JP6860293B2 - Light emitting element and manufacturing method of light emitting element - Google Patents

Description

The present invention relates to a light emitting element and a method for manufacturing the light emitting element, and more particularly to a light emitting element that emits deep ultraviolet light using a nitride semiconductor and a method for manufacturing the same.

In recent years, semiconductor light emitting devices such as light emitting diodes and laser diodes that output blue light have been put into practical use, and development of light emitting elements that output deep ultraviolet light having a shorter wavelength has been promoted. Since deep ultraviolet light has a high sterilizing ability, semiconductor light emitting devices capable of outputting deep ultraviolet light are attracting attention as mercury-free sterilizing light sources in medical and food processing sites. In such a light emitting device for deep ultraviolet light, for example, an aluminum gallium nitride (AlGaN) -based n-type semiconductor layer, an active layer, and an electron block layer are laminated in this order on a substrate, and p-type nitride is formed on the electron block layer. It is formed by providing a contact layer made of gallium (GaN) (see, for example, Non-Patent Document 1).

Applied physics express 3 (2010) 072103

The deep ultraviolet light emitted by the active layer is emitted in all directions and is directed to both the n-type semiconductor layer and the electron block layer that sandwich the active layer. Since the contact layer on the electron block layer is composed of GaN, it can absorb deep ultraviolet light from the active layer and become a factor of lowering the light extraction efficiency. If AlGaN having a higher aluminum (Al) concentration than the active layer is used, it may be possible to suppress the absorption of deep ultraviolet light. However, when AlGaN having a high Al concentration is used as the contact layer, the contact resistance with the p-side electrode increases, and the carrier injection efficiency into the active layer decreases.

The present invention has been made in view of these problems, and one of its exemplary purposes is to provide a light emitting device having improved light extraction efficiency.

The light emitting device according to an embodiment of the present invention includes an n-type clad layer formed of an n-type AlGaN-based semiconductor material on a substrate, an active layer formed of an AlGaN-based semiconductor material on the n-type clad layer, and an active layer. An electron block layer formed of a p-type AlGaN-based semiconductor material or a p-type AlN-based semiconductor material is formed on the top, and a material having a refractive index lower than that of the electron block layer is formed in the first region on the electron block layer. A p-type AlGaN-based semiconductor that is provided across both the reflection layer having an opening in the second region on the electron block layer adjacent to the region and the opening and the reflection layer and has a lower Al content than the electron block layer. A contact layer formed of a material or a p-type GaN-based semiconductor material is provided. The active layer emits deep ultraviolet light.

According to this aspect, since the reflective layer is provided in a part of the region between the electron block layer and the contact layer, the deep ultraviolet light from the active layer to the contact layer is reflected by the reflective layer and directed toward the substrate side, and is directed from the substrate. It is possible to increase the light extraction efficiency of. Further, by forming the contact layer on the reflective layer having an opening, the formation of the contact layer by epitaxial lateral growth (ELO) can be promoted, and the crystallinity of the contact layer can be enhanced. Thereby, the reliability of the light emitting element can be improved.

The reflective layer may be formed of an insulating material containing silicon (Si).

The reflective layer is formed so that the first region and the second region are alternately arranged in the direction in which the first region and the second region are adjacent to each other, and the width of the first region in the adjacent direction is 10 μm or less. May be formed in.

For the thickness d of the reflective layer, d = (λ / 4n) (2m-1) using the wavelength λ of the deep ultraviolet light emitted by the active layer, the refractive index n of the reflective layer with respect to the wavelength λ, and an integer m of 1 or more. The relationship may be satisfied.

An p-type clad layer formed of a p-type AlGaN-based semiconductor material having a lower Al content than the electron block layer may be further provided between the electron block layer and the reflection layer or the contact layer.

The p-type clad layer may have a superlattice structure composed of a p-type AlGaN-based semiconductor material.

