JP2023039519A - Semiconductor light-emitting element and method of manufacturing semiconductor light-emitting element - Google Patents

Abstract

To provide a semiconductor light-emitting element capable of increasing a coefficient of coupling between waveguide light and a high-order diffraction grating.SOLUTION: A semiconductor light-emitting element comprises a first conductivity type semiconductor layer, an active layer provided on the first conductivity type semiconductor layer, a second conductivity type semiconductor layer provided on the active layer, and a plurality of high-order diffraction gratings which are provided where they can be coupled to waveguide light guided in the active layer, and the greatest common divisors of which are different in order of 1 from one another, wherein the high-order diffraction gratings each comprise a region where at least one of a projection part and the center of the projection part, a recessed part and the center of the recessed part, and the centers of the projection part and recessed part are coincident with each other.SELECTED DRAWING: Figure 1

Description

The present invention relates to a semiconductor light emitting device and a method for manufacturing a semiconductor light emitting device.

In order to stabilize the oscillation wavelength of a semiconductor laser, a DFB (Distributed Feedback) structure may be used.
Patent Document 1 discloses a semiconductor device including a nitride semiconductor laminated structure having an optical waveguide formed between a pair of end faces forming a resonator, and a diffraction grating section that couples with guided light propagating through the optical waveguide. A laser device is disclosed. Further, it is described that the same diffraction grating section is composed of a plurality of high-order diffraction gratings having different orders with respect to guided light.

JP 2018-37495 A

However, with the configuration disclosed in Patent Literature 1, a desired coupling coefficient between the guided light and the high-order diffraction grating may not be obtained depending on the relative positional relationship and duty between the high-order diffraction gratings.

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide a semiconductor light-emitting device and a method of manufacturing a semiconductor light-emitting device capable of improving the coupling coefficient between guided light and high-order diffraction gratings.

According to a semiconductor light emitting device according to an aspect of the present invention, a first conductivity type semiconductor layer, an active layer provided on the first conductivity type semiconductor layer, and a second conductivity type semiconductor layer provided on the active layer a semiconductor layer; and a high-order diffraction grating provided at a position capable of coupling with guided light guided through the active layer, wherein the high-order diffraction grating has a greatest common divisor of 1 and a plurality of high-order diffraction gratings having different orders. It is a diffraction grating of order and has a region where at least one of centers of protrusions and protrusions, centers of recesses and recesses, and centers of protrusions and recesses coincides with each other.

As a result, the period of the diffraction grating can be increased while matching the diffraction condition of the diffraction grating with the waveguide direction of the guided light guided through the active layer. Therefore, it is possible to realize a blue-violet laser diode that stabilizes the oscillation wavelength while suppressing a decrease in oscillation efficiency. Furthermore, it is possible to alleviate the difficulty of manufacturing associated with miniaturization of the diffraction grating. In addition, it is possible to increase the difference between the energy densities of the electric fields of the standing waves formed by the respective high-order diffraction gratings, thereby increasing the stop band width. Therefore, the side mode suppression ratio (SMSR: Side Mode Suppression Ratio) of the high-order diffraction grating can be increased, and the coupling coefficient between the guided light and the high-order diffraction grating can be increased.

Further, according to the semiconductor light emitting device according to an aspect of the present invention, the second conductivity type semiconductor layer includes a ridge extending in the resonator direction, and the plurality of high-order diffraction gratings extend along the resonator direction. provided on both sides of the ridge.

This makes it possible to form the diffraction grating at the same time as the ridge forming process, thereby simplifying the manufacturing process. Furthermore, by providing diffraction gratings on both sides of the ridge, it is possible to efficiently confine the waveguided light that propagates through the active layer. Therefore, it is possible to stabilize the oscillation wavelength while suppressing a decrease in luminous efficiency.

Further, according to the semiconductor light emitting device according to one aspect of the present invention, the plurality of high-order diffraction gratings are arranged with different high-order diffraction gratings on both sides of the ridge.

As a result, high-order diffraction gratings of different orders can be collectively formed, and the oscillation wavelength can be stabilized while suppressing an increase in the number of steps.

Further, according to the semiconductor light emitting device according to one aspect of the present invention, the plurality of high-order diffraction gratings are arranged on the first conductivity type semiconductor layer side and/or the second conductivity type semiconductor layer side of the active layer. is provided.

As a result, the distance between the high-order diffraction grating and the active layer can be reduced, and the coupling coefficient between the guided light and the high-order diffraction grating can be increased.

Further, according to the semiconductor light emitting device according to an aspect of the present invention, each of the plurality of high-order diffraction gratings is located in one of the active layers by a distance equal to or greater than the period of each of the high-order diffraction gratings in the resonator direction. It is set back from the end face.

As a result, while providing a region where at least one of the convex portions and the centers of the convex portions of the plurality of high-order diffraction gratings, the centers of the concave portions and the centers of the concave portions, and the centers of the convex portions and the concave portions are aligned, a plurality of high-order diffraction gratings are provided. Fabrication of the grid can be facilitated.

Further, according to the semiconductor light emitting device according to one aspect of the present invention, the plurality of high-order diffraction gratings are arranged such that their coupling coefficients are equal to each other.

Thereby, even when a plurality of high-order diffraction gratings are used to form the DFB structure, it is possible to suppress a decrease in the coupling coefficient between the guided light and the high-order diffraction gratings.

Further, according to the semiconductor light emitting device according to one aspect of the present invention, the duties of the plurality of high-order diffraction gratings are different from each other.

As a result, by changing only the uneven pattern without changing the order of the high-order diffraction grating, it is possible to finely adjust the coupling coefficient between the guided light and the high-order diffraction grating, thereby maximizing the coupling coefficient. It is possible to further stabilize the oscillation wavelength.

Moreover, according to the semiconductor light emitting device according to an aspect of the present invention, the high-order diffraction grating includes a phase shift portion.

As a result, the phase of the standing wave can be controlled by using the phase shift portion as a reference even if the characteristics vary depending on the cleavage position. Luminous efficiency can be improved.

Further, according to the semiconductor light emitting device according to an aspect of the present invention, the length of the phase shift portion is such that N is a natural number (positive integer), neff is the effective refractive index of the high-order diffraction grating, and λ is the Bragg wavelength. Then, the length of the phase shift portion=λ/(4·neff)·(2N−1).

Accordingly, the phase shift portion can be arranged at a position where the peaks and the edges of the peaks, the edges of the valleys, or the edges of the peaks and the valleys of the standing wave formed by the diffraction grating match, thereby improving the SMSR. can.

Further, according to the semiconductor light emitting device according to one aspect of the present invention, the center of the phase shift portion is between 60% and 80% of the distance from the facet with the lower reflectance to the other facet in the active layer. located at a distance of

This makes it possible to improve the SMSR even when the reflectances of the two facets used in the resonator are different from each other. As a result, the energy input to the main emission wavelength can be used efficiently, the threshold value can be lowered during laser oscillation, and the output can be improved while stabilizing the oscillation wavelength.

