JP2021111785A - Manufacturing method of optical device and optical device - Google Patents

Abstract

To provide a manufacturing method of an optical device having a laser diode suitable for mass production, and an optical device having a laser diode capable of accurate characteristic evaluation and having a small measurement error.SOLUTION: A manufacturing method of an optical device includes an etching step of etching a semiconductor laminate having an n-type clad layer containing an n-type conductive nitride semiconductor layer formed on a substrate, a light emitting layer containing one or more quantum wells formed on the n-type clad layer, and a p-type clad layer including a nitride semiconductor layer having p-type conductivity formed on the light emitting layer, and forming a laser diode by forming a mesa structure with a resonator end face, and a reflective layer forming step of forming a light reflecting layer so as to cover all sides of the mesa structure.SELECTED DRAWING: Figure 2

Description

The present invention relates to a method for manufacturing an optical device and an optical device, and more particularly to a method for manufacturing an optical device having a laser diode and an optical device having a laser diode.

Laser diodes are usually made by forming two parallel mirror end faces facing each other using an appropriate technique and then forming a reflective layer on the end faces to reduce the threshold. Non-Patent Document 1 discloses a method for forming a mirror end face of a general laser diode. Specifically, it discloses a method of exposing a vertical and smooth end face by dividing a semiconductor crystal along a natural cleavage plane.

U.S. Pat. No. 5,394,426

Z. Zhang, M.M. Kushimoto, T.K. Sakai, N.M. Sugiyama, L. et al. J. Schowalter, C.I. Sasaoka and H. Amano, Appl. Phys. Express. 12,124003 (2019)

However, in the conventional method of exposing the end face of the resonator by splitting along the natural cleavage plane, when coating the end face of the resonator with a reflective layer, it is indispensable to handle the laser bar finely divided as in Patent Document 1. Therefore, there is a problem that it is not suitable for mass production. Further, in the laser diode obtained by the conventional method, it is difficult to accurately evaluate the characteristics of the laser diode due to the light emitted from other than the end face of the resonator, which is called stray light, and the laser diode is used. There was an error in the measurement.

That is, an object of the present invention is to provide a method for manufacturing an optical device having a laser diode suitable for mass production. Another object of the present invention is to provide an optical device having a laser diode capable of accurate characteristic evaluation and having a small measurement error.

In the first aspect of the present invention, an n-type clad layer formed on a substrate and including a nitride semiconductor layer having n-type conductivity and one or more quantum wells formed on the n-type clad layer. A semiconductor laminated portion having a light emitting layer containing the light emitting layer and a p-type clad layer including a nitride semiconductor layer having p-type conductivity formed on the light emitting layer is etched to have a mesa structure having a resonator end face. Provided is a method for manufacturing an optical device, comprising an etching step of forming a laser diode and a reflecting layer forming step of forming a light reflecting layer so as to cover all the side surfaces of the mesa structure.

In the second aspect of the present invention, one is formed on a substrate, an n-type clad layer formed on the substrate and including a nitride semiconductor layer having n-type conductivity, and the n-type clad layer. It has a light emitting layer including the above quantum well and a p-type clad layer including a nitride semiconductor layer having p-type conductivity formed on the light emitting layer, and at least a part of the n-type clad layer. Provided is an optical device including a laser diode in which the light emitting layer and the p-type clad layer have a mesa structure including a resonator end face, and all sides of the mesa structure are covered with a light reflecting layer.

Here, for example, in the expression "n-type clad layer formed on a substrate and including a nitride semiconductor layer having n-type conductivity", the word "on" means that an n-type clad layer is formed on the substrate. However, the case where another layer is further present between the substrate and the n-type clad layer is also included in this expression. The word "above" has the same meaning in the relationships between other layers.

Here, the outline of the above invention does not list all the features of the present invention. Moreover, the subcombination of these feature groups can be an invention.

According to the present invention, it becomes possible to provide a method for manufacturing an optical device having a laser diode suitable for mass production. Further, it becomes possible to provide an optical device having a laser diode capable of accurate characteristic evaluation and having a small measurement error.

1 (a), 1 (b), and 1 (c) are schematic views of an etching process of the manufacturing method of the optical device of the present embodiment. 2 (a) and 2 (b) are schematic views of a reflective layer forming step of the optical device of the present embodiment and the method of manufacturing the optical device of the present embodiment. FIG. 3 is a schematic view of an optical device including the photodetector of the present embodiment. FIG. 4 is a schematic view of a semiconductor laminated portion in the optical device of the present embodiment. 5 (a) and 5 (b) are cross-sectional TEM images of the side surface of the mesa structure in Example 1. FIG. 6 is a graph showing the theoretical reflectance and the actually measured reflectance of the light reflecting layer in Example 1. FIG. 7 is a cross-sectional TEM image including the resonator end face of the laser diode in the first embodiment. FIG. 8 shows the optical output (IL) characteristics plotted as a function of the current-voltage (IV) and forward pulse current of the laser diode in Example 1. FIG. 9 is a schematic view of an optical device including a laser diode and a photodetector according to the second embodiment.

Hereinafter, the present invention will be described through embodiments of the invention, but the following embodiments do not limit the inventions that fall within the scope of the claims. Also, not all combinations of features described in the embodiments are essential to the means of solving the invention.

<Manufacturing method of optical device>
The method for manufacturing the optical device of the present embodiment includes an n-type clad layer including an n-type conductive nitride semiconductor layer formed on a substrate and one or more quantum wells formed on the n-type clad layer. A semiconductor laminated portion having a light emitting layer containing a light emitting layer and a p-type clad layer containing a p-type conductive nitride semiconductor layer formed on the light emitting layer is etched to obtain a mesa structure having a resonator end face. It includes an etching step of forming and forming a laser diode, and a reflecting layer forming step of forming a light reflecting layer so as to cover all side surfaces including a resonator end face of a mesa structure.

By providing a step of forming a light reflecting layer so as to cover all the side surfaces including the resonator end face of the mesa structure of the laser diode, the problem of handling the finely divided laser bar is eliminated, and it is suitable for mass production.

Here, "covering all sides" means that when an object (here, a light reflecting layer) is vertically projected onto each side, substantially the entire side surface is covered with a vertically projected image of the object. Although another layer may be interposed between the light reflecting layer and each side surface, it may be preferable that the light reflecting layer is directly arranged on the side surface from the viewpoint of enabling accurate characteristic evaluation and reducing measurement error. be.

The "resonator end surface" is a surface that serves as a main light emitting surface of laser light, and is at least a cross section of a semiconductor laminated portion including a light emitting layer. Since it is a surface that serves as the main light emitting surface of laser light, it is generally an end surface that includes a light emitting layer on the short side when viewed in a plan view from above.

