JP6045832B2 - Surface emitting laser element - Google Patents

Description

  The present invention relates to a surface emitting laser element.

A surface-emitting laser element using a current confinement layer including a selective oxidation layer is disclosed (for example, see Patent Document 1). The selective oxidation layer is formed by subjecting an Al-containing semiconductor layer containing aluminum (Al) to selective oxidation heat treatment from the outer peripheral side of the mesa post structure. In the selectively oxidized region of the Al-containing semiconductor layer, Al is oxidized to form Al ₂ O ₃ which is an insulator, and the Al-containing semiconductor layer remains inside to form a current path. Thereby, a current confinement structure is realized.

JP 2011-14793 A

  In actual use of the surface emitting laser element, high reliability is required.

  The present invention has been made in view of the above, and an object thereof is to provide a highly reliable surface emitting laser element.

  In order to solve the above-described problems and achieve the object, a surface emitting laser element according to the present invention includes a first reflecting mirror and a second reflecting mirror that constitute an optical resonator, and the first reflecting mirror. An active layer disposed between the second reflecting mirror and an active layer disposed between the second reflecting mirror and the active layer and formed on an outer periphery of the current injecting portion by a current injecting portion and a selective oxidation heat treatment. And a carrier barrier layer disposed between the active layer and the current confinement layer and serving as an energy barrier for minority carriers overflowing from the active layer. It is characterized by that.

  The surface emitting laser element according to the present invention is characterized in that, in the above invention, the surface emitting laser element is made of a semiconductor material having a higher band gap energy than a semiconductor layer adjacent to the carrier barrier layer on the active layer side.

  The surface emitting laser element according to the present invention is characterized in that, in the above invention, the surface emitting laser element is made of a semiconductor material having an Al composition higher than that of the semiconductor layer.

  Further, in the surface emitting laser element according to the present invention, in the above invention, the carrier barrier layer has a lower oxidation rate than an Al-containing semiconductor layer for forming the current confinement layer by a selective oxidation heat treatment. The Al composition and / or the layer thickness is set.

  In the surface-emitting laser device according to the present invention, the Al composition of the carrier barrier layer is the same as or higher than the Al composition of the Al-containing semiconductor layer.

  In the surface-emitting laser device according to the present invention as set forth in the invention described above, the thickness of the carrier barrier layer is 20 nm or less.

  The surface emitting laser element according to the present invention is characterized in that, in the above invention, the carrier barrier layer is disposed at a position of a node of a standing wave of light formed by laser light in the optical resonator. To do.

  The surface emitting laser element according to the present invention is characterized in that, in the above invention, the carrier barrier layer is disposed at a position of a first node from the active layer side among the nodes of the standing wave. To do.

  The surface emitting laser element according to the present invention is characterized in that, in the above invention, the current confinement layer is disposed at a position of a second node from the active layer side among the nodes of the standing wave. To do.

  In the surface-emitting laser device according to the present invention as set forth in the invention described above, the current confinement layer and the carrier barrier layer are separated by 100 nm or more in the layer thickness direction.

  The surface emitting laser element according to the present invention is characterized in that, in the above invention, the minority carriers are electrons, and the carrier barrier layer is doped p-type.

  In the surface-emitting laser device according to the present invention as set forth in the invention described above, the minority carrier concentration of the carrier barrier layer is one digit or more higher than the minority carrier concentration of the semiconductor layer.

  According to the present invention, there is an effect that a highly reliable surface emitting laser element can be realized.

FIG. 1 is a schematic cross-sectional view of the surface emitting laser element according to the first embodiment. FIG. 2 is a diagram showing the energy band and carrier flow of a surface emitting laser element without a carrier barrier layer. FIG. 3 is a diagram showing energy bands and carrier flows of the surface emitting laser element according to the first embodiment. FIG. 4 is a diagram showing oxidation rates of AlGaAs layers having various Al compositions and layer thicknesses. FIG. 5 is a schematic cross-sectional view of the surface emitting laser element according to the second embodiment. FIG. 6 is a diagram showing the energy band and the carrier flow of the surface emitting laser element according to the second embodiment.

  Embodiments of a surface emitting laser element according to the present invention will be described below in detail with reference to the drawings. Note that the present invention is not limited to the embodiments. Moreover, in each drawing, the same code | symbol is attached | subjected suitably to the same or corresponding element. Furthermore, it should be noted that the drawings are schematic, and dimensional relationships between elements may differ from actual ones. Even between the drawings, there are cases in which portions having different dimensional relationships and ratios are included.