Further, according to the semiconductor light emitting device according to an aspect of the present invention, the centers of the phase shift portions are equidistant from the end surface with the lower reflectance among the plurality of high-order diffraction gratings.

This makes it possible to optimize the arrangement position of the phase shifter and improve the SMSR.

Further, according to the semiconductor light emitting device according to an aspect of the present invention, the high-order diffraction grating has a relationship of 1≦κ·L≦3, where κ is the coupling coefficient and L is the cavity length of the active layer. satisfy the formula.

As a result, it is possible to stabilize the oscillation wavelength while achieving a lower threshold value and a higher efficiency of the semiconductor light emitting device.

Further, according to the semiconductor light emitting device according to one aspect of the present invention, the reflectance of the first facet of the active layer is set to 2% or less, and the reflectance of the second facet of the active layer is set to 90% or more.

As a result, it is possible to reduce the amount of light leaking to the rear of the resonator while stabilizing the oscillation wavelength, thereby suppressing a decrease in luminous efficiency.

Further, according to the semiconductor light emitting device according to one aspect of the present invention, the plurality of high-order diffraction gratings includes a second-order diffraction grating and a third-order diffraction grating, and the duty of the second-order diffraction grating is 0.3. The duty of the third-order diffraction grating is 0.5, and the grating shift between the second-order diffraction grating and the third-order diffraction grating is zero.

In this way, by optimizing the pattern and arrangement position of the high-order diffraction grating, it is possible to maximize the coupling coefficient between the guided light and the high-order diffraction grating. Therefore, it is possible to stabilize the oscillation wavelength while suppressing an increase in the number of steps, and to realize a blue-violet laser diode while alleviating the difficulty of manufacturing due to miniaturization of the diffraction grating. can.

Further, according to the semiconductor light emitting device according to one aspect of the present invention, the plurality of high-order diffraction gratings includes a third-order diffraction grating and a fifth-order diffraction grating, and the duty of the third-order diffraction grating is 0.5. the duty of the fifth-order diffraction grating is 0.5 and the grating shift between the third-order diffraction grating and the fifth-order diffraction grating is 0.5; or the duty of the third-order diffraction grating is 0.5; the duty of the fifth-order diffraction grating is 0.1 and the grating shift between the third-order diffraction grating and the fifth-order diffraction grating is 0.5; or the duty of the third-order diffraction grating is 0.5; The duty of the fifth-order diffraction grating is 0.3, and the grating shift between the third-order diffraction grating and the fifth-order diffraction grating is zero.

As a result, it is possible to increase the resolution limit by more than three times compared to the case of using a first-order diffraction grating. The coupling coefficient between the order gratings can be maximized. Therefore, it is possible to stabilize the oscillation wavelength while suppressing an increase in the number of steps, and to realize a blue-violet laser diode while alleviating the difficulty of manufacturing due to miniaturization of the diffraction grating. can.

Further, according to the semiconductor light emitting device according to one aspect of the present invention, the first conductivity type semiconductor layer, the active layer, and the second conductivity type semiconductor layer are made of a nitride semiconductor.

This makes it possible to realize a semiconductor laser diode having an emission wavelength in the blue-violet region. With the same configuration, for example, a light source for exposure equipment in the 375 nm to 405 nm band and a light source (444 nm) that generates SHG (Second Harmonic Generation) waves of 222 nm wavelength, which is harmless to the human body and capable of sterilizing, can be realized.

Further, according to the method for manufacturing a semiconductor light emitting device according to an aspect of the present invention, the step of sequentially stacking the active layer and the second conductivity type semiconductor layer on the first conductivity type semiconductor layer, the greatest common divisor being 1, a step B of forming a ridge on both sides of which high-order diffraction gratings of different orders are provided on the second conductivity type semiconductor layer; The high-order diffraction grating is formed to have areas where at least one of the center, the center of the recesses and the center of the recesses, and the center of the protrusions and the recesses coincides with each other.

Thereby, diffraction gratings can be formed on both sides of the ridge simultaneously with the formation of the ridge. Therefore, a refractive index guided semiconductor laser having a DFB structure can be formed while suppressing an increase in the number of steps.

In one aspect of the present invention, the coupling coefficient between guided light and higher-order diffraction gratings can be increased.

1 is a perspective view showing the configuration of a semiconductor light emitting device according to a first embodiment; FIG. (a) is a plan view showing the configuration of the ridge and diffraction grating of the semiconductor light emitting device according to the first embodiment; 1 is a cross-sectional view cut along . (a) shows the refractive index distribution with respect to the position in the optical waveguide direction of the diffraction grating EA2 formed on the right side of FIG. (c) corresponds to (a), and (d) is the phase and amplitude of the standing wave formed in the resonator with respect to the position in the waveguide direction of the semiconductor light emitting device according to the first embodiment corresponding to (b). is a diagram showing the relationship of FIG. 3 is a relational diagram between a refractive index and a position in a waveguiding direction, exemplifying a second-order diffraction grating and a third-order diffraction grating shown in FIG. . FIG. 5 is a diagram showing the relationship between the intergrating shift and the stop band width when the duty of the diffraction grating of the semiconductor light emitting device according to the first embodiment is changed. It is a figure which shows the maximization method of the stop-band width of the semiconductor light-emitting device which concerns on 1st Embodiment. (a1) and (b1) are plan views showing an example of a method for manufacturing a semiconductor light emitting device according to the second embodiment; ) is an A1-A1 cross-sectional view. (a1) and (b1) are plan views showing an example of a method for manufacturing a semiconductor light emitting device according to the second embodiment; ) is an A1-A1 cross-sectional view. FIG. 11 is a plan view showing the configuration of a semiconductor light emitting device according to a third embodiment; (a) and (b) are diagrams showing the refractive index distribution of the diffraction grating of the semiconductor light emitting device according to the fourth embodiment, and (c) and (d) are views formed in the resonator of the semiconductor light emitting device according to the fourth embodiment. FIG. 10 is a diagram showing the relationship between the phase and amplitude of a standing wave to be applied; FIG. 12 is a diagram showing the relationship between the intergrating shift and the stop band width when the duty of the diffraction grating of the semiconductor light emitting device according to the fourth embodiment is changed. FIG. 11 is a plan view showing the configuration of a semiconductor light emitting device according to a fifth embodiment; FIG. 11 is a plan view showing the configuration of a semiconductor light emitting device according to a sixth embodiment; FIG. 4 is a diagram showing the relationship between the height of the diffraction grating and the coupling coefficient; (a) is a cross-sectional view showing the configuration of the semiconductor light emitting device according to the seventh embodiment cut along a direction perpendicular to the resonator direction, and (b) is the configuration of the semiconductor light emitting device according to the seventh embodiment. is a cross-sectional view taken along the direction of the resonator. (a1) and (b1) are plan views showing an example of a method for manufacturing a semiconductor light emitting device according to the eighth embodiment, (a2) is a cross-sectional view cut along the cavity direction of (a1), ) is a cross-sectional view taken along the cavity direction of (b1). (a1) and (b1) are plan views showing an example of a method for manufacturing a semiconductor light emitting device according to the eighth embodiment, (a2) is a cross-sectional view cut along the cavity direction of (a1), ) is a cross-sectional view taken along the cavity direction of (b1).