<< Etching process >>
1 (a), 1 (b) and 1 (c) are schematic views of the etching process. In the etching step, an n-type clad layer 12 including an n-type conductive nitride semiconductor layer formed on the substrate 11 and a light emitting layer including one or more quantum wells formed on the n-type clad layer 12 A mesa structure having a resonator end face 41 by etching a semiconductor laminated portion 30 having a 14 and a p-type clad layer 20 including a p-type conductive nitride semiconductor layer formed on the light emitting layer 14. Form 40. Yet another etching step may be performed to etch deeper than the etching depth of the mesa structure 40. For example, in order to reduce the influence of reflection on the bottom surface due to the spread of the emitted light in the vertical direction (direction perpendicular to the substrate surface), as shown in FIG. The side) may be etched deeper than the mesa structure 40. At that time, the etching may reach the substrate 11.

Although not particularly limited, it is preferable to apply dry etching and wet etching in this order from the viewpoint of forming a resonator end face that is nearly perpendicular to the substrate plane.

When the substrate is an AlN substrate and the semiconductor laminated portion contains AlGaN, wet etching is performed using tetramethylammonium hydroxide as an etching solution after performing arbitrary dry etching on the (0001) surface of the AlN substrate. The (1-100) plane of the AlGaN layer, which is almost vertical, can be exposed as the resonator end face. The dry etching is, for example, inductively coupled reactive ion etching (ICP-RIE) in a _{Cl 2} and B _{Cl 3 atmosphere with SiO 2} as a mask. Details will be described in Examples, but higher reflectance can be realized as the resonator end face is closer to perpendicular to the substrate.

<< Reflective layer forming process >>
2 (a) and 2 (b) are schematic views of the reflective layer forming process. In the reflection layer forming step, the light reflection layer 50 is formed so as to cover all the side surfaces of the mesa structure 40 of the laser diode. Although not particularly limited, the light reflecting layer 50 may be formed so as to cover only all the side surfaces of the mesa structure 40 as shown in FIG. 2A. Further, as shown in FIG. 2B, a light reflecting layer may be formed so as to cover all the side surfaces and a part or all of the upper surface of the mesa structure 40.

The method for forming the light reflecting layer is not particularly limited, but the atomic layer deposition method is preferable as the deposition method with good step coverage. The atomic layer deposition method is a thin film forming method for forming a film by alternately exposing a plurality of vapor phase raw materials (precursors) to the surface of a substrate. Unlike CVD, different types of precursors do not enter the reaction chamber at the same time, but are alternately introduced and discharged (purged) in pulses as independent steps. At each pulse, the precursor molecule behaves in a self-regulating manner on the substrate surface, and the reaction ends when there are no adsorbable sites on the surface. Therefore, the maximum film formation amount in one cycle is defined by the properties of how the precursor molecules and the substrate surface molecules are chemically bonded. Therefore, by controlling the thin film formation conditions such as the pulse cycle sequence, the reaction layer temperature, and the raw material species, it is possible to form a film with high accuracy and uniformly on a substrate having an arbitrary structure and size. For example, an ALD device manufactured by Veeco / CNT can be used.

When a multi-layer structure of hafnium oxide and aluminum oxide, which will be described later, is used, TDMAH (tetrakis (dimethylamino) hafnium) can be used as the gas phase raw material of the hafnium oxide. Further, TMA (trimethylaluminum) can be used as the vapor phase raw material of the aluminum oxide.

<< Insulation layer forming process and electrode part forming process >>
The method for manufacturing the optical device of the present embodiment includes an electrode portion forming step of forming a p-electrode portion electrically connected to the p-type clad layer of the laser diode and a p-electrode portion forming step between the etching step and the reflective layer forming step. An insulating layer forming step of forming an insulating layer so as to cover the above may be further provided.

By further providing the electrode portion forming step and the insulating layer forming step, the efficiency when electric power is applied to the optical device can be improved. The insulating layer may be formed so as to cover at least a part of the upper surface of the mesa structure of the photodetector described later.

Further, the insulating layer may be formed so as to cover at least a part of the side surface of the mesa structure.

Here, the p-electrode portion may be directly connected to the p-type clad layer and electrically connected, or may be electrically connected via another layer (for example, a contact layer) between them.

Examples of the material for forming the insulating layer include, but are not limited to, metal oxides and metal nitrides containing silicon, boron, hafnium, titanium, aluminum and the like.

<< Photodetector forming process >>
The method for manufacturing an optical device of the present embodiment further includes a photodetector forming step of forming a photodetector having a mesa structure capable of receiving and detecting light emitted from a resonator end face, and in the reflecting layer forming step. It is preferable to form a light reflecting layer on all sides of the mesa structure of the photodetector.

Although the details will be described later, by providing the photodetector on the same substrate, the light emitted from the laser diode can be detected by the photodetector. Since the laser diode and the photodetector of the present embodiment have light reflecting layers formed on all side surfaces of the mesa structure, the influence of stray light (light emitted from other than the end face of the resonator) that becomes noise for the detection is reduced. It becomes possible to do.

It is also preferable that the photodetector forming step is included in the etching step of the laser diode, that is, the mesa structure of the laser diode and the mesa structure of the photodetector are formed at the same time. This makes it possible to provide the laser diode and photodetector on the same substrate without any additional process.

From the viewpoint of enabling highly sensitive detection of the light emitted from the laser diode, it is preferable that the laser diode and the photodetector are formed adjacent to each other. Specifically, it is preferable to form the laser diode and the photodetector at a position where one of the resonator end faces of the laser diode and the light receiving surface of the photodetector face each other.

From the viewpoint of improving mass productivity, it is preferable that the substrate is in the form of a wafer, and the mesa structure of the laser diode and the mesa structure of the photodetector are each formed on the wafer-like substrate, and a plurality of each can be formed. More preferred. In addition, by forming a laser diode and a photodetector on the same substrate, it is possible to reduce the misalignment between the two to the error level of forming a mesa pattern by the manufacturing equipment, and efficiently detect the emitted light of the laser. It becomes possible to couple the vessel.

<< Dicing process >>
The method for manufacturing the optical device of the present embodiment can further include a dicing step of individualizing a laser diode having a mesa structure having a resonator end face into a laser diode chip after the step of forming a reflective layer. As a result, a laser diode chip having a reflecting layer on the end face of the resonator without coating the reflecting layer on the end face of the resonator in a laser bar (individualized laser diode) state, which was difficult to handle as in the prior art. Can be easily manufactured. In addition, the ability to form a laser diode chip with a photodetector on a single substrate in the same dicing process dramatically improves productivity.

