JP5167940B2 - Nitride semiconductor laser - Google Patents

Description

  The present invention relates to a nitride semiconductor laser.

Non-Patent Document 1 describes a nitride semiconductor laser formed on an m-plane GaN substrate. The oscillation wavelength is 459 nm. Non-Patent Documents 2 to 4 describe nitride semiconductor lasers formed on a c-plane GaN substrate. The oscillation wavelengths of the nitride semiconductor lasers described in Patent Documents 2 to 4 are 470 nm, 460 nm, and 422 nm, respectively. Patent Document 5 describes a semiconductor laser diode that emits light at two or three wavelengths. This semiconductor laser diode is formed on a sapphire substrate.
M. Kubota et. Al. “Continuous-Wave Operation of Blue Laser Diodes Based on Nonpolarm-Plane Gallium Nitride”, Applied Physics Express 1 011102, 2008, p.011102-1-011102-3 K. Kojima, et. Al. “Gain suppression phenomena observed in InXGa1-XNquantum well laser diodes emitting at 470 nm”, Applied Physics Letters 89, 241127, 2006, p.241127-1-241127-3 S. Nagahama et. Al. “Characteristics of InGaN Laser diodes in the pure blue region”, Applied Physics Letters, Volume 79, Number 13, 2001, p.1948-1950 S. Nagahama et. Al. “Wavelength Dependence of InGaN Laser Diode Characteristics”, Japanese Journal of Applied Physics, Vol.40, 2001, p.3075-3081 M. Yamada et. Al. “Phosphor Free High-Luminous-Efficiency White Light-Emitting Diodes Composed of InGaN Multi-Quantum Well”, Japanese Journal of Applied Physics, Vol.41, 2002, p.246-248

  The nitride semiconductor laser described in each of the above non-patent documents has a light emitting layer having a quantum well structure. These nitride semiconductor lasers oscillate at a wavelength corresponding to the band structure of the quantum well structure.

  However, in these nitride semiconductor lasers, the lasing wavelength is shorter than the wavelength corresponding to the band gap energy of the well layer due to band filling. This band filling must be reduced in order to obtain a nitride semiconductor laser that oscillates at long wavelengths.

  The present invention has been made in view of such circumstances, and an object thereof is to provide a nitride semiconductor laser capable of reducing the influence of band filling.

The nitride semiconductor laser according to the present invention includes a first conductive gallium nitride semiconductor layer, a second conductive gallium nitride semiconductor layer, a first conductive gallium nitride semiconductor layer, and a second conductive gallium nitride semiconductor. A light emitting layer provided between the first conductive type gallium nitride based semiconductor layer and the light emitting layer, a second conductive type gallium nitride based semiconductor layer, and the light emitting layer. and a second optical guiding layer provided between the light-emitting layer includes a well layer having a band gap E _W, a quantum well structure including a barrier layer having a band gap E _B, first optical guide layer, the second light guide layer, and at least one barrier layer comprises a first light-absorbing layer composed of a gallium nitride-based semiconductor layer having a band gap E _Y, the band gap E _Y of the first light-absorbing layer than the band gap _{E W} Large, the band gap _{E Y} band smaller than the gap _{E B,} the difference between the band gap _{E Y} and the band gap _{E W,} larger than 0, and is smaller than 0.3 eV.

According to the present invention, the emission spectrum in the LED mode prior to laser oscillation is wider than the emission spectrum in laser oscillation. The emission spectrum in the LED mode includes a wavelength component in a long wavelength region having a wavelength longer than the peak wavelength and a component in a short wavelength region having a wavelength shorter than the peak wavelength. Since the band gap E _Y of the first light-absorbing layer satisfies the above relationship, the first light-absorbing layer is capable of absorbing light having a wavelength component of the short-wavelength region. For this reason, light having a wavelength component in the short wavelength region does not contribute to laser oscillation. On the other hand, light having a wavelength component in the long wavelength region propagates in the resonator of the nitride semiconductor laser. As a result, laser oscillation is generated by light having a wavelength component in the long wavelength region, so that the effect of band filling can be reduced.

The nitride semiconductor laser according to the present invention, the light emitting layer is a wavelength corresponding to the energy E _X emission spectrum in the LED mode of the nitride semiconductor laser is provided so as to have a peak intensity of the first light-absorbing layer larger than the band gap _{E Y} energy _{E X,} the difference between the band gap _{E Y} and energy _{E X} greater than 0, the difference may be less than 0.09 eV.

Thus, the band gap _{E Y} of the first light-absorbing layer is larger than the band gap _{E W} of the well layer, the difference between the band gap _{E Y} and energy _{E X,} greater than 0, is smaller than 0.09eV The first light absorption layer can absorb light having a wavelength component in a short wavelength region.

  In the nitride semiconductor laser according to the present invention, a first light absorbing layer may be provided in at least one of the first light guide layer and the second light guide layer. Thereby, the 1st light absorption layer of a 1st light guide layer or a 2nd light guide layer can absorb the light of the component of the short wavelength region produced | generated by the well layer in LED mode.

  In the nitride semiconductor laser according to the present invention, the well layer of the light emitting layer can be made of InGaN.

In the nitride semiconductor laser according to the present invention, the first light guide layer includes a first light absorption layer, and a first InGaN guide portion provided between the first light absorption layer and the first conductivity type gallium nitride semiconductor layer. wherein the door, the band gap of the 1InGaN guide portion may be larger than the band gap E _Y of the first light-absorbing layer. Thereby, the 1st light absorption layer of a 1st light guide can absorb the light of the component of the short wavelength area | region produced | generated by the well layer in LED mode.

In the nitride semiconductor laser according to the present invention, the second light guide layer includes a first light absorption layer, and a second InGaN guide portion provided between the first light absorption layer and the second conductivity type gallium nitride semiconductor layer. wherein the door, the band gap of the 2InGaN guide portion may be larger than the band gap E _Y of the first light-absorbing layer. Thereby, the 1st light absorption layer of a 2nd light guide can absorb the light of the component of the short wavelength area | region produced | generated by the well layer in LED mode.

  In the nitride semiconductor laser according to the present invention, the barrier layer may be provided with a first light absorption layer. Thereby, the 1st light absorption layer of a barrier layer can absorb the light of the component of the short wavelength region produced | generated by the well layer in LED mode.

In the nitride semiconductor laser according to the present invention, the light emitting layer further includes another well layer, the barrier layer includes a first light absorption layer, first and second InGaN barrier portions, and the first and second InGaN barriers. parts are respectively provided between the first light-absorbing layer and the well layer and another well layer, the band gap E _B of the first and second 2InGaN barrier portion, the band gap E _Y of the first light-absorbing layer Can be bigger. Thereby, the 1st light absorption layer of a barrier layer can absorb the light of the component of the short wavelength region produced | generated by the well layer in LED mode.