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. The following embodiments do not limit the present invention, and not all combinations of features described in the embodiments are essential for the configuration of the present invention. The configuration of the embodiment can be appropriately modified or changed according to the specifications of the device to which the present invention is applied and various conditions (use conditions, use environment, etc.). The technical scope of the present invention is defined by the claims and is not limited by the following individual embodiments. In addition, the drawings used in the following description may differ from the actual structure in terms of scale, shape, etc., in order to make each configuration easier to understand.

In the following description, a nitride semiconductor laser capable of emitting blue laser light with a wavelength of 444 nm is taken as an example, but an AlGaInN semiconductor laser capable of emitting blue laser light with a wavelength of 405 nm may be used. An AlGaN-based semiconductor laser capable of emitting ultraviolet laser light having an emission wavelength of 390 nm or less may be used. Furthermore, an AlGaAs semiconductor laser capable of emitting infrared laser light in the 780 nm wavelength band, an AlGaInP semiconductor laser capable of emitting red laser light in the 650 nm wavelength band, or a communication laser in the 1.55 μm wavelength band may be used. An InGaAsP-based semiconductor laser capable of emitting laser light may be used.

1 is a perspective view showing the configuration of the semiconductor light emitting device according to the first embodiment, FIG. 2A is a plan view showing the configuration of the ridge and diffraction grating of the semiconductor light emitting device according to the first embodiment, and FIG. 4B is a cross-sectional view showing the configuration of the semiconductor light emitting device according to the first embodiment, cut along a direction perpendicular to the resonator direction; FIG. Note that FIG. 2(b) shows a configuration cut along the line X1-X1 in FIG. 2(a). 1, the end face reflection films 24 and 25 of FIG. 2(a) and the p-type nitride contact layer 21 and the electrode 22 of FIG. 2(b) are omitted from the viewpoint of clarity.

1, 2(a) and 2(b), the semiconductor laser LA includes an n-type nitride semiconductor layer E1, an active layer 15 and a p-type nitride semiconductor layer E2. The active layer 15 is laminated on the n-type nitride semiconductor layer E1. The p-type nitride semiconductor layer E2 is laminated on the active layer 15. As shown in FIG. _The nitride semiconductor can have a composition of, for example, _{InxAlyGa1 -x-yN} (0≤x≤1, 0≤y≤1, 0≤x+y≤1).

An undoped nitride guide layer 14 may be provided between the n-type nitride semiconductor layer E1 and the active layer 15 in order to suppress diffusion of impurities from the n-type nitride semiconductor layer E1 to the active layer 15 . An undoped nitride guide layer 16 may be provided between the p-type nitride semiconductor layer E2 and the active layer 15 in order to suppress diffusion of impurities from the p-type nitride semiconductor layer E2 to the active layer 15. FIG.

The n-type nitride semiconductor layer E1 includes an n-type nitride cladding layer 12 and an n-type nitride guide layer 13 . The n-type nitride cladding layer 12 and the n-type nitride guide layer 13 are sequentially laminated on the n-type nitride semiconductor substrate 11 .

The p-type nitride semiconductor layer E2 includes the p-type carrier block layer 17, the p-type nitride guide layer 18, the p-type nitride cladding layers 20 and 20A and the p-type nitride contact layer 21 (see FIG. 2(b)). Prepare. A p-type carrier block layer 17 , a p-type nitride guide layer 18 , p-type nitride cladding layers 20 and 20A and a p-type nitride contact layer 21 are sequentially laminated on the undoped nitride guide layer 16 . The p-type nitride cladding layers 20, 20A can be made of the same material.

The p-type nitride cladding layer 20A has a ridge RA, a second order diffraction grating EA2 and a third order diffraction grating EA3. The ridge RA is provided along the waveguide direction D1 of the waveguided light guided through the active layer 15, extending between the facets MA and MB of the semiconductor laser LA. At this time, the ridge RA can confine the guided light guided through the active layer 15 in the horizontal direction D2 and the vertical direction D3 of the waveguide direction D1. An etch stop layer may be provided between the p-type nitride cladding layers 20 and 20A in order to form the ridge RA, second-order diffraction grating EA2 and third-order diffraction grating EA3 in the p-type nitride cladding layer 20A.

A plurality of high-order diffraction gratings having a greatest common divisor of 1 and having different orders are provided at positions where they can be coupled with guided light traveling through the active layer 15 . In the example of FIGS. 1 and 2A, a second-order diffraction grating EA2 and a third-order diffraction grating EA3 are provided as a plurality of high-order diffraction gratings having a greatest common divisor of 1 and different orders. A second order grating EA2 and a third order grating EA3 are located on either side of the ridge RA. The pitch Λ2 of the second-order diffraction grating EA2 shown in FIG. 2(a) can be made to coincide with twice the oscillation period of the laser light guided through the ridge RA. The pitch Λ3 of the third-order diffraction grating EA3 can be matched to three times the oscillation period of the laser light guided through the ridge RA. At this time, concave portions SB2 and convex portions ST2 are alternately formed at a pitch Λ2 along the waveguide direction D1 in the second-order diffraction grating EA2. In the third-order diffraction grating EA3, concave portions SB3 and convex portions ST3 are alternately formed at a pitch Λ3 along the waveguide direction D1.

Here, the second-order diffraction grating EA2 and the third-order diffraction grating EA3 have regions in which at least one of the following a) to d) is matched in the D1 direction.
a) the center of the protrusion ST2 of the second-order diffraction grating EA2 and the center of the protrusion ST3 of the third-order diffraction grating EA3, b) the center of the recess SB2 of the second-order diffraction grating EA2 and the center of the recess SB3 of the third-order diffraction grating EA3, c) the center of the convex portion ST2 of the second-order diffraction grating EA2 and the center of the concave portion SB3 of the third-order diffraction grating EA3 d) the center of the concave portion SB2 of the second-order diffraction grating EA2 and the center of the convex portion ST3 of the third-order diffraction grating EA3

For example, the second-order diffraction grating EA2 and the third-order diffraction grating EA3 have points PC12 and PC14 at which the center of the projection ST2 of the second-order diffraction grating EA2 and the center of the projection ST3 of the third-order diffraction grating EA3 coincide. Also, in this embodiment, there are points PC11 and PC13 where the center of the concave portion SB2 of the second-order diffraction grating EA2 and the center of the convex portion ST3 of the third-order diffraction grating EA3 coincide.

