JP5533093B2 - Group III nitride semiconductor light emitting device manufacturing method - Google Patents

Description

  The present invention relates to a method for manufacturing a group III nitride semiconductor light emitting device.

  In recent years, group III nitride semiconductors have attracted attention as semiconductor materials for light-emitting elements that emit light of short wavelengths. In general, group III nitride semiconductors use various oxide crystals such as sapphire single crystal, silicon carbide single crystal, or group III-V compound semiconductor single crystal as a substrate, and metal organic vapor phase chemical reaction method ( MOCVD method), molecular beam epitaxy method (MBE method), hydride vapor phase epitaxy method (HVPE method), or the like.

The crystal growth method that has been widely adopted at present is a method of using sapphire, SiC, GaN, AlN, or the like as a substrate and using a metal organic chemical vapor deposition (MOCVD) method on the substrate. A method of growing an n-type semiconductor layer, an active layer, and a p-type semiconductor layer in a temperature range of about 700 ° C. to 1200 ° C. using a group III organometallic compound and a group V source gas in a reaction tube in which the substrate of FIG. It is.
Then, after the growth of each semiconductor layer, a negative electrode is formed on the substrate or the n-type semiconductor layer, and a positive electrode is formed on the p-type semiconductor layer, whereby a light emitting element is obtained.

  The conventional active layer uses InGaN with a composition adjusted to adjust the emission wavelength, and adopts a double hetero structure that sandwiches it between layers with a higher band gap than InGaN, and a multiple quantum well structure that uses the quantum well effect (For example, Patent Documents 1 to 4).

The p-type semiconductor layer has a band gap larger than that of the active layer, and a p-type cladding layer having a function of blocking electrons and holes by a potential barrier based on the gap difference is joined to the p-type electrode. The p-type contact layer is generally used.
Japanese Patent Laid-Open No. 10-79501 Japanese Patent Laid-Open No. 11-354839 JP 2001-68733 A US Patent Application Publication No. US2003 / 0160229A1

  By the way, as a conventional p-type cladding layer, a GaN layer doped with Mg or an AlGaN layer in which a part of Ga is replaced with Al is generally used, but the injection of holes into the active layer is not sufficient, and the output The improvement was not enough.

  The present invention has been made in view of the above circumstances, and an object thereof is to provide a method for manufacturing a group III nitride semiconductor light-emitting device having a high light emission output.

In order to achieve the above object, the present invention employs the following configuration.
[1] A step of sequentially laminating an n-type semiconductor layer and an active layer having a multiple quantum well structure, and then supplying a dopant gas containing an Mg source to the surface of the active layer at a first flow rate; with a raw material gas containing an Al source and a nitrogen source to continuously supply, by intermittently supplying the MOCVD method the dopant gas at a lower than said first flow rate a second flow rate, on the active layer, Al _x Forming a first p-type semiconductor layer having a composition of Ga _1-x N (x indicating a composition ratio is in a range of 0 <x ≦ 0.4), and on the first p-type semiconductor layer Forming a second p-type semiconductor layer having a composition of Al _c Ga _1-c N (where c indicating the composition ratio is in the range of 0 ≦ c ≦ 0.4). A method for producing a group III nitride semiconductor light-emitting device.
[2] The second p-type semiconductor layer is a p-type contact layer, and the step of forming the p-type contact layer includes a step of forming a first p-type contact layer containing Mg at a third concentration, and Mg And a second p-type contact layer forming step including a fourth concentration higher than the third concentration. The method for manufacturing a semiconductor light emitting element according to [1],

  ADVANTAGE OF THE INVENTION According to this invention, the manufacturing method of the group III nitride semiconductor light-emitting device which has high light emission output can be provided.

It is a cross-sectional schematic diagram of the group III nitride semiconductor light-emitting device which is embodiment of this invention. It is a graph explaining the manufacturing method of the group III nitride semiconductor light-emitting device which is embodiment of this invention.

  Hereinafter, a method for producing a group III nitride semiconductor light-emitting device (hereinafter referred to as a light-emitting device) according to an embodiment of the present invention will be described with reference to the drawings as appropriate. FIG. 1 is a schematic cross-sectional view of the light emitting device of this embodiment. The drawings referred to in the following description are drawings for explaining a semiconductor light emitting device, and the size, thickness, dimensions, and the like of each part shown in the drawings are different from the dimensional relationships of actual semiconductor light emitting devices.

"Light Emitting Element"
As shown in FIG. 1, a semiconductor light emitting device 1 manufactured by the manufacturing method of the present embodiment includes a substrate 11 and a stacked semiconductor layer 20 including an active layer 13 (hereinafter referred to as a light emitting layer) stacked on the substrate 11. A transparent electrode 16 laminated on the upper surface of the laminated semiconductor layer 20, a p-type bonding pad electrode 17 laminated on the transparent electrode 16, and an n-type electrode 18 laminated on the exposed surface 20a of the laminated semiconductor layer 20. It comprises. The light-emitting element 1 of the present embodiment is a face-up mount type light-emitting element that extracts light from the light-emitting layer 13 mainly from the side on which the p-type bonding pad electrode 17 is formed.

  As shown in FIG. 1, the laminated semiconductor layer 20 is configured by laminating a plurality of semiconductor layers. More specifically, the laminated semiconductor layer 20 includes an n-type semiconductor layer 12, a light emitting layer 13, a p-type cladding layer 14 (first p-type semiconductor layer), and a p-type contact layer 15 (second) from the substrate 11 side. The p-type semiconductor layers are stacked in this order.

Further, as shown in FIG. 1, the p-type contact layer 15, the p-type cladding layer 14, the light emitting layer 13 and the n-type semiconductor layer 12 are partially removed by means such as etching, and the removed portions. A part of the n-type semiconductor layer 12 is exposed. An n-type electrode 18 is stacked on the exposed surface 20 a of the n-type semiconductor layer 12.
A transparent electrode 16 and a p-type bonding pad electrode 17 are stacked on the upper surface 15 a of the p-type contact layer 15. The transparent electrode 16 and the p-type bonding pad electrode 17 constitute a p-type electrode.

As a semiconductor constituting the n-type semiconductor layer 12, the light emitting layer 13, the p-type cladding layer 14, and the p-type contact layer 15, a group III nitride semiconductor is preferably used, and a gallium nitride compound semiconductor is more preferably used. . As the gallium nitride compound semiconductor, a general formula Al _m In _n Ga _1-mn N (0 ≦ m <1, 0 ≦ n <) in which a part of Ga of gallium nitride (GaN) is substituted with Al and / or In. Semiconductors having various compositions represented by 1,0 ≦ m + n <1) are well known, and gallium nitride compound semiconductors constituting the n-type semiconductor layer 12, the light-emitting layer 13, and the p-type contact layer 15 in the present invention are generally used. Semiconductors of various compositions represented by the formula Al _m In _n Ga _1-mn N (0 ≦ m <1, 0 ≦ n <1, 0 ≦ m + n <1) can be used without any limitation. The composition of the p-type cladding layer 14 will be described later.

In the light emitting element 1 of the present embodiment, light is emitted from the light emitting layer 13 by passing a current between the p-type bonding pad electrode 17 and the n-type electrode 18.
Hereinafter, the configuration of the light emitting element 1 will be described in detail.