In the nitride semiconductor laser according to the present invention, the first light guide layer includes a second light absorption layer, and a third InGaN guide portion provided between the second light absorption layer and the first conductivity type gallium nitride based semiconductor layer. wherein the door, the second light-absorbing layer made of a gallium nitride-based semiconductor layer having a band gap E _Y2, the band gap E _Y2 of the second light absorbing layer is larger than the band gap E _W, the second light-absorbing layer the difference between the band gap _{E Y2} and the band gap _{E W} is greater than 0, less than 0.3 eV, the band gap of the 3InGaN guide portion may be larger than the band gap _{E Y2} of the second light absorbing layer . Thereby, the 2nd light absorption layer of a 1st light guide layer can absorb the light of the component of the short wavelength area | region produced | generated by the well layer in LED mode.

In the nitride semiconductor laser according to the present invention, the second light guide layer includes a third light absorption layer, and a fourth InGaN guide portion provided between the third light absorption layer and the second conductivity type gallium nitride semiconductor layer. wherein the door, the third light-absorbing layer made of a gallium nitride-based semiconductor layer having a band gap E _Y3, band gap E _Y3 of the third light-absorbing layer is larger than the band gap E _W, the third light-absorbing layer the difference between the band gap _{E Y3} and the band gap _{E W} is greater than 0, less than 0.3 eV, the band gap of the 4InGaN guide portion may be larger than the band gap _{E Y3} of the third light-absorbing layer. Thereby, the 3rd light absorption layer of a 2nd light guide layer can absorb the light of the component of the short wavelength area | region produced | generated by the well layer in LED mode.

  In the nitride semiconductor laser according to the present invention, the first light absorption layer can be made of InGaN. Thereby, since the first light absorption layer is made of the same material as the first light guide layer, the second light guide layer, and the well layer, the crystal quality of the semiconductor layer of the nitride semiconductor laser is improved. As a result, a nitride semiconductor laser with good emission characteristics can be obtained.

  In the nitride semiconductor laser according to the present invention, the first light absorption layer can be made of InAlGaN. Thereby, a 1st light absorption layer absorbs efficiently the light of the component of the short wavelength area | region produced | generated by the well layer in LED mode.

  In the nitride semiconductor laser according to the present invention, the first conductivity type gallium nitride based semiconductor layer can be made of AlGaN, and the second conductivity type gallium nitride based semiconductor layer can be made of AlGaN. The first and second conductivity type gallium nitride based semiconductor layers function as cladding layers. Thereby, the light generated in the well layer is effectively confined in the light emitting layer and the light guide layer.

In the nitride semiconductor laser according to the present invention, the light absorption layer may include an n-type or p-type dopant of 1 × 10 ¹⁸ cm ⁻³ or more. Thereby, the n-type or p-type dopant in the light absorption layer contributes to the absorption of light in the short wavelength region component generated in the well layer in the LED mode.

  The nitride semiconductor laser according to the present invention can further include a nitride semiconductor substrate. The first conductivity type gallium nitride based semiconductor layer, the second conductivity type gallium nitride based semiconductor layer, the light emitting layer, the first light guide layer, and the second light guide layer are provided on the main surface of the nitride semiconductor substrate. be able to.

  This improves the crystal quality of the semiconductor layer of the nitride semiconductor laser. As a result, a nitride semiconductor laser with good emission characteristics can be obtained.

  In the nitride semiconductor laser according to the present invention, the nitride semiconductor substrate includes a first region having a threading dislocation density smaller than a predetermined threading dislocation density and a second region having a threading dislocation density larger than the predetermined threading dislocation density. The first region and the second region extend from the back surface to the main surface of the nitride semiconductor substrate, and include a first conductivity type gallium nitride semiconductor layer, a second conductivity type gallium nitride semiconductor layer, a light emitting layer, The first light guide layer and the second light guide layer are provided on the first region of the main surface, the second region extends along the first region, and the resonator of the nitride semiconductor laser is , And can extend along the second region.

  Thereby, the resonator can be easily provided along the second region. Therefore, a nitride semiconductor laser having a resonator oriented along a predetermined crystal axis can be obtained.

  In the nitride semiconductor laser according to the present invention, the resonator can extend in the [10-10] direction of the nitride semiconductor substrate. Thereby, the cleavage plane of the (10-10) plane of the nitride semiconductor substrate can be used as a resonator of the nitride semiconductor laser.

In the nitride semiconductor laser according to the present invention, the predetermined threading dislocation density can be less than 1 × 10 ⁷ cm ⁻² . This improves the crystal quality of the semiconductor layer of the nitride semiconductor laser.

  In the nitride semiconductor laser according to the present invention, the nitride semiconductor substrate can be a GaN substrate. Thereby, since a nitride semiconductor laser can be created using a large GaN wafer, the manufacturing cost of the nitride semiconductor laser can be reduced.

  In the nitride semiconductor laser according to the present invention, the nitride semiconductor substrate can be an InGaN substrate. Thereby, when the first light guide layer, the second light guide layer, and the light emitting layer are made of InGaN, lattice mismatch between these layers and the nitride semiconductor substrate can be reduced. Therefore, it becomes easy to control the In composition in the first light guide layer, the light emitting layer, and the second light guide layer.

  In the nitride semiconductor laser according to the present invention, the main surface of the nitride semiconductor substrate can be semipolar. Thereby, a nitride semiconductor laser can be obtained in which the influence of shortening the oscillation wavelength due to the piezoelectric field is reduced.

  In the nitride semiconductor laser according to the present invention, the main surface of the nitride semiconductor substrate can be a nonpolar surface. Thereby, a nitride semiconductor laser can be obtained in which the influence of shortening the oscillation wavelength due to the piezoelectric field is further reduced.

  In the nitride semiconductor laser according to the present invention, the lasing wavelength of the nitride semiconductor laser can be 425 nm or more. Furthermore, in the nitride semiconductor laser according to the present invention, the lasing wavelength can be 460 nm or more.

  As described above, according to the present invention, a nitride semiconductor laser capable of reducing the influence of band filling is provided.

  Hereinafter, the nitride semiconductor laser according to the embodiment will be described in detail with reference to the accompanying drawings. Where possible, the same symbols are used for the same elements.

  FIG. 1 is a schematic diagram showing a cross-sectional structure of a nitride semiconductor laser according to this embodiment. As shown in FIG. 1, in the nitride semiconductor laser 40 according to the present embodiment, a semiconductor layer for the semiconductor laser is epitaxially grown on the main surface 1x and the back surface 1y of the nitride semiconductor substrate 1. For epitaxial growth, MOCVD (metal organic chemical vapor deposition) method, MBE (molecular beam growth) method, or the like can be used. In FIG. 1, an orthogonal coordinate system S is shown. The semiconductor layer of the nitride semiconductor laser 40 is disposed in the Z-axis direction. The directions along two directions orthogonal to the Z axis are taken as an X axis direction and a Y axis direction, respectively.

