JP2020021959A - Semiconductor light-emitting element - Google Patents

Abstract

To prevent the irregularity of the grating between a substrate and a first clad layer and a second clad layer and increase the light confinement ratio in the vertical direction, while reducing absorption loss in an electrode on a ridge.SOLUTION: A semiconductor light-emitting element comprises: a substrate (11); an n-type first clad layer (12) provided on the substrate (11) and composed of AlGaN; and a light guide layer (13) provided on the first clad layer (12). The semiconductor light-emitting element further includes: an active layer (14) provided on the light guide layer (13); an electron barrier layer (15) provided on the active layer (14); a p-type second clad layer (16) composed of AlGaN; a p-type contact layer (17) provided above the second clad layer (16); and a conductive oxide layer (18) provided on the p-type contact layer (17) composed of p-type GaN and composed of indium tin oxide. The p-type second clad layer (16) is formed with a ridge (23).SELECTED DRAWING: Figure 1

Description

  The present invention relates to a semiconductor light emitting device used for a vehicle-mounted head lamp, a projector light source, and the like.

  2. Description of the Related Art Conventionally, as a semiconductor light emitting device made of a group III nitride semiconductor such as GaN or AlGaN, for example, a semiconductor laser device described in Patent Document 1 is known. This conventional semiconductor light emitting device will be described with reference to FIG.

Conventional semiconductor light emitting element, a buffer layer ₁₀₂ made of _Al 0.05 _{Ga 0.95} N on the substrate 101 made of GaN, Al _{0.05 Ga 0.95} n-type contact layer 103 made of N, _{an In 0. A} crack prevention layer 104 made of ₀₆ Ga _0.94 N is formed. An n-type cladding layer 105 formed by alternately forming layers made of Al _0.05 Ga _0.95 N and a layer made of GaN, and an n-type light guide layer 106 made of GaN are formed thereon. An active layer 107 in which barrier layers made of undoped In _0.05 Ga _0.95 N and well layers made of undoped In _0.32 Ga _0.68 N are alternately formed thereon, and Al _0.3 A p-type electron confinement layer 108 of Ga _0.7 N is formed. A p-type light guide layer 109 made of GaN, a p-type clad layer 110 formed by alternately forming a layer made of Al _0.05 Ga _0.95 N and a layer made of GaN thereon, and a p-type light guide layer made of GaN Contact layers 111 are sequentially formed. Then, the side of the ridge structure formed by etching from the p-type contact layer 111 to the middle of the p-type light guide layer 109 until the remaining thickness of the p-type light guide layer 109 becomes 0.1 μm and the p-type light guide layer A protective film 162 made of a Zr oxide is formed on the upper surface of 109. On the p-type contact layer 111 and the second protection film 162, a p-electrode 120 made of Ni / Au is formed. Further, the n-type contact layer 103 is etched until a part of the n-type contact layer 103 is exposed. On the surface of the n-type contact layer 103, an n-electrode 121 made of Ti / Al is formed. A dielectric multilayer film 164 made of SiO ₂ and TiO ₂ is formed to cover. A pad electrode 122 is provided in an opening of the dielectric multilayer film 164 on the p-type contact layer 111 side so as to be in contact with the p electrode 120, and a pad electrode 123 is provided in an opening of the dielectric multilayer film 164 in the n electrode 121. Is provided.

JP 2002-270971 A

  In such a conventional semiconductor light emitting device, it is difficult to achieve both suppression of lattice irregularity between the substrate 101 and the n-type cladding layer 105 and the p-type cladding layer 110 and light confinement in a direction perpendicular to the substrate 101. Was a problem.

  That is, in the above-described conventional semiconductor light emitting device, when light confinement in the vertical direction is to be increased, it is necessary to reduce the refractive index of the n-type cladding layer 105 or the p-type cladding layer 110. There is. On the other hand, if the Al composition of the n-type cladding layer 105 or the p-type cladding layer 110 is increased, the lattice mismatch between the n-type cladding layer 105 and the p-type cladding layer 110 increases. When the lattice irregularity increases, lattice defects are likely to occur, leading to a decrease in luminous efficiency. For this reason, the Al composition of the n-type cladding layer 105 and the p-type cladding layer 110 cannot be made too large, and AlGaN having a low Al composition of 10% or less is used. In this case, the difference in the refractive index between the n-type and p-type cladding layers and the active layer becomes small, and the light distribution easily spreads greatly above and below the active layer. The foot reaches and absorption loss is likely to occur. In order to reduce such light absorption of guided light, it is necessary to increase the thickness of the cladding layer so that the foot of the light distribution does not reach the electrode formed on the ridge or the substrate. Become. However, as the thickness of the p-type cladding layer 110 on which the ridge-type waveguide is formed increases, the series resistance of the device increases, and the operating voltage increases. For this reason, heat generation during the laser oscillation operation increases, and the optical output is likely to be thermally saturated. As a result, the lattice mismatch between the substrate 101 and the n-type cladding layer 105 and the p-type cladding layer 110 is suppressed, the thickness of the p-type cladding layer 110 is prevented from increasing, and the vertical optical confinement is satisfied. It was getting harder.

  Accordingly, the present invention provides a grid between the substrate and the first and second cladding layers while reducing the absorption loss at the electrode on the ridge, even if the thickness of the conductive cladding layer on which the ridge is formed is small. The objective is to suppress irregularities and satisfy all vertical light confinement.

  In order to solve the above problems, a semiconductor light emitting device of the present invention includes a substrate, a one-conductivity-type first cladding layer formed of a group III nitride semiconductor having Al, and formed on the substrate. An active layer made of a group III nitride semiconductor formed on the cladding layer. A second clad layer of a reverse conductivity type made of a group III nitride semiconductor having Al formed on the active layer; a conductive compound layer formed on the second clad layer; And a ridge structure having the second clad layer as a lower surface. The Al composition of the second cladding layer is smaller than the Al composition of the first cladding layer, and the refractive index of the conductive compound layer is smaller than the refractive index of the second cladding layer.

  With this configuration, since the Al composition of the second cladding layer is smaller than the Al composition of the first cladding layer, the refractive index of the second cladding layer becomes relatively higher than that of the first cladding layer, so that the light distribution is reduced. The shape depends on the second clad layer. Further, since the refractive index of the conductive compound is smaller than the refractive index of the second cladding layer, the light distribution immediately below the ridge is distributed between the first cladding layer and the second cladding layer, The light confinement coefficient in the vertical direction of the light distribution to the active layer increases. As a result, the effective refractive index difference (ΔN) inside and outside the ridge increases.

