JP3794530B2 - Nitride semiconductor laser device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a nitride semiconductor (In _x Al _y Ga _1-xy N, 0.ltoreq.x, 0.ltoreq.y, x + y.ltoreq.1), and more particularly to a nitride semiconductor laser device having a good far field pattern.
[0002]
[Prior art]
The present inventors have proposed a nitride semiconductor laser element that can be used practically, for example, in Jpn. J. Appl. Phys. Vol. 37 (1998) pp. Proposed structure.
The technique of the above document is a partially formed SiO on the sapphire substrate. ₂ A device in which a plurality of nitride semiconductor layers having a laser element structure are stacked on a nitride semiconductor substrate made of GaN with few dislocations selectively grown through a film, allows continuous oscillation at room temperature of 10,000. It allows more than time. As an element structure, n-Al is formed on a selectively grown nitride semiconductor substrate. _k Ga _1-k N-type contact layer made of N (0 ≦ k <1), In _0.1 Ga _0.9 Crack prevention layer made of N, n-Al _0.14 Ga _0.86 N-type clad layer made of N / GaN multilayer film, n-type guide layer made of n-GaN, In _0.02 Ga _0.98 N / In _0.15 Ga _0.85 P-Al, an active layer having a multiple quantum well structure made of N _0.2 Ga _0.8 P-type electron confinement layer made of N, p-type guide layer made of p-GaN, p-Al _0.14 Ga _0.86 A p-type cladding layer made of a multilayer film of N / GaN and a p-type contact layer made of p-GaN are used.
[0003]
Of these, the n-type and p-type clad layers are multilayer films (superlattice structure), so that the generation of cracks can be prevented even when the Al composition ratio is increased, so that the laser can be guided sufficiently to confine light. It can be lower than the refractive index of the waveguide, and has a good optical confinement effect. If the light confinement is sufficient, in addition to the improvement of the life characteristics due to the decrease of the threshold value, the far field pattern (hereinafter sometimes referred to as FFP) becomes a single mode.
[0004]
[Problems to be solved by the invention]
However, in order to improve the suitability of the above laser device for application to various products, the FFP of the main laser beam will be examined in more detail. An n-type contact layer (nitride semiconductor substrate) It was confirmed that the main laser beam was in a small multimode because the weak light emitted from the end face of the main laser beam overlapped.
This is because when the p-electrode and the n-electrode are formed on the same surface side, the light emitted from the active layer leaks from the n-type cladding layer, and the support pair on the back surface of the n-type cladding layer and the nitride semiconductor substrate. Since the weak light emitted from the end face of the n-type contact layer overlaps with the main laser light emitted from the resonance surface by being guided in the n-type contact layer showing a value larger than the refractive index of , And FFP is considered to be a small multimode. Such a problem also occurs when the laser element is formed without removing the sapphire substrate because the refractive index of sapphire is small.
When a product using a laser element is put into practical use, it is desirable to suppress the ripple from riding on the FFP so that the laser beam functions well.
SUMMARY OF THE INVENTION An object of the present invention is to provide a nitride semiconductor laser element that has a good single mode in which no ripple is applied to the FFP of the main laser beam.
[0005]
[Means for Solving the Problems]
That is, the present invention can achieve the object of the present invention by the following configurations (1) to (6).
(1) On a nitride semiconductor substrate formed by selectively growing a nitride semiconductor in a lateral direction, at least an n-type contact layer, an n-type cladding layer having a nitride semiconductor containing Al, In _a Ga _1-a A well layer composed of N (0 <a <1) and In _b Ga _1-b An active layer having a multiple quantum well structure having a barrier layer made of N (0 ≦ b <1), and a p-type cladding layer having a nitride semiconductor layer containing Al, in order,
Indium having a smaller band gap energy than the well layer between the substrate and the n-type contact layer _d Ga _1-d A light absorption layer including at least one first nitride semiconductor composed of N (0 <d <1);
A nitride semiconductor laser device comprising a crack preventing layer containing In between the n-type contact layer and the n-type cladding layer.
(2) The nitride semiconductor laser element according to (1), wherein the p-type cladding layer and / or the n-type cladding layer is formed of a multilayer film layer.
(3) The light absorption layer has a smaller band gap energy than the well layer. _d Ga _1-d (1) or (2) comprising a multilayer film formed by laminating at least one layer of a first nitride semiconductor composed of N (0 <d <1) and a second nitride semiconductor composed of GaN. The nitride semiconductor laser device described in 1.
(4) The nitride semiconductor laser element according to any one of (1) to (3), wherein the light absorption layer is undoped.
(5) The nitride semiconductor laser element according to any one of (1) to (4), wherein the light absorption layer has a thickness of 0.02 to 1 μm.
(6) The film thickness of the first nitride semiconductor layer constituting the light absorption film of the multilayer film is 0.01 to 0.05 μm, and the film thickness of the second nitride semiconductor is 0.01 to 0. The nitride semiconductor laser element according to (3), which has a thickness of 0.05 μm.
[0006]
That is, in the present invention, in order to prevent FFP disturbance due to light leaking from the n-type cladding layer, the undoped InGaN having a smaller band gap energy than the well layer of the active layer between the n-type contact layer and the substrate. FFP is improved by forming a light absorption layer comprising
[0007]
Conventionally, the inventors have disclosed in JP-A-8-130327 a layer (for example, InGaN) having a smaller band gap energy than a nitride semiconductor layer constituting a light emitting layer between a substrate and an n-type contact layer. An LED element formed is disclosed. In this technique, a layer having a band gap energy smaller than that of the light emitting layer passes main light emission due to Zn or Si impurity levels, absorbs only light due to InGaN interband light emission, and exhibits a main emission spectrum due to impurity levels. The half width is narrowed to improve the color purity.
[0008]
In contrast, the undoped light absorption layer in the present invention absorbs substantially all of the light leaking from the n-type cladding layer provided as the light confinement layer, and emits light from the end surface of the n-type contact layer. This suppresses the FFP of the main laser light emitted from the laser waveguide to a good single mode. Therefore, the present invention solves a new problem caused by the realization of a laser element that is as good as practical.
[0009]
In the present invention, the reason why the light absorption layer is undoped is that, after absorbing light leaking from the n-type cladding layer, there is a tendency that light is slightly emitted inside the light absorption layer and emitted from the end face. This is because it is considered that the intensity of photoluminescence increases and the ripple on the FFP increases. If undoped as in the present invention, the intensity of photoluminescence is weaker than that of the impurity-doped layer, so even if light is emitted from the end face of the light absorption layer, it becomes weak enough to cause noise and has an effect on FFP. Can weaken. Further, when the light absorption layer is undoped, an InGaN light absorption layer can be formed with good crystallinity, and the crystallinity of the n-type contact layer, active layer, and the like formed thereon can be improved. If an element with good crystallinity is obtained, the life characteristics are improved.