A buffer layer provided between the electron block layer and the contact layer in contact with the contact layer and composed of a p-type AlGaN-based semiconductor material or a p-type GaN-based semiconductor material having a lower Al content than the electron block layer is further provided. You may. The Al content of the contact layer may be equal to or less than the Al content of the buffer layer.

The thickness of the buffer layer may be 100 nm or less.

Another aspect of the present invention is a method of manufacturing a light emitting device. This method includes a step of forming an n-type clad layer containing an n-type AlGaN-based semiconductor material on a substrate, a step of forming an active layer containing an AlGaN-based semiconductor material on the n-type clad layer, and a step of forming an active layer containing an AlGaN-based semiconductor material on the active layer. A step of forming an electron block layer containing a p-type AlGaN-based semiconductor material, a step of forming a reflection layer containing a material having a refractive index lower than that of the electron block layer on the electron block layer, and a part of the reflection layer are removed. A step of forming an opening penetrating the reflective layer and a p-type AlGaN-based semiconductor material or a p-type GaN-based semiconductor material having a lower Al content than the electron block layer straddling both the opening and the reflective layer. It comprises a step of forming a contact layer that includes.

A step of forming a buffer layer of a p-type AlGaN-based semiconductor material or a p-type GaN-based semiconductor material having a lower Al content than the electron block layer may be further provided on the electron block layer. The contact layer may be formed on the buffer layer in contact with the buffer layer, and the Al content of the contact layer may be equal to or less than the Al content of the buffer layer.

According to the light emitting device of the present invention, the light extraction efficiency of deep ultraviolet light can be improved.

It is sectional drawing which shows typically the structure of the light emitting element which concerns on embodiment. It is the top view which shows the structural example of the reflective layer schematicly. It is the top view which shows the structural example of the reflective layer schematicly. It is the top view which shows the structural example of the reflective layer schematicly. It is sectional drawing which shows typically the manufacturing process of a light emitting element. It is sectional drawing which shows typically the manufacturing process of a light emitting element. It is sectional drawing which shows typically the manufacturing process of a light emitting element. It is sectional drawing which shows typically the manufacturing process of a light emitting element. It is a figure which shows typically the effect which the light emitting element which concerns on embodiment play. It is sectional drawing which shows typically the structure of the light emitting element which concerns on the modification. It is a graph which shows the relationship between the thickness of a buffer layer and the amount of transmission of deep ultraviolet light.

Hereinafter, embodiments for carrying out the present invention will be described in detail with reference to the drawings. In the description, the same elements are designated by the same reference numerals, and duplicate description will be omitted as appropriate. Also, to aid in understanding the description, the dimensional ratio of each component in each drawing does not necessarily match the dimensional ratio of the actual light emitting element.

FIG. 1 is a cross-sectional view schematically showing the configuration of the light emitting element 10 according to the embodiment. The light emitting element 10 includes a substrate 12, a first base layer 14, a second base layer 16, an n-type clad layer 18, an active layer 20, an electron block layer 22, a p-type clad layer 24, a reflection layer 26, a contact layer 28, and p. A side electrode 32 and an n-side electrode 34 are provided. The light emitting device 10 is a semiconductor light emitting device configured to emit "deep ultraviolet light" having a center wavelength of about 355 nm or less. In order to output deep ultraviolet light having such a wavelength, the active layer 20 is made of an aluminum gallium nitride (AlGaN) -based semiconductor material having a bandgap of about 3.4 eV or more. In this embodiment, a case where deep ultraviolet light having a central wavelength of about 280 nm is emitted is particularly shown.

In the present specification, the "AlGaN-based semiconductor material" refers to a semiconductor material mainly containing aluminum nitride (AlN) and gallium nitride (GaN), and a semiconductor containing another material such as indium nitride (InN). It shall include materials. Thus, it referred to herein as "AlGaN-based semiconductor material", for _example, the composition of _{In 1-x-y Al x} Ga y N (0 ≦ x + y ≦ 1,0 ≦ x ≦ 1,0 ≦ y ≦ 1) It can be represented and includes AlN, GaN, AlGaN, indium aluminum nitride (InAlN), indium gallium nitride (InGaN), and indium gallium nitride (InAlGaN).