Next, the optical device of this embodiment will be described.

(Optical device)
As shown in FIGS. 2 (a) and 2 (b), the optical device of the present embodiment is an n-type cladding formed on a substrate 11 and a nitride semiconductor layer having n-type conductivity. A p-type including a light-emitting layer 14 formed on the layer 12 and an n-type clad layer 12 and containing one or more quantum wells, and a nitride semiconductor layer formed on the light-emitting layer 14 and having p-type conductivity. The clad layer 20, at least a part of the n-type clad layer, the light emitting layer, and the p-type clad layer is a mesa structure 40 including the resonator end face 41, and includes the resonator end face 41 of the mesa structure 40. A laser diode 1 whose entire side surface is covered with a light reflecting layer 50 is provided.

"All sides including the end face of the resonator of the mesa structure are covered with the light reflecting layer" means that the light reflecting layer is directly formed on all the side surfaces of the mesa structure and directly covers the side surface and the light reflection. It may be in the form of indirectly covering through another layer between the layers. That is, the light reflecting layer may cover the side surface of the mesa structure when viewed in a plane from a direction perpendicular to the side surface of the mesa structure.

As shown in FIG. 3, the optical device of the present embodiment further includes a photodetector 2 having a mesa structure that receives and detects light emitted from the laser diode 1, and the side surface of the mesa structure of the photodetector 2 is light. It may be covered with the reflective layer 51. The light reflecting layer 51 may be the same as or different from the light reflecting layer 50. From the viewpoint of realizing the characteristic evaluation of the laser diode with high accuracy, it is preferable that they are the same. The layer structure of the photodetector 2 may be the same as or different from that of the laser diode. The light receiving surface of the photodetector is preferably arranged at a position facing the main light emitting surface of the laser diode, that is, the end surface of the resonator. By providing a laser diode whose side surface is covered with a light reflecting layer and a photodetector, it is possible to evaluate the characteristics of the laser diode more easily and with high accuracy. By forming the laser diode and the photodetector on the same substrate, it is possible to reduce the misalignment between the two to the error level of the mesa pattern formation by the manufacturing apparatus, and it is possible to evaluate the characteristics with high accuracy. Further, as described above, when the layer structure of the laser diode and the photodetector is the same, the heights of the light emitting surface and the light receiving surface are substantially the same, so that more accurate characteristic evaluation becomes possible.

The optical device of this embodiment may include a control unit that controls a laser diode and a photodetector.

The optical device of this embodiment may have a plurality of laser diodes. The optical device of this embodiment may have a plurality of photodetectors. In the optical device of this embodiment, the substrate may be in the form of a wafer. When a plurality of laser diodes and / or photodetectors are provided, the wafer-like substrate further improves production efficiency.

Further, when the photodetector 2 is further provided, the light reflecting layers 50 and 51 may not be provided. In that case, from the viewpoint of improving the detection accuracy, the laser diode 1 and the photodetector 2 are preferably formed on the same substrate, and more preferably have the same layer structure. When the structure has the same layer structure, the end face of the resonator of the laser diode and the end face of the light receiving layer of the photodetector have the same height, so that light can be received with high efficiency and the measurement accuracy is further improved. The distance between the resonator end face of the laser diode and the light receiving layer of the photodetector is preferably close, preferably 50 μm or less, more preferably 20 μm or less, and even more preferably 5 μm or less. Normally, it is difficult in the process to form the distance between the resonator end face of the laser diode and the light receiving layer of the photodetector at such a distance, and the measurement accuracy is inferior due to the influence of positional deviation, etc., but on the same substrate. By adopting the same layer structure, it is possible to realize an optical device having both with high accuracy without introducing a complicated process.

(Light reflective layer)
From the viewpoint of designing a light-reflecting layer having a high light reflectance for a desired wavelength, the light-reflecting layer is preferably a dielectric laminated film. The dielectric laminated film may be a laminate of two or more different materials. The period may be one or more. For example, in the case of three layers of the first material / the second material / the first material, the period is 1.5.

The material of the light reflecting layer is preferably at least one oxide or fluoride selected from the group consisting of aluminum, hafnium, silicon, titanium, zirconium, lead, magnesium, and gallium, or a nitride. Further, the above-mentioned dielectric laminated film may be realized by combining two or more oxides.

The light reflecting layer is not particularly limited as long as the reflectance is larger than 0, but it is preferably 30% or more, more preferably 50% or more, and further preferably 70% or more.

(Laser diode)
The laser diode in the optical device of the present embodiment is formed on a substrate, an n-type clad layer including a nitride semiconductor layer having n-type conductivity, and one or more on the n-type clad layer. It has a semiconductor laminated portion including a light emitting layer including the quantum well of the above, and a p-type clad layer including a nitride semiconductor layer having p-type conductivity formed on the light emitting layer. A part of the n-type clad layer, the light emitting layer, and the p-type clad layer have a mesa structure including a resonator end face. All sides including the end face of the resonator of the mesa structure are covered with a light reflecting layer.

A resonator is a part that traps light between facing light reflecting surfaces and creates a standing wave of light. The resonator end face is a light reflecting surface. Although not particularly limited, the cleavage plane of the crystal can be used. When the resonator is an AlGaN layer, for example, the (1-100) plane of AlGaN can be used as the resonator end face. The resonator end face is preferably provided at an angle close to perpendicular to the substrate plane. Specifically, it is preferably 60 to 120 degrees, more preferably 80 to 100 degrees, further preferably 85 to 95 degrees, and 87.5 to 92 degrees with respect to the substrate plane. It is even more preferable that the temperature is 5.5 degrees.

The mesa structure is a structure including a region having a shape that is convex upward when viewed in cross section, and the shape of the structure when viewed in cross section is a quadrangle (typically a trapezoid). In other words, it is a structure including a region having a plane of the lower region as a bottom surface and a plane substantially parallel to the bottom surface as an upper surface when viewed in cross section. Generally, by etching a part of the semiconductor laminated portion, the unetched region becomes a mesa structure.

Next, the semiconductor laminated portion and each constituent requirement of the semiconductor laminated portion will be described with reference to FIG.

(Semiconductor laminated part)
The semiconductor laminated portion includes an n-type clad layer 12 including an n-type conductive nitride semiconductor layer formed on the substrate 11, and a light emitting layer including one or more quantum wells formed on the n-type clad layer. It has 14 and a p-type clad layer 20 including a nitride semiconductor layer having p-type conductivity formed on the light emitting layer.