  The nitride semiconductor laser 40 includes a lower cladding layer 2, a lower light guide layer 3, a first light guide layer 5, a light emitting layer 7, a second light guide layer 9, an upper light guide layer 11, an electron blocking layer 12, and an upper cladding layer. 13, an upper contact layer 15, and an anode electrode layer 17. These layers are mounted on the main surface 1x of the nitride semiconductor substrate 1. The nitride semiconductor laser 40 includes the cathode electrode layer 21. This layer is mounted on the back surface 1 y of the nitride semiconductor substrate 1.

  The nitride semiconductor laser 40 can include a first conductivity type gallium nitride based semiconductor layer. The first conductivity type gallium nitride based semiconductor layer can include a lower cladding layer 2.

The lower cladding layer 2 is made of an n-type gallium nitride based semiconductor layer. The lower cladding layer 2 supplies electrons as carriers to the light emitting layer 7. Further, since the lower cladding layer 2 is formed of a material having a refractive index lower than that of the material constituting the light emitting layer 7, the first light guide layer 5, and the lower light guide layer 3, the light generated in the light emitting layer 7 In the vicinity of the light emitting layer 7. As a material for forming the lower cladding layer 2, it is preferable to use Al _Z1 Ga _{1 -Z1} N, GaN, or the like. The Al composition Z1 of the Al _Z1 Ga _{1 -Z1} N is preferably 0.01 to 0.10. Moreover, it is preferable that the film thickness of the lower clad layer 2 is 100-5000 nm.

The lower light guide layer 3 is provided between the lower cladding layer 2 and the first light guide layer 5. The lower light guide layer 3 is formed of a gallium nitride based semiconductor. The film thickness of the lower light guide layer 3 can be set to 10 to 300 nm, for example. As the lower light guide layer 3, for example, n-type GaN can be used.
The first light guide layer 5 is provided between the light emitting layer 7 and the lower cladding layer 2. The first light guide layer 5 is made of a gallium nitride based semiconductor. The lower cladding layer 2 and the first light guide layer 5 are used to confine light generated in the light emitting layer 7 in the vicinity of the light emitting layer 7.

  The light emitting layer 7 is provided between the lower cladding layer 2 and the upper cladding layer 13. The light emitting layer 7 is provided between the first light guide layer 5 and the second light guide layer 9. The light emitting layer 7 has a quantum well structure including a well layer and a barrier layer. The configuration in the vicinity of the light emitting layer 7 will be described with reference to FIG. FIG. 2 is a schematic diagram showing a cross-sectional structure in the vicinity of the light emitting layer of the nitride semiconductor laser.

As shown in FIG. 2, the light emitting layer 7 includes barrier layers 34 a and 34 b and a well layer 35. Well layers 35 and barrier layers 34a are alternately arranged along the Z-axis direction. Between the well layer 35 and the first light guide layer 5 closest to the first light guide layer 5 and between the well layer 35 and the second light guide layer 9 closest to the second light guide layer 9, there is a barrier layer. 34b is provided.
The barrier layer 34a includes a first light absorption layer 31, a first InGaN barrier portion 33x, and a second InGaN barrier portion 33y. The first InGaN barrier portion 33x and the second InGaN barrier portion 33y are arranged between two adjacent well layers 35, between the first light absorption layer 31 and one well layer 35, and between the first light absorption layer 31 and the other. Are provided between the well layers 35.
That is, the first InGaN barrier portion 33 x is provided between the first light absorption layer 31 and the well layer 35. In addition, the second InGaN barrier portion 33y is provided between the first light absorption layer 31 and another well layer. The first light absorption layer 31 is formed of a gallium nitride based semiconductor. The first InGaN barrier portion 33x and the second InGaN barrier portion 33y are formed of a gallium nitride based semiconductor. The well layer 35 is formed of a gallium nitride semiconductor.

The first light guide layer 5 includes a third InGaN guide portion 5a and a second light absorption layer 5b. The second light absorption layer 5b is located between the light emitting layer 7 and the third InGaN guide portion 5a. The third InGaN guide part 5a is formed of a gallium nitride based semiconductor. The second light absorption layer 5b is formed of a gallium nitride based semiconductor. The film thickness of the third InGaN guide portion 5a can be set to 10 to 300 nm, for example. As the third InGaN guide portion 5a, undoped In _X1 Ga _1-X1 N can be used. The In composition X1 of the third InGaN guide portion 5a is preferably 0.01 to 0.10. This is because if the In composition X1 is 0.01 or less, a sufficient light confinement effect in the light emitting layer 7 cannot be obtained. If the In composition X1 is 0.10 or more, the crystal quality of InGaN deteriorates. Because.

The second light guide layer 9 is made of a gallium nitride based semiconductor. The second light guide layer 9 is provided between the light emitting layer 7 and the upper cladding layer 13. The second light guide layer 9 is provided between the light emitting layer 7 and the upper light guide layer 11. The second light guide layer 9 includes a fourth InGaN guide portion 9a and a third light absorption layer 9b. The third light absorption layer 9b is located between the light emitting layer 7 and the fourth InGaN guide portion 9a. The fourth InGaN guide portion 9a is formed of a gallium nitride based semiconductor. The third light absorption layer 9b is formed of a gallium nitride based semiconductor. The film thickness of the fourth InGaN guide portion 9a can be, for example, 10 to 300 nm. As the fourth InGaN guide portion 9a, undoped In _X1 Ga _1-X1 N can be used. The In composition X1 of the fourth InGaN guide portion 9a is preferably 0.01 to 0.10. This is because if the In composition X1 is 0.01 or less, a sufficient light confinement effect in the light emitting layer 7 cannot be obtained. If the In composition X1 is 0.10 or more, the crystal quality of InGaN deteriorates. Because.

  Next, the configuration in the vicinity of the light emitting layer 7 of the nitride semiconductor laser 40 will be described in more detail. FIG. 3 is a diagram showing a band structure in the vicinity of the light emitting layer of the nitride semiconductor laser according to the present embodiment, and shows the band structure corresponding to a cross-sectional structure in the vicinity of the light emitting layer of the nitride semiconductor laser.

As shown in FIG. 3, the well layer 35 has a band gap E _W. The first, second, and third light absorption layers 31, 5b, and 9b have band gaps E _Y , E _Y2 , and E _Y3 , respectively. Each first 1InGaN barrier portion 33x and the 2InGaN barrier portion 33y of the barrier layer 34a having a band gap _{E B.} The 4InGaN guide portion 9a of the 3InGaN guide portion 5a and the second optical guide layer 9 of the first optical guide layer 5 has a band gap _{E B,} respectively.

The band gaps E _Y, E _{Y2, and} E _Y3 are larger than the band gap E _W , and the band gaps E _B are larger than the band gaps E _Y, E _{Y2, and} E _Y3 (E _W <E _{Y, E Y2, E Y3 <} E B). Therefore, electrons and holes as carriers are confined in the well layer 35 in the light emitting layer 7, and the electrons and holes are recombined, and light is generated in the light emitting layer 7.