(substrate)
The substrate 11 of the light-emitting element 1 is not particularly limited as long as a group III nitride semiconductor crystal is epitaxially grown on the surface, and is not particularly limited. Manganese zinc iron, magnesium aluminum oxide, zirconium boride, gallium oxide, indium oxide, lithium gallium oxide, lithium aluminum oxide, neodymium gallium oxide, lanthanum strontium aluminum tantalum oxide, strontium titanium oxide, titanium oxide, hafnium, tungsten, molybdenum, etc. A substrate can be used. In particular, it is preferable to use a sapphire substrate having a c-plane as a main surface as the substrate 11. When a sapphire substrate is used, an intermediate layer 21 (buffer layer) is preferably formed on the c-plane of sapphire.

(Buffer layer)
Buffer layer 21 is preferably made of polycrystalline _{Al a Ga 1-a N (} 0 ≦ a ≦ 1) , the single crystal _{Al a Ga 1-a N (} 0 ≦ a ≦ 1) is more preferable. The thickness of the buffer layer 21 is preferably in the range of 0.01 to 0.5 μm. If the thickness of the buffer layer 21 is less than 0.01 μm, the buffer layer 21 may not sufficiently obtain an effect of relaxing the difference in lattice constant between the substrate 11 and the base layer 22. In addition, when the thickness of the buffer layer 21 exceeds 0.5 μm, although the function as the buffer layer 21 is not changed, the film forming process time of the buffer layer 21 becomes long, and the productivity may be reduced. There is.

  The buffer layer 21 serves to alleviate the difference in lattice constant between the substrate 11 and the base layer 22 and facilitate the formation of a C-axis oriented single crystal layer on the C surface of the substrate 11 made of sapphire. Therefore, when the single crystal underlayer 22 is laminated on the buffer layer 21, for example, the underlayer 22 with better crystallinity can be laminated.

  The buffer layer 21 has a hexagonal crystal structure made of a group III nitride semiconductor. The group III nitride semiconductor forming the buffer layer 21 preferably has a single crystal structure. By controlling the growth conditions, the group III nitride semiconductor crystal grows not only in the upward direction but also in the in-plane direction to form a single crystal structure. For this reason, the buffer layer 21 made of a group III nitride semiconductor having a single crystal structure can be obtained by controlling the film forming conditions of the buffer layer 21. When the buffer layer 21 having such a single crystal structure is formed on the substrate 11, the buffer function of the buffer layer 21 works effectively, so that the group III nitride semiconductor formed thereon has a good orientation. It becomes a crystal film having the property and crystallinity.

  Further, the group III nitride semiconductor forming the buffer layer 21 can be formed into columnar crystals (polycrystals) having a texture based on hexagonal crystals by controlling the film forming conditions. Note that the columnar crystal having a texture here refers to a crystal that is separated by forming a crystal grain boundary between adjacent crystal grains, and is itself a columnar shape as a longitudinal sectional shape.

(Underlayer)
Examples of the underlayer 22 include Al _p Ga _q In _r N (0 ≦ p ≦ 1, 0 ≦ q ≦ 1, 0 ≦ r ≦ 1, p + q + r = 1), and Al _s Ga _1-s N (0 ≦ s <1) is preferable because the underlayer 22 having good crystallinity can be formed. The film thickness of the underlayer 22 is preferably 0.1 μm or more, and more preferably 1 μm or more. When the thickness is greater than this, an Al _s Ga _1-s N layer with good crystallinity is easily obtained. Further, the film thickness of the base layer 22 is preferably 10 μm or less in terms of productivity and cost.

  In order to improve the crystallinity of the underlayer 22, it is desirable that the underlayer 22 is not doped with impurities. However, if n-type conductivity is required, a dopant can be added. When a dopant is added to the base layer 22, the base layer 22 functions as the n-type semiconductor layer 12.

(N-type semiconductor layer)
The n-type semiconductor layer 12 is generally composed of an n-type contact layer 12a and an n-type cladding layer 12b. The n-type contact layer 12a can also serve as the n-type cladding layer 12b. Further, the base layer 22 described above may be included in the n-type semiconductor layer 12.

The n-type contact layer 12 a is a layer for providing the n-type electrode 18. The n-type contact layer 12a is composed of an Al _b Ga _1-b N layer (0 ≦ b <1, preferably 0 ≦ b ≦ 0.5, more preferably 0 ≦ b ≦ 0.1). preferable. The n-type contact layer 12a is preferably doped with an n-type impurity, and the n-type impurity is preferably 1 × 10 ¹⁷ to 1 × 10 ²⁰ / cm ³ , preferably 1 × 10 ¹⁸ to 1 × 10 ¹⁹ /. When contained at a concentration of cm ³ , it is preferable in terms of maintaining good ohmic contact with the n-type electrode 18. Although it does not specifically limit as an n-type impurity, For example, Si, Ge, or Sn etc. are mentioned, Preferably Si or Ge is mentioned.

  The film thickness of the n-type contact layer 12a is preferably 0.5 to 5 μm, and more preferably set to a range of 1 to 3 μm. When the film thickness of the n-type contact layer 12a is in the above range, the crystallinity of the semiconductor is maintained well.

  An n-type cladding layer 12b is preferably provided between the n-type contact layer 12a and the light emitting layer 13. The n-type cladding layer 12b is a layer that injects carriers into the light emitting layer 13 and confines carriers. The n-type cladding layer 12b can be formed of AlGaN, GaN, GaInN, or the like. Alternatively, a heterojunction of these structures or a superlattice structure in which a plurality of layers are stacked may be used. Needless to say, when the n-type cladding layer 12b is formed of GaInN, it is desirable to make it larger than the band gap of GaInN of the light emitting layer 13.

The film thickness of the n-type cladding layer 12b is not particularly limited, but is preferably 0.005 to 0.5 μm, and more preferably 0.005 to 0.1 μm. The dopant concentration of the n-type cladding layer 12b is preferably 1 × 10 ¹⁷ to 1 × 10 ²⁰ / cm ³ , more preferably 1 × 10 ¹⁸ to 1 × 10 ¹⁹ / cm ³ . A dopant concentration within this range is preferable in terms of maintaining good crystallinity and reducing the operating voltage of the device.

  When the n-type cladding layer 12b is a layer including a superlattice structure, a detailed illustration is omitted, but an n-side first layer made of a group III nitride semiconductor having a thickness of 100 mm or less and The n-side second layer made of a group III nitride semiconductor having a composition different from that of the n-side first layer and having a thickness of 100 mm or less may be included. The n-type cladding layer 12b may include a structure in which n-side first layers and n-side second layers are alternately and repeatedly stacked. Preferably, either the n-side first layer or the n-side second layer may be in contact with the light emitting layer 13.

(Light emitting layer)
The light emitting layer 13 has a multiple well structure in which a plurality of barrier layers 13a and well layers 13b are alternately stacked. The number of stacks in the multi-well structure is preferably about 3 to 10 times, more preferably about 4 to 7 times. In addition, the barrier layer 13a is necessarily present on the surface of the light emitting layer 13 on the n-type semiconductor layer 12 side and the surface on the p-type cladding layer 14 side. Thereby, an electron and a hole can be effectively confined in the light emitting layer 13, and luminous efficiency can be improved. In particular, the barrier layer 13 a arranged closest to the p-type cladding layer 14 also has a function of blocking the diffusion of impurities from the p-type cladding layer 14. Examples of the diffusion of impurities in the p-type cladding layer 14 include diffusion of dopants in the p-type cladding layer 14 due to deterioration with time.

  The thickness of the well layer 13b is preferably in the range of 15 mm to 50 mm, and more preferably in the range of 20 mm to 35 mm. When the thickness of the well layer 13b is a thickness other than the above, the light emission output is reduced.