Further, among the "AlGaN-based semiconductor materials", a "GaN-based semiconductor material" may be used to distinguish a material that does not substantially contain AlN. The "GaN-based semiconductor material" mainly includes GaN and InGaN, and also includes a material containing a trace amount of AlN. Similarly, among the "AlGaN-based semiconductor materials", the material may be referred to as an "AlN-based semiconductor material" in order to distinguish a material that does not substantially contain GaN. The "AlN-based semiconductor material" mainly contains AlN and InAlN, and also includes a material containing a trace amount of GaN.

The substrate 12 is a sapphire (Al ₂ O ₃ ) substrate. For example, the first base layer 14 and the second base layer 16 are laminated on the (0001) surface of the sapphire substrate. The first base layer 14 is a layer formed of an AlN-based semiconductor material, and is, for example, an AlN (HT-AlN) layer grown at a high temperature. The second base layer 16 is a layer formed of an AlGaN-based semiconductor material, and is, for example, an undoped AlGaN (u-AlGaN) layer.

The substrate 12, the first base layer 14, and the second base layer 16 function as a base layer (template) for forming a layer above the n-type clad layer 18. Further, these layers function as a light extraction substrate for extracting the deep ultraviolet light emitted by the active layer 20 to the outside, and transmit the deep ultraviolet light emitted by the active layer 20.

The n-type clad layer 18 is an AlGaN layer formed of an n-type AlGaN-based semiconductor material and doped with silicon (Si) as an n-type impurity, for example. The composition ratio of the n-type clad layer 18 is selected so as to transmit the deep ultraviolet light emitted by the active layer 20, and the n-type clad layer 18 is formed so that, for example, the molar fraction of AlN is 40% or more, preferably 50% or more. To. The n-type clad layer 18 has a thickness of about 100 nm to 300 nm, and has a thickness of, for example, about 200 nm.

The active layer 20 is formed on a partial region of the n-type clad layer 18. The active layer 20 is formed of an AlGaN-based semiconductor material and is sandwiched between an n-type clad layer 18 and an electron block layer 22 to form a double heterojunction structure. The active layer 20 may form a single-layer or multi-layer quantum well structure. Such a quantum well structure is formed, for example, by laminating a barrier layer formed of an n-type AlGaN-based semiconductor material and a well layer formed of an undoped AlGaN-based semiconductor material.

The electron block layer 22 is formed on the active layer 20. The electron block layer 22 is a layer formed of a p-type AlGaN-based semiconductor material, and is, for example, an AlGaN layer doped with magnesium (Mg) as a p-type impurity. The electron block layer 22 is formed so that, for example, the molar fraction of AlN is 40% or more, preferably 50% or more. The electron block layer 22 may be formed so that the molar fraction of AlN is 80% or more, or may be formed of an AlN-based semiconductor material that does not substantially contain GaN. The electron block layer 22 has a thickness of about 1 nm to 10 nm, and has a thickness of, for example, about 2 nm to 5 nm.

The p-type clad layer 24 is formed on the electron block layer 22. The p-type clad layer 24 is a layer formed of a p-type AlGaN-based semiconductor material, and is, for example, an Mg-doped AlGaN layer. The composition ratio of the p-type clad layer 24 is selected so that the molar fraction of AlN is lower than that of the electron block layer 22. The p-type clad layer 24 has a thickness of about 300 nm to 700 nm, and has a thickness of, for example, about 400 nm to 600 nm.

The reflective layer 26 is provided in the first region W1 above the p-type clad layer 24. The reflective layer 26 is formed of a material having a lower refractive index than a layer made of an AlGaN-based semiconductor material such as the p-type clad layer 24. The reflective layer 26 is made _{of an insulator material containing silicon such as silicon oxide (SiO 2} ), silicon nitride (SiN), and silicon oxynitride (SiON). The reflective layer 26 has a function of reflecting deep ultraviolet light from the active layer 20 at the interface with the p-type clad layer 24 and directing it toward the substrate 12.