[0010]
Furthermore, in the present invention, since the light absorption layer is undoped as described above, in order to avoid an increase in forward voltage (Vf) due to an increase in bulk resistance, the light absorption layer is provided at a position not involved in the flow of electricity. In consideration of the formation, the light absorption layer is formed between the n-type contact layer and the substrate.
[0011]
As described above, the present invention can solve the conventional problems by making the light absorption layer smaller than the band gap energy of the active layer undoped and forming at a specific position of the element structure. It is.
[0012]
Furthermore, in the present invention, the light absorption layer is a multilayer film including a first nitride semiconductor composed of InGaN and a second nitride semiconductor composed of GaN, whereby the crystallinity of the light absorption layer is increased. It is preferable to make the film thick enough to absorb substantially all of the light leaking from the n-type cladding layer without lowering.
Furthermore, in this invention, it is preferable that the film thickness of a light absorption layer is 0.02-1 micrometer in order to absorb the light leaked from the n-type cladding layer favorably.
Furthermore, in the present invention, when the light absorption layer is composed of a multilayer film, the thickness of the first nitride semiconductor made of InGaN is 0.01 to 0.05 μm, and the second nitride semiconductor made of GaN. The film thickness of 0.01 to 0.5 μm is preferable for forming a multilayer light absorption layer with good crystallinity. In the case where the light absorption layer is a multilayer film including the first and second nitride semiconductors, the number of laminations is adjusted so that the film thickness of the light absorption layer is within the film thickness of each layer. A light absorption layer is formed.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
The nitride semiconductor laser device of the present invention includes an n-type cladding layer comprising at least an n-type contact layer and a multilayer film layer having a nitride semiconductor containing Al, and a multilayer film having a nitride semiconductor containing Al. In between the p-type cladding layer composed of layers _a Ga _1-a Well layer composed of N (0 <a <1) and In _b Ga _1-b An active layer having a multiple quantum well structure having a barrier layer made of N (0 ≦ b <1), and further having an band gap energy smaller than that of the well layer between the n-type contact layer and the substrate. In _d Ga _1-d A light absorption layer including at least one first nitride semiconductor layer made of N (0 <d <1).
[0014]
In the present invention, the light absorption layer may be formed at any position as long as it is formed between the n-type contact layer and the substrate. When the light absorption layer is formed at such a position, the resistance of the device is not increased even if the photoluminescence intensity is low, so that the resistance of the element is not increased. Property can be improved.
In the present invention, as the light absorption layer, the active layer In _a Ga _1-a Undoped In which has a lower band gap energy than a well layer made of N _d Ga _1-d It is only necessary to include at least one layer of the first nitride semiconductor made of N, and a single layer made of the first nitride semiconductor, or the first nitride semiconductor and the other nitride semiconductor are stacked. And a multilayer film. The light absorbing layer is preferably undoped In _d Ga _1-d This is a multilayer film in which at least one first nitride semiconductor composed of N (0 <d <1) and at least one second nitride semiconductor composed of undoped GaN are stacked.
It is preferable that the light absorption layer is composed of a multilayer film because the light absorption layer can be made thick without impairing the crystallinity of the first nitride semiconductor containing In. Furthermore, it is preferable to use the second nitride semiconductor made of GaN as the other layer constituting the multilayer film because the crystallinity of the first nitride semiconductor and the crystallinity of the light absorption layer can be improved.
[0015]
In _d Ga _1-d The value of d of the first nitride semiconductor composed of N (0 <d <1) is appropriately adjusted according to the In ratio of the well layer, that is, the wavelength of light emitted from the active layer, and leaks from the n-type cladding layer. The In composition ratio is adjusted to be smaller than the band gap energy of the well layer so that the emitted light can be satisfactorily absorbed.
The light absorption layer is at least In _d Ga _1-d The first nitride semiconductor made of N is preferable for absorbing light emitted from the active layer containing InGaN and leaking from the n-type cladding layer.
The value of d is the same whether the light absorption layer is made of only the first nitride semiconductor or a multilayer film in which the first nitride semiconductor and the second nitride semiconductor are stacked. Adjusted.
[0016]
The total film thickness of the light absorption layer, such as when the light absorption layer is composed of a single layer of the first nitride semiconductor, is 0.02 to 1 μm, preferably 0.1 to 0.3 μm. Within this range, even if the light absorption layer is a single layer, it can absorb light well and can be formed with better crystallinity.
When the light absorption layer is a multilayer film, the thickness of the single layer of the first nitride semiconductor is 0.01 to 0.05 μm, preferably 0.05 to 0.1 μm. The light emitted from the active layer and leaked from the n-type cladding layer can be favorably absorbed, and the single-layer crystallinity is preferable. On the other hand, the film thickness of the single layer of the second nitride semiconductor is 0.01 to 0.5 μm, preferably 0.05 to 0.3 μm. It is preferable in that the crystallinity can be improved.
The number of stacks of the first nitride semiconductor and the second nitride semiconductor is not particularly limited, and the first and second nitrides having a single thickness within the above range within the thickness of the light absorption layer. Stack semiconductors. For example, when the In composition ratio is large, the crystallinity of InGaN tends to be difficult to maintain. In this case, it is possible to reduce the thickness of the single layer of the first nitride semiconductor and increase the number of stacks. It is preferable to obtain a light absorbing film having good properties.
[0017]
As described above, the light absorption layer in the present invention prevents the light emitted from the active layer of the laser element and leaking from the n-type cladding layer from being guided by the n-type contact layer and disturbing the FFP. From this point, the present invention is supported on the back side of the substrate when the material for the substrate of the laser element is composed of a material having a refractive index smaller than that of the n-type contact layer, or a nitride semiconductor as the substrate. It solves the problems that occur when pairs are in contact.
In the present invention, the substrate is made of a material having a refractive index smaller than that of the n-type contact layer. For example, sapphire or spinel (MgA1) whose main surface is any one of the C-plane, R-plane, and A-plane. ₂ O _Four A conventionally known nitride semiconductor such as an insulating substrate such as), an oxide substrate lattice-matched with a nitride semiconductor, or the like can be used. These substrate materials can also be used as heterogeneous substrates used in the selective growth described later.
In the present invention, the substrate may be a material having the above-described substrate material and a nitride semiconductor with few dislocations selectively grown thereon using lateral growth of the nitride semiconductor.