Here, by setting the greatest common divisor of the orders of the second-order diffraction grating EA2 and the third-order diffraction grating EA3 to 1, the cavity direction (hereinafter also referred to as the waveguide direction) D1 of the guided light guided through the active layer 15 While matching the diffraction conditions to , the periods of the second-order diffraction grating EA2 and the third-order diffraction grating EA3 can be increased compared to the first-order diffraction grating. Therefore, it is possible to stabilize the oscillation wavelength while suppressing a decrease in oscillation efficiency. Furthermore, it is possible to realize a blue-violet laser diode that alleviates manufacturing difficulties associated with miniaturization of the second-order diffraction grating EA2 and the third-order diffraction grating EA3.

That is, the second-order diffraction grating EA2 diffracts the emitted light not only in the in-plane (180°) direction but also in the 90° direction. The third-order diffraction grating EA3 diffracts emitted light not only in the in-plane (180°) direction but also in the directions of about 70° and about 110°. However, since the greatest common divisor of the orders of the second-order diffraction grating EA2 and the third-order diffraction grating EA3 is 1, only the diffraction in the in-plane (180°) direction occurs by synthesizing the effects of these two diffraction gratings. , an effect similar to that of the first-order diffraction grating can be obtained.

In addition, by providing a region where at least one of the center of the projection and the center of the projection of the second-order diffraction grating EA2 and the third-order diffraction grating EA3, the center of the recess and the center of the recess, and the center of the projection and the recess are aligned, It is possible to increase the difference in the energy density of the electric field of the standing wave formed by the second-order diffraction grating EA2 and the third-order diffraction grating EA3. and another standing wave, the bandwidth of the spectrum where light propagation is prohibited (stop-bandwidth) can be increased. Therefore, the SMSR of a plurality of high-order diffraction gratings composed of the second-order diffraction grating EA2 and the third-order diffraction grating EA3 can be increased, and the coupling coefficient between the guided light and the high-order diffraction gratings can be increased. can be done.

The second-order diffraction grating EA2 and the third-order diffraction grating EA3 are recessed from the facets MA and MB of the semiconductor laser LA. At this time, the second-order diffraction grating EA2 and the third-order diffraction grating EA3 can be retreated from the facets MA and MB in the cavity direction by a distance equal to or longer than the period of each of the second-order diffraction grating EA2 and the third-order diffraction grating EA3. Here, by retreating the second-order diffraction grating EA2 and the third-order diffraction grating EA3 from the end surfaces MA and MB, the centers of the projections and the centers of the recesses of the second-order diffraction grating EA2 and the third-order diffraction grating EA3 It is possible to facilitate fabrication of the second-order diffraction grating EA2 and the third-order diffraction grating EA3 while providing a region in which at least one of the centers of the projections and the recesses coincides.

It is preferable that the relational expression 1≦κ·L≦3 is satisfied, where κ is the coupling coefficient of the diffraction grating and L is the cavity length of the semiconductor laser LA. As a result, it is possible to stabilize the oscillation wavelength while achieving a lower threshold value and a higher efficiency of the semiconductor laser LA.

As another configuration of the semiconductor laser LA, as shown in FIG. 2B, a p-type nitride contact layer 21 is laminated on the p-type nitride cladding layer 20 . The p-type nitride contact layer 21 can make ohmic contact with the electrode 22 that injects current into the active layer 15 .

An electrode 22 is formed on the p-type nitride contact layer 21 . The electrode 22 can have a laminated structure of Ni/Au. The thickness of Ni/Au can be set to 10/100 nm, for example.

As for other structures of each layer, for example, the following materials can be used. Using an n-type GaN substrate as the n-type nitride semiconductor substrate 11, an n-type Al _0.02 Ga _0.98 N layer as the n-type nitride cladding layer 12, and an n-type GaN layer as the n-type nitride guide layer 13 can be done. Also, an In _0.02 Ga _0.99 N layer can be used as the undoped nitride guide layer 14 . A single quantum well layer composed of In _0.02 Ga _0.98 N barrier layer/In _0.15 Ga _0.88 N well layer/In _0.02 Ga _0.98 N barrier layer is used for the active layer 15 . be able to. Also, an In _0.02 Ga _0.99 N layer can be used for the undoped nitride guide layer 16 . Further, a p-type Al _0.22 Ga _0.78 N layer as the p-type carrier block layer 17, a p-type GaN layer as the p-type nitride guide layer 18, and a p-type Al _0.02 as the p-type nitride cladding layer 20 A p-type GaN layer can be used as the Ga _0.98 N layer and the p-type nitride contact layer 21, respectively.

The thickness of the n-type nitride cladding layer 12 can be set to, for example, 700 nm, and the donor concentration N _D can be set to 1×10 ¹⁷ cm ⁻³ . The thickness of the n-type nitride guide layer 13 can be set to, for example, 50 nm, and the donor concentration N _D can be set to 1×10 ¹⁷ cm ⁻³ . The thickness of the undoped nitride guide layer 14 can be set to 136 nm, for example. The thicknesses of the barrier layer/well layer/barrier layer of the quantum well layers of the active layer 15 can be set to 10/9/10 nm, for example. The thickness of the undoped nitride guide layer 16 can be set to 135 nm, for example. The thickness of the p-type carrier block layer 17 can be set to, for example, 4 nm, and the acceptor concentration N _A can be set to 1×10 ¹⁸ cm ⁻³ . The thickness of the p-type nitride guide layer 18 can be set to, for example, 150 nm, and the acceptor concentration N _A can be set to 1×10 ¹⁸ cm ⁻³ . The thickness of the p-type nitride cladding layer 20 can be set to, for example, 700 nm, and the acceptor concentration N _A can be set to 1×10 ¹⁸ cm ⁻³ . The thickness of the p-type nitride contact layer 21 can be set to, for example, 60 nm, and the acceptor concentration N _A can be set to 1×10 ¹⁸ cm ⁻³ .

As shown in FIG. 2A, facet reflection films 24 and 25 are formed on facets MA and MB of the semiconductor laser LA. At this time, it is preferable to set the reflectance of the end face MA to 2% or less and the reflectance of the end face MB to 90% or more. As a result, light leaking to the rear of the resonator can be reduced while the oscillation wavelength is stabilized, and variations in the characteristics of the semiconductor laser LA can be reduced while suppressing a decrease in the luminous efficiency of the semiconductor laser LA.