The reflective layer 26 is preferably made of a material having a large difference in refractive index from the p-type clad layer 24 so that deep ultraviolet light can be effectively reflected at the interface with the p-type clad layer 24. .. Since the refractive index of the AlGaN-based semiconductor material constituting the p-type clad layer 24 is about 2.1 to 2.7, silicon oxide (refractive index of about 1.45) is particularly used as a material having a large difference in refractive index. Is preferable.

In the reflective layer 26, the deep ultraviolet light reflected at the interface with the p-type clad layer 24 and the deep ultraviolet light reflected at the interface with the contact layer 28 are strengthened by each other to increase the intensity of the reflected light. It preferably has a thickness d. The condition of such a thickness d is that d = (λ / 4n) (2m-1) using the wavelength λ of deep ultraviolet light, the refractive index n of the reflective layer 26 with respect to this wavelength λ, and an integer m of 1 or more. Can be expressed by the formula of. For example, when λ = 280 nm, n = 1.45, and m = 1, the preferable thickness d of the reflective layer 26 is about 50 nm. The thickness d of the reflective layer 26 is preferably 200 nm or less, and more preferably 100 nm or less.

The reflective layer 26 is provided on the p-type clad layer 24 so as to avoid the second region W2 adjacent to the first region W1, and the second region W2 is provided with an opening 30 penetrating the reflective layer 26. .. Further, the reflective layer 26 is provided so that the first region W1 and the second region W2 are alternately arranged in the direction in which the first region W1 and the second region W2 are adjacent to each other.

2 to 4 are top views schematically showing a configuration example of the reflective layer 26. The reflective layer 26 is provided in a mesh shape, a line shape, or a dot shape, as shown in FIGS. 2 to 4, respectively. For example, as shown in FIG. 2, the first region W1 provided with the reflective layer 26 is provided in a mesh shape, and the second region W2 provided with the opening 30 is arranged at intervals in a grid pattern. .. In another configuration example, as shown in FIG. 3, the first region W1 and the second region W2 are alternately formed in a line shape. In yet another configuration example, as shown in FIG. 4, the first region W1 provided with the reflective layer 26 is arranged at intervals in a grid pattern, and the second region W2 provided with the opening 30 is arranged in a mesh shape. It will be provided. It should be noted that these arrangements are examples, and each region may be provided in a circular shape, may be arranged in a hexagonal grid pattern, or each region may be arranged non-uniformly.

The first region W1 is preferably formed so that the width l of the first region W1 in the direction in which the first region W1 and the second region W2 are adjacent to each other is 10 μm or less. In the case of the mesh shape as shown in FIG. 2, it is desirable that the width of the first region W1 extending in the vertical direction or the horizontal direction in the lateral direction is 10 μm or less. Similarly, in the case of the line shape as shown in FIG. 3, it is desirable that the width of the first region W1 extending in the longitudinal direction in the lateral direction is 10 μm or less. Further, in the case of the dot shape as shown in FIG. 4, it is desirable that the length of one side of each first region W1 is 10 μm or less.

It is preferable that each region is formed so that the width l of the first region W1 is smaller than the diffusion length of the carriers in the p-type clad layer 24. This allows the carriers injected through the contact layer 28 provided in the opening 30 of the second region W2 to reach the entire area of the active layer 20. In other words, the carriers to be injected from the contact layer 28 are shielded by the reflective layer 26 to prevent the carriers from reaching the active layer 20 located immediately below the reflective layer 26. As a result, it is possible to suppress a decrease in the luminous efficiency of the active layer 20 as a whole.

Further, the width l of the first region W1 in which the reflective layer 26 is provided is preferably formed so as to be 1 μm or more, and has a width of about several times or more the wavelength λ of the ultraviolet light emitted by the active layer 20. It is desirable to be formed in. By making the width of the first region W1 sufficiently larger than the wavelength λ, deep ultraviolet light is suitably reflected by the reflection layer 26.