The well layer 13b is preferably a gallium nitride compound semiconductor containing In. This is because a gallium nitride compound semiconductor containing In is a crystal system that tends to have a structure having a thin film portion by a method described later. In addition, a gallium nitride-based compound semiconductor containing In can emit light in the blue wavelength region with strong intensity.
When the well layer 13b is a gallium nitride compound semiconductor containing In, it is preferable to provide a thin layer not containing In on the surface of the well layer 13b. The decomposition and sublimation of In in the active layer is suppressed, and the emission wavelength can be stably controlled, which is preferable.

The well layer 13b can be doped with impurities. As the dopant, Si or Ge known as a donor is suitable for increasing the emission intensity. The dope amount is preferably about 1 × 10 ¹⁶ cm ⁻³ to 1 × 10 ¹⁷ cm ⁻³ . If it is more than this, the emission intensity will be reduced.

  Next, the barrier layer 13a preferably has a thickness in the range of 20 to 100 inches, and more preferably in the range of 20 to 80 inches. If the thickness of the barrier layer 13a is too thin, flattening of the upper surface of the barrier layer 13a is hindered, resulting in a decrease in light emission efficiency and a decrease in aging characteristics. Moreover, when the film thickness is too thick, it causes an increase in driving voltage and a decrease in light emission. Therefore, the thickness of the barrier layer 13a is preferably 80 mm or less.

  In addition to GaN and AlGaN, the barrier layer 13a can be formed of GaInN having a smaller In ratio than GaInN constituting the well layer. Among these, GaN is preferable. The barrier layer 13a is preferably doped with Si as a dopant.

  The well layer 13b may be provided with a plurality of thin film portions. This thin film portion is formed by removing a part of the upper surface of each well layer 13b by vaporization or decomposition. In the case of a multiple quantum well structure, it is not necessary for all the well layers 13b to have a thin film portion, and the dimensions and area ratio of the thin film portion may be changed for each layer.

  The thin film portion means a portion whose thickness is less than the average thickness of the well layer 13b. The determination and measurement of the thin film portion can be made by a cross-sectional TEM photograph of the laminated semiconductor layer 20. For example, when observed with a cross-sectional TEM photograph of 500,000 times to 2,000,000 times, the thickness of the well layer 13b in the thin film portion and the thickness of the well layer 13b in the portion where the thin film portion is not formed are measured. be able to.

  The thickness of the thin film portion may be constant between the thin film portions, or may be different for each thin film portion. The thickness of the thin film portion in the case where the thickness is different for each thin film portion may be the average of the thicknesses of several to several tens of thin film portions observed by the cross-sectional TEM photograph.

The thickness of the well layer 13b in the thin film portion is preferably in the range of 0 mm to 20 mm, and more preferably in the range of 2 mm to 15 mm. Further, the film thickness difference between the thin film portion and the well layer 13b excluding the thin film portion is preferably in the range of 5 to 50 mm, and more preferably in the range of 5 to 35 mm.
When the film thickness difference is other than the above, the light emission output is reduced. In addition, the thin film portion may include a region having a thickness of 0 nm, that is, a region having no well layer at all.

  The well layer 13b having a thin film portion has a surface on the n-type semiconductor layer 12 side as a flat surface, a surface on the p-type cladding layer 14 side as an uneven surface, and a thin film portion is formed by the uneven surface. It has a structure. In the case of such a structure, the emission intensity is hardly lowered and there is an effect of suppressing deterioration due to aging. The flat surface as used herein refers to a case where the unevenness is 1 nm or less by observation with the cross-section TEM, for example. More preferably, it is 0.5 nm or less, and it is particularly desirable that irregularities are hardly visible.

  The n-type semiconductor of the well layer 13b when the unevenness of the surface on the n-type semiconductor layer 12 side is 1/5 or less compared to the unevenness of the surface on the p-type cladding layer 14 side. It can be said that the crystallinity of the barrier layer 13a on the layer 12 side is sufficiently high, which is effective in improving the characteristics. Among these, it is more desirable that the thickness is 1/10 or less, and it is most desirable that the surface of the well layer 13b on the n-type semiconductor layer 12 side is flat so that no irregularities are visible. Accordingly, the barrier layer 13a preferably fills the thin film portion of the well layer 13b and has a flat upper surface. By doing so, the surface of the next well layer 13b on the n-type semiconductor layer 12 side becomes flat.

The shape and distribution of the thin film portion when the well layer 13b is viewed in plan are, for example, regular or irregular with a plurality of thin film portions being independent on the surface of the well layer 13b on the p-type cladding layer 14 side. It is preferable that they are dispersed and arranged. The shape of the thin film portion in plan view may be any of a circular shape, an elliptical shape, and an indefinite shape, and these shapes may be mixed.
The area ratio of the thin film portion to the entire well layer 13b is preferably 30% or less, more preferably 20% or less, and particularly preferably 10% or less. By setting the area ratio to 30% or less, it is possible to prevent a decrease in light emission efficiency, and it is possible to realize both a reduction in driving voltage and maintenance of output.

  The width of the thin film portion when the laminated semiconductor layer 20 is viewed in cross section is preferably in the range of 1 to 100 nm. More preferably, 5-50 nm is suitable.

  Further, before forming the p-type cladding layer 14, a dopant gas containing an Mg source is supplied at a flow rate higher than the flow rate at the time of forming the p-type cladding layer 14 (also referred to as a second flow rate in this specification). To do. Thereby, the initial Mg uptake in the p-type cladding layer 14 is stabilized.

The p-type cladding layer 14 according to the present invention is a film having a composition of Al _x Ga _1-x N (where x indicating the composition ratio is in the range of 0 <x ≦ 0.4). The degree of activation of the dopant is lower than that of GaN, and the carrier concentration tends to be lower than that of the GaN-based film. Therefore, in the present invention, the carrier concentration of the p-type cladding layer 14 having a composition of Al _x Ga _1-x N is improved by supplying a dopant gas to the surface of the light emitting layer in advance before forming the p-type cladding layer 14. I am trying. Further, in the initial stage of the growth of the p-type cladding layer, it is normal that the Mg incorporation efficiency is low. However, before the p-type cladding layer 14 is formed, a large flow amount of dopant gas is allowed to flow, so that the Mg incorporation is performed. Efficiency can be improved (result of observation by SIMS). The flow rate of the dopant gas that flows before forming the p-type cladding layer 14 is preferably 2 to 20 times, more preferably 2 to 10 times the flow rate of the dopant gas that flows when forming the p-type cladding layer 14. When flowing the dopant gas at a large flow rate, the flow time may be short, and when the flow rate is small, the flow time is preferably long. That is, the dopant gas flow rate and the dopant gas flow time may be adjusted so that the Mg concentration in the p-type cladding layer 14 becomes a predetermined concentration.

(P-type cladding layer)
Next, the p-type cladding layer 14 is a layer for confining carriers in the light emitting layer 13 and injecting carriers.
As shown in FIG. 1, the p-type cladding layer 14 of this embodiment has a structure in which a plurality of undoped films 14a and doped films 14b are alternately stacked. The p-type cladding layer 14 is configured by disposing undoped films 14a on the surface on the light emitting layer 13 side and the surface on the p-type contact layer 15 side, respectively. In addition, Mg is mentioned as an impurity used for a p-type cladding layer as mentioned above.