(Embodiment 1)
FIG. 1 is a schematic cross-sectional view of a surface emitting laser element according to Embodiment 1 of the present invention. As shown in FIG. 1, a surface emitting laser element 100 includes an undoped lower DBR (Distributed Bragg Reflector) stacked on a substrate 1 made of n-type GaAs having a plane orientation (001) and functioning as a first reflecting mirror. Mirror 2, n-type contact layer 3, n-side electrode 4, n-type cladding layer 5, active layer 6, p-type cladding layer 7, carrier barrier layer 8, p-type spacer layer 9, current confinement layer 10, p-type A spacer layer 11, a p-type contact layer 12, a p-side electrode 13, a phase adjusting layer 14, and an upper dielectric DBR mirror 15 functioning as a second reflecting mirror are provided.

  The p-type contact layer 12 and the n-type contact layer 3 are disposed between the lower DBR mirror 2 and the upper dielectric DBR mirror 15. The active layer 6 is disposed between the lower DBR mirror 2 and the upper dielectric DBR mirror 15. The current confinement layer 10 is disposed between the p-type contact layer 12 and the active layer 6. The carrier barrier layer 8 is disposed between the current confinement layer 10 and the active layer 6. The p-type spacer layers 9 and 11 are respectively interposed between the carrier barrier layer 8 and the current confinement layer 10 and between the current confinement layer 10 and the p-type contact layer 12. The p-side electrode 13 is formed on the p-type contact layer 12, and the n-side electrode 4 is formed on the n-type contact layer 3.

  The laminated structure from the n-type cladding layer 5 to the p-type contact layer 12 is formed as a mesa post M formed into a columnar shape by an etching process or the like. The mesa post diameter is, for example, 30 μm. The n-type contact layer 3 extends on the outer peripheral side of the mesa post M. The lower DBR mirror 2 and the upper dielectric DBR mirror 15 constitute an optical resonator.

The lower DBR mirror 2 is formed on an undoped GaAs buffer layer (not shown) stacked on the n-type GaAs substrate 1. The lower DBR mirror 2 includes, for example, 40.5 pairs of compound semiconductor layers in which an Al _0.9 Ga _0.1 As layer functioning as a low refractive index layer and a GaAs layer functioning as a high refractive index layer are paired. It is formed as a semiconductor multilayer film mirror having a periodic structure. The layer thickness of each layer constituting the composite semiconductor layer of the lower DBR mirror 2 is λ / 4n (λ: laser oscillation wavelength, n: refractive index). For example, when λ is 1.06 μm, the Al _0.9 Ga _0.1 As layer has a thickness of about 88 nm, and the GaAs layer has a thickness of about 76 nm.

  The n-type contact layer 3 and the n-type cladding layer 5 are formed using n-type GaAs as a material.

The p-type cladding layer 7 is formed using p-type AlGaAs (for example, Al _0.3 Ga _0.7 As is desirable). The p-type spacer layers 9 and 11 are formed using p-type AlGaAs as a material. The p-type contact layer 12 is formed using p-type GaAs as a material.

The carrier concentration of the p-type cladding layer 7 and the p-type spacer layers 9 and 11 is, for example, about 3 × 10 ¹⁷ cm ^{−3 in} order to prevent an increase in absorption loss due to the p-type dopant. The carrier concentrations of the n-type cladding layer 5, the n-type contact layer 3, and the p-type contact layer 12 are, for example, about 1 × 10 ¹⁸ cm ⁻³ , 2 × 10 ¹⁸ cm ⁻³ , and 3 × 10 ¹⁹ cm ⁻³ , respectively. is there.

  The n-type contact layer 3, the n-type cladding layer 5, the p-type cladding layer 7, and the p-type spacer layers 9 and 11 sandwiched between the lower DBR mirror 2 and the upper dielectric DBR mirror 15 are formed of the active layer 6. An antinode of a standing wave of light formed by laser light in the optical resonator is formed at a position, and a node of the standing wave is formed at positions of the carrier barrier layer 8 and the current confinement layer 10. .

The current confinement layer 10 includes an opening 10a as a current injection portion and a selective oxidation layer 10b as a current confinement portion. The opening 10a is made of Al _1-x Ga _x As (0 ≦ x <0.1), and the selective oxidation layer 10b is made of (Al _1-x Ga _x ) ₂ O ₃ . X is 0.02, for example.