  In the semiconductor light emitting device of the present invention, it is preferable that the ridge structure propagates a second-order or higher-order transverse mode. According to this preferred configuration, even if transverse modes of different orders interfere with each other and light distribution is coupled to each other, and even if the light distribution is deformed, its influence is reduced, and a kink having a large nonlinearity is less likely to be generated.

  The semiconductor light emitting device of the present invention further has a waveguide formed by a front end face and a rear end face, the ridge structure is formed between the front end face and the rear end face, and is included in a side face of the ridge structure, and It is preferable that the direction from the front end face to the rear end face and the direction of the waveguide form a predetermined angle. According to this preferred configuration, since the waveguide has a taper, spatial hole burning hardly occurs.

  In the semiconductor light emitting device of the present invention, when the reflectance of the front end face is Rf, the reflectance of the rear end face is Rr, the width of the ridge on the front end face is Wf, and the width of the ridge on the rear end face is Wr, Rf <Rr and It is preferable that Wf> Wr.

  In the semiconductor light emitting device of the present invention, the angle formed between the direction from the front end face to the rear end face and the direction of the waveguide is preferably 0.05 ° or more and 0.15 ° or less. According to this preferred configuration, spatial hole burning is more unlikely to occur.

  In the semiconductor light emitting device of the present invention, the thickness of the second cladding layer is preferably 0.3 μm or more and 0.6 μm or less. According to this preferred configuration, the light confinement ratio of the active layer can be increased by the thickness of the second cladding layer being 0.3 μm or more, and the layer thickness of the second cladding layer is 0.6 μm or less. In addition, the series resistance of the semiconductor light emitting device can be reduced.

  In the semiconductor light emitting device of the present invention, the conductive compound layer is preferably made of an oxide containing indium and tin, and has a thickness of 0.15 μm or more and 0.3 μm or less. According to this preferred configuration, the waveguide loss can be reduced, ΔN and the optical confinement coefficient can be increased, and the electrical resistance of the semiconductor light emitting device can be reduced.

In the semiconductor light emitting device of the present invention, the first cladding layer is made of Al _X1 Ga _1-X1 N, the second cladding layer is made of Al _X2 Ga _1-X2 N, and X1-X2 ≧ 0.02, X1 It is preferable to satisfy the relationship of ≦ 0.1, 0.03 ≦ X2 ≦ 0.07.

  In the semiconductor light emitting device of the present invention, it is preferable that the thickness of the second cladding layer outside the ridge structure is more than 0 nm and 50 nm or less. According to this preferred configuration, it is possible to increase the effective refractive index difference between the inside and the outside of the ridge structure.

  In the semiconductor light emitting device of the present invention, it is preferable that a current blocking layer having a lower refractive index than the second cladding layer is formed on the side surface of the ridge structure.

  According to the semiconductor light emitting device of the present invention, even in a semiconductor laser using a group III nitride, particularly a green semiconductor laser having an oscillation wavelength of 530 nm, the optical confinement coefficient and ΔN are large, and the generation of lattice defects is suppressed. A laser with a small wave path loss can be realized. Therefore, it is possible to realize a semiconductor laser having excellent temperature characteristics and capable of operating for a long period of time.

FIG. 2 is a sectional view of the semiconductor light emitting device according to the first embodiment of the present invention. FIG. 4 is a view showing the ridge height dependency of a horizontal stress distribution generated in an active layer 14 of the semiconductor light emitting device. In the semiconductor light emitting device, when the thickness of the second cladding layer 16 is 0.3 μm, the Al composition X1 of the first cladding layer 12 and the second cladding layer of the waveguide loss, the optical confinement coefficient, and the effective refractive index difference (ΔN) 16 is a diagram showing the dependency of Al composition X2 on X16 and the relationship between X1 and X2. A second cladding layer showing the dependence of the waveguide loss, the optical confinement coefficient, and the effective refractive index difference (ΔN) of the Al composition X1 of the first cladding layer 12 and the Al composition X2 of the second cladding layer 16 on the semiconductor light emitting device. 16 is a diagram when the film thickness is 0.2 μm. FIG. 4 is a diagram when the thickness of the second cladding layer 16 is 0.3 μm. FIG. 4 is a diagram when the film thickness of the second cladding layer 16 is 0.4 μm. FIG. 4 is a diagram when the film thickness of the second cladding layer 16 is 0.5 μm. FIG. 4 is a diagram when the film thickness of the second cladding layer 16 is 0.6 μm. In the structure of the semiconductor light emitting device without the conductive oxide layer 18, the Al composition X1 of the first cladding layer 12 and the Al content of the second cladding layer 16 of the waveguide loss, the optical confinement coefficient, and the effective refractive index difference (ΔN) are different. FIG. 9 is a view showing the dependency of the composition X2 when the thickness of the second cladding layer 16 is 0.2 μm. FIG. 4 is a diagram when the thickness of the second cladding layer 16 is 0.3 μm. FIG. 4 is a diagram when the film thickness of the second cladding layer 16 is 0.4 μm. FIG. 4 is a diagram when the film thickness of the second cladding layer 16 is 0.5 μm. FIG. 4 is a diagram when the film thickness of the second cladding layer 16 is 0.6 μm. FIG. 4 is a diagram showing a waveguide loss when the thickness of the conductive oxide layer 18 is changed in the semiconductor light emitting device. FIG. 9 is a diagram showing a change in ΔN when the thickness of the conductive oxide layer 18 is changed in the semiconductor light emitting device. FIG. 9 is a plan view of a stripe shape of a semiconductor light emitting device according to a second embodiment of the present invention. FIG. 4 is a diagram showing a current-light output characteristic of the semiconductor light emitting device when a conductive oxide layer 18 is used. The figure in the case where the conductive oxide layer is not used. FIG. 9 is a plan view showing a modification of the stripe shape of the semiconductor light emitting device. FIG. 9 is a plan view showing a modification of the stripe shape of the semiconductor light emitting device. FIG. 9 is a plan view showing a modification of the stripe shape of the semiconductor light emitting device. Sectional drawing of the conventional semiconductor light emitting element.

(First Embodiment)
Hereinafter, the semiconductor light emitting device according to the first embodiment of the present invention will be described with reference to the drawings. Note that the AlGaN below is that of _{Al x Ga 1-x N (} 0 <x <1), and InGaN is that of _{In y Ga 1-y N (} 0 <y <1). In addition, the InAlGaN is that _{In z Al t Ga 1-z} -t N of (0 <z <1,0 <t <1). X, y, z, and t representing the composition can be appropriately determined depending on the layer structure of the semiconductor light emitting device.