[0018]
The method for selective growth of the nitride semiconductor is not particularly limited as long as it can reduce dislocations in the nitride semiconductor. For example, J. J. et al. A. P. And the methods described in the specifications of Japanese Patent Application No. 10-77245, Japanese Patent Application No. 10-275826, and Japanese Patent Application No. 10-363520 filed by the present applicant.
[0019]
In the present invention, an n-type cladding layer made of a multilayer film having a nitride semiconductor containing Al, a p-type cladding layer made of a multilayer film having a nitride semiconductor containing Al, In _a Ga _1-a Well layer composed of N (0 <a <1) and In _b Ga _1-b The active layer and the n-type contact layer having a multiple quantum well structure having a barrier layer made of N (0 ≦ b <1) are not particularly limited.
[0020]
A preferred embodiment will be described below with reference to FIG.
FIG. 1 is a schematic sectional view showing a nitride semiconductor laser device according to an embodiment of the present invention.
FIG. 1 shows an undoped In on a nitride semiconductor substrate 1 selectively grown on a different substrate such as sapphire. _d Ga _1-d Light absorption layer 2 including at least one first nitride semiconductor layer made of N, Al doped with n-type impurity (for example, Si) _a Ga _1-a N-type contact layer 3 made of N (0 <a <1), Si-doped In _g Ga _1-g Crack prevention layer 4 made of N (0.05 ≦ g ≦ 0.2), Al _e Ga _1-e A multilayer n-type cladding layer 5 containing N (0.12 ≦ e <0.15), an n-type guide layer 6 made of undoped GaN, In _b Ga _1-b Multi-quantum well structure active layer 7 made of N (0 ≦ b <1), Mg-doped Al _d Ga _1-d At least one p-type electron confinement layer 8 made of N (0 <d ≦ 1), p-type guide layer 9 made of undoped GaN, Al _f Ga _1-f A nitride semiconductor laser device having a multilayer p-type cladding layer 10 containing N (0 <f ≦ 1) and a ridge-shaped stripe made of a p-type contact layer 11 made of Mg-doped GaN is shown. .
The p-electrode is formed on the uppermost layer of the ridge-shaped stripe, and the n-electrode is formed on the n-type contact layer.
Each layer will be described in detail below.
[0021]
The selective growth that can be used in the present invention is any growth method that can temporarily stop the growth of the nitride semiconductor in the vertical direction and temporarily suppress dislocations using the growth in the horizontal direction. There is no particular limitation.
For example, specifically, a protective film made of a material that does not grow or is difficult to grow on a heterogeneous substrate made of a material different from the nitride semiconductor is partially formed, and the nitride semiconductor is grown thereon. As a result, a nitride semiconductor grows from the portion where the protective film is not formed, and a thick nitride semiconductor is obtained by growing in the lateral direction toward the protective film by continuing the growth.
[0022]
The heterogeneous substrate is not particularly limited as long as it is a substrate made of a material different from that of the nitride semiconductor. For example, sapphire, spinel (MgA1) having C-plane, R-plane, and A-plane as main surfaces shown in FIG. ₂ O _Four A substrate material different from a conventionally known nitride semiconductor, such as an insulating substrate such as) or an oxide substrate lattice-matched with a nitride semiconductor, can be used. Among the above, a preferred heterogeneous substrate is sapphire, and more preferably a C-plane of sapphire. Furthermore, the sapphire C-plane is off-angled stepwise from the viewpoint of preventing generation of fine cracks in the nitride semiconductor obtained by selective growth, and the off-angle angle θ (θ shown in FIG. 3). ) Is preferably in the range of 0.1 ° to 0.3 °. If the off-angle angle θ is less than 0.1 °, the characteristics of the laser element are likely to be stabilized, and fine cracks tend to be easily generated in the selectively grown nitride semiconductor, while the off-angle is 0. When the angle exceeds 3 °, the surface state of the selectively grown nitride semiconductor becomes a step shape, and when the device structure is grown on the step state, the step is slightly emphasized, and the device tends to cause a short circuit and an increase in threshold value. There is.
The fine crack is generated because the heterogeneous substrate and the nitride semiconductor are not lattice-matched, and may occur in any process of selective growth of the nitride semiconductor, or a nitride semiconductor substrate with reduced dislocations. For example, when an n-type contact layer or the like is formed, it may occur in the n-type contact layer. Such fine cracks may cause a decrease in life characteristics. Therefore, it is preferable to use the off-angled substrate as described above in terms of preventing the occurrence of fine cracks.
[0023]
A protective film is formed directly or once after a nitride semiconductor is grown on a heterogeneous substrate such as sapphire which is off-angled in a stepped manner as described above.
The protective film is not particularly limited as long as it is a material that does not grow or is difficult to grow on the surface of the protective film. For example, silicon oxide (SiO 2 _X ), Silicon nitride (Si _X N _Y ), Titanium oxide (TiO _X ), Zirconium oxide (ZrO) _X In addition to oxides and nitrides such as), and multilayer films thereof, metals having a melting point of 1200 ° C. or higher can be used. As a preferable protective film material, SiO ₂ And SiN.
In order to form the protective film material on the surface of the nitride semiconductor or the like, for example, a vapor deposition technique such as vapor deposition, sputtering, or CVD can be used. Further, in order to form partially (selectively), a photomask having a predetermined shape is produced by using a photolithography technique, and the material is vapor-deposited through the photomask. A protective film having a predetermined shape can be formed. The shape of the protective film is not particularly limited. For example, the protective film can be formed in the shape of a dot, stripe, or grid, and preferably formed in a stripe shape so that the stripe is perpendicular to the orientation flat surface (A surface of sapphire). Is done.
The surface area where the protective film is formed is larger than the surface area of the portion where the protective film is not formed, so that dislocation can be prevented and a nitride semiconductor substrate having good crystallinity can be obtained.
[0024]
Further, when the protective film has a stripe shape, the relationship between the stripe width of the protective film and the width of the portion (window) where the protective film is not formed is 10: 3 or more, preferably 16 to 18: 3. . When the stripe width of the protective film and the width of the window portion are in the above relationship, the nitride semiconductor can easily cover a good protective film, and dislocation can be prevented well. The stripe width of the protective film is, for example, 6 to 27 μm, preferably 11 to 24 μm, and the width of the window is, for example, 2 to 5 μm, preferably 2 to 4 μm.