In the nitride semiconductor laser 40 according to this embodiment, the band gap _{E Y,} the difference in _{E Y2, E Y3} and the band gap _{E W} is larger than 0, 0.3eV (4.8 × ^{10 -20} J) is smaller. More preferably, the band gaps E _Y, E _{Y2 and} E _Y3 are greater than the energy E _X (E _Y, E _Y2, E _Y3 > E _X ). Further, the band gap _{E Y,} the difference in _{E Y2, E Y3} and energy _{E X,} larger than 0 eV, less than _{0.09eV (0 <E Y, E} Y2, E Y3 -E X <0.09eV) . However, the energy E _X is energy corresponding to the wavelength λ _X at which the emission spectrum of the nitride semiconductor laser 40 in the LED mode has the peak intensity.

As described above, the band gap E _W of the well layer 35, the band gaps E _Y , E _Y2 , E _{Y3 of} the first, second, and third light absorption layers 31, 5b, and 9b, the first InGaN barrier portion 33x, and the second InGaN barrier portion 33y, in the band gap _{E B} of the 3InGaN guide portion 5a, and the 4InGaN guide portion _{9a, E W} <E _Y, a relationship of _{E Y2, E Y3 <E B} . _Here, E _{Y, E Y2,} and the difference between _{E Y3} and _{E W (E Y -E W,} E Y2 -E W, E Y3 -E W) is preferably respectively 0.05eV or more. The absorption of the light of the long wavelength region _RH component (see FIG. 4) generated in the well layer 35 by the first, second, and third light absorption layers 31, 5b, and 9b is reduced, and the oscillation threshold of the laser is reduced. This is because the increase in value current can be reduced. Also, _{E B} and _{E Y,} the difference between _{E Y2, E Y3 (E B} -E Y, E B -E Y2, E B -E Y3) is preferably respectively 0.8eV or more. This is because the carrier confinement effect in the well layer 35 is sufficiently obtained.

The energy E _X, will be described with reference to FIG. FIG. 4 is a diagram showing an emission spectrum in the LED mode of the nitride semiconductor laser. The emission spectrum in the LED mode of the nitride semiconductor laser 40 is wider than the emission spectrum in laser oscillation. Therefore, the emission spectrum in the LED mode has a long wavelength region _RH having a longer wavelength than the wavelength λ _X where the emission spectrum has a peak intensity, and a short wavelength region _RL having a shorter wavelength than the wavelength λ _X. Then, the energy corresponding to the wavelength lambda _X, the energy _{E X.}

The wavelength λ _X changes according to the current density of the current flowing through the nitride semiconductor laser 40 due to the band filling effect. For example, when the current density of the current passed through the nitride semiconductor laser 40 increases, carriers are accumulated at the bottom of the well layer in the light emitting layer 7. This accumulation of carriers shortens the peak wavelength of light emission in the LED mode. This emission, shows that the band gap E _W of the well layer 35 becomes effectively large. Therefore, for example, the peak wavelength is defined by the emission spectrum in the LED mode when a current density of 0.1 kA / cm ² is passed through the nitride semiconductor laser 40.

  The upper light guide layer 11 is made of a gallium nitride based semiconductor. The upper light guide layer 11 is provided between the upper cladding layer 13 and the light emitting layer 7. The upper light guide layer 11 and the second light guide layer 9 are used to confine light generated in the light emitting layer 7 in the vicinity of the light emitting layer 7. As the upper light guide layer 11, for example, undoped GaN can be used. The film thickness of the upper light guide layer 11 can be set to, for example, 10 to 300 nm.

The electron block layer 12 is formed of a p-type gallium nitride semiconductor. Since the electron blocking layer 12 is formed of a material having a band gap larger than that of the second light guide layer 9 and the upper light guide layer 11, it functions to confine electrons serving as carriers in the vicinity of the light emitting layer 7. The electron blocking layer 12, for example, can be used p-type _{Al Y Ga 1-Y} N. Moreover, the film thickness of the electronic block layer 12 can be 5-100 nm, for example. The Al composition Y of the electron block layer 12 is preferably 0.05 to 0.30. This is because if the Al composition Y is 0.05 or less, electrons cannot be sufficiently blocked in the light-emitting layer 7, and if the Al composition Y is 0.30 or more, cracks occur and the AlGaN This is because the crystal quality deteriorates.

  The nitride semiconductor laser 40 can include a second conductivity type gallium nitride based semiconductor layer. The second conductivity type gallium nitride based semiconductor layer can include an upper cladding layer 13.

The upper cladding layer 13 is formed of a p-type gallium nitride semiconductor. The upper cladding layer 13 supplies holes serving as carriers to the light emitting layer 7. Further, since the upper cladding layer 13 is formed of a material having a refractive index lower than that of the material constituting the light emitting layer 7, the second light guide layer 9, and the upper light guide layer 11, the light generated in the light emitting layer 7 In the vicinity of the light emitting layer 7. As a material for forming the upper clad layer 13, Al _{Z2Ga1 -Z2N} is preferably used. The Al composition Z2 of the upper cladding layer 13 is preferably 0.01 to 0.10. This is because if the Al composition Z2 is 0.01 or less, a sufficient light confinement effect in the light-emitting layer 7 cannot be obtained. If the Al composition Z2 is 0.10 or more, cracks occur and the AlGaN This is because the crystal quality deteriorates. The film thickness of the upper cladding layer 13 can be 50 to 1000 nm.

  An upper contact layer 15 and an anode electrode layer 17 are formed on the upper cladding layer 13.

  The nitride semiconductor laser 40 has end faces 25 and 27 that intersect the X axis. A reflection layer is provided on the end faces 25 and 27. The end faces 25 and 27 and the optical waveguide between the end faces 25 and 27 constitute a resonator of the nitride semiconductor laser 40. End faces 25 and 27 are formed by cleaving nitride semiconductor substrate 1. This cleavage is preferably performed on the (10-10) plane of the nitride semiconductor substrate 1 and the resonator is preferably oriented in the [10-10] direction. This is because a good wall opening is easily obtained.

  As the nitride semiconductor substrate 1, for example, a GaN substrate or an InGaN substrate can be used. When the nitride semiconductor substrate 1 is a GaN substrate, a large GaN wafer can be obtained. Therefore, a large number of nitride semiconductor laser elements can be formed on the GaN wafer, and the manufacturing cost of the nitride semiconductor laser 40 can be reduced. When an InGaN substrate is used as the nitride semiconductor substrate 1, when the first light guide layer 5, the light emitting layer 7, and the second light guide layer 9 are made of InGaN, these layers and the nitride semiconductor substrate 1 The lattice mismatch can be reduced. Therefore, it becomes easy to control the In composition in the first light guide layer 5, the light emitting layer 7, and the second light guide layer 9.