The current confinement layer 10 is formed by subjecting an Al-containing semiconductor layer made of Al _1-x Ga _x As to selective oxidation heat treatment. That is, the selective oxidation layer 10b is formed in a ring shape on the outer periphery of the opening 10a by oxidizing the Al-containing semiconductor layer by a predetermined range from the outer periphery of the mesa post M along the laminated surface. The selective oxidation layer 10b has insulating properties, and the current injected from the p-side electrode 13 is narrowed and concentrated in the opening 10a, whereby the current density injected into the active layer 6 immediately below the opening 10a. It has a function to enhance. The opening diameter of the opening 10a is, for example, 6 μm, but from the viewpoint of high speed operation and reliability, for example, 4 μm to 15 μm is preferable. Furthermore, in order to suppress high-order transverse mode oscillation, for example, 4 μm to 8 μm is more preferable.

The carrier barrier layer 8 is formed using p-type AlGaAs having a higher Al composition than the p-type cladding layer 7 and the p-type spacer layer 9 sandwiching the carrier barrier layer 8. For example, when the p-type cladding layer 7 and the p-type spacer layer 9 are made of Al _0.3 Ga _0.7 As, the carrier barrier layer 8 has an Al _y Ga _{1− in which the} Al composition y is higher than 0.3 (30%). _y As.

  The active layer 6 has an MQW-SCH structure in which both sides of a multiple quantum well (MQW) layer in which well layers and barrier layers are alternately stacked are sandwiched between separate confinement heterostructure (Separate Confinement Heterostructure) layers. The well layer is made of a material selected so as to emit light having a desired wavelength, for example, a GaInAs-based semiconductor material. The barrier layer is made of, for example, GaAs. The active layer 6 is a spontaneous emission light including light having a wavelength of, for example, 1.0 μm to 1.1 μm (1.0 μm band) due to a current injected from the p-side electrode 13 and confined by the current confinement layer 10. The composition and layer thickness of the semiconductor material are set so as to emit light.

The upper dielectric DBR mirror 15 has a periodic structure in which, for example, 9 pairs of composite dielectric layers each having a pair of SiO ₂ layer functioning as a low refractive index layer and SiNx layer functioning as a high refractive index layer are laminated. As in the lower DBR mirror 2, the thickness of each layer is λ / 4n.

  The p-side electrode 13 is formed in a ring shape along the outer extension of the p-type contact layer 12. On the other hand, the n-side electrode 4 is formed on the surface of the extended portion of the n-type contact layer 3 extending on the outer peripheral side of the mesa post M, and is formed in a C shape so as to surround the periphery of the mesa post M.

  The phase adjustment layer 14 is made of a dielectric such as SiNx, and is formed immediately below the upper dielectric DBR mirror 15. By adjusting the layer thickness of the phase adjustment layer 14, the p-type contact layer 12 is positioned at the node of the standing wave of light, and the lowermost surface of the upper dielectric DBR mirror 15 is positioned at the antinode of the standing wave. The function to adjust to.

  Next, the operation of the surface emitting laser element 100 will be described. First, a laser controller (not shown) applies a bias voltage and a modulation voltage between the p-side electrode 13 and the n-side electrode 4 to inject current. The p-side carriers (holes) flow in the p-type contact layer 12 in the horizontal direction in the drawing, and then pass through the p-type spacer layer 11 and concentrate in the opening 10a of the current confinement layer 10 to increase the density. In this state, it is injected into the active layer 6. On the other hand, n-side carriers (electrons) are injected from the n-side electrode 4 into the active layer 6 through the n-type contact layer 3 and the n-type cladding layer 5.

  As described above, the surface emitting laser element 100 according to the first embodiment has a so-called double intracavity structure in which both the p-side carrier and the n-side carrier are injected into the active layer without passing through the DBR mirror. Have

  The active layer 6 into which carriers are injected generates spontaneous emission light. The generated spontaneous emission light is laser-oscillated at any wavelength in the 1.0 μm wavelength band by the optical amplification action of the active layer 6 and the action of the optical resonator. As a result, the surface emitting laser element 100 outputs laser signal light including a modulation signal from the upper dielectric DBR mirror 15. During laser oscillation, a standing wave of laser light is formed in the optical resonator.