In the case where an element structure is formed on a nitride semiconductor obtained by selective growth and a ridge-shaped stripe is formed on the uppermost layer of the p-type nitride semiconductor layer, the ridge-shaped stripe is above the protective film, In addition, it is preferable to avoid the central portion of the protective film because the threshold value can be lowered and the reliability of the element is improved. This is because the crystallinity of the nitride semiconductor on the upper part of the protective film is better than that on the upper part of the window, which is preferable for lowering the threshold value. The vicinity of the center of the protective film is a portion where adjacent nitride semiconductors grown from the window are joined by lateral growth, and there may be a gap at such a joint, and a ridge shape is formed above the gap. This is because the dislocation tends to propagate from the gap during the operation of the laser element, and the reliability of the element tends to deteriorate.
[0025]
The protective film may be formed directly on a different substrate, but it is preferable to form a low-temperature grown buffer layer and further grow a high-temperature grown nitride semiconductor in order to prevent dislocation.
As the low temperature growth buffer layer, for example, any one of AlN, GaN, AlGaN, InGaN, etc. is grown at a temperature of 900 ° C. or lower and 200 ° C. or higher with a film thickness of several tens of angstroms to several hundreds of angstroms. This buffer layer is preferable for mitigating the lattice constant irregularity between the heterogeneous substrate and the high-temperature-grown nitride semiconductor layer and preventing the occurrence of dislocations.
As the nitride semiconductor grown at a high temperature, undoped GaN, GaN doped with an n-type impurity, or Si-doped GaN can be used, and preferably undoped GaN. These nitride semiconductors are grown on the buffer layer at a high temperature, specifically 900 ° C. to 1100 ° C., preferably 1050 ° C. Although a film thickness is not specifically limited, For example, it is 1-20 micrometers, Preferably it is 2-10 micrometers.
[0026]
Next, after forming a protective film, a nitride semiconductor is selectively grown to obtain the nitride semiconductor substrate 1. In this case, the nitride semiconductor to be grown includes undoped GaN or GaN doped with impurities (for example, Si, Ge, Sn, Be, Zn, Mn, Cr, and Mg). The growth temperature is, for example, 900 ° C. to 1100 ° C., more specifically, a temperature around 1050 ° C. Doping with impurities is preferable for suppressing dislocations.
In the initial stage of growth on the protective film, growth is performed by MOCVD (metal organic chemical vapor deposition) or the like which allows easy control of the growth rate, and the growth after the protective film is covered with the nitride semiconductor of selective growth is performed by HVPE (halide). You may make it grow by a vapor phase growth method etc.
[0027]
Next, a light-absorbing layer 2 is grown on a nitride semiconductor (having a heterogeneous substrate such as sapphire) obtained by selective growth as a substrate.
As described above, as the light absorption layer 2, undoped In having a band gap energy smaller than that of the well layer. _d Ga _1-d At least one light absorbing layer including a first nitride semiconductor composed of N (0 <d <1) or at least one first nitride semiconductor and a second nitride semiconductor composed of undoped GaN. A light absorption layer made of a multilayer film formed by laminating as described above can be formed. The details of the light absorption layer 2 are as described above.
[0028]
Next, the n-type contact layer 3 is grown on the light absorption layer 2. As the n-type contact layer, Al doped with an n-type impurity (preferably Si) is used. _a Ga _1-a N (0 ≦ a <1) is grown, and preferably Al is 0.01 to 0.05 _a Ga _1-a Grow N. When the n-type contact layer is formed of a ternary mixed crystal containing Al, even if fine cracks are generated in the nitride semiconductor substrate 1, propagation of the fine cracks can be prevented, and further, the nitride semiconductor It is preferable because the generation of fine cracks in the n-type contact layer or the like due to the difference in lattice constant and thermal expansion coefficient between the substrate 1 and the light absorption layer 2 or the n-type contact layer can be prevented. The doping amount of n-type impurities is 1 × 10 ¹⁸ / Cm ^Three ~ 5x10 ¹⁸ / Cm ^Three It is. An n-electrode is formed on the n-type contact layer 3. The film thickness of the n-type contact layer 3 is 1 to 10 μm.
Further, between the light absorption layer 2 and the n-type contact layer 3, undoped Al _a Ga _1-a N (0 <a <1) may be grown. Growing this undoped layer is preferable for improving crystallinity and improving life characteristics. The film thickness of the undoped n-type contact layer is several μm.
[0029]
Next, the crack prevention layer 4 is grown on the n-type contact layer 3. As the crack prevention layer 4, Si-doped In _g Ga _1-g N (0.05 ≦ g ≦ 0.2) is grown, preferably In is 0.05 to 0.08 g _g Ga _1-g Grow N. Although the crack preventing layer 4 can be omitted, it is preferable to form the crack preventing layer 4 on the n-type contact layer 3 in order to prevent the occurrence of cracks in the element. As a doping amount of Si, 5 × 10 ¹⁸ / Cm ^Three It is.
Further, when the crack prevention layer 4 is grown, if the mixed crystal ratio of In is increased (x ≧ 0.1), the crack prevention layer 4 emits light from the active layer 7 and leaks from the n-type cladding layer 5. It is preferable that the far field pattern of the laser beam can be prevented from being disturbed.
The thickness of the crack prevention layer 4 is a thickness that does not impair the crystallinity, and specifically, for example, 0.05 to 0.3 μm.
[0030]
Next, the n-type cladding layer 5 is grown on the crack prevention layer 4. As the n-type cladding layer 5, Al _e Ga _1-e A multilayer film including a nitride semiconductor containing N (0.12 ≦ e <0.15) is formed. The multilayer film refers to a multilayer film structure in which nitride semiconductor layers having different compositions are laminated, for example, Al _e Ga _1-e N (0.12 ≦ e <0.15) layer and this Al _e Ga _1-e A nitride semiconductor having a composition different from that of N, for example, one having a different mixed crystal ratio of Al, a ternary mixed crystal containing In, or a layer formed by combining layers made of GaN or the like. Among these, a preferable combination is Al. _e Ga _1-e A multilayer film in which N and GaN are stacked is preferable because a nitride semiconductor layer having good crystallinity can be stacked at the same temperature. A more preferable multilayer film is undoped Al. _e Ga _1-e This is a combination of N and n-type impurity (for example, Si) -doped GaN stacked. n-type impurities are Al _e Ga _1-e N may be doped. The doping amount of the n-type impurity is 4 × 10 ¹⁸ / Cm ^Three ~ 5x10 ¹⁸ / Cm ^Three It is. When the n-type impurity is doped in this range, the resistivity can be lowered and the crystallinity is not impaired.