  The main surface 1x of the nitride semiconductor substrate 1 is a c-plane of the nitride semiconductor substrate 1 or a semipolar surface inclined by a predetermined angle from the c-plane of the nitride semiconductor substrate 1 in the m-axis direction or the a-axis direction. it can. When the main surface 1x is a semipolar surface, the effect of shortening the oscillation wavelength due to the piezoelectric field is reduced. Further, the main surface 1x of the nitride semiconductor substrate 1 may be a nonpolar surface such as an m-plane or a-plane of the nitride semiconductor substrate 1. In this case, the influence of shortening the oscillation wavelength due to the piezoelectric field is further reduced.

Since the nitride semiconductor laser 40 according to the present embodiment satisfies the above-described conditions, the nitride semiconductor laser 40 capable of reducing the effect of band filling can be obtained. First, second, and third light-absorbing layer 31,5B, since 9b is capable of absorbing light having a wavelength component of the short-wavelength region R _L, light having a wavelength component in a short wavelength range R _L is contribute to laser oscillation do not do. On the other hand, light having a wavelength component in the long wavelength region _RH propagates in the resonator of the nitride semiconductor laser 40. As a result, since laser oscillation is generated by light having a wavelength component in the long wavelength region _RH , the nitride semiconductor laser 40 capable of reducing the effect of band filling can be obtained.

The well layer 35 can be formed of, for example, In _R Ga _1- RN. In this case, the In composition R is preferably 0.13 to 0.30. This is because if the In composition R is 0.13 or less, a long oscillation wavelength of 425 nm or more cannot be obtained. If the In composition R is 0.30 or more, the crystal quality of InGaN deteriorates and laser oscillation occurs. It is because it becomes impossible to obtain. The thickness t35 of the well layer 35 is preferably 2 to 10 nm. This is because if the thickness t35 of the well layer 35 is 2 nm or more, the In composition when obtaining a desired oscillation wavelength can be reduced, and if the thickness t35 of the well layer 35 is 10 nm or less, InGaN. This is because the crystal quality of the is improved. The number of well layers 35 in the light emitting layer 7 is not particularly limited, and may be one layer, two layers, or four or more layers.

The first, second, and third light absorption layers 31, 5b, and 9b are preferably formed of In _U Ga _1- UN. This is because In _U Ga _1- UN can be grown on the nitride semiconductor substrate 1 with high crystal quality. In this case, the In composition U is preferably 0.10 to 0.27. This is because if the In composition U is 0.10 or less, it tends to be difficult to absorb light of the wavelength component of the short wavelength region _RL , and if the In composition U is 0.27 or more, the long wavelength region R _This is because it is difficult to obtain laser oscillation by absorbing light having a wavelength component of _H.

  The first, second, and third light absorption layers 31, 5b, 9b are preferably formed of InAlGaN. Since InAlGaN absorbs light generated in the light emitting layer 7 more efficiently than InGaN, it is possible to efficiently absorb light in the short wavelength region component generated in the well layer in the LED mode.

The first, second, and third light absorption layers 31, 5b, and 9b are added with an n-type dopant of 1 × 10 ¹⁸ cm ⁻³ or more and 5 × 10 ¹⁹ cm ⁻³ or less. Is preferred. This is because if the concentration of the n-type dopant is 1 × 10 ¹⁸ cm ⁻³ or more, the light absorption efficiency of the component of the short wavelength region _RL generated in the well layer 35 increases, This is because the crystal quality of the first, second, and third light absorption layers 31, 5b, and 9b is improved when the concentration of the dopant is 5 × 10 ¹⁹ cm ⁻³ or less. As the n-type dopant, for example, Si, Ge, Te or the like can be used.

The first, second, and third light absorption layers 31, 5b, and 9b are added with a p-type dopant of 1 × 10 ¹⁸ cm ⁻³ or more and 5 × 10 ¹⁹ cm ⁻³ or less. Is preferred. This is because if the concentration of the p-type dopant is 1 × 10 ¹⁸ cm ⁻³ or more, the light absorption efficiency of the component of the short wavelength region _RL generated in the well layer 35 increases, and the p-type dopant This is because the crystal quality of the first, second, and third light absorption layers 31, 5b, and 9b is improved when the concentration of is less than 5 × 10 ¹⁹ cm ⁻³ . As the p-type dopant, for example, Mg, Zn, Be, or the like can be used.

The thicknesses t31, t5b and t9b of the light absorption layers 31, 5b and 9b are preferably thinner than the thickness t35 of the well layer 35. For example, the thicknesses t31, t5b, and t9b of the light absorption layers 31, 5b, and 9b are preferably 1 to 9 nm. This is because when the thickness t31, t5b, t9b of the light absorption layers 31, 5b, 9b is 1 nm or more, the light of the component of the short wavelength region _RL generated by the well layer 35 can be sufficiently absorbed, This is because when the thicknesses t31, t5b, and t9b of the light absorption layers 31, 5b, and 9b are 9 nm or less, the crystal quality of the light absorption layers 31, 5b, and 9b is improved. In addition, the number of the 1st light absorption layers 31 in the light emitting layer 7 is not restrict | limited in particular, For example, it can be made into 1 layer or 2 layers or more. Further, the number of the second light absorption layer 5b in the first light guide layer 5 and the number of the third light absorption layers 9b in the second light guide layer 9b are not particularly limited, and may be two or more.

The ratio (t31 / t35, 5b / t35, or 9b / t35) of the thickness of the light absorption layers 31, 5b, 9b and the thickness t35 of the well layer 35 is preferably 0.3 to 0.7. This is because when the ratio is 0.3 or more, the light absorption layers 31, 5b, 9b can sufficiently contribute to the absorption of light of the component of the short wavelength region _RL generated by the well layer 35, and this When the ratio is 0.7 or less, the well layer 35 mainly contributes to light emission due to recombination of injected carriers, and the light absorption layers 31, 5 b, and 9 b are mainly short wavelength regions generated by the well layer 35. This is because it contributes to the absorption of light of the _RL component.

The first InGaN barrier portion 33x, the second InGaN barrier portion 33y, and the barrier layer 34b can be formed of, for example, In _P Ga _1-PN . In this case, the In composition P is preferably 0.001 to 0.05. This is because the crystal quality deteriorates when the In composition P is 0.001 or less, and the carrier confinement effect in the well layer 35 cannot be sufficiently obtained when the In composition P is 0.05 or more. is there. The thicknesses t33x and t33y of the first InGaN barrier part 33x and the second InGaN barrier part 33y are preferably 2 to 10 nm. This is because when the thicknesses t33x and t33y are 2 nm or more, a carrier confinement effect in the well layer 35 is sufficiently obtained. Further, when the thicknesses t33x and t33y are 10 nm or less, the driving voltage can be lowered. The thicknesses t33x and t33y of the first InGaN barrier portion 33x and the second InGaN barrier portion 33y are the distances between the first, second, and third light absorption layers 31, 5b, and 9b and the well layer 35.