(1) Structure of Semiconductor Light-Emitting Element As shown in FIG. 1, a semiconductor light-emitting element of the present embodiment has a substrate 11 made of GaN and an n-type first cladding layer 12 made of AlGaN provided on the substrate 11. A light guide layer 13 made of n-type GaN provided on the first clad layer 12, and an active layer 14 having a quantum well structure provided on the light guide layer 13. Then, an electron barrier layer 15 made of p-type AlGaN provided on the active layer 14, a second clad layer 16 made of AlGaN, and a p-type layer provided above the second clad layer 16 of p-type GaN p-type contact layer 17 is provided. Further, a conductive oxide layer 18 made of indium tin oxide (hereinafter referred to as ITO) provided on the p-type contact layer 17 is provided. Further, a ridge 23 is formed on the p-type second cladding layer 16, and a current blocking layer 20 made of SiO ₂ is provided on a side wall of the ridge 23, and the current blocking layer 20 and the conductive oxide layer 18 are provided. On the upper side, a p-type electrode 22 is provided. On the back surface of the substrate 11, an n-type electrode 21 is provided.

  In the above description, the n-type semiconductor layer is doped with Si, and the p-type semiconductor layer is doped with Mg.

  The active layer 14 has a multiple quantum well structure using a well layer made of InGaN having a thickness of 3 nm and an In composition of 0.3 and a quantum barrier layer made of GaN having a thickness of 7.5 nm. It is advantageous that the number of wells be as large as possible because the light confinement coefficient in the vertical direction to the active layer can be increased. However, if the number of wells exceeds four, the operating carrier density of each quantum well layer is not uniform. This leads to a decrease in luminous efficiency. In this embodiment, the number of well layers is three. As a result, it is possible to increase the optical confinement coefficient while making the operating carrier density in each well uniform. In addition, using GaN as the quantum barrier layer, the generation of lattice defects due to lattice irregularity occurring in an InGaN well layer having a high In composition is suppressed by sandwiching the well layer between GaN at the top and bottom.

In the semiconductor light emitting device of the present embodiment, the direction perpendicular to the plane of FIG. 1 is defined as the direction of the resonator, and two surfaces perpendicular to the direction of the resonator are defined as end faces. That is, the semiconductor light emitting device of the present embodiment is a semiconductor laser. The front end face and the rear end face of the two end faces are coated with a multilayer film of an AlN film and an Al ₂ O ₃ film, and the reflectivity is 5% for the front end face and 95% for the rear end face, respectively. That is, the reflectance of the front end face is made smaller than the reflectance of the rear end face.

  The emission wavelength of the semiconductor light emitting device in this embodiment is 530 nm.

  The semiconductor light emitting device in the present embodiment is a semiconductor laser device having a stripe structure in which two side walls of the ridge 23 are parallel to the direction of the resonator when viewed from above the substrate 11.

  In the semiconductor light emitting device of the present embodiment, the Al composition of the first cladding layer 12 is X1, and the Al composition of the second cladding layer 16 is X2. As shown in FIG. 1, the width of the ridge 23 is W, the thickness of the second cladding layer 16 inside the ridge 24 is M2, the height of the ridge 23 is H, the layer of the second cladding layer 16 outside the ridge 25. Let the thickness be dp. The difference in effective refractive index between the ridge inside 24 and the ridge outside 25 is ΔN. Note that the ridge 23 is formed by performing etching (usually dry etching). That is, since the second cladding layer 16 in the ridge exterior 25 is made thinner than the second cladding layer 16 in the ridge exterior 24 by performing etching, dp is the unetched thickness of the second cladding layer 16 in the ridge exterior 25. You can also.

As is clear from FIG. 1, the following relational expression (Equation 1) holds between M2, H, and dp.
(Equation 1) M2 = H + dp
(2) Examination The inventor of the present application has proposed that the semiconductor light emitting device of this embodiment using the conductive oxide layer 18 has X1, X2, W, M2, H, ΔN, dp and We examined what value of thickness is desirable. The results of the study will be described below.

(2-1) dp To explain the magnitude of the layer thickness dp, if dp is large, ΔN becomes small, so that dp is preferably as small as possible. However, if the dp is too small, the influence of the damage of the crystal structure due to the dry etching reaches the active layer 14 due to the variation in the etching depth in the wafer surface, particularly when the dry etching is performed, and the long-term reliability. It is a factor that hinders the guarantee. For this reason, the etching is controlled so that dp is in the range of 0 nm to 50 nm.

  Even if dp changes from 0 nm to 50 nm, M2 remains unchanged, so that the light confinement coefficient in the vertical direction and the waveguide loss that occurs in the light distribution in the p-type contact layer 17 and the p-type electrode 22 hardly change.

On the other hand, when dp changes from 0 nm to 50 nm, ΔN changes because the effective refractive index outside the ridge 25 changes. In the case of the present embodiment, since SiO ₂ having a low refractive index is used as the current blocking layer 20, if dp increases, the effective refractive index outside the ridge 25 increases. That is, ΔN decreases as dp increases.

  As will be described later, ΔN should be as high as possible in order to stably oscillate the laser in the second or higher-order transverse mode. Therefore, when dp at which ΔN becomes smallest is 50 nm, X1 and X2 are determined so as to obtain as large ΔN as possible without causing a large increase in waveguide loss. At dp smaller than 50 nm, ΔN becomes larger. Therefore, in the following description, dp is set to 50 nm.

(2-2) SiO ₂ on stress applied to the semiconductor light-emitting device to the current blocking layer 20 (thermal expansion ^{coefficient: 0.6 × 10 -6 /K~0.9×10 -6 /} K) in the case of using the Since the thermal expansion coefficient is smaller than that of GaN (thermal expansion coefficient: 5.6 × 10 ⁻⁶ / K) or AlN (thermal expansion coefficient: 4.2 × 10 ⁻⁶ / K), the current blocking layer 20 A stress is generated between the ridge 23 and the ridge 23 due to a difference in thermal expansion coefficient. Therefore, in the second cladding layer 16 between the current blocking layer 20 and the active layer 14, compressive stress is generated in a region parallel to the active layer 14 in regions on both sides of the lower end of the ridge 23, and The structure is distorted. When the crystal structure is distorted, the refractive index at that portion changes. Generally, the refractive index of a group III nitride semiconductor increases when compressive stress is applied. Therefore, the refractive index of the second cladding layer 16 in the region near the lower end of the ridge 23 changes so as to increase in size due to compressive stress. As a result, ΔN decreases.