The semiconductor laminated portion further includes a p-type longitudinal conductive layer 16, a p-type transverse conductive layer 17, an n-side waveguide layer 13, a p-side waveguide layer 15, a p-type contact layer 18, and an electrode portion (not shown). You can.

(substrate)
The substrate 11 is preferably one capable of growing the semiconductor laminated portion on the upper surface of the substrate 11 having a low in-plane dislocation density. One of the embodiments in which the effect of the present invention can be maximized is a high-quality layer having an in- ^{plane dislocation density of 5 × 10 4} cm- ^{2 or less in various layers of the laser diode 1.} In particular, in crystals with an in-plane dislocation density of 5 × 10 ⁴ cm- ² or less, carrier scattering due to dislocations is reduced, resulting in a decrease in longitudinal resistivity, and as a result, the ratio of longitudinal and transverse resistivity tends to be further reduced. Therefore, the substrate 11 is required to have a defect density lower than the above-mentioned defect density (for example, 1 × 10 ³ to 1 × 10 ⁴ cm- ^2). Of the various substrates 11, for example, an Al _x Ga _1-x ^{N mixed crystal of 1 × 10 4} cm- ² or less can be obtained on the substrate 11 of an AlN single crystal, which is preferable, but not limited to this. The through-dislocation density of the substrate 11 can be measured, for example, by performing KOH-NaOH eutectic etching at 450 ° C. for 5 minutes and then using etch pit density measurement.

The substrate 11 contains or consists of different materials (eg, SiC, Si, MgO, Ga ₂ O ₃ , alumina, ZnO, GaN, InN, and / or sapphire), or consists of, and on top of it. The Al _u Ga _1-u N material (0 ≦ u ≦ 1.0) may be formed, for example, by epitaxial growth. Such materials can be substantially completely lattice relaxed and have a thickness of, for example, at least 1 μm. The substrate 11 can be covered with a homoepitaxial layer containing, essentially consisting of, or made of the same material present in or on the substrate 11, such as AlN.

In addition to N, the substrate 11 is mixed with Group V elements other than N such as P, As, and Sb, and impurities such as H, C, O, F, Mg, and Si for the purpose of obtaining conductivity. However, this is not the case as an element.

The laser diode 1 can preferably be formed on a (0001) plane or a plane inclined at some angle from the (0001) plane normal direction, but is not limited to this. This angle is set, for example, -4 ° to 4 °, preferably −0.4 ° to 0.4 °.

The various layers of the multilayer structure arranged on the substrate 11 include, for example, an organometallic chemical vapor deposition (MOCVD), a deposition method such as halide vapor deposition (HVPE), and a molecular beam epitaxy method (MBE). It can be formed by any of a wide variety of different techniques, such as epitaxial growth techniques.

(P-type clad layer)
The p-type clad layer 20 includes a nitride semiconductor layer having p-type conductivity. The p-type clad layer 20 is preferably completely strained with respect to the substrate 11. Since the layer of the laser diode 1 formed by complete strain can suppress an increase in the through-dislocation density, the effect of the present invention is maximized. Here, the phrase "complete distortion with respect to the substrate 11" means that the layers constituting the multilayer have a very small strain relaxation with a lattice relaxation rate of 5% or less with respect to the substrate 11. The lattice relaxation rate is the reciprocal lattice of the diffraction peaks of any of the asymmetric planes, such as the (105) plane, (114) plane, or (205) plane, where sufficient diffraction intensity can be obtained by X-ray diffraction measurement of the asymmetric plane. It can be defined from the coordinates and the reciprocal lattice coordinates of the diffraction peak of the substrate 11.

When the p-type longitudinal conductive layer 16 and the p-type transverse conductive layer 17 are provided, both form a p-type clad layer.

(P-type longitudinal conductive layer)
_{The p-type longitudinal conductive layer 16 is a layer made of Al s} Ga _1-s N inclined so that the Al composition s decreases in the direction away from the upper surface of the substrate 11 for the purpose of obtaining p-type conductivity. That is, the p-type longitudinal conductive layer 16 constituting the p-type clad layer has a composition inclination. The film thickness and Al composition s range of the p-type longitudinal conductive layer 16 are bandgap materials that do not absorb light of a desired emission wavelength, and the electric field intensity distribution of the optical mode and the light emitting layer 14 that are fixed in the device. The Al composition and film thickness may be limited for the purpose of increasing the overlap (that is, increasing the light confinement). When the emission wavelength of the light emitting layer 14 is 210 nm or more and 300 nm or less, for example, in the range where the Al composition s is 0.3 or more and 1.0 or less, the light emitting layer 14 is composed of _{Al s} Ga _{1-s N decreasing in the direction away from the upper surface of the substrate 11.} The layer preferably has a film thickness of 250 nm or more and 450 nm or less, more preferably 300 nm or more and 400 nm or less. By appropriately controlling the film thickness, the internal loss of the laser diode 1 can be reduced.

The internal loss of the laser diode 1 can be measured by, for example, a method such as a known Variable Stripe Length Method (hereinafter, VSLM).

The amount of change in the Al composition of the p-type longitudinal conductive layer 16 with respect to the film thickness does not have to be uniform. For the purpose of increasing light confinement or the like, the amount of change in the Al composition may decrease asymptotically or stepwise as it approaches the light emitting layer 14.

The p-type longitudinal conductive layer 16 does not intentionally mix impurities such as H, Mg, Be, Zn, Si, and B in the region close to the p-side waveguide layer 15 for the purpose of suppressing the diffusion of impurities. Is preferable, that is, it is preferably in an undoped state. Here, the word "undoped" means that the above is not intentionally supplied as an element in the process of forming the target layer. However, this does not apply when elements derived from raw materials and manufacturing equipment are ^{mixed in a range of, for example, 10 16} cm ^{-3 or less.} The amount of elements mixed can be specified by a method such as secondary electron ion mass spectrometry. "Undope" in the present application has essentially the same meaning. Further, the region of the p-type longitudinal conductive layer 16 in the undoped state includes at least the boundary with the p-side waveguide layer 15. However, the size of the area is not limited. For example, all regions of the p-type longitudinal conductive layer 16 may be in an undoped state. As another example, 50% of the p-type longitudinal conductive layer 16 that is closer to the p-side waveguide layer 15 than the p-type transverse conductive layer 17 may be in an undoped state. Further, as another example, in the p-type longitudinal conductive layer 16, about 10% of the region close to the p-side waveguide layer 15 may be in an undoped state.