At this time, the facet reflection film 24 can have a laminated structure of AlN/SiO ₂ . The thickness of AlN/SiO ₂ can be set to 30/300 nm, for example. The facet reflection film 25 can have a laminated structure of AlN/(SiO ₂ /Ta ₂ O ₅ ) ⁶ /SiO ₂ . Here, (SiO ₂ /Ta ₂ O ₅ ) ⁶ represents a 6-layer multilayer film of SiO ₂ /Ta ₂ O ₅ . The thickness of AlN/(SiO ₂ /Ta ₂ O ₅ ) ⁶ /SiO ₂ can be set to 30/(60/40)×6/10 nm, for example.

This semiconductor laser LA can be used as a light source for generating SHG waves of 222 nm. It can be realized by combining with a wavelength conversion element that converts the 444 nm laser light emitted from the semiconductor laser LA into the 222 nm SHG wave. This can replace the KrCl excimer lamp that generates ultraviolet rays of 222 nm.

FIG. 3(a) shows the refractive index distribution of the diffraction grating EA2 formed on the right side of FIG. 2(a) with respect to the position in the optical waveguide direction. It is a figure which shows. 3(c) corresponds to FIG. 3(a), and FIG. 3(d) shows the position of the resonator in the waveguide direction of the semiconductor light emitting device according to the first embodiment corresponding to FIG. 3(b). It is a figure which shows the relationship of the phase of the standing wave to be formed, and amplitude.

In FIGS. 3A and 3B, the period (pitch: Λ2) of the second-order diffraction grating EA2 in FIG. 2A is set to 178.3 nm, and the duty is set to 0.2. Also, the period (pitch: Λ3) of the third-order diffraction grating EA3 was set to 267.5 nm, and the duty was set to 0.2. At this time, FIG. 3(a) shows the refractive index distribution of the second-order diffraction grating EA2 in the waveguide direction D1, and FIG. 3(b) shows the refractive index distribution of the third-order diffraction grating EA3 in the waveguide direction D1. Note that the duty is the ratio of the width of the convex portion to the width within one period of the diffraction grating.

3(a) and 3(b), the second-order diffraction grating EA2 and the third-order diffraction grating EA3 are located at the center of the projection ST2 of the second-order diffraction grating EA2 and the projection ST3 of the third-order diffraction grating EA3. There are points PC12 and PC14 with coincident centers. Further, there are points PC11 and PC13 where the center of the concave portion SB2 of the second-order diffraction grating EA2 and the center of the convex portion ST3 of the third-order diffraction grating EA3 coincide. At this time, even if the wavelength is the same, the energy density u=1/2εE2 of the electric field E differs depending on the position in the waveguide direction D1 of the standing waves VE1 and ^VE2 with respect to the diffraction grating. ε is the refractive index of the medium in which the electric field E is created. The difference in energy density u between the standing waves VE1 and VE2 corresponds to the stopband width. At this time, points PC12 and PC14 at which the center of the convex portion ST2 of the second-order diffraction grating EA2 and the center of the convex portion ST3 of the third-order diffraction grating EA3 coincide with the points PC12 and PC14, and the center of the concave portion SB2 of the second-order diffraction grating EA2 and the third-order diffraction grating At points PC11 and PC13 where the centers of the protrusions ST3 of EA3 coincide, the difference in amplitude between the standing waves VE1 and VE2 increases, and the difference in energy density u between the standing waves VE1 and VE2 increases. For this reason, points PC12 and PC14 at which the center of the convex portion ST2 of the second-order diffraction grating EA2 and the center of the convex portion ST3 of the third-order diffraction grating EA3 match, and the center of the concave portion SB2 of the second-order diffraction grating EA2 and the third-order diffraction grating By providing the points PC11 and PC13 at which the centers of the projections ST3 of EA3 coincide, the stop band width can be increased, and the coupling coefficient between the guided light and the high-order diffraction grating can be increased.

FIG. 4 shows parameters that can be adjusted when changing the relative positional relationship of a plurality of diffraction gratings, showing the refractive index and the position in the waveguiding direction, exemplifying the second-order diffraction grating and the third-order diffraction grating shown in FIG. It is a relationship diagram.
In FIG. 4, there are countless ways to select the relative positional relationship between the unevenness of the second-order diffraction grating and the third-order diffraction grating. When changing the relative positional relationship between the unevenness of the second-order diffraction grating and the third-order diffraction grating, the inter-grating shift FK between the second-order diffraction grating and the third-order diffraction grating may be changed. may be changed, the duty DY3 of the third-order diffraction grating may be changed, or these changes may be combined. The intergrating shift FK is the deviation of the physical distance from the cavity facet between the second-order diffraction grating and the third-order diffraction grating. It forms a phase shift.

FIG. 5A is a diagram showing the relationship between the intergrating shift and the stop band width when the duty of the diffraction grating of the semiconductor light emitting device according to the first embodiment is changed. Note that the unit of the interstitial shift and the stopband width is a. u. (Arbitration Unit).
In FIG. 5A, when the duty DY2 of the second-order diffraction grating and the duty DY3 of the third-order diffraction grating are set to the same value, the stop band width when the grating shift FK is changed between 0.1 and 0.5 estimated. Here, the duty DY2 of the 2nd-order diffraction grating and the duty DY3 of the 3rd-order diffraction grating are as follows: In the case of 0.4, the asterisk indicates the case of 0.5.

From this result, it was found that the stop band width changes depending on the relative positional relationship of the plurality of diffraction gratings. In this estimate, the largest stopband value was obtained when the duty DY2 of the second-order diffraction grating and the duty DY3 of the third-order diffraction grating were 0.2 and the inter-grating shift FK was 0.5.

FIG. 5B is a diagram showing a method of maximizing the stopband width of the semiconductor light emitting device according to the first embodiment;
In FIG. 5B, when the duty DY2 of the second-order diffraction grating and the duty DY3 of the third-order diffraction grating are changed respectively, the duty DY2 of the second-order diffraction grating is 0.3, the duty DY3 of the third-order diffraction grating is 0.5, and the duty DY3 of the third-order diffraction grating is 0.5. When the intergrating shift FK is 0, it is found that a larger stop band width can be obtained than when the duty DY2 of the second-order diffraction grating and the duty DY3 of the third-order diffraction grating are each set to the same value of 0.2. rice field.

6(a1), 6(b1), 7(a1) and 7(b1) are plan views showing an example of the method for manufacturing the semiconductor light emitting device according to the second embodiment. 6(a2), FIG. 6(b2), FIG. 7(a2) and FIG. 7(b2) correspond to FIG. 6(a1), FIG. 6(b1), FIG. 7(a1) and FIG. 7(a1) 1 is an A1-A1 cross-sectional view of FIG. This second embodiment can be applied to the manufacture of the semiconductor laser LA of FIG. 2(b). However, in this second embodiment, the p-type nitride contact layer 21 in FIG. 2(b) is omitted.