  Further, the band gap energy in the active layer 14 on both sides of the lower end of the ridge 23 is reduced, so that the current injected into the ridge 23 easily flows in both side regions of the ridge 23. Therefore, current is not uniformly injected into the active layer immediately below the ridge 23, leading to a decrease in slope efficiency. For this reason, it is necessary to reduce as much as possible distortion generated on both sides of the lower end of the ridge 23 due to the difference between the thermal expansion coefficients of the current block layer 20 and the second cladding layer 16.

  The inventors of the present application examined the relationship between the thickness M2 of the second cladding layer 16 inside the ridge 24 and the stress applied to the second cladding layer 16 in the ridge inside 24 and the ridge outside 25 for the semiconductor light emitting device shown in FIG. did. FIG. 2 shows the results of the study. 2, the abscissa represents the position of the second cladding layer 16 in a direction parallel to the GaN substrate 11 and parallel to the end face, with the origin at the center of the ridge 23, and the ordinate represents the second cladding layer at a predetermined position. The magnitude of the stress applied to the layer 16 is expressed in arbitrary units. If it is larger than 0 on the vertical axis, a compressive stress is applied to the second cladding layer 16, and if it is smaller than 0, a tensile stress is applied to the second cladding layer 16. The ridge width W was set to 16 μm for the semiconductor light emitting devices studied. Further, three M3s of 0.3 μm, 0.6 μm, and 0.8 μm were examined.

  As shown in FIG. 2, it was found that the larger the M2, that is, the higher the height H of the ridge 23, the larger the compressive stress inside the ridge 24. In particular, it was found that the compressive stress was remarkably large near the boundary between the ridge inside 24 and the ridge outside 25. It was also found that the distribution of the compressive stress inside the ridge 24 was more uneven as M2 was larger. From this, as the height H of the ridge 23 increases, the compressive stress in the ridge interior 24 near the boundary with the ridge exterior 25 increases significantly, the band gap there decreases, and the ridge interior 24 and the ridge exterior 25 Current flows near the boundary of. And it turns out that it is difficult to make a current flow through the ridge 23 uniformly. It can also be seen from this that the higher the height H of the ridge 23, the narrower the path of the current flowing through the ridge 23, and the greater the electrical resistance of the semiconductor light emitting element.

  That is, it is necessary to reduce the height H of the ridge 23 in order to reduce the stress generated in the regions on both sides of the lower end of the ridge 23 and reduce the electric resistance of the semiconductor light emitting device.

  It is understood from FIG. 2 that when M2 is reduced from 0.8 μm to 0.3 μm, the strain generated in the active layers on both sides of the lower end of the ridge 23 is almost halved, and the stress distribution is flat. That is, if M2 ≦ 0.3 μm, the electric resistance of the semiconductor light emitting device can be reduced.

(2-3) ΔN The effective refractive index difference ΔN between the ridge inside 24 and the ridge outside 25 will be described.

  When ΔN is small, the confinement mechanism of the horizontal lateral light distribution (horizontal lateral mode) with respect to the second or higher lateral mode is weak even if the ridge width W is widened, and only in the basic (0th) lateral mode and the first lateral mode. It becomes easy to operate. As a result, the interaction due to the interference between the transverse modes is increased, the light distribution shape is largely changed, a kink in which the current-light output characteristic is nonlinear occurs, and the light output is likely to be unstable.

  On the other hand, when the transverse mode of the second or higher order oscillates, the transverse modes of different orders interfere with each other, coupling of the light distribution occurs, and even if the light distribution is deformed, the effect is reduced and a kink having a large nonlinearity is obtained. Is less likely to occur, so that the linearity of the current-light output characteristics is improved.

  In other words, a semiconductor light emitting device that oscillates in a second-order or higher transverse mode is desirable in order to improve the linearity of the current-light output characteristics by preventing the occurrence of kink.

A semiconductor light emitting element used for a projector light source or the like is required to have a high output operation of several hundred mW or more. On the other hand, in the high-power laser, the ridge width W is 5 μm in order to reduce the light density at the cavity facet and to suppress the occurrence of COD (Catastrophic Optical Damage) in which the facet is melted and destroyed by the laser's own light. The above-mentioned wide stripe structure is used. In order to confine the secondary transverse mode light within the ridge and cause laser oscillation in such a wide stripe structure, the value of ΔN needs to be at least 2.5 × 10 ⁻³ . If ΔN is further increased, the light confinement rate in the horizontal direction of the second-order or higher-order transverse mode is increased, and laser oscillation including the second-order or higher-order transverse mode is stably generated.

(2-4) Regarding Light Confinement Coefficient In order to obtain good temperature characteristics in a semiconductor light emitting device, in particular, a semiconductor light emitting device having an emission wavelength around 530 nm, the light confinement coefficient in the vertical direction to the active layer 14 must be Larger is better, and it is necessary to have a light confinement coefficient (vertical direction) of at least 1%. Hereinafter, the light confinement coefficient in the vertical direction is referred to as a vertical transverse mode confinement coefficient.

(2-5) Values of X1 and X2 Next, the values of the Al composition X1 of the first cladding layer 12 and the Al composition X2 of the second cladding layer 16 will be described.

  When the Al composition X1 of the first cladding layer 12 is increased, the refractive index of the first cladding layer 12 becomes lower, the difference in the refractive index from the active layer 14 can be increased, and the light confinement coefficient in the vertical direction can be increased. . When the optical confinement coefficient is increased, a large gain can be obtained even when the current injected into the active layer is small, so that the oscillation threshold current value and the operating carrier density in the active layer are reduced. Therefore, at the time of high-temperature operation, it is possible to suppress overflow of carriers that are injected into the active layer and are thermally excited and leak to the cladding layer. For this reason, the increase in the vertical optical confinement coefficient increases the light output that is thermally saturated in the current-light output characteristics even at the time of high-temperature high-power operation, and realizes a laser excellent in temperature characteristics with a low operating current value. It is effective.

  However, if X1 is too large, both the difference in lattice constant and the difference in thermal expansion coefficient between the substrate 11 made of GaN and the first cladding layer 12 made of AlGaN become large, which leads to the generation of lattice defects and cracks. . Therefore, it is necessary to satisfy X1 ≦ 0.1.

  Further, if the Al composition X2 of the second cladding layer 16 is also increased similarly to X1, the vertical optical confinement coefficient to the active layer is increased. However, if it is too large, the activation rate of Mg, which is a p-type impurity, decreases, the electric resistance of the second cladding layer 16 increases, and the electric resistance of the semiconductor light emitting element increases. The increase in the electric resistance of the semiconductor light emitting element increases the self-heating during the laser oscillation operation of the semiconductor light emitting element, and leads to a decrease in the light output level at which the current-light output characteristic is thermally saturated. Therefore, in order to not increase the resistance of the second cladding layer 16 while obtaining the effect of increasing the light confinement coefficient in the vertical direction, it is necessary to satisfy X2 ≦ 0.07.