  Here, the present inventors have intensively studied to realize a highly reliable surface-emitting laser device. In the surface-emitting laser device having a conventional configuration, the electrons injected into the active layer overflow and are selected. It was discovered that the reliability of the surface emitting laser element may be reduced by reaching the oxide layer.

  FIG. 2 is a diagram showing the energy band and carrier flow of the surface emitting laser element having the same configuration as that of the surface emitting laser element according to the first embodiment except that the carrier barrier layer is not provided. A symbol VB indicates a valence band, and a symbol CB indicates a conduction band. The active layer 6 includes an MQW layer 6b in which well layers and barrier layers are alternately stacked, and an n-side SCH layer 6a and a p-side SCH layer 6c that sandwich the MQW layer 6b.

  The hole H injected from the p side and the electron E1 injected from the n side are respectively injected into the active layer 6, but the electron E2, which is a part of the electron E1, overflows from the active layer 6 and becomes a minority carrier. It flows to the p-type semiconductor layer and reaches the selective oxidation layer 10b. The electrons E2 may recombine with a part of the holes H in the vicinity of the selective oxidation layer 10b.

  Here, in the selective oxidation layer 10b, due to volume shrinkage when Al is oxidized to form an oxide, stress strain is generated inside, and the strain stress extends to the periphery. For this reason, when non-radiative recombination of carriers occurs in the vicinity of the selective oxidation layer 10b, proliferation of defects in the semiconductor crystal around the carrier is induced. Such growth of crystal defects lowers the reliability of the device, and further, when the crystal defect reaches the active layer 6, the device may fail.

  On the other hand, FIG. 3 is a diagram showing the energy band and the carrier flow of the surface emitting laser element 100 according to the first embodiment. As shown in FIG. 3, in the surface emitting laser element 100, a carrier barrier layer 8 is disposed between the active layer 6 and the selective oxidation layer 10b. The carrier barrier layer 8 functions as an energy barrier that suppresses or prevents the electrons E2 from reaching the selective oxidation layer 10b. This suppresses or prevents non-radiative recombination in the vicinity of the selective oxidation layer 10b of the electrons E2 and the growth of crystal defects due to the non-radiative recombination. As a result, the reliability of the surface emitting laser element 100 is greatly improved.

In particular, when a relatively large current of about 5 kA / cm ² or more is injected as a drive current density in order to increase the output of the surface-emitting laser element 100, the amount of overflowing electrons E2 also increases. Therefore, the effect of improving the reliability of the device by suppressing or preventing the electrons E2 from reaching the selective oxidation layer 10b by the carrier barrier layer 8 becomes even more remarkable.

Next, preferable characteristics of the carrier barrier layer 8 will be described. First, the energy level of the conduction band minimum (CBM) of the carrier barrier layer 8 is lower than that of the semiconductor layer (p-type cladding layer 7 in the surface emitting laser device 100) adjacent to the carrier barrier layer 8 on the active layer 6 side. It is preferable that the energy level is higher than the energy level of CBM because it becomes an energy barrier against electrons. For example, if the bandgap energy of the carrier barrier layer 8 is made larger than the bandgap energy of the p-type cladding layer 7, the CBM energy level of the carrier barrier layer 8 is made higher than the CBM energy level of the p-type cladding layer 7. Can be easily done. Note that, as described above, the carrier barrier layer 8 is formed using p-type AlGaAs having a higher Al composition than the p-type cladding layer 7, so that the band gap energy of the carrier barrier layer 8 is less than that of the p-type cladding layer 7. It becomes larger than the band gap energy. Furthermore, since the band gap energy can be increased when the Al composition of p-type AlGaAs is high, the barrier effect against electrons can be increased. From the viewpoint of enhancing the barrier effect against electrons, the height of the heterobarrier ΔEc in the conduction band of the p-type cladding layer 7 and the carrier barrier layer 8 is better, but as a guide, it is more than the thermal energy at room temperature (about 26 meV). It should be about 100 meV or larger. For example, when the p-type cladding layer 7 and the p-type spacer layer 9 are Al _0.3 Ga _0.7 As, when the Al composition y of the carrier barrier layer 8 is higher than 0.41, Al _y Ga _1-y As Since ΔEc is 100 meV or more, a barrier effect against electrons can be obtained. Further, when the Al composition y of the carrier barrier layer 8 is set to about 0.7, ΔEc is as large as about 400 meV, so that a very large barrier effect against electrons can be obtained. Here, ΔEc: ΔEv = 0.65: 0.35 was used as the band offset ratio between the conduction band and the valence band.