For the purpose of improving conductivity between the p-type longitudinal conductive layer 16 and the p-side waveguide layer 15 and / or for forming the p-type transverse conductive layer 17 and the p-type contact layer 18 with complete strain. _{, An intermediate layer made of Al v} Ga _1-v N (0 <v ≦ 1.0) can be provided so that the Al composition v increases in the direction away from the upper surface of the substrate 11. The intermediate layer between the p-type longitudinal conductive layer 16 and the p-side waveguide layer 15 may be a mixed crystal having no bandgap that does not absorb light having a desired emission wavelength, and is preferably undoped with a film thickness of 50 nm or less. It may be.

The resistivity of the p-type longitudinal conductive layer 16 is, for example, a resistance value Rs'= Rs-Rn obtained by subtracting the resistance value Rn contributed by the n-type clad layer 12 from the series resistance value Rs of the laser diode 1 of the embodiment of the present application. It can be calculated using. The longitudinal resistivity of the p-type clad layer 20 is calculated as Rs'× A / T from the area A of the p-type electrode in contact with the p-type contact layer 18 of the laser diode 1 and the film thickness T of the p-type clad layer 20. .. The resistance value R of the n-type clad layer 12 can be determined by, for example, a transmission line measurement method and a non-contact resistance measurement using an eddy current.

(P-type transverse conductive layer)
The p-type transverse conductive layer 17 may have a thin film thickness so as to facilitate quantum transmission of carriers penetrating the p-type transverse conductive layer 17. For example, it is 20 nm or less, or 10 nm or less, preferably 5 nm or less.

Impurities such as H, Mg, Be, Zn, Si, and B can be intentionally mixed into the p-type transverse conductive layer 17 for the purpose of controlling the longitudinal resistivity of the p-type transverse conductive layer 17. The amount of impurities to be mixed depends on the amount of the net electric field attracted to the surface and the inside of the p-type transverse conductive layer 17, and as an example, 1 × 10 ¹⁹ cm ^-3 or more and 5 × 10 ²¹ cm ^-3 . It can be taken.

The Al composition of the p-type transverse conductive layer 17 at the interface with the p-type contact layer 18 is preferably in the range of 0.9 or more and 1.0 or less, and is preferably completely strained with respect to the substrate 11. In such a p-type transverse conductive layer 17, the net internal electric field accumulated on the surface of the p-type transverse conductive layer 17 and the inside near the surface becomes negative, and holes are attracted to increase the lateral conductivity. It has the effect of improving. Further, it is preferable that the distribution of the Al composition of the p-type transverse conductive layer 17 is limited to 5% or less in the region of the laser diode 1. Such a p-type transverse conductive layer 17 can realize higher transverse conductivity because carrier scattering due to the distribution of the composition is reduced.

_{The p-type transverse conductive layer 17 holds Al y} Ga _1-y N having an Al composition y smaller than the Al composition t of the final p-type transverse conductive layer 17 in a high temperature state where the Al raw material and the Ga raw material are not supplied. by, the Al composition t is formed such that a _{0.9 ≦ t ≦ 1.0 Al t Ga} 1-t N are preferred.

(N-type clad layer)
The n-type clad layer 12 includes a nitride semiconductor layer having n-type conductivity. The n-type clad layer 12 is preferably formed with complete strain on the substrate 11, and for the purpose of forming the n-type clad layer 12 with complete strain on the substrate 11, the n-type clad layer 12 and the substrate 11 There may be an intermediate layer in which the Al composition changes uniformly at the interface between the two, and the Al composition and the film thickness of the n-type clad layer 12 may be restricted. The Al composition of the n-type clad layer 12 may be limited for the purpose of obtaining low contact resistance (for example, 1 × 10 ^-6 to 1 × 10 ^-4 Ωcm ^{2) with respect to a suitable electrode.} As an embodiment of the n-type clad layer 12 in consideration of the above restrictions, the Al composition may be 0.6 to 0.8 and the thickness may be 0.3 to 0.5 μm.

The n-type clad layer 12 may be an inclined layer that increases the Al composition in the direction away from the substrate 11 for the purpose of controlling its longitudinal conductivity. In this case, the same embodiment can be taken as the above limitation on the Al composition as the Al composition obtained by averaging the Al composition at each film thickness direction position in the n-type clad layer 12 with the film thickness of the n-type clad layer 12. ..

In addition to N, the n-type clad layer 12 contains Group V elements other than N such as P, As, and Sb, H, C, O, F, Mg, Ge, and Si for the purpose of controlling its longitudinal conductivity. Impurities such as these may be mixed, but this is not the case as an element. The appropriate amount of impurities mixed is limited by the Al composition of the n-type clad layer 12. It is preferably 1 × 10 ¹⁹ to 1 × 10 ²⁰ cm ^-3 .

(Wife path layer)
The waveguide layer is a nitride semiconductor containing Al and Ga having a band gap that does not absorb light of a desired emission wavelength, and increases the electric field intensity distribution of light resident in the device and the overlap of the light emitting layer 14. The Al composition and film thickness can be limited for the purpose. For example, the Al composition is preferably 0.55 to 0.65 and the film thickness is 70 to 150 nm with respect to the light emitting layer 14 having a diameter of 260 nm to 280 nm.

The waveguide layer is a portion on the n-type clad layer 12 side (n-side waveguide layer 13) with respect to the light emitting layer 14 and a p-type clad layer 20 side (p-side waveguide layer 15) with respect to the light emitting layer 14. It may consist of two layers. That is, the n-side waveguide layer 13 can be formed between the n-type clad layer 12 and the light emitting layer 14. The p-side waveguide layer 15 can be formed between the p-type clad layer 20 and the light emitting layer 14. The film thickness ratio of the n-side waveguide layer 13 and the p-side waveguide layer 15 can be variously determined depending on the light confinement in the light emitting layer 14 and the Al composition of the n-type clad layer 12 and the p-type clad layer 20. The Al composition of the n-side waveguide layer 13 and the p-side waveguide layer 15 is preferably uniform in the film thickness direction, but this is not the case. It is possible that the Al composition of the p-side waveguide layer 15 is higher than the Al composition of the n-side waveguide layer 13 in order to avoid light absorption into the metal present on the p-type contact. For the same purpose, the film thickness of the p-side waveguide layer 15 may be thicker than the film thickness of the n-side waveguide layer 13. The n-side waveguide layer 13 includes V group elements other than N such as P, As, Sb, H, C, O, F, Mg in addition to N for the purpose of obtaining the same conduction type as the n-type clad layer 12. Impurities such as Si and Si may be mixed, but this is not the case as an element.