Such a multilayer film is formed by stacking nitride semiconductor layers having a single layer thickness of 100 angstroms or less, preferably 70 angstroms or less, more preferably 40 angstroms or less, preferably 10 angstroms or more. When the single film thickness is 100 angstroms or less, the n-type cladding layer has a superlattice structure, and even though Al is contained, the generation of cracks can be prevented and the crystallinity can be improved. The total film thickness of the n-type cladding layer 5 is 0.7 to 2 μm.
The average composition of Al in the entire n-type cladding layer is 0.05 to 0.1. When the average composition of Al is within this range, the composition ratio is such that cracks are not generated, and the composition ratio is preferable for obtaining a sufficient refractive index difference from the laser waveguide.
[0031]
Next, the n-type guide layer 6 is grown on the n-type cladding layer 5. As the n-type guide layer 6, a nitride semiconductor made of undoped GaN is grown. The film thickness of the n-type guide layer 6 is preferably 0.1 to 0.07 μm because the threshold value decreases. By making the n-type guide layer 6 undoped, it is preferable that the propagation loss in the laser waveguide is reduced and the threshold is lowered.
[0032]
Next, the active layer 7 is grown on the n-type guide layer 6. As the active layer 7, In _b Ga _1-b It is a multiple quantum well structure including N (0 ≦ b <1). As a well layer of the active layer 7, b is 0.1 to 0.2 In. _b Ga _1-b N and as the barrier layer, b is 0 to 0.01 In. _b Ga _1-b N.
Further, impurities may be doped into one or both of the well layer and the barrier layer constituting the active layer 7. It is preferable that the barrier layer is doped with impurities because the threshold value is lowered.
The thickness of the well layer is 30 to 60 Å, and the thickness of the barrier layer is 90 to 150 Å.
[0033]
The multi-quantum well structure of the active layer 6 starts with a barrier layer and ends with a well layer, starts with a barrier layer and ends with a barrier layer, starts with a well layer and ends with a barrier layer, and starts with a well layer. It may end with Preferably, starting from a barrier layer, a pair of a well layer and a barrier layer is repeated 2 to 5 times, and preferably a pair of a well layer and a barrier layer is repeated 3 times to lower the threshold and reduce the lifetime. It is preferable for improving the characteristics.
[0034]
Next, the p-type electron confinement layer 8 is grown on the active layer 7. As the p-type electron confinement layer 8, Mg-doped Al _d Ga _1-d At least one layer of N (0 <d ≦ 1) is grown. Preferably Mg-doped Al with d of 0.1 to 0.5 _d Ga _1-d N. The film thickness of the p-type electron confinement layer 8 is 10 to 1000 angstroms, preferably 50 to 200 angstroms. When the film thickness is in the above range, it is preferable because electrons in the active layer 7 can be confined well and the bulk resistance can be suppressed low.
The amount of Mg doped in the p-type electron confinement layer 8 is 1 × 10 ¹⁹ / Cm ^Three ~ 1x10 ^{twenty one} / Cm ^Three It is. When the doping amount is within this range, in addition to lowering the bulk resistance, Mg is favorably diffused into a p-type guide layer grown by undoped described later, and Mg is added to the p-type guide layer 9 which is a thin film layer. × 10 ¹⁶ / Cm ^Three ~ 1x10 ¹⁸ / Cm ^Three It can contain in the range of.
The p-type electron confinement layer 8 is preferably grown at a low temperature, for example, a temperature similar to the temperature at which the active layer is grown at a temperature of about 850 to 950 ° C., because the active layer can be prevented from decomposing.
The p-type electron confinement layer 8 may be composed of two layers: a low-temperature grown layer and a layer grown at a high temperature, for example, a temperature about 100 ° C. higher than the growth temperature of the active layer. Thus, when it is composed of two layers, the low temperature growth layer prevents the active layer from being decomposed, and the high temperature growth layer lowers the bulk resistance.
The thickness of each layer when the p-type electron confinement layer 8 is composed of two layers is not particularly limited, but the low temperature growth layer is preferably 10 to 50 Å, and the high temperature growth layer is preferably 50 to 150 Å.
[0035]
Next, the p-type guide layer 9 is grown on the p-type electron confinement layer 8. The p-type guide layer 9 is grown as a nitride semiconductor layer made of undoped GaN. The film thickness is 0.1 to 0.07 μm, and if it is in this range, the threshold value is lowered, which is preferable. Further, as described above, the p-type guide layer 9 is grown as an undoped layer, but Mg doped in the p-type electron confinement layer 8 diffuses and becomes 1 × 10 6. ¹⁶ / Cm ^Three ~ 1x10 ¹⁸ / Cm ^Three Mg is contained in the range.
[0036]
Next, the p-type cladding layer 10 is grown on the p-type guide layer 9. As the p-type cladding layer 10, Al is used. _f Ga _1-f Nitride semiconductor layer comprising N (0 <f ≦ 1), preferably Al _f Ga _1-f It is formed as a layer of a multilayer film having a nitride semiconductor layer containing N (0.05 ≦ f ≦ 0.15). The multilayer film is a multilayer film structure in which nitride semiconductor layers having different compositions are laminated, for example, Al _f Ga _1-f N layer and Al _f Ga _1-f A nitride semiconductor having a composition different from that of N, for example, one having a different mixed crystal ratio of Al, a ternary mixed crystal containing In, or a layer formed by combining layers made of GaN or the like. Among these, a preferable combination is Al. _f Ga _1-f A multilayer film in which N and GaN are stacked is preferable because a nitride semiconductor layer having good crystallinity can be stacked at the same temperature. A more preferable multilayer film is undoped Al. _f Ga _1-f This is a combination of N and p-type impurity (for example, Mg) -doped GaN stacked. The p-type impurity is Al _f Ga _1-f N may be doped. The doping amount of the p-type impurity is 1 × 10 ¹⁷ / Cm ^Three ~ 1x10 ¹⁹ / Cm ^Three It is. It is preferable that the p-type impurity is doped in this range because the doping amount is such that the crystallinity is not impaired and the bulk resistance is lowered.
Such a multilayer film is formed by stacking nitride semiconductor layers having a single layer thickness of 100 angstroms or less, preferably 70 angstroms or less, more preferably 40 angstroms or less, preferably 10 angstroms or more. When the single film thickness is 100 angstroms or less, the n-type cladding layer has a superlattice structure, and even though Al is contained, the generation of cracks can be prevented and the crystallinity can be improved.
The total film thickness of the p-type cladding layer 10 is 0.4 to 0.5 μm, and this range is preferable for reducing the forward voltage (Vf).
Moreover, the average composition of Al of the whole p-type cladding layer is 0.05 to 0.1. This value is preferable for suppressing the occurrence of cracks and obtaining a difference in refractive index from the laser waveguide.