6(a1) and 6(a2), by epitaxial growth, an n-type nitride cladding layer 12, an n-type nitride guide layer 13, an undoped nitride guide layer 14, an active layer 15, an undoped nitride guide layer 16, A p-type carrier block layer 17 , a p-type nitride guide layer 18 and p-type nitride cladding layers 20 and 20 A are sequentially laminated on an n-type nitride semiconductor substrate 11 . The epitaxial growth may be MOCVD (Metal Organic Chemical Vapor Deposition), MBE (Molecular Beam Epitaxy), or HVPE (Hydride Vapor Phase Epitaxy).

Next, as shown in FIGS. 6(b1) and 6(b2), a mask material is deposited on the p-type nitride cladding layer 20A by plasma CVD (Chemical Vapor Deposition) or sputtering. Then, based on photolithography technology and dry etching technology, the mask material is patterned to form a mask pattern 26 corresponding to the ridge RA, the second-order diffraction grating EA2 and the third-order diffraction grating EA3 in FIG. It is formed on the clad layer 20A. For the mask pattern 26, for example, an SiO- ₂ film with a thickness of 300 nm can be used.

Next, as shown in FIGS. 7(a1) and 7(a2), by etching the p-type nitride cladding layer 20A through the mask pattern 26, the mask pattern 26 is formed on the p-type nitride cladding layer 20A. to be transcribed. Thereby, a ridge RA, a second-order diffraction grating EA2 and a third-order diffraction grating EA3 made of the p-type nitride cladding layer 20A are formed on the p-type nitride cladding layer 20. Next, as shown in FIG. Then, as shown in FIGS. 7(b1) and 7(b2), the mask pattern 26 on the p-type nitride cladding layer 20A is removed. The heights of the ridge RA, second-order diffraction grating EA2, and third-order diffraction grating EA3 are set to 500 nm, for example. The period of the second-order diffraction grating EA2 was set to 178.3 nm, and the period of the third-order diffraction grating EA3 was set to 267.5 nm.

Next, an insulating film is formed to cover the entire surface of the wafer by a method such as plasma CVD. A 300 nm-thickness SiO- ₂ film, for example, can be used as this insulating film. Then, the insulating film on the ridge RA is removed by photolithography and dry etching, and an electrode 22 made of Ni/Au with a Ni film thickness of 10 nm and an Au film thickness of 100 nm is formed on the ridge RA. Furthermore, an electrode made of Ti/Pt/Au is formed thereon. For example, the film thickness of the Ti/Pt/Au electrode is 100/50/300 nm. A laser chip having a cavity length L of 3000 μm, for example, is cut out from the wafer produced as described above by a cleaving process or the like. After that, an AR coating with a reflectance of 2% or less is applied to the facet MA of the laser chip, and an HR coating with a reflectance of 90% or more is applied to the facet MB of the laser chip.

FIG. 8 is a plan view showing the configuration of a semiconductor light emitting device according to the third embodiment.
In FIG. 8, the semiconductor laser LB has a ridge RB, a second-order diffraction grating EB2 and a third-order diffraction grating EB3 instead of the ridge RA, second-order diffraction grating EA2 and third-order diffraction grating EA3 of the semiconductor laser LA in FIG. Prepare. Other configurations of the semiconductor laser LB can be configured in the same manner as the semiconductor laser LA.

In the second-order diffraction grating EB2 and the third-order diffraction grating EB3, the center of the projection of the second-order diffraction grating EB2 and the center of the projection of the third-order diffraction grating EB3 are aligned at the position PC1 in the waveguide direction D1. Also, at the position PC2 in the waveguide direction D1, the center of the convex portion of the second-order diffraction grating EB2 and the center of the concave portion of the third-order diffraction grating EB3 are aligned. Furthermore, at the position PC3 in the waveguide direction D1, the center of the concave portion of the second-order diffraction grating EB2 coincides with the center of the convex portion of the third-order diffraction grating EB3. In FIG. 8, white portions are convex portions in the direction perpendicular to the plane of the paper, and colored portions are concave portions in the diffraction grating, which are at the same height as the other surfaces.

As a result, the difference in energy density of the standing wave electric field formed by the second-order diffraction grating EB2 and the third-order diffraction grating EB3 can be increased, and the stop band width can be increased. Therefore, the SMSR of a plurality of high-order diffraction gratings composed of the second-order diffraction grating EB2 and the third-order diffraction grating EB3 can be increased, and the coupling coefficient between the guided light and the high-order diffraction gratings can be increased. can be done.

9(a) and 9(b) show the refractive index distribution of the diffraction grating in the semiconductor light emitting device of the fourth embodiment. 9(c) and 9(d) are diagrams showing the relationship between the phase and amplitude of the standing wave formed in the resonator in the semiconductor light emitting device of the fourth embodiment. In addition, in this fourth embodiment, a combination of a third-order diffraction grating and a fifth-order diffraction grating is used instead of the combination of the second-order diffraction grating and the third-order diffraction grating in FIG.

In FIGS. 9A and 9B, the pitch of the third-order diffraction grating can be matched to three times the oscillation period of the laser light. The pitch of the fifth-order diffraction grating can be matched to five times the oscillation period of the laser light. Also, in the case of a combination of the 3rd order diffraction grating and the 5th order diffraction grating, the greatest common divisor of the orders of these diffraction gratings is 1, so that only diffraction occurs in the in-plane (180°) direction. Therefore, an effect similar to that of the first-order diffraction grating can be obtained.

In the combination of the 3rd-order diffraction grating and the 5th-order diffraction grating, there are points PC21 and PC23 at which the centers of the projections of the 3rd-order diffraction grating and the centers of the recesses of the 5th-order diffraction grating coincide. Further, there are points PC22 and PC24 where the center of the concave portion of the third-order diffraction grating and the center of the convex portion of the fifth-order diffraction grating are aligned. At this time, points PC21 and PC23 where the centers of the convex portions of the third-order diffraction grating and the centers of the concave portions of the fifth-order diffraction grating are aligned, and the center of the concave portions of the third-order diffraction grating and the center of the convex portions of the fifth-order diffraction grating are matched, the difference in amplitude between the standing waves VE3 and VE4 increases, and the difference in energy density u between the standing waves VE3 and VE4 increases. By providing such points PC21, PC23 and points PC22, PC24, the stop band width can be increased, and the coupling coefficient between the guided light and the high-order diffraction grating can be increased.

FIG. 10 is a diagram showing the relationship between the intergrating shift and the stop band width when the duty of the diffraction grating for the semiconductor light emitting device according to the fourth embodiment is changed.
In FIG. 10, the stop band width is estimated when the shift between gratings is changed between 0.1 and 0.5 when the duty of the 3rd order diffraction grating and the duty of the 5th order diffraction grating are the same value. .

From this result, it can be seen that the stop band width changes depending on the relative positional relationship of the plurality of diffraction gratings. In this estimation, the largest stopband value was obtained when the duty of the third-order diffraction grating and the duty of the fifth-order diffraction grating were 0.5 and the shift between gratings was 0.5.