The composition of the undoped film 14 a and the doped film 14 b is preferably a composition that is larger than the band gap energy of the light emitting layer 13 and can confine carriers in the light emitting layer 13.
Specifically, the undoped film 14a preferably has a composition of Al _x Ga _1-x N (x indicating the composition ratio is in the range of 0 <x ≦ 0.4) and does not contain a dopant. A more preferable range of the composition ratio x is 0 <x ≦ 0.2, and a most preferable range is 0 <x ≦ 0.1. Thus, the crystallinity of the undoped film 14a can be improved by comprising the undoped film 14a from the AlGaN-type semiconductor which does not contain a dopant. As a result, the crystallinity of the entire p-type cladding layer 14 is improved, and the drive voltage can be reduced. Further, the inclusion of Al in the undoped film 14a facilitates the confinement of carriers in the light emitting layer 13. However, if the Al composition ratio is too high, the crystallinity of the undoped film 14a decreases, so the upper limit of the composition ratio x is preferably set as described above.

Next, the doped film 14b is a film having the same composition as the undoped film 14a (composition of Al _x Ga _1-x N (x is 0 <x ≦ 0.4)) and containing a dopant. The dopant concentration in the doped film 14b is preferably in the range of 1 × 10 ^{16 to} 5 × 10 ²¹ cm ⁻³ , more preferably in the range of 1 × 10 ¹⁷ to 1 × 10 ²¹ cm ⁻³ , and 1 × 10 ^{18 to} 5 ×. The range of 10 ²⁰ cm ⁻³ is most preferred. Moreover, it is preferable that the dopant concentration of the plurality of doped films 14b constituting the p-type cladding layer 14 is constant.

  By making the p-type cladding layer a laminated structure of the undoped film 14a and the doped film 14b, the carrier concentration can be increased while keeping the crystallinity of the entire p-type cladding layer high. Thereby, it becomes possible to inject a lot of holes into the light emitting layer 13, and the output of the light emitting element 1 can be increased. Further, since the dopant concentration of each doped film 14 b is constant, the carrier concentration of the entire p-type cladding layer 14 becomes uniform, and a large number of holes can be injected into the light emitting layer 13.

The thicknesses of the undoped film 14a and the doped film 14b are each preferably 60 mm (6 nm) or less, more preferably 40 mm (4 nm) or less, and in the range of 10 mm (1 nm) to 25 mm (2.5 nm). Most preferably it is. If the thickness of each of the undoped film 14a and the doped film 14b exceeds 100 mm (10 nm), it becomes a layer containing many crystal defects and the like.
The total film thickness of the p-type cladding layer 14 is not particularly limited, but is preferably 1 to 400 nm, and more preferably 5 to 100 nm.

In the p-type cladding layer 14, the number of pairs of undoped films 14a and doped films 14b that are alternately stacked is preferably 1 pair or more, and more preferably 10 pairs or more. When the number of pairs of the undoped films 14a and the doped films 14b that are alternately stacked is less than one pair (when there is no pair structure), the carrier concentration of the entire p-type cladding layer 14 cannot be increased, and as a result, the light emitting layer 13 As a result, it is impossible to inject a large number of holes with respect to the light emitting element, and the output of the light emitting element cannot be increased.
Furthermore, in the present invention, the number of pairs of the undoped films 14a and the doped films 14b that are alternately stacked is preferably within 100 pairs in view of the productivity of the light emitting element and the cost.

  In the case of a laminated structure (superlattice structure) having a different composition in the p-type cladding layer 14, for example, an AlGaN / GaN superlattice structure, if the interface steepness between the AlGaN layer and the GaN layer deteriorates, the light emission output may be reduced. is there. In the present invention, since the p-type cladding layer 14 has a single layer structure with a constant Al composition, the above problem does not occur.

(P-type contact layer)
Next, the p-type contact layer 15 is a layer for providing a positive electrode. The p-type contact layer 15 is preferably Al _c Ga _1-c N (0 ≦ c ≦ 0.4). When the Al composition is in the above range, it is preferable in terms of maintaining good crystallinity and good ohmic contact with the p ohmic electrode. When a p-type impurity (dopant) is contained at a concentration of 1 × 10 ¹⁸ to 1 × 10 ²¹ / cm ³ , preferably 5 × 10 ^{19 to} 5 × 10 ²⁰ / cm ³ , good ohmic contact can be obtained. It is preferable in terms of maintenance, prevention of crack generation, and good crystallinity. Although it does not specifically limit as a p-type impurity, For example, Preferably Mg is mentioned. Although the film thickness of the p-type contact layer 15 is not specifically limited, 10-500 nm is preferable, More preferably, it is 50-200 nm. When the film thickness of the p-type contact layer 15 is within this range, it is preferable in terms of light emission output.

The p-type contact layer 15 includes a first p-type contact layer whose dopant concentration is a third concentration and a second p-type contact layer whose dopant concentration is a fourth concentration higher than the third concentration. A layered product may be used. In this case, a transparent electrode and a p-type bonding pad electrode are laminated on the second p-type contact layer. The third concentration of the first p-type contact layer is preferably in the range of 5 × 10 ^{17 to} 3 × 10 ²⁰ / cm ³ . The fourth concentration of the second p-type contact layer is in the range of 2 × 10 ^{18 to} 5 × 10 ²⁰ / cm ³ and is preferably higher than that of the first p-type contact layer. Compared with the case where the p-type contact layer has a single layer structure, the dopant concentration of the first p-type contact layer is made relatively low, so that the crystallinity can be improved and the driving voltage can be reduced. Also, by making the dopant concentration of the second p-type contact layer relatively high, the ohmic resistance with the transparent electrode can be reduced and the drive voltage can be reduced.

  The thickness of the first p-type contact layer is preferably in the range of 30 to 300 nm, more preferably in the range of 50 to 200 nm. The thickness of the second p-type contact layer is preferably in the range of 5 to 40 nm, and more preferably in the range of 10 to 30 nm.

(Transparent electrode)
The transparent electrode 16 laminated on the p-type contact layer 15 preferably has a small contact resistance with the p-type contact layer 15. Moreover, in order to take out the light from the light emitting layer 13 to the exterior of the light emitting element 1 efficiently, the transparent electrode 16 is preferably excellent in light transmittance. In addition, the transparent electrode 16 preferably has excellent conductivity in order to diffuse current uniformly over the entire surface of the p-type contact layer 15.

From the above, the constituent material of the transparent electrode 16 is a conductive oxide containing any one of In, Zn, Al, Ga, Ti, Bi, Mg, W, and Ce, zinc sulfide, or chromium sulfide. A transparent conductive material selected from the group consisting of any one of them is preferred. Examples of the conductive oxide include ITO (indium tin oxide (In ₂ O ₃ —SnO ₂ )), IZO (indium zinc oxide (In ₂ O ₃ —ZnO)), and AZO (aluminum zinc oxide (ZnO—Al ₂ O _3)), GZO (gallium oxide, zinc _{(ZnO-Ga 2 O 3)} ), fluorine-doped tin oxide, titanium oxide and the like are preferable.

  Moreover, the structure of the transparent electrode 16 can be used without any limitation, including a conventionally known structure. The transparent electrode 16 may be formed so as to cover almost the entire surface of the p-type contact layer 15, or may be formed in a lattice shape or a tree shape with a gap. After the transparent electrode 16 is formed, thermal annealing for alloying or transparency may be performed, but it may not be performed.

(P-type bonding pad electrode)
The p-type bonding pad electrode 17 also serves as a bonding pad and is laminated on the transparent electrode 16. As the p-type bonding pad electrode 17, various compositions and structures are known, and these known compositions and structures can be used without any limitation, and can be provided by conventional means well known in this technical field.