Further, by performing doping so that the carrier barrier layer 8 becomes p-type, the Fermi surface moves, so that the CBM energy level of the carrier barrier layer 8 is further increased and the barrier effect on the electrons E2 is enhanced. it can. Further, as the energy level of the CBM increases, the energy level of the upper end of the valence band (Valence Band Maximum: VBM) also increases, so that the barrier effect against holes H as majority carriers can be reduced. As a result, the electrical resistance when holes H are injected into the active layer 6 is reduced. As p-type doping, for example, p-type dopants such as zinc (Zn), carbon (C), and magnesium (Mg) may be doped so as to have a carrier concentration of about 1 × 10 ¹⁸ cm ⁻³ or more. Good.

  However, when the carrier barrier layer 8 has a high Al composition, when the selective oxidation layer 10b is formed by selective oxidation heat treatment of the Al-containing semiconductor layer for forming the current confinement layer 10, the carrier barrier layer 8 also has a mesa post M. May be selectively oxidized from the outer periphery side. If the carrier barrier layer 8 is oxidized to the inside of the opening 10a of the current confinement layer 10, the current path formed by the opening 10a of the current confinement layer 10 may be obstructed and the reliability may be reduced. There is. In order to avoid such a problem, the oxidation rate of the carrier barrier layer 8 is preferably lower than the oxidation rate of the Al-containing layer.

  In order to make the oxidation rate of the carrier barrier layer 8 lower than the oxidation rate of the Al-containing layer, the Al composition of the carrier barrier layer 8 is made lower than the Al composition of the Al-containing layer and / or the carrier barrier layer 8 It is preferable to make the layer thickness thinner than the layer thickness of the Al-containing layer.

FIG. 4 is a diagram showing an oxidation rate when an AlGaAs layer having various Al compositions and layer thicknesses is subjected to an oxidation reaction by performing a heat treatment at about 450 ° C. in a water vapor atmosphere. As shown in FIG. 4, in the AlGaAs layer, the oxidation rate can be lowered by lowering the Al composition and / or reducing the layer thickness.
As shown in FIG. 4, when the Al composition is 94% or less, the oxidation rate becomes very low, so that the oxidation rate is easily different from that of the Al-containing semiconductor layer.

  Further, as shown in FIG. 4, the oxidation rate decreases rapidly when the layer thickness is 20 nm or less. Therefore, the thickness of the carrier barrier layer 8 is set to 20 nm or less, and the layer thickness of the Al-containing semiconductor layer is set to the layer of the carrier barrier layer 8. A thickness larger than the thickness is preferable because it is easy to make a difference in oxidation rate between the carrier barrier layer 8 and the Al-containing semiconductor layer. Note that the Al composition of the carrier barrier layer 8 may be the same as or higher than the Al composition of the Al-containing layer as long as a necessary difference can be made in the oxidation rate. The thickness of the carrier barrier layer 8 is preferably 10 nm or more because the barrier function can be sufficiently exhibited. On the other hand, the layer thickness of the Al-containing semiconductor layer can be set to, for example, 20 nm to 60 nm.

  If the distance in the plane direction between the opening 10a and the region selectively oxidized in the carrier barrier layer 8 is about 5 μm or more, the selectively oxidized region adversely affects the current flowing through the opening 10a. Is more preferably prevented. For example, if the oxidation rate of the carrier barrier layer 8 is ½ or less of the oxidation rate of the Al-containing semiconductor layer, the distance in the plane direction between the opening 10a and the region selectively oxidized in the carrier barrier layer 8 can be easily obtained. It is preferable because it can be separated.

  Next, a preferred arrangement of the carrier barrier layer 8 and the current confinement layer 10 will be described. As described above, the carrier barrier layer 8 and the current confinement layer 10 are formed at the nodes of standing waves of light formed by the laser light in the optical resonator composed of the lower DBR mirror 2 and the upper dielectric DBR mirror 15. Placed in position. By arranging the carrier barrier layer 8 at the position of the node where the light intensity is weak, even if the carrier barrier layer 8 is doped p-type at a high concentration, the threshold value caused by the light absorption loss due to the p-type dopant having light absorption. An increase in current and a decrease in luminous efficiency are suppressed.