_{Al w} Ga _1-w such that the Al composition w decreases in the direction away from the upper surface of the substrate 11 for the purpose of improving the longitudinal conductivity between the n-side waveguide layer 13 and the n-type clad layer 12. A composition gradient layer composed of N can be provided. The intermediate layer between the n-side waveguide layer 13 and the n-type clad layer 12 preferably has a film thickness of 10 nm or less.

_{From Al x} Ga _1-x N such that the Al composition x increases in the direction away from the upper surface of the substrate 11 for the purpose of improving the longitudinal conductivity between the p-side waveguide layer 15 and the p-type clad layer 20. A composition gradient layer consisting of the above can be provided. The intermediate layer between the p-side waveguide layer 15 and the p-type clad layer 20 is preferably thin enough (for example, 30 nm or less, or 20 nm or less) so as not to deteriorate the light confinement in the waveguide layer.

Inside the p-side waveguide layer 15, between the p-side waveguide layer 15 and the light emitting layer 14, or between the p-side waveguide layer 15 and the p-type longitudinal conduction layer 16, or a part of the p-side waveguide layer 15. , An electron block layer having a band gap larger than that of the p-side waveguide layer 15 can be provided. The electron block layer can be 30 nm or less, or 20 nm or less, more preferably 15 nm or less so that holes can easily penetrate the electron block layer.

(Light emitting layer)
The light emitting layer 14 may be a single or a plurality of quantum wells directly or indirectly sandwiched between an n-type clad layer and a p-type clad layer. The number of quantum wells can be 3 or 2 or 1 depending on the longitudinal conductivity of the n-type clad and the p-type clad.

For the purpose of reducing the influence of crystal defects in the light emitting layer 14, a part or all of the light emitting layer 14 may be intentionally mixed with ^{elements such as Si, Sb, and P in an amount of 1 × 10 15} cm ^{-3 or more.}

(P-type contact layer)
The p-type contact layer 18 may be a nitride semiconductor formed on the p-type clad layer 20 and containing GaN. In addition to N, group V elements other than N such as P, As, and Sb, and impurities such as H, B, C, O, F, Mg, Ge, and Si are mixed in for the purpose of reducing contact resistance. It may be, but it is not limited to this as an element. For example, Mg can be mixed in ^{from 1 × 10 20} to 1 × 10 ²² cm ^-3.

The electrical contact with the laser diode 1 can be performed by an electrode portion arranged on the p-type contact layer 18 and by an electrode portion arranged so as to contact the n-type clad layer 12. For example, an electrode portion may be arranged on the back side of the substrate 11, or various upper layers of the laser diode 1 may be provided so that the n-type clad layer 12 is exposed in one or more regions near the p-type contact layer 18. It can be achieved by, for example, removing by chemical etching or dry etching and arranging an electrode on the exposed n-type clad layer 12.

(Electrode part)
The electrode portion arranged on the p-type contact layer 18 may be a metal containing one or more elements of Ni, Pt, Au, and Pd.

The electrode portion arranged on the back surface of the n-type clad layer 12 or the substrate 11 may be a metal containing one or more elements of V, Al, Au, Ti, Ni, and Mo. The metal layer in contact with the substrate 11 is preferably a metal containing V or Ti.

[Example 1]
As Example 1, an optical device including the following nitride semiconductor laser diode was manufactured. MOCVD is used to fabricate laser diodes, and trimethylgallium (TMG), triethylgallium (TEG), trimethylaluminum (TMA), ammonia (NH ₃ ), silane (SiH ₄ ), and bis (cyclopentadienyl) are used as raw materials. ) Magnesium (Cp ₂ Mg) and the like were used. _{By reacting TMA and NH 3} in an H ₂ atmosphere at 1200 ° C. on a plane inclined by 0.1 ° to 0.3 ° with respect to the (0001) plane of the single crystal AlN substrate 11, 0.2 μm. A homoepitaxial growth layer made of AlN was formed.

The AlGaN intermediate layer and the n-type clad layer 12 are laminated in this order by reacting _{TMA, TMG, NH 3} and SiH ₄ in an H ₂ atmosphere at 1055 ° C. on a homoepitaxial growth layer made of AlN. rice field. The AlGaN intermediate layer has a film thickness of 30 nm, and the Al composition uniformly decreases from 1.0 to 0.71 in the direction away from the upper surface of the substrate 11. The n-type clad layer 12 is a layer of _{Al 0.7} Ga _0.3 N having a film thickness of 0.35 μm and doped with ^{5 × 10 19} cm ^{-3 Si.} The AlN homoepitaxial growth layer, the intermediate layer and the n-type clad layer 12 were formed so as to be completely strained with respect to the substrate 11 by being formed at a rate of 0.3 to 0.6 μm / h.

on the n-type cladding layer 12, TMA, TMG, by reacting NH ₃ in a _{H 2} atmosphere of 1055 ° C., the n-side waveguide layer 13, a light-emitting layer 14, but are stacked in this order. The n-side waveguide layer 13 has a film thickness of 60 nm and is composed of _{Al 0.63} Ga _{0.37 N.} The light emitting layer 14 is composed of a multilayer quantum well layer having a total film thickness of 30 nm. During the formation of a portion of the barrier layer of the light emitting layer 14, 3 × 10 ¹⁹ cm ^-3 Si was doped by _{introducing SiH 4 as a raw material.} Further, a p-side waveguide layer 15 having a film thickness of 50 nm and made of Al _0.62 Ga _{0.38 N was formed on the light emitting layer 14.} The n-side waveguide layer 13, the light emitting layer 14, and the p-side waveguide layer 15 were formed at a speed of 0.4 μm / h so as to be completely strained with respect to the substrate 11.

_{By reacting TMA, TMG, and NH 3} on the p-side waveguide layer 15 in _{an H 2} atmosphere at 1055 ° C., the film has a film thickness of 20 nm, and the Al composition is 0 in the direction away from the upper surface of the substrate 11. It had an AlGaN intermediate layer that uniformly increased from .62 to 1.0 and a film thickness of 0.32 μm, and the Al composition decreased from 1.0 to 0.3 in the direction away from the upper surface of the substrate 11. The p-type longitudinal conductive layer 16 and the p-type longitudinal conductive layer 16 were laminated in this order. The p-type longitudinal conductive layer 16 was formed so as to be completely strained with respect to the substrate 11 by being formed at a speed of 0.3 to 0.5 μm / h. Further, the p-type longitudinal conductive layer 16 is in an undoped state in all regions.