  When X2 is reduced, ΔN increases because the light distribution in the vertical direction approaches the second cladding layer 16. However, if X2 is too small, the light distribution becomes too close to the second cladding layer 16, and the free carrier absorption loss due to impurities in the p-type contact layer 17 and the second cladding layer 16 and the absorption loss in the p-type electrode 22 are reduced. And the waveguide loss increases. When the waveguide loss increases, the ratio of the change in the optical output to the change in the injected current amount (slope efficiency) after the laser oscillation in the current-optical output characteristics decreases, and the optical output level that thermally saturates during high-temperature operation decreases. Leads to. Therefore, the value of X2 needs to be 0.03 or more to suppress a large increase in the waveguide loss.

(2-6) Relationship between X1 and X2 In the semiconductor light emitting device as shown in FIG. 1, since the second cladding layer 16 is thinner outside the ridge 25, it is perpendicular to the active layer 14 outside the ridge 25. The light distribution in the direction (vertical transverse mode) depends on the first cladding layer 12 side. In the ridge interior 24, the vertical and transverse modes are substantially symmetric with respect to the active layer 14.

  Here, when the Al composition X1 of the first cladding layer 12 is larger than the Al composition X2 of the second cladding layer 16, the refractive index of the first cladding layer 12 becomes smaller than the refractive index of the second cladding layer 16. The effective refractive index outside the ridge 25 can be even smaller than the effective refractive index inside the ridge 24. That is, ΔN can be increased, and the light confinement ratio in the horizontal and horizontal modes can be increased.

Therefore, the inventor of the present application obtained ΔN for the semiconductor light emitting device shown in FIG. 1 with X1 and X2 as parameters and N2 = 0.3 μm. Note that the study was performed with W being 6 μm and the thickness of the conductive oxide layer 18 being 0.17 μm. The result is shown in FIG. In FIG. 3, 1%, 1.1%, 1.2%, 1.3%, and 1.4% are vertical and transverse mode confinement coefficients, and are 1.5 × 10 ⁻³ and 2 ×. ΔN refers to 10 ⁻³ , 2.5 × 10 ⁻³ , 3 × 10 ⁻³ , and 3.5 × 10 ⁻³ . Moreover, the ^{curve cm -1} are assigned as ^{6 cm -1} and 10 cm ^-1 represents the waveguide loss in the semiconductor light emitting element. In FIG. 3, the waveguide loss is indicated by a solid line, the vertical transverse mode confinement coefficient is indicated by a dashed line, and the effective refractive index difference (ΔN) is indicated by a broken line.

As shown in FIG. 3, the relationship between X1 and X2 in which ΔN is 2.5 × 10 ⁻³ or more is such that when X1 ≦ 0.1 and X2 ≦ 0.07,
(Equation 2) X1−X2 ≧ 0.02
, That is, the area on the right side of the straight line AB in FIG.

In summary, in order to reduce the electric resistance of the semiconductor light emitting device shown in FIG. 1 in terms of ΔN being 2.5 × 10 ⁻³ or more and obtaining the effect of increasing the light confinement coefficient in the vertical direction, Is
(Equation 2) X1−X2 ≧ 0.02
(Equation 3) X1 ≦ 0.1
(Equation 4) 0.03 ≦ X2 ≦ 0.07
Is required.

(2-8) Examination of Layer Thickness of Conductive Oxide Layer 18 Next, when M2 was changed to investigate the effect of the conductive oxide layer 18 and the condition of the layer thickness of the conductive oxide layer 18 The characteristics of the semiconductor light-emitting device will be described.

  FIGS. 4A to 4E show the characteristics of the semiconductor light emitting device when the thickness of the conductive oxide layer 18 is changed to 0.17 μm, W is changed to 6 μm, and M2 is changed to 0.2 μm to 0.6 μm. In addition, as a comparison, when the conductive oxide layer 18 was not provided, that is, when the semiconductor light emitting device in which the conductive oxide layer 18 was removed from the semiconductor light emitting device shown in FIG. 1 was used, M2 was changed from 0.2 μm to 0.6 μm. 5A to 5E show the characteristics of the semiconductor light emitting element of FIG. 4A to 4E, 5A to 5E, and the relationship between the value of M2 and the presence or absence of the conductive oxide layer 18 are as shown in Table 1.

In FIGS. 4A to 4E and FIGS. 5A to 5E, 1%, 1.1%, 1.2%, 1.3%, and 1.4% are the vertical and transverse mode confinement coefficients. , 1.5 × 10 ⁻³ , 2 × 10 ⁻³ , 2.5 × 10 ⁻³ , 3 × 10 ^−3, etc. are ΔN. Moreover, the ^{curve cm -1} are assigned as ^{6 cm -1} and 10 cm ^-1 is a curve representing the waveguide loss in the semiconductor light emitting element.

4 and 5, the waveguide loss is indicated by a solid line, the vertical transverse mode confinement coefficient is indicated by a dashed line, and the effective refractive index difference (ΔN) is indicated by a broken line. In these figures, the hatched area (hatched area) satisfies (Equation 2) to (Equation 4), the light confinement coefficient is 1% or more, and ΔN is 2.5 × 10 ⁻³ or more. Are shown.

As shown in FIGS. 4A to 4E, when M2 is 0.3 μm or more, (Equation 1) to (Equation 3) are satisfied, the vertical / transverse mode confinement coefficient is 1% or more, and ΔN is 2.5 × 10 ^It can be seen that there is a region of ⁻³ or more. Also, it can be seen that as M2 increases, ΔN in the region satisfying (Equation 1) to (Equation 3) increases, while the waveguide loss decreases. When M2 is 0.8 μm or more, the ridge height H increases, and the strain generated in the active layer and the resistance of the element increase. In order not to increase the series resistance of the semiconductor light emitting element, it is sufficient to set M2 ≦ 0.6 μm.

Therefore, from the results shown in FIG. 2 and FIGS. 4A to 4E, the generation of distortion in the active layers on both sides of the lower end of the ridge is suppressed, and the optical confinement coefficient of 1% or more and ΔN of 2.5 × 10 ⁻³ or more It can be seen that in order to obtain, (Equation 1) to (Equation 3) should be satisfied, and M2 should be 0.3 μm or more and 0.6 μm or less. In this case, it can be seen that the waveguide loss is 12.5 cm ^{-1 at the} maximum.