[0037]
Next, the p-type contact layer 11 is grown on the p-type cladding layer 10. The p-type contact layer is formed by growing a nitride semiconductor layer made of Mg-doped GaN. The film thickness is 10 to 200 angstroms. Mg doping amount is 1 × 10 ¹⁹ / Cm ^Three ~ 1x10 ^{twenty two} / Cm ^Three It is. By adjusting the film thickness and the Mg doping amount in this way, the carrier concentration of the p-type contact layer 11 is increased, and it becomes easy to take ohmic contact with the p-electrode.
[0038]
In the element of the present invention, the ridge-shaped stripe is formed by etching from the p-type contact layer to the lower side (substrate side) than the p-type contact layer. For example, a stripe formed by etching from the p-type contact layer 11 to the middle of the p-type cladding layer 10 as shown in FIG. 1 or a stripe formed by etching from the p-type contact layer 11 to the n-type contact layer 2 can be used.
[0039]
As shown in FIG. 1, for example, an insulating film having a value smaller than the refractive index of the laser waveguide region is formed on the side surface of the ridge-shaped stripe formed by etching and the plane of the nitride semiconductor layer continuous to the side surface. Has been. The insulating film formed on the side surface of the stripe is selected from the group consisting of Si, V, Zr, Nb, Hf, Ta having a refractive index of about 1.6 to 2.3, for example. Examples include oxides containing at least one element, BN, AlN, and the like, and preferably one or more elements of Zr and Hf oxides and BN.
Further, a p-electrode is formed on the surface of the p-type contact layer 11 in the uppermost layer of the stripe via this insulating film.
The width of the ridge-shaped stripe formed by etching is 0.5 to 4 μm, preferably 1 to 3 μm. When the width of the stripe is within this range, it is preferable that the horizontal and transverse mode easily becomes a single mode.
Further, if the etching is performed on the substrate side with respect to the interface between the p-type cladding layer 10 and the laser waveguide region, it is preferable to bring the aspect ratio close to 1.
As described above, by specifying the etching amount of the ridge-shaped stripe, the stripe width, and the refractive index of the insulating film on the side surface of the stripe, single mode laser light can be obtained, and the aspect ratio can be made closer to a circle. The laser beam and lens design are easy and preferable.
In the element of the present invention, various conventionally known p electrodes and n electrodes can be appropriately selected and used.
[0040]
【Example】
An example which is one embodiment of the present invention will be described below. However, the present invention is not limited to this.
In addition, although this embodiment shows MOVPE (metal organic vapor phase epitaxy), the method of the present invention is not limited to the MOVPE method. For example, HVPE (halide vapor phase epitaxy), MBE (molecular beam) All methods known for growing nitride semiconductors, such as vapor phase growth, can be applied.
[0041]
[Example 1]
As Example 1, a nitride semiconductor laser device according to an embodiment of the present invention shown in FIG. 1 is manufactured.
[0042]
As shown in FIG. 3, a C-plane that is off-angled stepwise as a main surface is used as the dissimilar substrate, the off-angle angle θ = 0.15 °, the step step is about 20 angstroms, and the terrace width W is about 800 angstroms. A sapphire substrate whose surface is the A plane and whose steps are perpendicular to the A plane is prepared.
This sapphire substrate is set in a reaction vessel, the temperature is set to 510 ° C., hydrogen is used as a carrier gas, ammonia and TMG (trimethyl gallium) are used as a source gas, and a low-temperature growth buffer layer made of GaN is formed on the sapphire substrate. Grow with a film thickness of 200 Å.
After growing the buffer layer, only TMG is stopped, the temperature is raised to 1050 ° C., and when it reaches 1050 ° C., TMG, ammonia, silane gas is used as the source gas, and a high-temperature growth buffer layer made of undoped GaN is formed to a thickness of 5 μm. Grow in.
Next, a stripe-shaped photomask is formed on the wafer on which the high-temperature growth buffer layer is laminated, and SiO 2 having a stripe width of 18 μm and a window width of 3 μm is formed by a CVD apparatus. ₂ A protective film is formed with a thickness of 0.1 μm. The stripe direction of the protective film is a direction perpendicular to the sapphire A plane.
After forming the protective film, the wafer is transferred to a reaction vessel, and a nitride semiconductor layer made of undoped GaN is grown to a thickness of 15 μm at 1050 ° C. using TMG and ammonia as source gases to form a nitride semiconductor substrate 1. .
The obtained nitride semiconductor is used as a nitride semiconductor substrate 1 to grow the following element structure.
[0043]
(Light absorption layer 2)
On the nitride semiconductor substrate 1, undoped In using TMI (trimethylindium), TMG, and ammonia gas as source gases at 780 ° C. _0.15 Ga _0.85 A first nitride semiconductor made of N is grown to a thickness of 500 angstroms. Subsequently, TMI is stopped and a second nitride semiconductor made of undoped GaN is grown to 1000 angstroms. Then, this operation is repeated three times, and the first nitride semiconductor and the second nitride semiconductor are stacked to grow the light absorption layer 2 made of a multilayer film having a total film thickness of 4500 angstroms.
[0044]
(Undoped n-type contact layer) [not shown in FIG. 1]
On the light absorption layer 2, undoped Al using TMA (trimethylaluminum), TMG, and ammonia gas as source gases at 1050 ° C. _0.05 Ga _0.95 An n-type contact layer made of N is grown to a thickness of 1 μm.
(N-type contact layer 3)
Next, at the same temperature, TMA, TMG, and ammonia gas are used as source gas, and silane gas (SiH) is used as impurity gas. _Four ) And Si 3 × 10 ¹⁸ / Cm ^Three Doped Al _0.05 Ga _0.95 An n-type contact layer 3 made of N is grown to a thickness of 3 μm.
[0045]
(Crack prevention layer 4)
Next, the temperature is set to 800 ° C., TMG, TMI (trimethylindium) and ammonia are used as the source gas, silane gas is used as the impurity gas, and Si is 5 × 10 5. ¹⁸ / Cm ^Three Doped In _0.08 Ga _0.92 A crack prevention layer 4 made of N is grown to a thickness of 0.15 μm.
[0046]
(N-type cladding layer 5)
Next, the temperature is set to 1050 ° C., TMA, TMG, and ammonia are used as source gases, and undoped Al _0.14 Ga _0.86 An A layer made of N is grown to a thickness of 25 Å, then TMA is stopped, silane gas is used as an impurity gas, and Si is 5 × 10 5 ¹⁸ / Cm ^Three A B layer made of doped GaN is grown to a thickness of 25 Å. This operation is repeated 160 times, and the A layer and the B layer are laminated to grow the n-type cladding layer 5 made of a multilayer film (superlattice structure) having a total film thickness of 8000 angstroms.