(N-type electrode)
The n-type electrode 18 also serves as a bonding pad, and is formed in contact with the n-type semiconductor layer 12 of the laminated semiconductor layer 20. For this reason, when forming the n-type electrode 18, the p-type contact layer 15, the p-type cladding layer 14, the light emitting layer 13 and the n-type cladding layer 12b are partially removed to expose the n-type contact layer 12a. Then, an n-type electrode 18 that also serves as a bonding pad is formed on the exposed surface 20a. As the n-type electrode 18, various compositions and structures are known, and these known compositions and structures can be used without any limitation, and can be provided by conventional means well known in this technical field.

"Manufacturing method of semiconductor light emitting device"
Next, the manufacturing method of the light emitting element of this embodiment is demonstrated.
In order to manufacture the light emitting device 1 of the present embodiment, first, a substrate 11 such as a sapphire substrate is prepared. Next, the buffer layer 21 is formed on the upper surface of the substrate 11 by sputtering or MOCVD. When the buffer layer 21 is formed by sputtering, the ratio of the nitrogen flow rate to the nitrogen source flow rate and the inert gas flow rate in the chamber is 1% to 100%, preferably 25% to 75%. Is desirable.

Next, after forming the buffer layer 21, the base layer 22 is formed on the surface of the substrate 11 on which the buffer layer 21 is formed.
When the previously formed buffer layer 21 has columnar crystals made of AlN, it is necessary to loop dislocations by migration so that the underlying layer 22 does not inherit the crystallinity of the buffer layer 21 as it is. For this reason, as a method for laminating the underlayer 22, any crystal growth method capable of looping dislocations from the buffer layer 21 can be used without any limitation. For example, the MOCVD method, the MBE method, and the VPE method are suitable as means for forming a film having a favorable crystallinity because migration as described above can be caused. Among these, the MOCVD method is a more preferable means in that a film having the best crystallinity can be obtained.

After the formation of the foundation layer 22, the n-type contact layer 12a and the n-type cladding layer 12b are stacked to form the n-type semiconductor layer 12. The n-type contact layer 12a and the n-type clad layer 12b may be formed by sputtering or MOCVD.
When the n-type cladding layer 12b has a superlattice structure, the composition of the n-side first layer made of a group III nitride semiconductor having a thickness of 100 mm or less is different from that of the n-side first layer and is 100 mm. What is necessary is just to laminate | stack alternately the n side 2nd layer which consists of a group III nitride semiconductor with the following film thickness alternately. When the n-cladding layer 12b having a superlattice structure is formed, the MOCVD method is preferable in terms of production efficiency. A dopant may be added to each of the n-side first layer and the n-side second layer, or a combination of a doped structure / undoped structure may be used. As the impurity to be doped, conventionally known impurities can be applied to the material composition without any limitation.

The light emitting layer 13 may be formed by either sputtering or MOCVD, but MOCVD is particularly preferable. Specifically, the barrier layer 13a and the well layer 13b are alternately and repeatedly stacked by the MOCVD method using a reaction gas having a group III metal source and a nitrogen source, and the n-type cladding layer 12b side and the p-type are stacked. What is necessary is just to laminate | stack in order with which the barrier layer 13a is distribute | arranged to the clad layer 14 side.
Emitting layer 13, the temperature of the substrate _{T 1} (° C.) and the well layer 13b is grown a barrier layer 13a is grown from a, _{T 2} (° C.) the substrate temperature from _{T 1} (℃) _{(where, T} 1 ( ° C) <T ₂ (° C)), the barrier layer 13a is further grown, the substrate temperature is lowered to T ₁ (° C), and the barrier layer 13a is further grown in the lowered state. It is formed by repeating the process.

T ₁ (° C.) is preferably in the range of 650 to 900 ° C., more preferably in the range of 650 to 850 ° C., and still more preferably in the range of 680 to 800 ° C. By the temperature T ₁ of above 650 ° C., it is possible to enhance the crystallinity of the well layer 13b, thereby improving the light emission characteristics. In addition, by setting the temperature T ₁ (° C.) to 900 ° C. or less, an element that emits an intended wavelength can be obtained without reducing the amount of In taken into the well layer 13b.

T ₂ (° C.) is preferably in the range of 700 to 1000 ° C., more preferably in the range of 850 to 1000 ° C., and still more preferably in the range of 900 to 980 ° C. By setting T ₂ (° C.) to 700 ° C. or higher, the crystallinity of the barrier layer 13a can be improved, and the light emission characteristics can be improved. Further, by _{T 2} a (℃) to 1000 ° C. or less, can be reduced damage to the well layer 13b.

Further, by stopping the supply of the group III metal source while raising the substrate temperature between T ₁ (° C.) and T ₂ (° C.), a part of the well layer is decomposed or sublimated at the time of temperature rise. A thin film portion can be formed in the well layer.

(Step of supplying only the dopant gas before forming the p-type cladding layer)
Next, a dopant gas containing an Mg source is supplied to the surface of the light emitting layer 13 at a first flow rate.
Specifically, the substrate formed up to the light emitting layer 13 is placed in a reaction chamber of an MOCVD apparatus, and a dopant gas containing an Mg source is supplied at a first flow rate while the substrate is heated.
As the dopant gas, biscyclopentadienyl magnesium (Cp ₂ Mg) or the like can be used.
Moreover, as a 1st flow volume, the range of 500-1500 sccm is preferable, for example, the range of 700-1300 sccm is more preferable, The range of 800-1000 sccm is the most preferable. If the first flow rate is equal to or higher than the lower limit value, the carrier concentration of the p-type cladding layer can be increased without a shortage of the supplied Mg amount. Further, if the first flow rate is equal to or lower than the upper limit value, Mg does not become excessive, and there is no possibility that Mg is diffused into the light emitting layer 13 and the light emission output is lowered. The time for flowing the dopant gas before forming the p-type cladding layer 14 is more preferably 3 seconds to 120 seconds and 5 to 60 seconds. When the dopant gas is flowed at a large flow rate, the flow time may be short, and when the flow rate is small, the flow time is preferably long.
Furthermore, the lower limit of the temperature of the substrate 11 is 600 ° C. or higher, more preferably 700 ° C. or higher, and most preferably 800 ° C. or higher. The upper limit of the substrate temperature is 1300 ° C. or lower, more preferably 1200 ° C. or lower, and most preferably 1100 ° C. or lower. By setting the lower limit of the substrate temperature as described above, it is possible to stabilize the Mg uptake at the initial growth stage of the p-type cladding layer 14. Moreover, the damage with respect to the light emitting layer 13 can be reduced by making the upper limit of substrate temperature into the above.

(P-type cladding layer forming process)
Next, a p-type cladding layer 14 is formed on the light emitting layer 13. The step of forming the p-type cladding layer 14 (first p-type semiconductor layer) is performed by alternately repeating the following undoped film forming step and doped film forming step by MOCVD, thereby undoped film 14a and doped film 14b. Is a step of forming a structure in which a plurality of layers are alternately stacked. In the present embodiment, a pause process may be arranged between the undoped film forming process and the doped film forming process.

