution in the plane, so NFP is often not ideal, and as a result, the yield deteriorates. End up.

On the other hand, in the surface-emitting type semiconductor laser 2 of the present embodiment, the current confinement layer 15C is made of AlAs having a low impurity concentration of, for example, 1.0 × 10 ¹⁷ / cm ³ or less and in the vicinity of the current confinement layer 15C. This layer is also composed of a semiconductor with a low impurity concentration. This suppresses the diffusion of impurities into the current confinement layer 15C, so that it is possible to form the disc-shaped current injection region 15C-1 in the central portion of the opening 16A without adding Ga. (See FIG. 8). As a result, the deterioration rate of the element can be reduced, so that the life of the element can be extended and the reliability of the element can be improved.

  Moreover, since the oxidation rate is slowed by setting the impurity concentration to be low, the controllability of the shape of the current injection region can be improved, and the yield can be improved.

  Next, an example of the surface emitting semiconductor laser 2 according to the second embodiment will be described in comparison with a second comparative example. In this example, the configuration, operation, manufacturing method, and effects common to the surface emitting semiconductor laser 2 of the above embodiment are omitted as appropriate.

In this embodiment, the substrate 10 is made of n-type GaAs having a thickness of 100 μm and an impurity concentration of 1.0 × 10 ¹⁹ / cm ³ . Further, the lower DBR mirror layer 11 is made of n-type Al _0.1 Ga _0.9 As (low-refractive index layer 11Ai) / n-type Al _0.9 Ga _0.1 As (λ is the oscillation wavelength and n is the refractive index). One set of high refractive index layers 11Bi) is included, and 25 sets thereof are included.

The lower cladding layer 12 was 90 nm thick and undoped Al _0.75 Ga _0.25 As, the active layer 13 was 8 nm thick, undoped GaAs, the upper cladding layer 14 was 90 nm thick, and undoped Al _0.75 Ga _0.25 As. The upper DBR mirror layer 15 is made of p-type Al _0.1 Ga _0.9 As (low refractive index layer 15Aj) / p-type Al _0.9 Ga _0.1 As (high refractive index) having a thickness of λ / 4n (where λ is an oscillation wavelength and n is a refractive index). The rate layer 15Bj) is set as one set and includes 20 sets. The current confinement layer 15C is disposed in the second low-refractive index layer 15B-2 counted from the active layer 13, and the first to third layers counted from the current confinement layer 15C and the current confinement layer 15C. The impurity concentration of the layers up to is 1.0 × 10 ¹⁷ / cm ³ .

  The p-type contact layer 16 is made of p-type GaAs having a thickness of 300 nm, the insulating layer 17 is made of polyimide, and the n-type contact layer 19 is made of n-type GaAs. The p-side electrode 18 is laminated in the order of the Ti layer, the Pt layer and the Au layer from the p-side contact layer 16 side, and the n-side electrode 20 is laminated with the alloy layer of Au and Ge, the Ni layer and the Au layer on the substrate 10. Laminated in order from the side.

On the other hand, in this comparative example, the current confinement layer and the adjacent layer contain an impurity having a concentration of 1.0 × 10 ¹⁸ / cm ³ . Other configurations are the same as in this embodiment.

  FIG. 9 shows the series resistances of the present example and this comparative example normalized to 1 in this comparative example. FIG. 10 shows the deterioration rates of the present example and this comparative example normalized to 1 as the value of this comparative example. As shown in FIGS. 9 and 10, it can be confirmed that the series resistance and the deterioration rate according to this example are lower than the series resistance and the deterioration rate according to this comparative example.

  Therefore, it can be said that the series resistance and the deterioration rate can be reduced by lowering the impurity concentration of the current confinement layer 15C and its neighboring layers.

  Although the present invention has been described with reference to two embodiments and one example, the present invention is not limited to the above-described embodiments, and various modifications can be made.

  For example, in the above embodiment, the case where the substrate 10 made of n-type GaAs is used has been described as an example. However, the substrate 10 made of p-type GaAs may be used.

1 is a cross-sectional configuration diagram of a surface emitting semiconductor laser according to a first embodiment of the present invention. It is a figure showing the principal part of the laser of FIG. 1 with impurity concentration distribution. It is a figure showing the principal part of the specific example of the laser of FIG. 1 with impurity concentration distribution. It is sectional drawing for demonstrating the manufacturing process of the laser shown in FIG. It is a figure showing the principal part of the surface emitting semiconductor laser which concerns on the 2nd Embodiment of this invention with impurity concentration distribution. It is a figure showing the principal part of the specific example of the laser of FIG. 5 with impurity concentration distribution. It is a top view of the current injection region of the surface emitting semiconductor laser according to the first comparative example. FIG. 6 is a top view of a current injection region of the laser of FIG. 5. It is a figure showing the series resistance of the Example of the laser of FIG. 5, and the 2nd comparative example. It is the figure showing the deterioration rate of the Example of the laser of FIG. 5, and the 2nd comparative example.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1,2 ... Semiconductor laser, 10 ... Substrate, 11 ... Lower DBR mirror layer, 11Ai, 15Aj ... High refractive index layer, 11Bi, 15Bj ... Low refractive index layer, 12 ... Lower cladding layer, 13 ... Active layer, 14 ... Upper Clad layer, 15 ... Upper DBR mirror layer, 15C ... Current confinement layer, 15C-1 ... Current injection region, 15C-2 ... Current confinement region, 15D ... AlAs layer, 16 ... p-side contact layer, 16A ... opening, 17 Insulating layer, 18 ... p-side electrode, 19 ... n-side contact layer, 20 ... n-side electrode, 30 ... mesa post,

Claims (5)

A surface emitting semiconductor laser comprising a pair of multilayer reflectors with an active layer in between and a current confinement layer in a part of the layers constituting the multilayer reflector,
The surface emitting semiconductor laser characterized in that the vicinity of the current confinement layer has an impurity concentration lower than an average concentration of the multilayer reflector. 2. The surface-emitting type semiconductor laser according to claim 1, wherein an impurity concentration in the vicinity of the current confinement layer is 1.0 × 10 ¹⁷ / cm ³ or less. The surface emitting semiconductor laser according to claim 1, wherein the current confinement layer and the vicinity thereof have an impurity concentration lower than an average concentration of the multilayer reflector. 4. The surface-emitting type semiconductor laser according to claim 3, wherein an impurity concentration in the current confinement layer and the vicinity thereof is 1.0 × 10 ¹⁷ / cm ³ or less. The surface emitting semiconductor laser according to claim 3, wherein the current confinement layer is made of AlAs.

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