The laser oscillation wavelength of the nitride semiconductor laser 40 according to this embodiment is preferably 425 nm or more. When the laser oscillation wavelength is less than 425 nm, the tendency of the oscillation wavelength to be shortened by band filling is particularly weak, so the amount of light of the component in the short wavelength region _RL that is the absorption target of the light absorption layer is reduced. For this reason, it is almost impossible to expect a longer oscillation wavelength by the nitride semiconductor laser 40 of the present embodiment. Further, the lasing wavelength of the nitride semiconductor laser 40 is preferably 460 nm or more. If the laser oscillation wavelength is less than 460 nm, the tendency of the oscillation wavelength to be shortened by band filling is weak, so the amount of light in the short wavelength region _RL that is the absorption target of the light absorption layer is reduced. For this reason, it is not possible to expect much longer oscillation wavelength by the nitride semiconductor laser 40 of the present embodiment.

  Next, a modification of the nitride semiconductor laser according to this embodiment will be described. FIG. 5 is a diagram showing a band structure in the vicinity of the light emitting layer of the nitride semiconductor laser according to the modification, and shows the band structure corresponding to a cross-sectional structure in the vicinity of the light emitting layer of the nitride semiconductor laser.

  As shown in FIG. 5, the light emitting layer 7 may include a barrier layer 34 and a well layer 35. The light emitting layer 7 does not include a light absorbing layer. The barrier layer 34 can be formed of the same material as the first InGaN barrier 33x and the second InGaN barrier 33y described above. The thickness t34 of the barrier layer 34 is preferably 5 to 20 nm. This is because the carrier confinement effect in the well layer 35 is sufficiently obtained when the thickness t34 is 5 nm or more. Further, when the thickness t34 is 20 nm or less, the driving voltage can be lowered.

The first light guide layer 5 includes a first light absorption layer 5b and a first InGaN guide portion 5a. The first light absorption layer 5 b is located between the first InGaN guide portion 5 a and the light emitting layer 7. The second light guide layer 9 includes a second light absorption layer 9b and a second InGaN guide portion 9a. The second light absorption layer 9 b is located between the second InGaN guide portion 9 a and the light emitting layer 7. Bandgap _{E B} of the 1InGaN guide portion 5a is larger than the band gap _{E Y} of the first light-absorbing layer _{5b (E B> E Y)} . Further, the band gap _{E B} of the 2InGaN guide portion 9a is larger than the band gap _{E Y} of the second light-absorbing layer _{9b (E B> E Y)} . The ratio of the thicknesses of the first and second light absorption layers 5b and 9b to the thickness t35 of the well layer 35 (5b / t35 or 9b / t35) is preferably 0.3 to 0.7. . This is because when the ratio is 0.3 or more, the first and second light absorption layers 5b and 9b can sufficiently contribute to the absorption of light of the component of the short wavelength region _RL generated by the well layer 35, When this ratio is 0.7 or less, the well layer 35 mainly contributes to light emission by recombination of injected carriers, and the first and second light absorption layers 5b and 9b are mainly the well layer 35. This is because it contributes to the absorption of light of the component of the generated short wavelength region _RL .

Even with the nitride semiconductor laser 40 having such a configuration, the effect of band filling is reduced. Since the first light-absorbing layer 5b and the second light-absorbing layer 9b is capable of absorbing light having a wavelength component of the short-wavelength region R _L, light having a wavelength component in a short wavelength range R _L does not contribute to laser oscillation. On the other hand, light having a wavelength component in the long wavelength region _RL propagates in the resonator of the nitride semiconductor laser 40. As a result, since laser oscillation is generated by light having a wavelength component in the long wavelength region _RH , the nitride semiconductor laser 40 capable of reducing the effect of band filling can be obtained.

  Hereinafter, description will be made using Examples 1 to 3 and Comparative Example 1.

  FIG. 6 is a flowchart of main steps of the method for manufacturing a nitride semiconductor laser according to the first to third embodiments. As shown in the flowchart 100, the nitride semiconductor laser manufacturing method according to the first to third embodiments includes a step S101 for preparing a semiconductor wafer, a step S103 for forming a semiconductor multilayer S103 for the semiconductor laser, an anode electrode, and a cathode electrode. And step S107 for separating the wafer into individual semiconductor laser elements.

Example 1
A method for manufacturing the nitride semiconductor laser of Example 1 will be described. FIG. 7 is a schematic diagram showing a cross-sectional structure of the nitride semiconductor laser 40a of the first embodiment. First, in step S101, a c-plane GaN stripe core wafer 1 was prepared.

The stripe core wafer 1, the wafer comprising a second region 1b having a first region 1a having a threading dislocation density of 1 × ¹⁰ 7 ^{cm -2} or less, the 1 × ¹⁰ 7 ^{cm -2} or more threading dislocation density is there. The first region 1a and the second region 1b are called a low threading transition region and a high threading transition region, respectively. The first region 1a and the second region 1b extend from the back surface 1y of the stripe core wafer 1 to the main surface 1x. The second region 1 b extends along the first region 1 a and extends in the m-axis direction of the hexagonal GaN crystal constituting the stripe core wafer 1.

Next, in step S103, an epitaxial film of a semiconductor layer was sequentially grown on the main surface 1x of the stripe core wafer 1 by the MOCVD method under the following conditions.
Lower cladding layer 2: n-type Al _0.04 Ga _0.96 N, 2300 nm, growth temperature 1150 degrees Celsius.
Lower light guide layer 3: n-type GaN, 50 nm, growth temperature 1150 degrees Celsius.
First light guide layer 5: a third InGaN guide portion 5a and a second light absorption layer 5b are stacked.
Third InGaN guide portion 5a: undoped In _0.05 Ga _0.95 N, 50 nm, growth temperature 840 degrees centigrade.
Second light absorption layer 5b: In _0.20 Ga _0.80 N, 1.5 nm, growth temperature 780 degrees Celsius.
Light emitting layer 7: Barrier layers 34a and 34b and well layers 35 are grown alternately.
Barrier layer 34b: In _0.05 Ga _0.95 N, 7 nm, growth temperature 840 degrees Celsius.
Well layer 35: In _0.23 Ga _0.77 N, 3 nm, growth temperature 780 degrees Celsius.
Barrier layer 34a: a first InGaN barrier portion 33x, a first light absorption layer 31, and a second InGaN barrier portion 33y are sequentially stacked.
First InGaN barrier portion 33x: In _0.05 Ga _0.95 N, 7 nm, growth temperature 840 degrees Celsius.
First light absorption layer 31: In _0.20 Ga _0.80 N, 1.5 nm, growth temperature 780 degrees Celsius.
Second InGaN barrier portion 33y: In _0.05 Ga _0.95 N, 7 nm, growth temperature 840 degrees centigrade.
Light guide layer 9: a third light absorption layer 9b and a fourth InGaN guide portion 9a are sequentially stacked.
Third light absorption layer 9b: In _0.20 Ga _0.80 N, 1.5 nm, growth temperature 780 degrees Celsius.
Fourth InGaN guide portion 9a: In _0.20 Ga _0.80 N, 1.5 nm, growth temperature 780 degrees Celsius.
Upper light guide layer 11: undoped GaN, 50 nm, growth temperature 1100 degrees Celsius.
Electron blocking layer 12: p-type Al _0.18 Ga _0.82 N, 20 nm, growth temperature 1100 degrees Celsius.
Upper cladding layer 13: p-type Al _0.06 Ga _0.94 N, 400 nm, growth temperature 1100 degrees Celsius.
Upper contact layer 15: p-type GaN, 50 nm, grown at a growth temperature of 1100 degrees Celsius.