Note that the duty of the third-order diffraction grating and the duty of the fifth-order diffraction grating may be different from each other.

FIG. 11 is a plan view showing the configuration of the semiconductor light emitting device according to the fifth embodiment.
In FIG. 11, the semiconductor laser LC includes a ridge RC, second-order diffraction grating EC2 and third-order diffraction grating EC3 instead of the ridge RB, second-order diffraction grating EB2 and third-order diffraction grating EB3 of the semiconductor laser LB in FIG. Other points of the semiconductor laser LC can be configured in the same manner as the semiconductor laser LB in FIG.

The second-order diffraction grating EC2 is provided with a phase shift portion SF2, and the third-order diffraction grating EC3 is provided with a phase shift portion SF3. At this time, an AR coating with a reflectance of 1% or less was applied to the end face MA of the laser chip, and an HR coating with a reflectance of 95% or more was applied to the end face MB of the laser chip. The phase shift section makes it possible to slightly shift the phase of the standing wave formed by each diffraction grating by removing a part of each diffraction grating, thereby forming a stable phase as a whole.

Here, the characteristics vary according to the cleavage position of the semiconductor laser LC. At this time, by providing the second-order diffraction grating EC2 with the phase shift part SF2 and the third-order diffraction grating EC3 with the phase shift part SF3, the phase of the standing wave can be controlled using the phase shift parts as a reference. As a result, it is possible to improve the SMSR of the diffraction grating and improve the luminous efficiency of the desired oscillation wavelength while coping with the variation in characteristics depending on the cleavage position.

Such a phase shift distributed feedback semiconductor laser LC can easily obtain a larger SMSR than a semiconductor laser LB having a diffraction grating without phase shift portions SF2 and SF3 for the following reasons. Furthermore, the threshold gain can be lowered, and the characteristics of the nitride semiconductor light emitting device can be further improved.

The center of each phase shift portion SF2, SF3 is preferably positioned at a distance L1 between 60% and 80% of the distance (L1+L2) between the facets MA with lower reflectance and the facets MA, MB. In particular, the distance L1 from the facet MA to the center of each phase shift portion SF2, SF3 is preferably set to 70% (L1:L2=7:3) of the distance (L1+L2) between the facets MA, MB. As a result, the phase shift portions SF2 and SF3 are arranged at positions corresponding to the edges of the peaks, the edges of the valleys, or the edges of the peaks and valleys of the standing wave formed by the second-order diffraction grating EC2 and the third-order diffraction grating EC3. can be deployed and can improve SMSR.

Further, when N is a natural number (positive integer), neff is the effective refractive index of the diffraction grating, and λ is the Bragg wavelength, the length of the phase shift portion is given by the formula λ/(4·neff)·(2N−1). preferably fulfilled. For example, when λ=444 nm and neff=2.49, the length of the phase shift portion in the resonator direction can be set to 222.9 nm. Thereby, the phase shift portions can be arranged at positions corresponding to the edges of the peaks, the edges of the valleys, or the edges of the peaks and the valleys of the standing wave formed by the diffraction grating, and the SMSR can be improved. .

FIG. 12 is a plan view showing the configuration of a semiconductor light emitting device according to the sixth embodiment.
In FIG. 12, the semiconductor laser LD has a ridge RD, second-order diffraction gratings ED2, ED2' and third-order diffraction gratings ED3 instead of the ridge RB, second-order diffraction gratings EB2 and third-order diffraction gratings EB3 of the semiconductor laser LB in FIG. , ED3′. Other points of the semiconductor laser LD can be configured in the same manner as the semiconductor laser LB in FIG.

Second-order gratings ED2, ED2' and third-order gratings ED3, ED3' are located on both sides of ridge RD along waveguide direction D1. At this time, the third-order diffraction gratings ED3 and ED3' are arranged closer to the ridge RD than the second-order diffraction gratings ED2 and ED2'. This places the higher order gratings closer to the emitted light distribution and the lower order gratings further away from the light distribution. Therefore, the coupling coefficient of the low-order diffraction grating and the coupling coefficient of the high-order diffraction grating can be made substantially the same, and the emitted light can be efficiently diffracted in the 180° direction.

FIG. 13 is a diagram showing the relationship between the height of the diffraction grating and the coupling coefficient.
In FIG. 13, according to a non-patent document (IEEE J. Quantum Electron. QE-11, p867, 1975), the coupling coefficient decreases as the order increases even if the height of the diffraction grating is the same. Coupling coefficients of diffraction gratings of different orders were estimated for the case of TE mode and rectangular diffraction grating by a method similar to that shown in this document. As a result, as shown in FIG. 13, as the order (number represented by "m" in the figure) increases, the coupling coefficient decreases even if the height of the diffraction grating is the same. Here, the refractive indices used for estimating the coupling coefficient were n ₁ =2.48, n ₂ =2.49, and n ₃ =2.48. Further, as variables common to the method of this document, the guide layer thickness t=3 μm, the oscillation wavelength λ=444 nm, and the duty=0.4.

FIG. 14(a) is a cross-sectional view showing the configuration of a semiconductor light emitting device according to the seventh embodiment cut along a direction perpendicular to the resonator direction, and FIG. 14(b) is a semiconductor device according to the seventh embodiment. FIG. 4 is a cross-sectional view showing the configuration of a light-emitting element cut along the resonator direction;
14(a) and 14(b), the semiconductor laser LE has a ridge RE instead of the ridge RA, second-order diffraction grating EA2 and third-order diffraction grating EA3 of the semiconductor laser LA in FIG. It has a diffraction grating EE2 and a third-order diffraction grating EE3. Other configurations of the semiconductor laser LE can be configured in the same manner as the semiconductor laser LA.

The second-order diffraction grating EE2 is located on the first-conductivity-type semiconductor layer side with respect to the active layer 15, and the third-order diffraction grating EE3 is located on the second-conductivity-type semiconductor layer side with respect to the active layer 15. FIG. At this time, the second-order diffraction grating EE2 can be formed in the n-type nitride cladding layer 12A on the n-type nitride cladding layer 12. FIG. The n-type nitride cladding layers 12, 12A can be integrally formed from the same material. The second order diffraction grating EE2 can be covered with an n-type nitride guide layer 13 . A third-order diffraction grating EE3 can be formed in the p-type nitride guide layer 18A on the p-type nitride guide layer 18. FIG. The p-type nitride guide layers 18, 18A can be integrally formed from the same material. The third order grating EE3 can be covered with a p-type nitride cladding layer 20. FIG.