[0047]
(N-type guide layer 6)
Next, an n-type guide layer 6 made of undoped GaN is grown to a thickness of 0.075 μm using TMG and ammonia as source gases at the same temperature.
[0048]
(Active layer 7)
Next, the temperature is set to 800 ° C., TMI, TMG, and ammonia are used as source gases, silane gas is used as an impurity gas, and Si is 5 × 10 5. ¹⁸ / Cm ^Three Doped In _0.01 Ga _0.99 A barrier layer made of N is grown to a thickness of 100 Å. Subsequently, silane gas was turned off and undoped In _0.11 Ga _0.89 A well layer made of N is grown to a thickness of 50 Å. This operation is repeated three times. Finally, an active layer 7 having a total quantum film thickness of 550 angstroms (MQW) with a barrier layer stacked thereon is grown.
[0049]
(P-type electron confinement layer 8)
Next, at the same temperature, TMA, TMG, and ammonia are used as source gases, and Cp is used as an impurity gas. ₂ Mg (cyclopentadienylmagnesium) is used and Mg is 1 × 10 ¹⁹ / Cm ^Three Doped Al _0.4 Ga _0.6 A p-type electron confinement layer 8 made of N is grown to a thickness of 100 Å.
[0050]
(P-type guide layer 9)
Next, the temperature is set to 1050 ° C., TMG and ammonia are used as source gases, and a p-type guide layer 9 made of undoped GaN is grown to a thickness of 0.075 μm.
The p-type guide layer 9 is grown as undoped, but due to the diffusion of Mg from the p-type electron confinement layer 8, the Mg concentration is 5 × 10 5. ¹⁶ / Cm ^Three And p-type.
[0051]
(P-type cladding layer 10)
Next, at the same temperature, TMA, TMG and ammonia are used as source gases, and undoped Al _0.1 Ga _0.9 An A layer made of N is grown to a film thickness of 25 Å, and then TMA is stopped and Cp is used as an impurity gas. ₂ Mg is used, and Mg is 5 × 10 ¹⁸ / Cm ^Three A B layer made of doped GaN is grown to a thickness of 25 Å. This operation is repeated 100 times, and the A layer and the B layer are stacked to grow the p-type cladding layer 10 made of a multilayer film (superlattice structure) having a total film thickness of 5000 angstroms.
[0052]
(P-type contact layer 11)
Next, at the same temperature, TMG and ammonia are used as the source gas, and Cp is used as the impurity gas. ₂ Mg is used, and Mg is 1 × 10 ²⁰ / Cm ^Three A p-type contact layer 11 made of doped GaN is grown to a thickness of 150 Å.
[0053]
After the completion of the reaction, the wafer is annealed in a reaction vessel at 700 ° C. in a nitrogen atmosphere to further reduce the resistance of the p-type layer.
After annealing, the wafer is taken out of the reaction vessel, and the surface of the uppermost p-side contact layer is SiO. ₂ A protective film is formed, and SiCl is formed using RIE (reactive ion etching). _Four Etching with gas exposes the surface of the n-side contact layer 3 where the n-electrode is to be formed, as shown in FIG.
Next, as shown in FIG. 4A, Si oxide (mainly SiO 2) is formed on almost the entire surface of the uppermost p-side contact layer 11 by a PVD apparatus. ₂ ) Is formed to a thickness of 0.5 μm, a mask having a predetermined shape is put on the first protective film 61, and a third protective film 63 made of photoresist is formed. The stripe width is 1.8 μm and the thickness is 1 μm.
Next, as shown in FIG. 4B, after the formation of the third protective film 63, CF is performed by an RIE (reactive ion etching) apparatus. _Four Using gas, the first protective film is etched using the third protective film 63 as a mask to form stripes. Thereafter, the first protective film 61 having a stripe width of 1.8 μm can be formed on the p-side contact layer 10 as shown in FIG.
[0054]
Further, as shown in FIG. 4D, after the first protective film 61 having a stripe shape is formed, SiCl is again performed by RIE. _Four The p-side contact layer 11 and the p-side cladding layer 10 are etched using gas to form a ridge-shaped stripe having a stripe width of 1.8 μm. However, as shown in FIG. 1, the ridge-shaped stripe is formed so as to avoid the central portion of the protective film on the protective film formed during the selective growth.
After forming the ridge stripe, the wafer is transferred to a PVD apparatus, and as shown in FIG. 4 (e), Zr oxide (mainly ZrO ₂ The second protective film 62 is formed continuously on the first protective film 61 and on the p-side cladding layer 10 exposed by etching with a thickness of 0.5 μm. The formation of the Zr oxide in this manner is preferable because the transverse mode can be stabilized because the pn plane is insulated.
Next, the wafer is immersed in hydrofluoric acid, and as shown in FIG. 4F, the first protective film 61 is removed by a lift-off method.
[0055]
Next, as shown in FIG. 4G, a p-electrode 20 made of Ni / Au is formed on the surface of the p-side contact layer 11 exposed by removing the first protective film 61 on the p-side contact layer 11. Form. However, the p electrode 20 has a stripe width of 100 μm and is formed over the second protective film 62 as shown in FIG.
After the formation of the second protective film 62, an n electrode 21 made of Ti / Al is formed in a direction parallel to the stripes on the exposed surface of the n-side contact layer 3 as shown in FIG.
[0056]
As described above, after polishing the sapphire substrate of the wafer on which the n-electrode and the p-electrode are formed to 70 μm, the substrate is cleaved in a bar shape from the substrate side in a direction perpendicular to the stripe-shaped electrode. A resonator is formed on the 11-00 plane, a plane corresponding to the side surface of the hexagonal columnar crystal = M plane). SiO on the resonator surface ₂ And TiO ₂ A dielectric multilayer film is formed, and finally the bar is cut in a direction parallel to the p-electrode to obtain a laser element as shown in FIG. The resonator length is preferably 300 to 500 μm.
The obtained laser element was placed on a heat sink, and each electrode was wire-bonded to attempt laser oscillation at room temperature.
As a result, the threshold value is 2.5 kA / cm at room temperature. ² In addition, continuous oscillation at an oscillation wavelength of 400 nm was confirmed at a threshold voltage of 5 V, showing a lifetime of 10,000 hours or more at room temperature, and further, emission of light from the end face of the n-type contact layer was suppressed and emitted from the resonance surface. The laser light FFP has a good single mode without ripples.