When such a semiconductor layer is grown, a high transition region is formed on the second region 1b (high transition region) of the stripe core wafer 1 from the lower cladding layer 2 to the upper contact layer 15 along the stacking direction of the layers. It was done. Further, since the threading transition density of the first region 1a of the stripe core wafer 1 is 1 × 10 ⁷ cm ⁻² or less, a semiconductor film having a good crystal quality is epitaxially grown on the first region 1a.

  In step S105, an electrode was formed. First, the insulating layer 23 having the contact window 23 a was formed on the upper contact layer 15. At this time, the contact window 23 a is set along the high transition region formed in each layer from the lower cladding layer 2 to the upper contact layer 15. As a result, the nitride semiconductor laser resonator can be easily oriented in the m-axis direction as described later. The contact window 23a extends in the direction along the X axis in FIG. The contact window 23a has a width of 10 μm and a length of 600 μm.

  Subsequently, 10 nm of Ni and 300 nm of Au were formed on the insulating layer 23 and the contact window 23a, and the anode 17 was formed.

  Subsequently, the back surface 1y of the stripe core wafer 1 was shaved to thin the wafer. Thereafter, a cathode electrode layer 21 made of Ti 30 nm, Al 100 nm, and Au 300 nm was formed on the back surface 1 y of the stripe core wafer 1.

Next, in step S107, the stripe core wafer 1 was cleaved and cut to separate the stripe core wafer 1 into individual semiconductor laser elements. In FIG. 7, two surfaces intersecting with the X axis of the nitride semiconductor laser 40a are shown as cleavage planes. The two surfaces and the optical waveguide between the two surfaces constitute a resonator of the nitride semiconductor laser 40a.
(Example 2)

FIG. 8 is a schematic diagram showing a cross-sectional structure of the nitride semiconductor laser 40b of the second embodiment. Example 2 is different from Example 1 in the structure of the light emitting layer 7. The structure of Example 2 is the same as that of Example 1 except for the light emitting layer 7. The light emitting layer of Example 2 has the following structure.
Light emitting layer 7: Barrier layers 34 and well layers 35 are alternately grown.
Barrier layer 34: In _0.05 Ga _0.95 N, 15 nm, growth temperature 840 degrees Celsius.
Well layer 35: In _0.23 Ga _0.77 N, 3 nm, growth temperature 780 degrees Celsius.

(Example 3)
FIG. 9 is a schematic diagram showing a cross-sectional structure of the nitride semiconductor laser 40c of the third embodiment. In the third embodiment, the structure of the wafer on which the semiconductor layer is grown is different from the first embodiment. The third embodiment is the same as the first embodiment except for the wafer structure. In step S101, a c-plane In _0.20 Ga _0.80 N wafer 1 without a stripe core was prepared.

(Comparative Example 1)
FIG. 10 is a schematic diagram showing a cross-sectional structure of the nitride semiconductor laser 40d of Comparative Example 1. Comparative Example 1 is different from Example 1 in the structure of the light emitting layer 7, the light guide layer 5, and the light guide layer 9. The structure of Comparative Example 1 is the same as that of Example 1 except for these layers. The light emitting layer 7, the light guide layer 5, and the light guide layer 9 of Comparative Example 1 have the following structure.
Optical guide layer 5: undoped In _0.05 Ga _0.95 N, 50 nm, growth temperature 840 degrees Celsius.
Light emitting layer 7: Barrier layers 33 and well layers 35 are grown alternately.
Barrier layer 33: In _0.05 Ga _0.95 N, 15 nm, growth temperature 840 degrees centigrade.
Well layer 35: In _0.23 Ga _0.77 N, 3 nm, growth temperature 780 degrees Celsius.
Optical guide layer 9: undoped In _0.05 Ga _0.95 N, 50 nm, growth temperature 840 degrees Celsius.

For the nitride semiconductor lasers 40a, 40b, 40c, and 40d of Examples 1 to 3 and Comparative Example 1 manufactured as described above, the emission spectrum in the LED mode peaks under the condition of a current density of 0.1 kA / cm ^2. The wavelength λ _X having the intensity, the lasing wavelength, and the lasing threshold current were measured. Then, the following results were obtained.
Example 1: Wavelength λ _X = 480 nm, laser oscillation wavelength = 470 nm, laser oscillation threshold current = 500 mA
Example 2: Wavelength λ _X = 480 nm, laser oscillation wavelength = 470 nm, laser oscillation threshold current = 500 mA
Example 3: wavelength λ _X = 530 nm, laser oscillation wavelength = 520 nm, laser oscillation threshold current = 1000 mA
Comparative Example 1: Wavelength λ _X = 480 nm, laser oscillation wavelength = 442 nm, laser oscillation threshold current = 300 mA

From these results, in the example of the present invention, the values of the wavelength λ _X and the laser oscillation wavelength are close compared to the comparative example. As a result, in the nitride semiconductor lasers 40a, 40b, and 40c according to the embodiments of the present invention, the first, second, and third light absorption layers 31, 5b, and 9b have the short wavelength region R _L in the LED mode (FIG. 4). It is considered that the laser oscillation was caused by the light having the wavelength component in the long wavelength region _RH . Therefore, it has been found that the effects of band filling are reduced in the nitride semiconductor lasers 40a, 40b, and 40c according to the examples of the present invention.

It is a schematic diagram showing a cross-sectional structure of the nitride semiconductor laser according to the embodiment. It is a schematic diagram which shows the cross-section of the light emitting layer vicinity of the nitride semiconductor laser which concerns on embodiment. It is a figure which shows the band structure of the light emitting layer vicinity of the nitride semiconductor laser which concerns on embodiment. It is a figure which shows the emission spectrum in LED mode of a nitride semiconductor laser. It is a figure which shows the band structure of the light emitting layer vicinity of the nitride semiconductor laser which concerns on a modification. It is a figure which shows the flowchart which shows the main processes of the manufacturing method of the nitride semiconductor laser which concerns on an Example and a comparative example. It is a figure which shows the cross-section of the nitride semiconductor laser which concerns on an Example. It is a figure which shows the cross-section of the nitride semiconductor laser which concerns on an Example. It is a figure which shows the cross-section of the nitride semiconductor laser which concerns on an Example. It is a figure which shows the cross-section of the nitride semiconductor laser which concerns on a comparative example.