(2-9) Examination of Effect of Conductive Oxide Layer 18 Next, the effect of the conductive oxide layer 18 will be examined. 5A to 5E, in a region satisfying (Equation 2) to (Equation 4), a light confinement coefficient of 1% or more, a ΔN of 2.5 × 10 ⁻³ or more, and a waveguide loss of 12.5 cm ^−1. The following range is indicated by a hatched area. This region for the semiconductor light emitting device without the conductive oxide layer 18 is much smaller than the region shown in FIGS. 4A to 4E for the semiconductor light emitting device with the conductive oxide layer 18. This is because, when ITO is used for the conductive oxide layer 18, since the refractive index is as small as 2.02, the light distribution in the vertical direction is rapidly attenuated by the conductive oxide layer 18, and the p-type contact layer This is because the ratio of the light distribution in No. 17 decreases and the waveguide loss decreases. This effect is greater as M2 is smaller. Comparing FIGS. 4D and 5D, FIGS. 4C and 5C, and FIGS. 4B and 5B, the waveguide loss is relatively small even if M2 is the same. I understand. By providing the conductive oxide layer 18 in this manner, a light confinement coefficient of 1% or more, a ΔN of 2.5 × 10 ⁻³ or more, and a waveguide loss of 12.5 cm ⁻¹ or less can be simultaneously realized. It becomes possible. As a result, even at the time of high-temperature operation, it is possible to realize high-output characteristics without heat saturation. Further, since the strain in the active layer 14 on both sides of the lower end of the ridge 23 is small, not only the in-plane distribution of the band gap in the active layer 14 can be reduced, but also the generation of lattice defects in the active layer 14 can be suppressed. Therefore, it is possible to realize a highly reliable 530 nm band nitride-based laser capable of performing high-output operation for a long period of time.

In particular, even in the region where M2 is 0.4 μm or less, a light confinement coefficient of 1% or more, a ΔN of 2.5 × 10 ⁻³ or more, and a low waveguide loss of 12.5 cm ⁻¹ or less can be simultaneously realized. It is possible to reduce distortion in the active layers on both sides of the lower end of the ridge 23. As a result, the electric resistance of the semiconductor light emitting device further decreases. In addition, since generation of lattice defects in the active layer 14 can be further suppressed, a highly reliable semiconductor laser device that can perform high-output operation for a long time can be obtained.

(2-10) Regarding Layer Thickness of Conductive Oxide Layer 18 Further, the minimum thickness of the conductive oxide layer 18 when ITO is used as the conductive oxide layer 18 will be described. 6A and 6B show the results of studying the waveguide loss and ΔN when the thickness of ITO is changed in the semiconductor light emitting device according to the present embodiment. 6A and 6B, the horizontal axis represents the thickness of the conductive oxide layer 18, the vertical axis represents the waveguide loss in FIG. 6A, and ΔN in FIG. 6B. As shown in FIGS. 6A and 6B, it can be seen that as the thickness of the conductive oxide layer 18 increases from 0 μm to 0.15 μm, the waveguide loss decreases, while ΔN increases. That is, by forming the conductive oxide layer 18 having a thickness of 0.15 μm or more on the p-type contact layer 17, not only the effect of reducing the waveguide loss but also the ΔN is increased, and It can be seen that there is an effect of stabilizing the transverse mode oscillation.

  It can be seen that when the thickness of the ITO film is 0.15 μm or more, the waveguide loss, ΔN, and light confinement coefficient are all substantially constant. Therefore, in the structure in which ITO is used as the conductive oxide layer 18, it is understood that the thickness of the conductive oxide film layer may be set to 0.15 μm or more. If the ITO film is too thick, the electric resistance of the semiconductor light emitting element may increase due to the electric resistance of the ITO film. Therefore, the thickness of the ITO film is preferably 0.3 μm or less.

(2-11) Summary A conductive oxide layer 18 having a refractive index lower than 2.36 of AlGaN having an Al composition of 0.1 is formed on the p-type contact layer 17, and a layer of the second cladding layer 16 is formed. The thickness (M2) was changed from 0.3 μm to 0.6 μm, and a structure satisfying (Equation 2) to (Equation 4) was studied. In the case where the higher-order transverse mode is not cut off when the stripe width W is 5 μm or more, the above-described structure can be obtained even when the height of the ridge 23 is reduced as compared with the structure not using the conductive oxide layer 18. Wave path loss is reduced. It can be seen that stable higher-order transverse mode oscillation of the second or higher order is realized by the effect of increasing ΔN, and distortion in the region near both sides of the lower end of the ridge due to the low ridge can be reduced.

  Reduction of distortion leads to prevention of reduction of ΔN. As a result, the kink in the current-light output characteristics is suppressed, the slope efficiency is increased, and the light output level at which the heat is saturated at the time of high-temperature operation is improved. In addition, the in-plane distortion of the active layer 14 immediately below the ridge 23 is reduced, the variation in the bandgap energy of the active layer 14 can be suppressed, and the reduction in luminous efficiency of the semiconductor light emitting device and the growth of lattice defects are suppressed. Thus, long-term operation reliability can be improved. Further, when the thickness (M2) of the second cladding layer 16 is 0.3 μm or more and 0.5 μm or less, the electric resistance of the semiconductor light emitting device can be reduced. preferable.

(3) Example of Semiconductor Light-Emitting Element of Present Embodiment Next, an example of the semiconductor light-emitting element of the present embodiment studied above will be briefly described.

  In the semiconductor light emitting device according to the present embodiment, X1 was 0.09, X2 was 0.05, and M2 was 0.4 μm. Table 2 summarizes the layer structure of the semiconductor light emitting device of the present embodiment. In Table 2, the refractive index is a value with respect to the emission wavelength of 530 nm.

In the semiconductor light emitting device shown in Table 2, the waveguide loss was 8.0 cm ⁻¹ , the light confinement coefficient was 1.4%, and the ΔN was 3.6 × 10 ⁻³ . The emission wavelength was 530 nm, and green laser oscillation was obtained.

(Second embodiment)
(1) Tapered Stripe Structure The semiconductor light emitting device according to the first embodiment has a stripe structure in which the two side walls of the ridge 23 are parallel to the direction of the resonator when viewed from above the substrate 11. It is.

  The semiconductor light emitting device according to the second embodiment of the present invention is a semiconductor light emitting device having a so-called tapered stripe structure. The laminated structure of each semiconductor layer and the conductive oxide layer 18 constituting the semiconductor light emitting element and the structure of the electrodes are the same as those in the first embodiment. Further, the end face reflectance is the same as that of the first embodiment.