The contact layer 28 is provided so as to cover both the reflective layer 26 and the p-type clad layer 24 exposed to the opening 30. The contact layer 28 is formed of a p-type AlGaN-based semiconductor material, and the composition ratio is selected so that the Al content is lower than that of the electron block layer 22 and the p-type clad layer 24. The contact layer 28 preferably has an AlN mole fraction of 20% or less, and more preferably an AlN mole fraction of 10% or less. The contact layer 28 may be formed of a p-type GaN-based semiconductor material that does not substantially contain AlN. By reducing the mole fraction of AlN in the contact layer 28, good ohmic contact with the p-side electrode 32 can be obtained. Further, the bulk resistance of the contact layer 28 can be lowered, and the carrier injection efficiency into the active layer 20 can be improved.

The contact layer 28 is formed using the reflective layer 26 having the opening 30 as a template, and is formed on the reflective layer 26 so that epitaxial lateral growth (ELO) is dominant. By using ELO, it is possible to prevent the occurrence of defects due to lattice mismatch at the interface with the p-type clad layer 24 having different Al contents, and improve the crystallinity of the contact layer 28.

The p-side electrode 32 is provided on the contact layer 28. The p-side electrode 32 is formed of a material capable of achieving ohmic contact with the contact layer 28, and is formed of, for example, a nickel (Ni) / gold (Au) laminated structure. The thickness of each metal layer is, for example, about 60 nm for the Ni layer and about 50 nm for the Au layer.

The n-side electrode 34 is provided on the n-type clad layer 18 in an exposed region where the active layer 20 is not provided. The n-side electrode 34 is formed, for example, by a laminated structure of titanium (Ti) / Al / Ti / Au. The thickness of each metal layer is, for example, about 20 nm for the first Ti layer, about 100 nm for the Al layer, about 50 nm for the second Ti layer, and about 100 nm for the Au layer.

Subsequently, a method for manufacturing the light emitting element 10 will be described with reference to FIGS. 5 to 8.
First, as shown in FIG. 5, the first base layer 14, the second base layer 16, the n-type clad layer 18, the active layer 20, the electron block layer 22, and the p-type clad layer 24 are laminated in this order on the substrate 12. .. The second base layer 16, the n-type clad layer 18, the active layer 20, the electron block layer 22 and the p-type clad layer 24 formed of an AlGaN-based semiconductor material are formed by a metalorganic chemical vapor deposition (MOVPE) method or a molecular beam epitaxy. It can be formed using a well-known epitaxial growth method such as epitaxy (MBE) method.

Subsequently, the reflective layer 26 is formed on the p-type clad layer 24. The reflective layer 26 is formed of, for example, SiO _2. The method for forming the reflective layer 26 is not particularly limited, and the reflective layer 26 can be formed by using a well-known method such as a MOVPE method or another CVD method.

Next, as shown in FIG. 6, the reflective layer 26 is patterned to form the opening 30. The opening 30 can be formed by preparing a mask patterned on the reflective layer 26 by using a photolithography technique or the like, and etching a part of the reflective layer 26 through the mask. The opening 30 may be formed by dry etching using plasma or the like, or may be formed by wet etching using hydrofluoric acid (HF) or the like.

Next, as shown in FIG. 7, the contact layer 28 is formed on the reflection layer 26 and the p-type clad layer 24 exposed from the opening 30. The contact layer 28 is formed of, for example, a p-type AlGaN-based semiconductor material or a p-type GaN-based semiconductor material. The contact layer 28 can be formed by using a well-known epitaxial growth method such as the MOVPE method or the MBE method.

Next, as shown in FIG. 8, a part of the active layer 20, the electron block layer 22, the p-type clad layer 24 and the contact layer 28 formed on the n-type clad layer 18 is removed to remove the n-type clad. It forms an exposed area 38 where the layer 18 is exposed. The exposed region 38 can be formed, for example, by masking a part of the contact layer 28 and etching each layer through the mask. The exposed region 38 can be formed by, for example, dry etching using plasma.