Explanation of symbols

2 ... lower cladding layer (first conductivity type gallium nitride based semiconductor layer), 5 ... first light guide layer, 7 ... light emitting layer, 9 ... second light guide layer, 13 ... Upper cladding layer (first conductivity type gallium nitride based semiconductor layer), 31... First light absorption layer, 34, 34a, 34b... Barrier layer, 35. laser.

Claims (21)

A nitride semiconductor laser comprising:
A first conductivity type gallium nitride based semiconductor layer;
A second conductivity type gallium nitride based semiconductor layer;
A light emitting layer provided between the first conductive type gallium nitride based semiconductor layer and the second conductive type gallium nitride based semiconductor layer;
A first light guide layer provided between the first conductive type gallium nitride based semiconductor layer and the light emitting layer;
A second light guide layer provided between the second conductivity type gallium nitride based semiconductor layer and the light emitting layer;
With
The emission layer includes a well layer having a band gap E _W, and a barrier layer having a band gap E _B, a quantum well structure including,
The well layer of the light emitting layer is made of InGaN,
It said first optical guide layer, the second optical guide layer, and at least one of said barrier layer includes a first light-absorbing layer composed of a gallium nitride-based semiconductor layer having a band gap E _Y,
The band gap E _Y of the first light-absorbing layer is larger than the band gap E _W, the band gap E _Y is smaller than the band gap E _B,
The difference between the band gap _{E Y} and the band gap _{E W} is greater than 0, rather smaller than 0.3eV,
The nitride semiconductor laser has a laser oscillation wavelength of 460 nm or more . The light emitting layer is an emission spectrum at a wavelength corresponding to the energy E _X in the LED mode of the nitride semiconductor laser is provided so as to have a peak intensity,
The band gap E _Y of the first light-absorbing layer is greater than the energy E _X,
Wherein the difference between the band gap E _Y and the energy E _X greater than 0,
The nitride semiconductor laser according to claim 1, wherein the difference is smaller than 0.09 eV.   3. The nitride according to claim 1, wherein at least one of the first light guide layer and the second light guide layer is provided with the first light absorption layer. 4. Semiconductor laser. The first light guide layer includes the first light absorption layer, and a first InGaN guide portion provided between the first light absorption layer and the first conductivity type gallium nitride based semiconductor layer,
The band gap of the 1InGaN guide portion, a nitride semiconductor laser according to any one of claims 1 to 3, wherein greater than the band gap E _Y of the first light-absorbing layer. The second light guide layer includes the first light absorption layer, and a second InGaN guide portion provided between the first light absorption layer and the second conductivity type gallium nitride based semiconductor layer,
The band gap of the 2InGaN guide portion, a nitride semiconductor laser according to any one of claims 1 to 4, wherein greater than the band gap E _Y of the first light-absorbing layer. Wherein the barrier layer, a nitride semiconductor laser according to any one of claims 1 to 3, wherein the first light-absorbing layer is provided. The light emitting layer further includes another well layer,
The barrier layer includes the first light absorption layer, first and second InGaN barrier portions,
The first InGaN barrier portion is provided between the first light absorption layer and the well layer,
The second InGaN barrier portion is provided between the first light absorption layer and the another well layer,
The band gap E _B of the first and second 2InGaN barrier portion, nitride according to any one of claims 1 to 3, wherein greater than the band gap E _Y of the first light-absorbing layer Semiconductor laser. The first light guide layer includes a second light absorption layer, and a third InGaN guide portion provided between the second light absorption layer and the first conductivity type gallium nitride semiconductor layer,
The second light absorption layer includes a gallium nitride based semiconductor layer having a band gap _EY2 .
The band gap E _Y2 of the second light absorbing layer is larger than the band gap E _W,
The difference between the band gap _{E W} and the band gap _{E Y2} of the second light absorbing layer is greater than 0, less than 0.3 eV,
The band gap of the 3InGaN guide portion, a nitride semiconductor laser according to claim 7, wherein greater than the band gap E _Y2 of the second light-absorbing layer. The second light guide layer includes a third light absorption layer, and a fourth InGaN guide portion provided between the third light absorption layer and the second conductivity type gallium nitride based semiconductor layer,
The third light absorption layer includes a gallium nitride based semiconductor layer having a band gap _EY3 .
The band gap E _Y3 of the third light-absorbing layer is larger than the band gap E _W,
The difference between the band gap _{E Y3} and the band gap _{E W} of the third light-absorbing layer is greater than 0, less than 0.3 eV,
The band gap of the 4InGaN guide portion, a nitride semiconductor laser according to claim 7 or claim 8, characterized in that greater than the band gap E _Y3 of the third light-absorbing layer. The nitride semiconductor laser according to any one of claims 1 to 9 wherein the first light-absorbing layer is characterized by comprising InGaN. The nitride semiconductor laser according to any one of claims 1 to 9 , wherein the first light absorption layer is made of InAlGaN. The first conductive type gallium nitride-based semiconductor layer is made of AlGaN, the second conductive type gallium nitride based semiconductor layer, nitride according to any one of claims 1 to 11, characterized in that it consists of AlGaN Semiconductor laser. The first light-absorbing layer, a nitride semiconductor laser according to any one of claims 1 to 12, characterized in that it comprises a 1 × 10 ¹⁸ cm ^-3 or more n-type or p-type dopant . A nitride semiconductor substrate;
The first conductive type gallium nitride based semiconductor layer, the second conductive type gallium nitride based semiconductor layer, the light emitting layer, the first light guide layer, and the second light guide layer are formed on a main surface of the nitride semiconductor substrate. the nitride semiconductor laser according to any one of claims 1 to 13, characterized in that provided above. The nitride semiconductor substrate includes a first region having a threading dislocation density smaller than a predetermined threading dislocation density, and a second region having a threading dislocation density larger than the predetermined threading dislocation density. The region and the second region extend from the back surface of the nitride semiconductor substrate to the main surface,
The first conductivity type gallium nitride based semiconductor layer, the second conductivity type gallium nitride based semiconductor layer, the light emitting layer, the first light guide layer, and the second light guide layer are formed in the first region of the main surface. Provided on the
The second region extends along the first region;
15. The nitride semiconductor laser according to claim 14 , wherein the resonator of the nitride semiconductor laser extends along the second region. 16. The nitride semiconductor laser according to claim 15 , wherein the resonator extends in a [10-10] direction of the nitride semiconductor substrate. The predetermined threading dislocation density, a nitride semiconductor laser according to claim 15 or claim 16, characterized in that less than 1 × ¹⁰ 7 ^{cm -2.} The nitride semiconductor laser according to any one of claims 14 to 17 , wherein the nitride semiconductor substrate is a GaN substrate. The nitride semiconductor laser according to any one of claims 14 to 17 , wherein the nitride semiconductor substrate is an InGaN substrate. The nitride semiconductor laser according to any one of claims 14 to 19 , wherein the main surface of the nitride semiconductor substrate has a semipolar property. Said main surface of said nitride semiconductor substrate, nitride semiconductor laser according to any one of claims 15 14 to claim 19, characterized in that the non-polar surface.

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