  Further, the current confinement layer 10 is often doped p-type in order to suppress the barrier of the hole H as a majority carrier. However, by arranging the current confinement layer 10 at the position of the standing wave node, Similarly to the above, an increase in threshold current and a decrease in light emission efficiency are suppressed. Further, since the current confinement layer 10 is arranged at the position of the node of the standing wave, the lateral light confinement effect by the current confinement layer 10 is prevented from becoming excessively strong, and higher-order transverse mode oscillation is prevented. It is suppressed.

  Further, a carrier barrier layer 8 is arranged at the position of the first node of the standing wave from the active layer 6 side (position λ / 4n away from the center of the active layer 6), and the position of the second node (active layer 6). The current confinement layer 10 is preferably arranged at a position 3λ / 4n away from the center of the current. As a result, the active layer 6 and the current confinement layer 10 are close to each other and the effect of current confinement is more effectively exhibited, and the cavity length of the surface emitting laser element 100 can be shortened, so that the photon lifetime is reduced. It becomes small and a faster response characteristic can be realized.

  Further, if the carrier barrier layer 8 and the current confinement layer 10 are separated from each other in this manner, the influence of the stress strain of the current confinement layer 10 on the carrier barrier layer 8 is small. This is preferable because the growth of crystal defects due to bonding is suppressed. When the thickness of the current confinement layer 10 is 30 nm, the stress strain range is within a range of about 100 nm from the center in the layer thickness direction. When the wavelength λ is 1060 nm and the refractive index n is 3.5, the carrier barrier layer 8 is disposed at a position λ / 4n (about 70 nm) away from the center of the active layer 6 as described above. When the current confinement layer 10 is disposed at a position 3λ / 4n (about 210 nm) away from the center, the distance in the thickness direction between the carrier barrier layer 8 and the current confinement layer 10 is about 140 nm. In this case, the carrier barrier layer 8 (more strictly speaking, the boundary surface of the carrier barrier layer 8 on the active layer 6 side) is separated from the current confinement layer 10 by more than the distance (for example, 100 nm) exerted by the stress strain of the current confinement layer 10. This is preferable.

  As described above, the surface emitting laser element 100 according to the first embodiment has high reliability.

(Embodiment 2)
FIG. 5 is a schematic cross-sectional view of a surface emitting laser element according to Embodiment 2 of the present invention. As shown in FIG. 5, the surface emitting laser element 200 has a configuration in which the carrier barrier layer 8 is replaced with a carrier barrier layer 28 in the surface emitting laser element 100 shown in FIG. 1.

The carrier barrier layer 28 is formed using the same p-type AlGaAs as the p-type cladding layer 7 and the p-type spacer layer 9 sandwiching the carrier barrier layer 28, but is higher than the p-type cladding layer 7 and the p-type spacer layer 9. The concentration is doped p-type. If the carrier concentration of the carrier barrier layer 28 is higher than the carrier concentration of the p-type cladding layer 7 and the p-type spacer layer 9, there is an energy barrier action against electrons as minority carriers. A high value is recommended. For example, p-type doping may be performed so that the carrier concentration is about 3 × 10 ¹⁸ cm ⁻³ . The higher the carrier concentration of the carrier barrier layer 28, the higher the barrier effect, while the light absorption loss increases. In order to suppress the absorption loss even at a high carrier concentration, the carrier barrier layer 28 is preferably arranged at the node of the standing wave of the light formed by the laser light, or the doping profile is made as steep as possible. If absorption loss is allowed, the carrier concentration of the carrier barrier layer 28 may be increased to about 1 × 10 ²⁰ cm ⁻³ .

  The band gap energy of the carrier barrier layer 28 is the same as that of the p-type cladding layer 7 and the p-type spacer layer 9. However, since the Fermi surface moves when the carrier barrier layer 28 is doped p-type at a high concentration, the energy level of the CBM of the carrier barrier layer 28 is CBM of the p-type cladding layer 7 and the p-type spacer layer 9. Higher than the energy level. Thus, the carrier barrier layer 28 exhibits an energy barrier effect against electrons as minority carriers.

  FIG. 6 is a diagram showing the energy band and the carrier flow of the surface emitting laser element according to the second embodiment. As shown in FIG. 6, the carrier barrier layer 28 functions as an energy barrier that suppresses or prevents the electrons E2 from reaching the selective oxidation layer 10b, but holes H as majority carriers are formed in the active layer 6. It is not a barrier to being injected. Therefore, it is preferable because the electric resistance when holes H are injected into the active layer 6 does not increase.