Next, the p-side electrode 32 of Ni / Au is formed on the contact layer 28, and the n-side electrode 34 of Ti / Al / Ti / Au is formed in the exposed region 38 on the n-type clad layer 18. Each metal layer constituting the p-side electrode 32 and the n-side electrode 34 can be formed by a well-known method such as the MBE method. As a result, the light emitting element 10 shown in FIG. 1 is completed.

Next, the effect of the light emitting element 10 according to the present embodiment will be described.
FIG. 9 is a diagram schematically showing the effect of the light emitting element 10 in the embodiment. According to the present embodiment, since the reflective layer 26 is provided between the p-type clad layer 24 and the contact layer 28, the deep ultraviolet light A from the active layer 20 toward the electron block layer 22 is reflected by the reflective layer 26. It can be directed toward the substrate 12 and taken out of the light emitting element 10 from the main surface 12a of the substrate 12. In particular, by providing the reflective layer 26 at a position closer to the active layer 20 than the contact layer 28 that absorbs deep ultraviolet light, the deep ultraviolet light A reflected by the reflective layer 26 is absorbed by the contact layer 28 and attenuated. Can be prevented. As a result, the light extraction efficiency of deep ultraviolet light can be improved.

Further, according to the present embodiment, of the deep ultraviolet light from the active layer 20 toward the substrate 12, the deep ultraviolet light B reflected by the main surface 12a of the substrate 12 and directed toward the contact layer 28 is reflected by the reflection layer 26. Then, it can be directed to the substrate 12 again. As a result, a part of the deep ultraviolet light that is reflected by the main surface 12a of the substrate 12 and absorbed by the contact layer 28 can be taken out of the light emitting element 10. As a result, the light extraction efficiency of deep ultraviolet light can be improved.

Further, according to the present embodiment, since the contact layer 28 is formed on the reflective layer 26 having the patterned opening 30, the contact layer 28 can be formed by the ELO using the reflective layer 26 as a template. If the contact layer is epitaxially grown on the p-type clad layer 24 without providing the reflective layer 26, dislocations occur in the contact layer due to lattice mismatch between the p-type clad layer 24 and the contact layer, resulting in defects. .. If there are many defects in the contact layer, the reliability of the light emitting element may be significantly affected. On the other hand, according to the present embodiment, by using ELO, the contact layer 28 having few defects can be formed, and the reliability of the light emitting element 10 can be improved.

FIG. 10 is a cross-sectional view schematically showing the configuration of the light emitting element 10 according to the modified example. This modification differs from the above-described embodiment in that a buffer layer 40 is further provided, and the contact layer 28 has a first contact layer 42 and a second contact layer 44. The reflective layer 26 and the contact layer 28 are formed on the buffer layer 40. Hereinafter, this modification will be described focusing on the differences from the above-described embodiment.

The buffer layer 40 is provided between the p-type clad layer 24 and the reflective layer 26 and the contact layer 28. The buffer layer 40 is formed of a p-type AlGaN-based semiconductor material, and the composition ratio is selected so that the Al content is lower than that of the p-type clad layer 24. The buffer layer 40 preferably has an AlN mole fraction of 20% or less, and more preferably an AlN mole fraction of 10% or less. The buffer layer 40 may be formed of a p-type GaN-based semiconductor material that does not substantially contain AlN.

The buffer layer 40 functions as a seed layer for the first contact layer 42 to grow epitaxially, and promotes ELO of the first contact layer 42 to enhance the crystallinity of the first contact layer 42. The buffer layer 40 is preferably formed thick enough to function as a seed layer, and has a thickness of 5 nm or more, preferably 10 nm or more. On the other hand, the buffer layer 40 is deep ultraviolet light from the active layer 20 through the buffer layer 40 toward the reflection layer 26, and the depth reflected by the reflection layer 26 and passing through the buffer layer 40 again before heading to the substrate 12. It is preferably formed thin so that the amount of ultraviolet light absorbed can be suppressed. The buffer layer 40 has a thickness of 100 nm or less, preferably 50 nm or less or 20 nm or less.