At this time, at the position PC31 in the waveguide direction D1, the center of the convex portion of the second-order diffraction grating EE2 and the center of the concave portion of the third-order diffraction grating EE3 match. Also, at the position PC32 in the waveguide direction D1, the center of the concave portion of the second-order diffraction grating EE2 and the center of the concave portion of the third-order diffraction grating EE3 are aligned. As a result, the difference in energy density of the standing wave electric field formed by the second-order diffraction grating EE2 and the third-order diffraction grating EE3 can be increased, and the stop band width can be increased. As a result, the SMSR of a plurality of high-order diffraction gratings composed of the second-order diffraction grating EE2 and the third-order diffraction grating EE3 can be increased, and the coupling coefficient between the guided light and the high-order diffraction gratings can be increased. can be done.

Further, by forming the second-order diffraction grating EE2 on the n-type nitride cladding layer 12A and forming the third-order diffraction grating EE3 on the p-type nitride guide layer 18A, the third-order diffraction grating EE3 is formed from the second-order diffraction grating EE2. can also be placed near the active layer 15 . This allows the higher order diffraction gratings to be arranged closer to the light distribution of the emitted light and the lower order diffraction gratings to be arranged further away from the light distribution. Therefore, the coupling coefficient of the low-order diffraction grating and the coupling coefficient of the high-order diffraction grating can be made substantially the same, and the emitted light can be efficiently diffracted in the 180° direction.

15(a1), 15(b1), 16(a1), and 16(a1) are plan views showing an example of a method for manufacturing a semiconductor light emitting device according to the eighth embodiment. 15(a2), FIG. 15(b2), FIG. 16(a2) and FIG. 16(a2) correspond to FIG. 15(a1), FIG. 15(b1), FIG. 3A and 3B are cross-sectional views taken along the direction of the resonator of FIG.

15(a1) and 15(a2), n-type nitride cladding layers 12 and 12A are successively laminated on n-type nitride semiconductor substrate 11 by epitaxial growth.

Next, as shown in FIGS. 15(b1) and 15(b2), the n-type nitride cladding layer 12A is patterned based on the photolithography technique and the dry etching technique, and the n-type nitride cladding layer 12A is provided with 2 layers. A second diffraction grating EE2 is formed.

Next, as shown in FIGS. 16(a1) and 16(a2), an n-type nitride guide layer 13, an undoped nitride guide layer 14, an active layer 15, an undoped nitride guide layer 16, and a p-type are grown by epitaxial growth. A carrier block layer 17 and p-type nitride guide layers 18 and 18A are sequentially laminated on the n-type nitride cladding layers 12 and 12A.

Next, as shown in FIGS. 16(b1) and 16(b2), the p-type nitride guide layer 18A is patterned by photolithography and dry etching techniques, and the p-type nitride guide layer 18A is provided with 3 layers. A second diffraction grating EE3 is formed.

Next, as shown in FIGS. 14A and 14B for the semiconductor laser LE, contact layers are formed on the p-type nitride guide layers 18 and 18A. Specifically, by epitaxial growth, p-type nitride cladding layers 20, 20A and p-type nitride contact layer 21 are sequentially laminated on p-type nitride guide layers 18, 18A. Then, the p-type nitride cladding layer 20A and the p-type nitride contact layer 21 are patterned on the basis of photolithography technology and dry etching technology, and the p-type nitride cladding layer 20A and the p-type nitride contact layer 21 are provided with a ridge RE. to form

E1 n-type nitride semiconductor layer E2 p-type nitride semiconductor layer RA ridge EA2 second-order diffraction grating EA3 third-order diffraction grating 11 n-type nitride semiconductor substrate 12 n-type nitride cladding layer 13 n-type nitride guide layer 14, 16 undoped nitride guide layer 15 active layer 17 p-type carrier block layer 18 p-type nitride guide layer 20 p-type nitride cladding layer 21 p-type nitride contact layer 22 electrode

Claims (13)

a first conductivity type semiconductor layer;
an active layer provided on the first conductivity type semiconductor layer;
a second conductivity type semiconductor layer provided on the active layer;
A plurality of high-order diffraction gratings of different orders provided at positions that can be coupled with guided light guided through the active layer,
The plurality of high-order diffraction gratings have a greatest common divisor of 1, and have regions in which at least one of centers of protrusions and protrusions, centers of recesses and recesses, and centers of protrusions and recesses coincides with each other. A semiconductor light emitting device characterized by: the second conductivity type semiconductor layer has a ridge extending in the resonator direction,
2. The semiconductor light emitting device according to claim 1, wherein said plurality of high-order diffraction gratings are provided on both sides of said ridge along said cavity direction. 3. The semiconductor light-emitting device according to claim 2, wherein said plurality of high-order diffraction gratings are arranged on both sides of said ridge with different high-order diffraction gratings. 2. The semiconductor according to claim 1, wherein the plurality of high-order diffraction gratings are provided on the first conductivity type semiconductor layer side and/or the second conductivity type semiconductor layer side of the active layer. light-emitting element. 2. The method according to claim 1, wherein each of the plurality of high-order diffraction gratings is recessed from one end surface of the active layer by a distance equal to or greater than the period of each of the high-order diffraction gratings in the cavity direction. semiconductor light emitting device. 2. The semiconductor light emitting device according to claim 1, wherein said plurality of high-order diffraction gratings are arranged such that coupling coefficients thereof are equal to each other. 2. The semiconductor light emitting device of claim 1, wherein the duties of the plurality of high-order diffraction gratings are different from each other. 2. The semiconductor light emitting device of claim 1, wherein the higher order diffraction grating comprises a phase shifter. Assuming that N is a natural number (positive integer), neff is the effective refractive index of the high-order diffraction grating, and λ is the Bragg wavelength, the length of the phase shift portion is
Length of the phase shift portion = λ/(4·neff)·(2N−1)
9. The semiconductor light emitting device according to claim 8, wherein: 9. The method according to claim 8, wherein the center of the phase shift portion is located at a distance between 60% and 80% of the distance from the facet of the active layer with the lower reflectance to the other facet. Semiconductor light emitting device. 9. The semiconductor light-emitting device according to claim 8, wherein the centers of said phase shift portions are equidistant from the facet with lower reflectance among said plurality of high-order diffraction gratings. 2. The semiconductor light emitting device according to claim 1, wherein said first conductivity type semiconductor layer, said active layer and said second conductivity type semiconductor layer are made of a nitride semiconductor. A step A of sequentially stacking an active layer and a second conductivity type semiconductor layer on the first conductivity type semiconductor layer;
A step B of forming a ridge on both sides of which high-order diffraction gratings having a greatest common divisor of 1 and having different orders are provided on the second conductivity type semiconductor layer;
In the step B, the high-order diffraction grating is provided with a region where at least one of the centers of the projections and the centers of the projections, the centers of the recesses and the centers of the recesses, and the centers of the projections and the recesses of the high-order diffraction grating is aligned with each other. A method of manufacturing a semiconductor light emitting device, comprising forming a folding grating.

Images