<Undoped film formation process>
In the undoped film forming step, first, a composition of Al _x Ga _1-x N (x indicating a composition ratio is 0 <x using a source gas containing at least an Al source, a Ga source, and a nitrogen source on the light emitting layer 13. ≦ 0.4), and an undoped film 14 a containing no dopant is stacked on the light emitting layer 13.
Trimethylaluminum (TMA) can be used as the Al source contained in the source gas. As the Ga source, for example, trimethylgallium (TMG) or triethylgallium can be used. As the nitrogen source, ammonia, hydrazine, an azide compound, or the like can be used. The source gas is supplied into the reaction chamber using hydrogen or nitrogen as a carrier gas. The lower limit of the formation temperature of the undoped film 14a is, for example, 600 ° C. or higher, more preferably 700 ° C. or higher, and most preferably 800 ° C. or higher as the temperature of the substrate 11. Moreover, the upper limit of the formation temperature of the undoped film 14a is 1300 ° C. or less, more preferably 1200 ° C. or less, and most preferably 1100 ° C. or less as the temperature of the substrate 11. By setting the lower limit of the formation temperature as described above, the crystallinity of the undoped film 14a can be enhanced and the light emission characteristics can be improved. Moreover, the damage with respect to the light emitting layer 13 can be reduced by making the upper limit of formation temperature into the above.

<Dope film formation process>
Next, a doped film forming step is performed after the undoped film forming step. In the doped film forming step, the raw material gas used in the undoped film forming step is continuously supplied, and the dopant gas is supplied at a second flow rate lower than the first flow rate, so that the composition is the same as that of the undoped film 14a. Then, a doped film 14b containing a dopant is laminated.
Moreover, as a 2nd flow volume, the range of 50-750 sccm is preferable, for example, the range of 70-650 sccm is more preferable, and the range of 80-500 sccm is the most preferable. If the second flow rate is equal to or higher than the lower limit value, the carrier concentration of the p-type cladding layer can be increased without insufficient dopant concentration. If the second flow rate is equal to or lower than the upper limit value, Mg does not become excessive, the crystallinity of the p-type cladding layer 14 is improved, and the driving voltage of the element can be lowered. Further, it is preferable that the first flow rate is equal to or lower than the second flow rate because the carrier concentration of the p-type cladding layer in the region close to the light emitting layer decreases, the drive voltage of the element increases, and the light emission output decreases. Absent. The Mg concentration of the doped film 14b is preferably 1 × 10 ^{19 to} 3 × 10 ²⁰ / cm ³ .

  Furthermore, the lower limit of the formation temperature of the doped film 14b is, for example, 600 ° C. or higher, more preferably 700 ° C. or higher, most preferably 800 ° C. or higher as the temperature of the substrate 11. Moreover, the upper limit of the formation temperature of the dope film 14b is 1300 ° C. or less, more preferably 1200 ° C. or less, and most preferably 1100 ° C. or less as the temperature of the substrate 11. By setting the lower limit of the formation temperature as described above, the crystallinity of the doped film 14b can be enhanced, and the light emission characteristics can be improved. Moreover, the damage with respect to the light emitting layer 13 can be reduced by making the upper limit of formation temperature into the above.

Further, the temperature for forming the doped film and the undoped film may be the same or different. By setting the same temperature, it is not necessary to provide an extra stabilization waiting time, which is effective in shortening the process. In particular, in the present invention, since the doped film and the undoped film are films having the same composition of Al _x Ga _1-x N, the substrate temperature in the p-type cladding layer forming process is set to the doped film forming process and the undoped film forming process. Can always be constant. This eliminates the time required for changing and stabilizing the substrate temperature, and shortens the process.

  Further, the p-type cladding layer 14 is formed by repeating the undoped film forming step and the doped film forming step, and finally performing the undoped film forming step.

FIG. 2 illustrates a nitrogen source (NH ₃ ), a Ga source (TMG), an Al source (TMA), and a step of supplying a dopant gas (Cp ₂ Mg) containing the Mg source and a step of forming a p-clad layer according to the present embodiment. is a graph illustrating the supply procedure of the dopant gas _(Cp 2 Mg). The horizontal axis in FIG. 2 is time, and the vertical axis is the supply amount. As shown in FIG. 2, in the step of supplying the dopant gas, the dopant gas is supplied in a state where the nitrogen source (NH ₃ ) and the carrier gas are always supplied. The supply flow rate of the dopant gas at this time is the first flow rate.
Next, in the undoped film forming step of the p-type cladding layer, a source gas including a nitrogen source (NH ₃ ), a Ga source (TMG) and an Al source (TMA) is supplied, and in the doped film forming step, the source gas is continuously supplied. At the same time, the dopant gas is supplied at a second flow rate lower than the first flow rate. The supply amount of the dopant gas is constant in each dope film forming step.

As described above, before the p-type cladding layer 14 is formed, the step of flowing a dopant gas at a large flow rate is provided, thereby improving the Mg incorporation efficiency at the interface between the light-emitting layer 13 and the p-type cladding layer 14.
In the p-type cladding layer forming step, a source gas containing a Ga source, an Al source, and a nitrogen source is continuously supplied, and a dopant gas is intermittently supplied at a second flow rate lower than the first flow rate. Thus, a p-type cladding layer having a composition of Al _x Ga _1-x N (x indicating the composition ratio is in the range of 0 <x ≦ 0.4) is formed on the active layer 13.

  Next, the p-type contact layer 15 is formed. The p-type contact layer 15 may be formed by either sputtering or MOCVD. However, in order to form the p-type contact layer 15 subsequent to the step of forming the p-type cladding layer 14, the p-type contact layer 15 is formed. Is preferably formed by MOCVD. In order to form the p-type contact layer 15 by the MOCVD method, a nitrogen source, a Ga source, and a dopant gas are supplied, and an Al source is supplied as necessary, whereby a III-layer structure having a single layer structure is formed on the p-type cladding layer 14. It is formed by depositing a group nitride semiconductor.

  Further, when the p-type contact layer has a stacked structure of the first p-type contact layer and the second p-type contact layer, as in the case of forming the p-type contact layer 15 having a single layer structure, a nitrogen source, a Ga source, A dopant gas is supplied and an Al source is supplied as necessary. At this time, when forming the first p-type contact layer, the flow rate of the dopant gas is made relatively low, and when forming the second p-type contact layer, the flow rate of the dopant gas is made higher than that in the case of the first p-type contact layer. To do. In this manner, the first p-type contact layer and the second p-type contact layer containing Mg at a predetermined concentration can be sequentially formed.

Thereafter, the transparent electrode 16 is laminated on the p-type contact layer 15, and the transparent electrode 16 other than the predetermined region is removed by, for example, a generally known photolithography technique. Subsequently, the laminated semiconductor layer 20 is patterned by using, for example, a photolithography technique, a part of a predetermined region of the laminated semiconductor layer 20 is etched to expose a part of the n-type contact layer 12a, and the n-type contact layer An n-type electrode 18 is formed on the exposed surface 20a of 12a. Further, a p-type bonding pad electrode 17 is formed on the transparent electrode 16.
As described above, the light emitting device 1 shown in FIG. 1 is manufactured.

According to the method for manufacturing the light-emitting element 1 of the present embodiment, the entire composition of the p-type cladding layer 14 is set to a composition of Al _x Ga _1-x N, and then the p-type cladding layer 14 is made into the undoped film 14a and the doped film. By adopting a structure in which the layers 14b are alternately stacked, the carrier concentration of the entire p-type cladding layer 14 is increased. Moreover, by supplying the dopant gas intermittently, the Mg concentration does not become excessive, and the crystallinity of the p-type cladding layer 14 can be maintained high.
Thus, by increasing the carrier concentration of the p-type cladding layer 14, it becomes possible to inject many holes into the light emitting layer 13, and the light emitting device 1 with high output can be manufactured. At the same time, by increasing the crystallinity of the p-type cladding layer 14, the light-emitting element 1 having a low driving voltage can be manufactured.