FIG. 11 is a graph showing the relationship between the thickness of the buffer layer 40 and the amount of deep ultraviolet light transmitted. This figure shows a case where the buffer layer 40 is made of a p-type GaN-based semiconductor material that does not substantially contain AlN, and a case where deep ultraviolet light reflected by the reflection layer 26 passes through the buffer layer 40 in a reciprocating manner. Indicates the amount of transmission. As shown, it can be seen that the permeation amount decreases as the thickness of the buffer layer 40 increases, and the permeation amount becomes less than 10% when the thickness of the buffer layer 40 reaches 100 nm. From this, it can be said that it is preferable that the thickness of the buffer layer 40 is 100 nm or less in order to increase the extraction efficiency of deep ultraviolet light by the reflection of the reflection layer 26. When the buffer layer 40 is made of an AlGaN-based semiconductor material containing AlN, the absorption rate of ultraviolet light is lower than that of the GaN-based semiconductor material. Therefore, even if the thickness of the buffer layer 40 is 100 nm or more. Good.

The first contact layer 42 is provided so as to cover both the top of the reflection layer 26 and the top of the buffer layer 40 exposed to the opening 30. The first contact layer 42 is provided so as to be in contact with the buffer layer 40. The first contact layer 42 is formed of a p-type AlGaN-based semiconductor material like the contact layer 28 according to the above-described embodiment, and has a lower Al content than the electron block layer 22 and the p-type clad layer 24. The composition ratio is selected as follows. The composition ratio of the first contact layer 42 is selected so that the Al content is the same as that of the buffer layer 40 or the Al content is lower than that of the buffer layer 40. By forming the first contact layer 42 on the buffer layer 40, the ELO of the first contact layer 42 can be promoted and the crystallinity of the first contact layer 42 can be improved.

The second contact layer 44 is provided on the first contact layer 42. The second contact layer 44 is made of a p-type AlGaN-based semiconductor material or a p-type GaN-based semiconductor material that does not substantially contain AlN, and has the same Al content as that of the first contact layer 42 or is more than the buffer layer 40. The composition ratio is selected so that the Al content is low. A p-side electrode 32 is provided on the second contact layer 44.

According to this modification, by inserting the buffer layer 40 between the p-type clad layer 24 and the contact layer 28, the crystallinity of the contact layer 28 can be further enhanced and the bulk resistance of the contact layer 28 can be reduced. Further, by setting the thickness of the buffer layer 40 to 5 nm or more and 100 nm or less, preferably 10 nm or more and 50 nm or less, both the carrier injection efficiency into the active layer 20 and the light extraction efficiency from the active layer 20 can be improved. ..

The present invention has been described above based on examples. It is understood by those skilled in the art that the present invention is not limited to the above-described embodiment, various design changes are possible, various modifications are possible, and such modifications are also within the scope of the present invention. It is about to be.

In another modification, a superlattice structure made of a p-type AlGaN-based semiconductor material may be formed on the p-type clad layer 24. The superlattice structure can be formed, for example, by laminating an AlGaN layer having a relatively large AlN molar ratio and an AlGaN layer having a small AlN molar ratio. Specifically, it is formed by laminating an AlGaN layer having an AlN molar ratio of 60% and an AlGaN layer having an AlN molar ratio of 40%.

This superlattice structure is configured such that the carriers (holes) injected from the contact layer 28 form a two-dimensionally distributed two-dimensional hole gas (2DHG), facilitating the lateral movement of the carriers. It is composed. By forming such a superlattice structure, carriers are supplied to a region where carriers from the contact layer 28 are difficult to be injected (for example, a region directly below the reflective layer 26) because they are shielded by the reflective layer 26. Can be done. Thereby, the luminous efficiency of the active layer 20 can be increased.

In another modification, the reflection layer 26 and the contact layer 28 may be formed on the electron block layer 22 without providing the p-type clad layer 24. In this case, the contact layer 28 may be formed over the reflective layer 26 and the electronic block layer 22 exposed to the opening 30.