On the p-type longitudinal conductive layer 16, a p-type transverse conductive layer 17 _{having a film thickness of 3 nm and made of Al 0.45} Ga _{0.05 N was formed.} Further, by stopping the supply of TMA and TMG raw materials at 1055 ° C. and _{holding (annealing) the state in which only Cp 2} Mg is supplied for 10 minutes or more, the p-type transverse conductive layer 17 is 1 × 10 ^20. It was transformed into an _{Al 0.97} Ga _0.03 N layer doped with cm- ^{3 Mg.} By altering the quality by such a procedure, the p-type transverse conductive layer 17 was formed so as to be completely strained with respect to the substrate 11. Here, the p-type longitudinal conductive layer 16 and the p-type transverse conductive layer together form the p-type clad layer 20.

When the XRD measurement of the (002) plane was performed, the dispersion of the Al composition of the p-type transverse conductive layer 17 was 3.5% in the region range corresponding to the region of the laser diode 1. When the atomic arrangement of the p-type transverse conductive layer 17 was confirmed by a transmission image in the <11-20> direction of a transmission electron microscope at a plurality of positions, it was completely distorted with respect to the substrate 11.

_{By reacting TMG, Cp 2} Mg, and NH ₃ on the p-type transverse conductive layer 17 in _{an H 2} atmosphere at 940 ° C., the film thickness is 20 nm and doped with ^{5 × 10 20} cm ^{-3 Mg.} A p-type contact layer 18 made of GaN was formed.

The laser diode 1 of the fabricated nitride semiconductor as described above, N ₂ atmosphere, by performing annealing for 10 minutes or more at 700 ° C., and further reduce the resistance of the p-type layer.

By performing dry etching with a gas containing Cl ₂ , the n-type clad layer 12 was exposed in a rectangular region parallel to the <1-100> direction and long in the <1-100> direction. Further, a passivation layer containing _{SiO 2} was formed on the surface of the laser diode 1 of the nitride semiconductor.

A plurality of electrode metal regions (p-type electrodes) including rectangular Ni or Au parallel to the <1-100> direction and long in the <1-100> direction were formed on the p-type contact layer 18. Further, in the region where the n-type clad layer 12 is exposed, an electrode metal (n) made of a rectangular V, Al, Ni, Ti or Au parallel to the <1-100> direction and long in the <1-100> direction. A plurality of mold electrodes) were formed.

Next, using the 500 nm SiO ₂ deposited by the PECVD method as a mask, using an ICP-RIE apparatus (CE-S) manufactured by ULVAC, in a Cl ₂ and B _{Cl 3} atmosphere, from the p-type contact layer in the depth direction. 1.2 μm dry etching was performed. Dry etching was performed along the (1-100) plane of the AlGaN layer to form a mesa structure having a length of 400 μm and a width of 100 μm including the resonator end face. At this time, the resonator end face had an inclination of 60 degrees with respect to the (0001) plane of the AlN substrate (FIG. 5 (a)).

Then, it was immersed in a TMAH (tetramethylammonium hydroxide) solution (concentration 25%) at 80 ° C. for 7.5 minutes, and wet etching was performed. As a result, a mirror end face substantially perpendicular (91.5 degrees) to the (0001) plane of the AlN substrate was formed (FIG. 5 (b)).

Subsequently, by the atomic layer deposition method using an ALD device (Fiji G2) manufactured by Veeco / CNT, a light reflecting layer composed of a laminated film of _{hafnium oxide (HfO 2} ) and aluminum oxide (Al ₂ O _{3) is formed.} Been formed. The laminated film had a structure in which hafnium oxide at 41 nm and aluminum oxide at 22 nm were alternately deposited for 4.5 cycles from the side surface side of the mesa structure.

Here, prior to this embodiment, a light reflecting layer having the same structure was formed on the sapphire substrate, and the reflectance was measured. As shown in FIG. 6, the maximum reflectance was about 80% at a wavelength of 275 nm. It was confirmed that it was consistent with the theoretical value.

FIG. 7 is a cross-sectional TEM image including the resonator end face of the laser diode. It can be seen that the light reflecting layer obtained by the method of this example uniformly covers the side surface of the mesa structure. That is, it is understood that it is possible to form a uniform light reflecting layer on the side surface of the mesa structure including the resonator end face by On-Wafer.

FIG. 8 shows the end face emission intensity (IL) characteristics with respect to the current-voltage (IV) and forward pulse current of the manufactured laser diode. The end face emission intensity was detected by a photomultiplier tube. A non-linear rising edge of the end face emission intensity occurs when the forward current exceeds 0.3 A, which corresponds to ^{the current density of 20 kA / cm 2} assuming that the current path is limited to the region directly under the p electrode. It was observed that the LD whose mirror end face was formed by using the etching method and the ALD method oscillated under a room temperature pulse current. A sharp spectral peak appeared at a wavelength of 278.9 nm. The inset of FIG. 8 is a spectrum measured by a spectroscope when the forward current is 0.37 A. The drive voltage at the threshold current was 13.8 V.

[Example 2]
In the etching process in Example 1, a mesa structure of a photodetector 2 was formed in addition to the laser diode 1. FIG. 9 is a schematic view of one repeating unit of the optical device including the laser diode 1 and the photodetector 2 in the second embodiment. A plurality of laser diodes 1 and photodetectors 2 were manufactured using the structure of FIG. 9 as a repeating unit.

In the figure, 61 is a p-type electrode. Reference numeral 62 denotes an n-type electrode. The structure of the semiconductor laminated portion of the laser diode 1 and the photodetector 2 is the same. Here, the code of the structure on the photodetector side is the one corresponding to the laser diode 1 with "'". Further, although not shown, the same light reflecting layer as in Example 1 was formed on the entire surface and all the side surfaces including the resonator end surface except for the region for contacting the p-type electrode and the n-type electrode with the outside. ..

The length L1 of the long side of the mesa structure of the laser diode 1 was set to 400 μm. The length W1 of the short side was set to 100 μm. The length L2 of the mesa structure of the photodetector 2 was set to 50 μm. The distance L3 between the laser diode 1 and the photodetector 2 was 16 μm. The side surface of the laser diode 1 on the resonator end face side was etched until the substrate 11 (11') was exposed in order to mitigate the influence of bottom surface reflection.

Although the present invention has been described above using the embodiments, the technical scope of the present invention is not limited to the scope described in the above embodiments. It will be apparent to those skilled in the art that various changes or improvements can be made to the above embodiments. It is clear from the description of the claims that such modified or improved forms may also be included in the technical scope of the present invention.

The execution order of each process such as operation, procedure, step, and step in the device, system, program, and method shown in the claims, the specification, and the drawing is particularly "before" and "prior to". It should be noted that it can be realized in any order unless the output of the previous process is used in the subsequent process. Even if the scope of claims, the specification, and the operation flow in the drawings are explained using "first", "next", etc. for convenience, it means that it is essential to carry out in this order. It's not a thing.