Further, according to the method for manufacturing the light emitting element 1 of the present embodiment, the carrier concentration of the entire p-type cladding layer 14 can be made uniform by making the dopant concentration of the doped film 14 b constant, and the light emitting layer 13 On the other hand, it becomes possible to inject many holes, and the light-emitting element 1 with high output can be manufactured.
Further, according to the method for manufacturing the light emitting device 1 of the present embodiment, the p-type contact layer 14 and the doped film 14b are formed by forming the surface of the p-type cladding layer 14 on the p-type contact layer 15 side with the undoped film 14a. Therefore, the crystallinity of the p-type contact layer 14 can be improved, and the manufactured light emitting device 1 is effective in reducing leakage current and improving the electrostatic withstand voltage.

  In addition, according to the method for manufacturing the light-emitting element 1 of the present embodiment, the dopant gas is supplied at a flow rate higher than that for forming the doped film 14b before the p-type cladding layer is formed. The carrier concentration of the film 14b can be made constant.

  Moreover, according to the light emitting element 1 of this embodiment, since the thickness of the barrier layer 13a is as thin as less than 70 mm, the strain applied to the well layer 13b is reduced, and the amount of strain in the well layer 13b is reduced. As a result, the output can be increased. Further, when the barrier layer 13a is thinned, the leakage current may increase. However, in this embodiment, the p-cladding layer 14 has a structure in which the undoped films 14a and the doped films 14b are alternately stacked, so that the crystallinity is excellent and the barrier It is possible to eliminate the adverse effects caused by the thinning of the layer 13a.

Hereinafter, the present invention will be described in more detail with reference to examples.
Example 1
A light emitting device made of the gallium nitride compound semiconductor shown in FIG. 1 was manufactured. First, an underlayer 22 made of undoped GaN having a thickness of 8 μm, a Si-doped n-type GaN contact layer 12 a having a thickness of 2 μm, and an n-type having a thickness of 250 nm are formed on a substrate 11 made of sapphire via a buffer layer 21 made of AlN. A type Ga _0.9 In _0.1 N clad layer 12b was sequentially laminated. Then, a 5 nm thick Si-doped GaN barrier layer and a 2.5 nm thick Ga _0.8 In _0.2 N well layer are alternately stacked five times on each of them, and finally a multiple quantum well structure provided with a barrier layer The light emitting layer 13 was laminated. All of these films were formed by MOCVD using trimethylgallium (TMG), trimethylaluminum (TMA), trimethylindium (TMI), ammonia (NH ₃ ), silane (SiH ₄ ), or the like as a reaction gas.

Next, biscyclopentadienyl magnesium (Cp ₂ Mg) was supplied onto the light emitting layer 13 using the same MOCVD apparatus following the above-described steps.
More specifically, after the supply of triethylgallium (TEG) was stopped and the growth of the GaN barrier layer was completed, the substrate temperature was raised to 975 ° C. while supplying NH ₃ gas. The carrier gas type was switched from nitrogen to hydrogen at 975 ° C. Subsequently, the pressure in the chamber of the MOCVD apparatus was changed to 15 kPa, and the substrate temperature was changed to 1050 ° C. After waiting for the pressure in the chamber and the substrate temperature to stabilize, Cp ₂ Mg was supplied into the chamber at a flow rate (first flow rate) of 950 sccm for 15 seconds.

Then, following the steps described above, using the same MOCVD _apparatus, and an undoped film of 11 layers consisting of Al _{0.06 Ga 0.94} N, consisting of _Al 0.06 _{Ga 0.94} N doped with Mg A p-type cladding layer 14 having a structure in which ten doped films are alternately stacked was formed.
More specifically, while supplying hydrogen as a carrier gas while maintaining the substrate temperature and the pressure in the chamber, by supplying TMG and TMA together with NH ₃ into the chamber for 30 seconds, Al ₀ having a thickness of 3 nm is supplied. _An undoped film made of _0.06 Ga _0.94 N was formed.
Next, while maintaining the supply of NH ₃ , TMG, and TMA, Cp ₂ Mg was supplied at a flow rate of 295 sccm (second flow rate) for 15 seconds, thereby doping Mg with a thickness of 1.5 nm _{. A} doped film made of ₀₆ Ga _0.94 N was formed.
Thereafter, an undoped film forming step and a doped film forming step were sequentially repeated, and finally an undoped film made of Al _0.06 Ga _0.94 N was formed, thereby forming a p-type cladding layer.

Then, while supplying NH ₃ gas, the substrate temperature in the chamber, the pressure, and the type of carrier gas are kept as they are, and only Cp ₂ Mg and TMG are supplied into the furnace, and p made of 200 nm Mg-doped GaN is formed. A mold contact layer was formed.

Further, a transparent electrode made of ITO having a thickness of 200 nm was formed on the p-type contact layer by a generally known photolithography technique.
Then, a p-type bonding pad having a three-layer structure including a metal reflective layer made of 200 nm Al, a barrier layer made of 80 nm Ti, and a bonding layer made of 1000 nm Au is formed on the transparent electrode using a photolithography technique. Formed.
Next, this is also etched using a photolithography technique to expose an n-type contact layer in a desired region, and an n-type electrode having a metal laminated structure is formed on the n-type contact layer to extract light. The surface was the semiconductor side.

In this structure, the Si dopant concentration of the n-type contact layer is 7 × 10 ¹⁸ cm ⁻³ , the Si dopant concentration of the n-type cladding layer is 2 × 10 ¹⁸ cm ⁻³ , and the Si dopant concentration of the GaN barrier layer is 1 × 10 ¹⁸ cm ⁻³ , the Mg dopant concentration of the doped film of the p-type cladding layer is 1 × 10 ²⁰ cm ⁻³ , and the Mg dopant concentration of the p-type contact layer is 1.5 × 10 ²⁰ cm ^−3. Met.

When the forward voltage was measured for the light-emitting element of Example 1, the forward voltage at a current application value of 20 mA was 2.9 V when the probe needle was energized.
After that, when mounted on a TO-18 can package and measured for light output by a tester, the light output at an applied current of 20 mA was 23 mW. Further, it was confirmed that the light emission distribution on the light emitting surface emitted light on the entire surface under the positive electrode. Table 1 shows the manufacturing conditions of the light-emitting element manufactured in Example 1, the thickness of each layer, and the like.

(Example 2)
A light emitting device of Example 2 was manufactured in the same manner as Example 1 except that the first flow rate was changed to 1200 sccm and the second flow rate was changed to 500 sccm. The forward voltage at 20 mA of the light emitting element was 2.9 V, and the light emission output was 22 mW. The emission distribution on the light emitting surface was confirmed to emit light on the entire surface under the positive electrode. As in the case of Example 1, the manufacturing conditions of the light emitting device of Example 2 and the thickness of each layer are shown in Table 1.

(Example 3)
A light emitting device of Example 3 was manufactured in the same manner as Example 1 except that the first flow rate was changed to 1500 sccm and the second flow rate was changed to 400 sccm. The forward voltage at 20 mA of the light emitting element was 3.0 V, and the light emission output was 21.5 mW. The emission distribution on the light emitting surface was confirmed to emit light on the entire surface under the positive electrode. In the same manner as in Example 1, Table 1 shows the manufacturing conditions of the light-emitting element of Example 3, the thickness of each layer, and the like.

Example 4
A light emitting device of Example 4 was manufactured in the same manner as Example 1 except that the first flow rate was changed to 800 sccm and the second flow rate was changed to 200 sccm. The forward voltage at 20 mA of the light emitting element was 3.0 V, and the light emission output was 23 mW. The emission distribution on the light emitting surface was confirmed to emit light on the entire surface under the positive electrode. In the same manner as in Example 1, Table 1 shows the manufacturing conditions of the light-emitting element of Example 4, the thickness of each layer, and the like.