  Here, as shown in FIG. 7, the angle between the direction along the ridge side wall and the direction of the resonator is θ. Is the taper angle. In the semiconductor laser device having a stripe structure in which the taper angle θ is 0 ° described in the first embodiment, the light density in the active layer in the waveguide on the front end face side with low end face reflectivity increases. For this reason, the number of electrons and holes injected into the active layer 14 on the front end face side is increased per unit time due to stimulated emission, and the carrier space where the active carrier density of the active layer 14 on the front end face side is increased. Spatial Hole Burning (SHB for short) occurs. Here, as the taper angle θ is increased, the width of the ridge on the front end face side increases, so that the width of the light distribution in the horizontal and horizontal directions perpendicular to the resonator direction increases, and the light density decreases. Accordingly, as the taper angle θ increases, the number of electrons and holes consumed per unit time on the front end face side decreases. Conversely, on the rear end face side, the width of the light distribution in the horizontal and horizontal directions becomes narrower and the light density increases with an increase in the taper angle, so the number of electrons and holes consumed per unit time on the rear end face side is Increase. As a result, when the taper angle is too large, the operating carrier density in the active layer 14 on the rear end face side decreases, and SHB occurs. When the degree of SHB increases, electrons and holes are thermally excited in the active layer 14 on the side where the operating carrier concentration in the active layer 14 is high, and leak from the active layer to the first cladding layer 12 or the second cladding layer 16. Carriers (carrier overflow) increase, and the thermal saturation level of the optical output decreases.

  Also, when SHB occurs in the direction of the resonator, the wavelength at which the largest amplification gain is obtained in the active layer 14 varies, leading to an increase in the oscillation threshold current value. When the oscillation threshold current value increases, carrier overflow during high-temperature operation increases, which leads to deterioration of temperature characteristics. Further, when the taper angle θ is large, propagation loss occurs in the guided light propagating through the waveguide. For this reason, it is preferable that the taper angle θ be set in the range of 0.1 ° ± 0.05 ° (0.05 ° or more and 0.15 ° or less). In this case, the occurrence of SHB is suppressed in the active layer 14 below the ridge 23, and the occurrence of carrier overflow is suppressed. Further, the uniformity of the operating carrier concentration is improved, and the wavelength at which the largest amplification gain is obtained in the active layer 14 becomes uniform. Therefore, the slope efficiency and the temperature characteristics are improved, and the high-temperature and high-output operation can be performed.

  Further, when the ridge width Wr on the rear end face side is reduced, higher-order horizontal and transverse modes cannot be guided, but are cut off, so that the number of oscillatable horizontal and transverse modes decreases. If the higher-order transverse mode is not cut off, if the order of the higher-order transverse modes that can oscillate at the same time becomes smaller, the deformation of the light distribution shape in the resonator direction becomes larger when the transverse modes are coupled during laser oscillation, A large nonlinearity occurs in the current-light output characteristics, and the temperature characteristics deteriorate. In order to prevent this, Wr needs to have a width at which a higher-order transverse mode of at least the third-order mode is guided. In the case of a wide stripe width in which the high-order transverse mode is not cut off, it is effective that the third-order mode or higher can be guided in order to prevent a large nonlinearity due to kink in the current-light output characteristics. For example, in the case of a waveguide that can guide up to the third transverse mode, the effective refractive index of the third order mode, which is the highest order that can be guided, is almost the same as the effective refractive index of the region outside the ridge, so On the other hand, the light distribution has a large spread with a large tail outside the ridge. In this case, since the tertiary transverse mode greatly exudes the light distribution outside the ridge, a large amount of current injection is required to cause laser oscillation. Therefore, the oscillation threshold current value of the third-order mode is relatively higher than the fundamental (0-order) transverse mode, the first-order transverse mode, and the second-order transverse mode, and the third-order mode can be guided. The three types of modes from the fundamental transverse mode to the secondary transverse mode cause substantial laser oscillation. If at least three types of transverse modes are simultaneously laser-oscillated, the interaction due to the interference between the transverse modes can be relatively reduced, and even if the transverse modes interfere with each other and couple, the change in the light distribution shape can be reduced. Therefore, a kink occurs in the current-light output characteristic, and the nonlinearity can be reduced, so that the light output can be stabilized.

  If a waveguide having such a tapered shape is formed for the semiconductor light emitting device according to the present embodiment, the height of the ridge 23 can be reduced, so that the electric resistance of the semiconductor light emitting device is further reduced, and It is advantageous for operation. Even if the height of the ridge 23 is reduced, using the conductive oxide layer 18 has the effect of increasing ΔN as shown in FIG. 6B. For this reason, even if Wr is narrowed, higher-order transverse modes of the third order or higher are not cut off, so that a kink having a large nonlinearity in current-light output can be prevented. In the case of the present embodiment, Wr may be at least 4 μm. The effect of increasing ΔN is more effective as the amount of light distribution exuding into the conductive oxide layer 18 is greater. Therefore, the effect of increasing the second cladding layer thickness (M2) is more advantageous. If the waveguide shape is tapered in the range of M2 of 0.3 μm or more and 0.5 μm or less, the series resistance of the element is further reduced, the slope efficiency and the temperature characteristics are improved, and the current-light output characteristics are improved. Further high-temperature and high-output operation can be performed while suppressing the generation of kink having large nonlinearity.

(2) One Example of Semiconductor Light-Emitting Element of this Embodiment and Its Characteristics In the semiconductor light-emitting element according to the second embodiment of the present invention, X1 is 0.05, X2 is 0.09, and the second cladding layer thickness is 0. .4 μm, and the resonator length is 600 μm. Table 2 shows the parameters of each layer according to the semiconductor light emitting device. In addition, the width of the ridge 23 is 6 μm on the rear end face side, and becomes wider toward the front end face side. The taper angle θ on the side surface of the ridge 23 is θ = 0.1 °.

The semiconductor light emitting device has a waveguide loss of 7.9 cm ⁻¹ , an optical confinement coefficient of 1.45%, and ΔN of 3.7 × 10 ⁻³ .

FIG. 8A shows a current-light output characteristic of the semiconductor light emitting device according to the second embodiment of the present invention. In addition, the current-light output characteristics of a semiconductor light emitting device having a structure in which the conductive oxide layer 18 having a thickness of 0.17 μm is eliminated from the structure of the semiconductor light emitting device according to the second embodiment of the present invention are compared. 8B. The waveguide loss of the semiconductor light emitting device according to this comparative example is 13.5 cm ⁻¹ , the light confinement coefficient is 1.4%, and ΔN is 3.3 × 10 ⁻³ . Note that the device temperature of the semiconductor light emitting device was examined at 25 ° C. and 50 ° C.