In another modification, the buffer layer 40 may be provided on the electron block layer 22 without the p-type clad layer 24, and the reflection layer 26 and the contact layer 28 may be formed on the buffer layer 40. In the above-described modification, the p-side electrode 32 may be formed directly above the first contact layer 42 without providing the second contact layer 44.

10 ... light emitting element, 12 ... substrate, 18 ... n-type clad layer, 20 ... active layer, 22 ... electron block layer, 24 ... p-type clad layer, 26 ... reflective layer, 28 ... contact layer, 30 ... opening, 40 ... Buffer layer, W1 ... 1st region, W2 ... 2nd region.

Claims (9)

An n-type clad layer formed of an n-type AlGaN-based semiconductor material on a substrate, and an n-type clad layer.
An active layer formed of an AlGaN-based semiconductor material on the n-type clad layer and
An electron block layer formed of a p-type AlGaN-based semiconductor material or a p-type AlN-based semiconductor material on the active layer,
The first region on the electron block layer is formed of an insulator material containing silicon (Si) having a refractive index lower than that of the electron block layer, and is opened in a second region on the electron block layer adjacent to the first region. A reflective layer with a part and
A p-type contact layer provided across both the opening and the reflection layer and formed of a p-type AlGaN-based semiconductor material or a p-type GaN-based semiconductor material having an Al content lower than that of the electron block layer. , Equipped with
A light emitting device characterized in that the active layer emits deep ultraviolet light. The reflective layer is formed so that the first region and the second region are alternately arranged in a direction in which the first region and the second region are adjacent to each other, and the first region in the adjacent direction. The light emitting element according to claim 1, wherein the light emitting element is formed so as to have a width of 10 μm or less. The thickness d of the reflective layer is d = (λ / 4n), using the wavelength λ of the deep ultraviolet light emitted by the active layer, the refractive index n of the reflective layer with respect to the wavelength λ, and an integer m of 1 or more. The light emitting element according to claim 1 or 2 , wherein the relationship of 2m-1) is satisfied. A p-type clad layer formed of a p-type AlGaN-based semiconductor material having a lower Al content than the electron block layer is further provided between the electron block layer and the reflection layer or the contact layer. The light emitting element according to any one of claims 1 to 3. The light emitting device according to claim 4 , wherein the p-type clad layer has a superlattice structure composed of a p-type AlGaN-based semiconductor material. A buffer provided between the electron block layer and the contact layer in contact with the contact layer and composed of a p-type AlGaN-based semiconductor material or a p-type GaN-based semiconductor material having a lower Al content than the electron block layer. With more layers,
The light emitting device according to any one of claims 1 to 5 , wherein the Al content of the contact layer is equal to or less than the Al content of the buffer layer. The light emitting device according to claim 6 , wherein the thickness of the buffer layer is 100 nm or less. A step of forming an n-type clad layer containing an n-type AlGaN-based semiconductor material on a substrate, and
A step of forming an active layer containing an AlGaN-based semiconductor material on the n-type clad layer,
A step of forming an electron block layer containing a p-type AlGaN-based semiconductor material on the active layer, and
A step of forming a reflective layer composed of an insulating material containing silicon (Si) having a refractive index lower than that of the electronic block layer on the electronic block layer.
A step of removing a part of the reflective layer to form an opening penetrating the reflective layer,
A step of forming a contact layer containing a p-type AlGaN-based semiconductor material or a p-type GaN-based semiconductor material having an Al content lower than that of the electron block layer is provided across both the opening and the reflective layer. A method for manufacturing a light emitting element. A step of forming a buffer layer of a p-type AlGaN-based semiconductor material or a p-type GaN-based semiconductor material having a lower Al content than the electron block layer on the electron block layer is further provided.
The light emitting device according to claim 8 , wherein the contact layer is formed on the buffer layer in contact with the buffer layer, and the Al content of the contact layer is equal to or less than the Al content of the buffer layer. Manufacturing method.

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