(Example 5)
A light emitting device of Example 5 was manufactured in the same manner as Example 1 except that the first flow rate was changed to 500 sccm and the second flow rate was changed to 100 sccm. The forward voltage at 20 mA of the light emitting element was 3.1 V, and the light emission output was 22 mW. The emission distribution on the light emitting surface was confirmed to emit light on the entire surface under the positive electrode. In the same manner as in Example 1, Table 1 shows the manufacturing conditions of the light emitting device of Example 5, the thickness of each layer, and the like.

(Example 6)
A light emitting device of Example 6 was manufactured in the same manner as Example 1 except that the first flow rate was changed to 475 sccm and the second flow rate was changed to 295 sccm. The forward voltage at 20 mA of the light emitting element was 2.9 V, and the light emission output was 23 mW. The emission distribution on the light emitting surface was confirmed to emit light on the entire surface under the positive electrode. Table 1 shows the manufacturing conditions of the light emitting device of Example 6, the thickness of each layer, and the like in the same manner as in Example 1.

(Example 7)
A light emitting device of Example 7 was manufactured in the same manner as Example 1 except that the first flow rate was changed to 600 sccm and the second flow rate was changed to 250 sccm. The forward voltage at 20 mA of the light emitting element was 2.9 V, and the light emission output was 23 mW. The emission distribution on the light emitting surface was confirmed to emit light on the entire surface under the positive electrode. In the same manner as in Example 1, Table 1 shows the manufacturing conditions of the light emitting device of Example 7, the thickness of each layer, and the like.

(Comparative Example 1)
A light emitting device of Comparative Example 1 was fabricated in the same manner as Example 1 except that the composition of the undoped film in the p-type cladding layer 14 was changed to In _0.06 Ga _0.94 N. The forward voltage at 20 mA of this light emitting element was 3.3 V, and the light emission output was 8 mW. The light emission distribution on the light emitting surface was darker on the entire surface under the positive electrode than in Example 1. In the same manner as in Example 1, Table 1 shows the manufacturing conditions of the light emitting device of Comparative Example 1, the thickness of each layer, and the like.

(Comparative Example 2)
The light emitting device of Comparative Example 2 is manufactured in the same manner as in Example 1 except that the first flow rate is set to 0 sccm and the undoped film in the p-type cladding layer 14 is changed to In _0.06 Ga _0.94 N. did. The forward voltage at 20 mA of this light emitting element was 3.8 V, and the light emission output was 6 mW. The light emission distribution on the light emitting surface was darker on the entire surface under the positive electrode than in Example 1. In the same manner as in Example 1, Table 1 shows the manufacturing conditions of the light emitting device of Comparative Example 2, the thickness of each layer, and the like.

(Comparative Example 3)
A light emitting device of Comparative Example 3 was manufactured in the same manner as in Example 1 except that the first flow rate was changed to 0 sccm. The forward voltage at 20 mA of this light emitting element was 4.0 V, and the light emission output was 10 mW. The light emission distribution on the light emitting surface was darker on the entire surface under the positive electrode than in Example 1. Table 1 shows the manufacturing conditions of the light emitting device of Comparative Example 3, the thickness of each layer, and the like in the same manner as in Example 1.

(Comparative Example 4)
A light emitting device of Comparative Example 4 was manufactured in the same manner as in Example 1 except that the undoped film in the p-type cladding layer 14 was changed to GaN. The forward voltage at 20 mA of this light emitting element was 3.3 V, and the light emission output was 18 mW. The light emission distribution on the light emitting surface was slightly darker on the entire surface under the positive electrode than in Example 1. As in the case of Example 1, Table 1 shows the manufacturing conditions of the light-emitting element of Comparative Example 4, the thickness of each layer, and the like.

(Comparative Example 5)
A light emitting device of Comparative Example 5 was fabricated in the same manner as in Example 1 except that the first flow rate was set to 0 sccm and the undoped film in the p-type cladding layer 14 was changed to GaN. The forward voltage at 20 mA of this light emitting element was 3.7 V, and the light emission output was 14 mW. Compared to Example 1, it was slightly darker on the entire surface under the positive electrode. Table 1 shows the manufacturing conditions of the light emitting device of Comparative Example 5, the thickness of each layer, and the like in the same manner as in Example 1.

(Comparative Example 6)
A light emitting device of Comparative Example 6 was manufactured in the same manner as in Example 1 except that the second flow rate was changed to 1300 sccm. The forward voltage at 20 mA of the light emitting element was 4.2 V, and the light emission output was 11 mW. Compared to Example 1, it was slightly darker on the entire surface under the positive electrode. Table 1 shows the manufacturing conditions of the light emitting device of Comparative Example 6, the thickness of each layer, and the like in the same manner as in Example 1.

(Comparative Example 7)
A light emitting device of Comparative Example 7 was manufactured in the same manner as in Example 1 except that the second flow rate was changed to 950 sccm. The forward voltage at 20 mA of the light emitting element was 3.9 V, and the light emission output was 13 mW. Compared to Example 1, it was slightly darker on the entire surface under the positive electrode. Table 1 shows the manufacturing conditions of the light emitting device of Comparative Example 7, the thickness of each layer, and the like in the same manner as in Example 1.

As shown in Table 2, in all of Examples 1 to 7, the forward voltage was relatively low, the light emission output was 20 mW or more, and the light emitting device had high luminance and low power consumption.
On the other hand, in Comparative Examples 1-7, the drive voltage increased significantly or the light emission output decreased significantly.

  DESCRIPTION OF SYMBOLS 1 ... Light emitting element (Group III nitride semiconductor light emitting element), 12 ... n-type semiconductor layer, 13 ... Light emitting layer (active layer), 13a ... Barrier layer, 13b ... Well layer, 14 ... p-type cladding layer (first type p-type semiconductor layer), 14a, 114a ... undoped film, 14b, 114b, 114m ... doped film, 15 ... p-type contact layer (second p-type semiconductor layer).

Claims (2)

After sequentially stacking an active layer made of n-type semiconductor layer and the multi-quantum well structure,
Supplying a dopant gas containing a Mg source at a first flow rate to the surface of the active layer;
A source gas containing a Ga source, an Al source, and a nitrogen source is continuously supplied, and the dopant gas is intermittently supplied at a second flow rate lower than the first flow rate by the MOCVD method on the active layer. Forming a first p-type semiconductor layer having a composition of Al _x Ga _1-x N (where x indicating the composition ratio is in the range of 0 <x ≦ 0.4);
Forming a second p-type semiconductor layer having a composition of Al _c Ga _1-c N (where c is a range of 0 ≦ c ≦ 0.4) on the first p-type semiconductor layer; When,
Equipped with,
At least one of the well layers of the multiple well structure contains In, and the surface on the n-type semiconductor side is a flat surface, and the surface on the p-type semiconductor side is an uneven surface,
Further, at least one of the well layers containing In has a thin film portion not containing In, and the thickness of the thin film portion is less than the average thickness of the well layer containing In. Manufacturing method of light emitting element. The second p-type semiconductor layer is a p-type contact layer, and the step of forming the p-type contact layer includes:
Forming a first p-type contact layer containing Mg at a third concentration, and forming a second p-type contact layer containing Mg at a fourth concentration higher than the third concentration. The method for producing a group III nitride semiconductor light-emitting device according to claim 1, wherein:

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