[0057]
[Example 2]
In Example 1, a nitride semiconductor laser device is manufactured in the same manner except that the light absorption layer 2 is formed of a single layer as follows.
(Light absorption layer 2)
On the nitride semiconductor substrate 1, undoped In using TMI (trimethylindium), TMG, and ammonia gas as source gases at 780 ° C. _0.15 Ga _0.85 A first nitride semiconductor made of N is grown to a thickness of 0.2 μm to grow the light absorption layer 2.
The obtained laser device is a good FFP and has a good lifetime characteristic in substantially the same manner as in Example 1.
[0058]
[Example 3]
A nitride semiconductor laser device is fabricated in the same manner as in Example 1 except that the p-type electron confinement layer 8 is composed of two layers as follows.
(P-type electron confinement layer 8)
The temperature is set to 800 ° C., TMA, TMG and ammonia are used as source gases, and Cp is used as impurity gas. ₂ Mg (cyclopentadienylmagnesium) is used and Mg is 5 × 10 ¹⁸ / Cm ^Three Doped Al _0.4 Ga _0.6 A low-temperature growth A layer made of N is grown to a thickness of 30 angstroms, followed by a temperature of 900 ° C. ¹⁸ / Cm ^Three Doped Al _0.4 Ga _0.6 A p-type electron confinement layer 8 consisting of two layers of a low-temperature-grown A layer and a high-temperature-grown B layer is grown by growing a high-temperature-grown B layer of N to a thickness of 70 angstroms.
The obtained laser device emits a good FFP laser beam in the same manner as in Example 1 and is a device with good lifetime characteristics.
[0059]
[Example 4]
In Example 1, when the crack prevention layer 4 was grown, the In composition ratio was 0.2, and Si was 5 × 10 5. ¹⁸ / Cm ^Three Doped In _0.2 Ga _0.8 A laser element is fabricated in the same manner except that the crack prevention layer 4 made of N is grown to a thickness of 0.15 μm.
The obtained laser device has good lifetime characteristics as in Example 1, and light emitted from the active layer 6 and leaked from the n-type cladding layer is absorbed by the light absorption layer 2 and the cladding prevention layer 4. Absorbed and FFP is better than Example 1.
[0060]
[Example 5]
In Example 1, a laser element is manufactured in the same manner except that the light absorption layer 2 is changed as follows.
(Light absorption layer 2)
On the nitride semiconductor substrate 1, undoped In using TMI (trimethylindium), TMG, and ammonia gas as source gases at 780 ° C. _0.15 Ga _0.85 A first nitride semiconductor made of N is grown to a thickness of 0.1 μm, then TMI is stopped, and a second nitride semiconductor made of undoped GaN is grown to 0.3 μm. Then, this operation is repeated twice, and the first nitride semiconductor and the second nitride semiconductor are stacked, and the light absorption layer 2 made of a multilayer film having a total film thickness of 0.8 μm is grown.
The obtained laser device can obtain good results in substantially the same manner as in Example 1.
[0061]
[Example 6]
In Example 1, a laser element is manufactured in the same manner except that the light absorption layer 2 is changed as follows.
(Light absorption layer 2)
On the nitride semiconductor substrate 1, undoped In using TMI (trimethylindium), TMG, and ammonia gas as source gases at 780 ° C. _0.15 Ga _0.85 A first nitride semiconductor made of N is grown to a thickness of 0.01 μm, and then the TMI is stopped, and a second nitride semiconductor made of undoped GaN is grown to 0.02 μm. Then, this operation is repeated five times, and the first nitride semiconductor and the second nitride semiconductor are stacked, and the light absorption layer 2 made of a multilayer film having a total film thickness of 0.15 μm is grown.
The obtained laser device can obtain good results in substantially the same manner as in Example 1.
[0062]
[Example 7]
In Example 2, a laser element is fabricated in the same manner except that the thickness of the light absorption layer 2 is 0.5 μm.
The obtained laser device can obtain good results in substantially the same manner as in Example 2.
[0063]
【The invention's effect】
The present invention can provide a nitride semiconductor laser device in which the FFP of the laser light has a good single mode with no ripple.
[Brief description of the drawings]
FIG. 1 is a schematic cross-sectional view showing a nitride semiconductor laser device according to an embodiment of the present invention.
FIG. 2 is a unit cell diagram showing the plane orientation of sapphire.
FIG. 3 is a schematic cross-sectional view showing a partial shape of an off-angled dissimilar substrate.
FIG. 4 is a schematic cross-sectional view showing a partial structure of a wafer in each step of a method which is an embodiment of forming a ridge-shaped stripe.
[Explanation of symbols]
1 ... Nitride semiconductor substrate
2. Light absorption layer
3 ... n-type contact layer
4 ... Crack prevention layer
5 ... n-type cladding layer
6 ... n-type guide layer
7 ... Active layer
8 ... p-type electron confinement layer
9 ... p-type guide layer
10 ... p-type cladding layer
11 ... p-type contact layer

Claims (6)

On a nitride semiconductor substrate formed by selectively growing a nitride semiconductor in a lateral direction, at least an n-type contact layer, an n-type cladding layer having a nitride semiconductor containing Al, In _a Ga _1-a N ( An active layer having a multiple quantum well structure having a well layer made of 0 <a <1) and a barrier layer made of In _b Ga _1-b N (0 ≦ b <1), and a p having an nitride semiconductor layer containing Al It has a mold cladding layer in order,
Between the substrate and the n-type contact layer, at least one layer of a first nitride semiconductor made of In _d Ga _1-d N (0 <d <1) having a band gap energy smaller than that of the well layer is included. A light absorption layer consisting of
A nitride semiconductor laser device comprising a crack preventing layer containing In between the n-type contact layer and the n-type cladding layer. The nitride semiconductor laser element according to claim 1, wherein the p-type cladding layer and / or the n-type cladding layer is formed of a multilayer film layer. The light absorption layer includes a first nitride semiconductor made of In _d Ga _1-d N (0 <d <1) having a band gap energy smaller than that of the well layer, and a second nitride semiconductor made of GaN. 3. The nitride semiconductor laser device according to claim 1, comprising a multilayer film in which at least one layer is laminated. The nitride semiconductor laser element according to claim 1, wherein the light absorption layer is undoped. 5. The nitride semiconductor laser device according to claim 1, wherein the light absorption layer has a thickness of 0.02 to 1 μm. The film thickness of the first nitride semiconductor layer constituting the light absorption film of the multilayer film is 0.01 to 0.05 μm, and the film thickness of the second nitride semiconductor is 0.01 to 0.05 μm. The nitride semiconductor laser device according to claim 3.

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