1 Laser diode 2 Photodetector 11 Substrate 12 n-type clad layer 13 n-side waveguide layer 14 Light-emitting layer 15 p-side waveguide layer 16 p-type longitudinal conduction layer 17 p-type transverse conduction layer 18 p-type contact layer 20 p-type cladding Layer 30 Semiconductor laminated part 40 Mesa structure 41 Resonator end face 50 Optical reflection layer 51 Optical reflection layer 61 p-type electrode 62 n-type electrode

Claims (30)

An n-type clad layer containing an n-type conductive nitride semiconductor layer formed on a substrate, and an n-type clad layer.
A light emitting layer containing one or more quantum wells formed on the n-type clad layer, and
A p-type clad layer including a p-type conductive nitride semiconductor layer formed on the light emitting layer and a semiconductor laminated portion having the p-type clad layer are etched to form a mesa structure having a resonator end face and a laser diode. And the etching process to form
A reflective layer forming step of forming a light reflecting layer so as to cover all the side surfaces of the mesa structure,
A method of manufacturing an optical device. Further comprising a photodetector forming step of forming a photodetector having a mesa structure capable of receiving and detecting the light emitted from the end face of the resonator.
The method for manufacturing an optical device according to claim 1, wherein in the reflective layer forming step, the light reflecting layer is also formed on all sides of the mesa structure of the photodetector. The method for manufacturing an optical device according to claim 2, wherein the photodetector forming step is included in the etching step. The method for manufacturing an optical device according to claim 2 or 3, wherein the laser diode and the photodetector are formed adjacent to each other. The invention according to any one of claims 2 to 4, wherein the substrate is wafer-shaped, and a plurality of mesa structures of the laser diode and a plurality of mesa structures of the photodetector are formed on the wafer-shaped substrate. Manufacturing method of optical device. The method for manufacturing an optical device according to any one of claims 1 to 5, wherein the method for forming the light reflecting layer is an atomic layer deposition method. The etching process has dry etching and wet etching in this order.
The substrate is an AlN substrate, and the substrate is an AlN substrate.
The method for manufacturing an optical device according to any one of claims 1 to 6, wherein the etching solution for wet etching contains tetramethylammonium hydroxide. A dicing step is further provided after the reflective layer forming step.
The method for manufacturing an optical device according to any one of claims 1 to 7, wherein in the dicing step, a laser diode having a mesa structure having a resonator end face is fragmented. Between the etching step and the reflection layer forming step, an electrode portion forming step of forming a p electrode portion electrically connected to the p-type clad layer of the laser diode, and an electrode portion forming step.
The method for manufacturing an optical device according to claim 1, further comprising an insulating layer forming step of forming an insulating layer so as to cover the p-electrode portion. With the board
An n-type clad layer formed on the substrate and containing a nitride semiconductor layer having n-type conductivity, and an n-type clad layer.
A light emitting layer formed on the n-type clad layer and containing one or more quantum wells,
It has a p-type clad layer formed on the light emitting layer and including a nitride semiconductor layer having p-type conductivity.
At least a part of the n-type clad layer, the light emitting layer, and the p-type clad layer have a mesa structure including a resonator end face.
A laser diode whose entire side surface of the mesa structure is covered with a light reflecting layer,
An optical device equipped with. A photodetector having a mesa structure, which is formed on the substrate and receives and detects light emitted from the laser diode, is further provided.
The optical device according to claim 10, wherein the side surface of the mesa structure of the photodetector is covered with the light reflecting layer. The optical device according to claim 11, wherein the light receiving surface of the photodetector is arranged at a position facing the main light emitting surface of the laser diode. The optical device according to any one of claims 10 to 12, which has a plurality of the laser diodes. An electrode portion electrically connected to the p-type clad layer and
The optical device according to any one of claims 10 to 13, further comprising an insulating layer arranged between the light reflecting layer and the electrode portion. The optical device according to claim 11 or 12, which has a plurality of the photodetectors. The optical device according to any one of claims 10 to 15, wherein the substrate is in the form of a wafer. The p-type clad layer contains Al _s Ga _1-s N (0.3 ≦ s ≦ 1), has a composition gradient in which the Al composition s decreases as the distance from the substrate increases, and the film thickness is less than 0.5 μm. The p-type longitudinal conductive layer and
Al _t Ga having a p-type lateral conduction layer containing _1-t N a (0 <t ≦ 1), an optical device according to any one of claims 10 16. An n-side waveguide layer formed between the n-type clad layer and the light emitting layer to confine light in the light emitting layer,
The optical device according to claim 17, further comprising a p-side waveguide layer formed between the p-type clad layer and the light emitting layer and confining light in the light emitting layer. A composition formed between the p-type longitudinal conductive layer and the p-side waveguide layer, containing Al _v Ga _1-v N (0 <v ≦ 1), and the Al composition v increases as the distance from the substrate increases. The optical device according to claim 18, comprising an intermediate layer having an inclination. The optical device according to claim 18 or 19, wherein the p-type longitudinal conductive layer is undoped in a region including an interface with the p-side waveguide layer. The optical device according to any one of claims 17 to 20, wherein the p-type longitudinal conductive layer has a film thickness of 250 nm or more and 450 nm or less. The optics according to any one of claims 17 to 21, wherein the p-type transverse conductive layer has an Al composition t larger than the minimum value of the Al composition s on an adjacent surface to the p-type longitudinal conductive layer. Device. The optical device according to any one of claims 17 to 22, wherein the p-type longitudinal conductive layer and the p-type transverse conductive layer are completely strained with respect to the substrate. The optical device according to any one of claims 10 to 23, wherein the emission wavelength of the light emitting layer is 210 nm or more and 300 nm or less. The optical device according to any one of claims 10 to 24, wherein the light reflecting layer is a dielectric laminated film. The optical device according to any one of claims 10 to 25, wherein the light reflecting layer is at least one oxide selected from the group consisting of aluminum, hafnium, silicon, titanium, zirconium, lead, and gallium. The optical device according to claim 25, wherein the dielectric laminated film is a laminated film of a hafnium oxide film and an aluminum oxide film having one cycle or more. The substrate is an AlN substrate, and the substrate is an AlN substrate.
The optical device according to any one of claims 10 to 27, wherein the surface of the light reflecting layer in contact with the end surface of the resonator is at an angle of 85 degrees or more and 95 degrees or less with respect to the (0001) surface of the AlN substrate. 10. Optical device. The optical device according to claim 10, further comprising the plurality of laser diodes.

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