  The present invention can also be applied to a surface emitting laser element that does not have an intracavity structure. That is, the present invention can also be applied to a surface emitting laser element having a structure in which carriers injected into the active layer are injected into the active layer via the lower DBR mirror and / or the upper and lower DBR mirrors.

  In the above embodiment, the n-type semiconductor layer is disposed below the active layer and the p-type semiconductor layer is disposed above the active layer. The n-type semiconductor layer is disposed above the active layer, A p-type semiconductor layer may be disposed below the active layer.

  In the above embodiment, the carrier barrier layer is disposed on the p-type semiconductor layer side with respect to the active layer and serves as an energy barrier for electrons as minority carriers. However, the carrier barrier layer is n with respect to the active layer. It may be arranged on the side of the type semiconductor layer and function as an energy barrier against holes as minority carriers. In this case, for example, the barrier effect against holes can be enhanced by doping the carrier barrier layer n-type.

  In the above embodiment, the material, size, etc. of the compound semiconductor are set for the 1.0 μm wavelength band. However, each material, size, and the like are appropriately set according to the desired oscillation wavelength of the laser beam, and are not particularly limited. For example, an InP-based material may be used as a semiconductor material constituting each semiconductor layer. In this case, the Al-containing layer and the carrier barrier layer can be composed of an InAlAs layer.

  Further, the present invention is not limited by the above embodiment. What was comprised combining each component mentioned above suitably is also contained in this invention. Further effects and modifications can be easily derived by those skilled in the art. Therefore, the broader aspect of the present invention is not limited to the above-described embodiment, and various modifications can be made.

1 substrate 2 lower DBR mirror 3 n-type contact layer 4 n-side electrode 5 n-type cladding layer 6 active layer 7 p-type cladding layer 8, 28 carrier barrier layer 9, 11 p-type spacer layer 10 current confinement layer 10a opening 10b selection Oxide layer 12 p-type contact layer 13 p-side electrode 14 phase adjusting layer 15 upper dielectric DBR mirror 100, 200 surface emitting laser element CB conduction band E1, E2 electron H hole M mesa post VB valence band

Claims (5)

A first reflecting mirror and a second reflecting mirror constituting an optical resonator;
An active layer disposed between the first reflecting mirror and the second reflecting mirror;
A current confinement layer disposed between the second reflecting mirror and the active layer and having a current injection portion and a selective oxidation layer formed on an outer periphery of the current injection portion by a selective oxidation heat treatment;
A carrier barrier layer disposed between the active layer and the current confinement layer, having a region selectively oxidized on the outer peripheral side, and serving as an energy barrier against minority carriers overflowing from the active layer;
With
The carrier barrier layer is made of a semiconductor material having a higher Al composition and a higher band gap energy than the semiconductor layer adjacent to the carrier barrier layer on the active layer side, and the Al composition is formed in the current injection portion of the current confinement layer . Same as or higher than the Al composition, the layer thickness is 20 nm or less, and is arranged at the position of the first node from the active layer side among the nodes of the standing wave of the light formed by the laser light in the optical resonator And
The current confinement layer is disposed at the position of the second node from the active layer side among the nodes of the standing wave,
The selectively oxidized region of the carrier barrier layer does not reach the inside of the current injection portion of the current confinement layer,
A distance in a plane direction between the current injection portion and the selectively oxidized region in the carrier barrier layer is 5 μm or more;
A surface-emitting laser device, characterized in that an oxidation rate of the carrier barrier layer is not more than ½ of an oxidation rate of the current injection portion of the current confinement layer .   2. The surface emitting laser element according to claim 1, wherein an energy barrier difference in a conduction band between the carrier barrier layer and the semiconductor layer is 100 meV or more.   3. The surface emitting laser element according to claim 1, wherein the current confinement layer and the carrier barrier layer are separated from each other by 100 nm or more in the layer thickness direction.   The surface emitting laser element according to claim 1, wherein the minority carriers are electrons, and the carrier barrier layer is doped p-type.   5. The surface emitting laser device according to claim 4, wherein the carrier concentration of the carrier barrier layer is one digit or more higher than the carrier concentration of the semiconductor layer.

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