  8A and FIG. 8B, it is found that the use of the conductive oxide layer 18 improves the slope efficiency by 1.4 times. This is thought to be because even if the thickness of the second cladding layer 16 is reduced to 0.4 μm by using the conductive oxide layer 18, the absorption loss at the metal electrode is reduced and the high slope efficiency is improved. Further, it can be seen that the use of the conductive oxide layer 18 also increases ΔN, and has a function of increasing the confinement ratio of the transverse mode.

  That is, the semiconductor light emitting device of the present embodiment using the conductive oxide layer 18 has an improved slope efficiency and an improved transverse mode confinement ratio as compared with the semiconductor light emitting device not using the conductive oxide layer 18. You can do it.

(3) Modified Example of Tapered Stripe Structure In the second embodiment, the shape of the tapered stripe structure viewed from above the substrate 11 is not limited to the shape shown in FIG. For example, as shown in FIG. 9A, a semiconductor light emitting element in which the vicinity of the front end face and the vicinity of the rear end face have a stripe shape with a taper angle of 0 °, and the taper angle of the stripe shape between the front end face and the rear end face is not 0 ° is the same as above. Similar effects can be obtained.

  Further, the rate of change of the ridge width in the resonator direction may not be constant. For example, as shown in FIGS. 9B and 9C, a curved tapered stripe may be used.

  In the stripe structure of the ridge 23 including FIG. 7 and FIGS. 9A to 9C, it is more preferable that the maximum value of the angle formed by the ridge 23 and the normal direction of the resonator is 0.05 ° or more and 0.15 ° or less. .

(Other embodiments)
Although the conductive oxide layer 18 used in the semiconductor light emitting devices described in the first embodiment and the second embodiment uses indium tin oxide (ITO), the invention is not limited thereto. For example, in the case of a conductive oxide having a refractive index smaller than the refractive index of 2.36 of AlGaN having an Al composition of 0.1 in the 530 nm wavelength band, the waveguide loss can be reduced by reducing the ridge height (H). It is possible to obtain Specifically, a conductive oxide made of an oxide containing at least one of indium (In), zinc (Zn), tin (Sn), gallium (Ga), and magnesium (Mg) may be used. Further, for example, a conductive oxide such as In ₂ O ₃ , SnO ₂ , ZnO, Zn ₂ SnO ₄ , In ₂ O ₃ —ZnO, MgInO ₄ , and Ga ₂ O ₃ may be used.

  Further, instead of the conductive oxide, a conductive nitride such as TiN or ZrN can be used. In the conductive oxide layer 18 having a low refractive index, the light distribution in the vertical direction is rapidly attenuated, so that the influence of the absorption loss in the p-type electrode 22 can be reduced.

  Table 3 shows examples of conductive oxides, conductive nitrides, and conductive materials that can be used in the above embodiments and modifications.

Although the current blocking layer 20 is made of SiO ₂ having a smaller refractive index than the second cladding layer 16 in the above embodiment, the current blocking layer 20 is not limited to SiO ₂ and may be made of another insulator having a smaller refractive index than the second cladding layer 16. layers, it is possible to use, for example, _Al 2 _{O 3} and SiN.

  In the semiconductor light emitting device according to the above embodiment, the Al composition of the first cladding layer 12 is X1, but the first cladding layer may be a superlattice layer made of AlGaN and GaN. In this case, X1 may be the average Al composition in the superlattice layer. That is, when the superlattice layer is formed of an AlGaN layer having a thickness of 3 nm and an Al composition of 0.2 and a superlattice layer of GaN having a thickness of 3 nm, X1 is 0.1. When the superlattice layer is formed of a 4 nm-thick AlGaN layer having an Al composition of 0.2 and a 6 nm-thick GaN superlattice layer, X1 is 0.08.

  Further, in the semiconductor light emitting device according to the above embodiment, the Al composition of the second cladding layer 16 is X2, but the second cladding layer may be a superlattice layer made of AlGaN and GaN. In this case, X2 may be the average Al composition in the superlattice layer. That is, when the superlattice layer is formed of an AlGaN layer having a thickness of 3 nm and an Al composition of 0.1 and a superlattice layer of GaN having a thickness of 3 nm, X2 is 0.05.

  Further, in the semiconductor light emitting device according to the above embodiment, the emission wavelength is 530 nm, but the emission wavelength can be changed by changing the composition or the layer structure of the active layer 14. The present invention can be applied to a semiconductor light emitting device having a light emission wavelength ranging from a near ultraviolet region having a wavelength of about 370 nm to a red region having a wavelength of about 600 nm.

  The semiconductor light emitting device of the present invention can reduce the series resistance of the device, achieve excellent current-light output characteristics with excellent linearity due to stable higher-order transverse mode oscillation, reduce waveguide loss, and achieve vertical optical confinement. It has the effect of being able to be used, and is useful for vehicle headlamps, projector light sources, and the like.

Reference Signs List 11 substrate 12 first clad layer 13 light guide layer 14 active layer 15 electron barrier layer 16 second clad layer 17 p-type contact layer 18 conductive oxide layer 20 current blocking layer 21 n-type electrode 22 p-type electrode 23 ridge

Claims (4)

Board and
A first cladding layer of one conductivity type containing AlGaN formed on the substrate;
An active layer containing GaN formed on the first cladding layer;
A second cladding layer of opposite conductivity type having AlGaN formed on the active layer;
A conductive compound layer formed on the second clad layer,
The second cladding layer has a ridge structure,
The width of the ridge is 5 μm or more;
The Al composition of the second cladding layer is smaller than the Al composition of the first cladding layer,
The conductive compound layer is a layer containing an oxide containing indium and tin and having a thickness of 0.15 μm or more and 0.3 μm or less,
A semiconductor light emitting device, wherein a film thickness inside the ridge of the second cladding layer is 0.3 μm or more and 0.4 μm or less.   2. The semiconductor light emitting device according to claim 1, wherein the thickness of the second cladding layer outside the ridge structure is greater than 0 nm and 50 nm or less.   2. The semiconductor light emitting device according to claim 1, wherein a current blocking layer having a smaller refractive index than the second cladding layer is formed on a side surface of the ridge structure. The first cladding layer is made of Al _X1 Ga _1-X1 N, and the second cladding layer is made of Al _X2 Ga _1-X2 N, where X1-X2 ≧ 0.02, X1 ≦ 0.1,. 2. The semiconductor light emitting device according to claim 1, wherein a relationship of 03 ≦ X2 ≦ 0.07 is satisfied.

Images