JP5601281B2 - 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 Group III nitride semiconductor light emitting devices 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.

At present, a crystal growth method that is widely adopted is a method of using sapphire, SiC, GaN, AlN, or the like as a substrate and using a metal organic chemical vapor deposition method (MOCVD method) thereon. For example, an n-type semiconductor layer, a light emitting layer, and a p-type semiconductor layer are grown in a temperature range of 700 ° C. to 1200 ° C. using a group III organometallic compound and a group V source gas in a reaction tube in which the above-described substrate is installed. Let
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, thereby obtaining a group III nitride semiconductor light emitting device.

  The p-type semiconductor layer is generally composed of a p-type cladding layer and a p-type contact layer, and has a band gap higher than that of the light emitting layer. The p-type semiconductor layer has a function of blocking electrons and holes by a potential barrier based on this gap difference. For this reason, the p-type semiconductor layer is required to have a high band gap. Therefore, the p-type semiconductor layer is required to contain a high concentration of dopant and to have high crystallinity.

  As a method of improving the crystallinity of the p-type semiconductor layer and containing a high concentration of dopant, a method of changing the supply amount of the dopant gas when forming the p-type contact layer is disclosed (patent) References 1, 2).

Japanese Patent Laid-Open No. 10-32348 JP 2002-33514 A

  However, in the method of forming the p-type contact layer in Patent Documents 1 and 2, since the dopant gas is intermittently supplied when the carrier gas and the source gas are supplied at a constant flow rate, each time the dopant gas is supplied. The pressure in the growth chamber fluctuates. For this reason, the movement of the pump for supplying the dopant gas cannot follow the fluctuation of the pressure in the growth chamber. As a result, as the number of stacked layers of the dopant-undoped film and the doped film increases, the fluctuation in the flow rate of the dopant gas and the shift in timing for supplying the dopant gas increase. Therefore, if the p-type contact layer is formed thick by increasing the number of stacked undoped films and doped films, a high-quality p-type contact layer cannot be obtained.

In addition, since the p-type contact layer is generally formed thicker than the p-type cladding layer, the flow rate of the dopant gas is changed and the dopant gas is supplied as compared with the case where the formation method is applied to the p-type cladding layer. It is easy to be affected by the timing difference.
For this reason, the above-described formation method tends to cause problems such as a decrease in dopant concentration in the p-type contact layer and non-uniform concentration distribution.

  As a result, the crystallinity of the p-type contact layer is lowered, and a light-transmitting electrode having high crystallinity cannot be formed on the p-type contact layer in the subsequent process. As described above, the increase in VF and the decrease in light emission output of the group III nitride semiconductor light emitting device due to the decrease in dopant concentration and crystallinity in the p-type contact layer have been problems.

  The present invention has been made in view of the above problems, and the Group III nitride semiconductor light-emitting device has a high VF and a light emission output less likely to decrease due to a decrease in dopant concentration and crystallinity in the p-type contact layer. It is an object of the present invention to provide a nitride semiconductor light emitting device and a method for manufacturing the same.

In order to achieve the above object, the present invention provides the following means.
[1] An n-type semiconductor layer, a light emitting layer having a multiple quantum well structure, and a p-type cladding layer are sequentially stacked on a substrate, and then a carrier gas and a source gas including a Ga source and a nitrogen source are continuously supplied. At the same time, Al _x Ga _y In _z N (0 ≦ x ≦ 0.1, 0 ≦ y ≦ 1, 0 ≦ z) is formed on the p-type cladding layer by MOCVD method in which a dopant gas containing Mg source is intermittently supplied. ≦ 0.1, x + y + z = 1), and forming a p-type contact layer by reducing the flow rate of the carrier gas when supplying the dopant gas. A method for producing a group III nitride semiconductor light emitting device, characterized in that a total flow rate of the carrier gas, source gas and dopant gas is kept constant.
[2] In the step of forming the p-type contact layer, the first p-type contact layer is formed on the p-type cladding layer by an MOCVD method in which the source gas is continuously supplied and the dopant gas is intermittently supplied. And the first p-type contact by the MOCVD method in which the source gas is continuously supplied and the dopant gas is continuously supplied at a higher concentration than in the first p-type contact layer forming step. And a step of forming a second p-type contact layer on the layer. The method for producing a group III nitride semiconductor light-emitting device according to [1].
[3] The step of forming the p-type contact layer includes supplying the dopant gas to the surface of the p-type cladding layer at a first flow rate, continuously supplying the source gas, and the dopant gas. And a step of forming a p-type contact layer on the p-type cladding layer by an MOCVD method in which is intermittently supplied at a second flow rate lower than the first flow rate [1] Or the manufacturing method of the group III nitride semiconductor light-emitting device in any one of [2].
[4] An n-type semiconductor layer, a light emitting layer having a multiple quantum well structure, a p-type cladding layer, and Al _x Ga _y In _z N (0 ≦ x ≦ 0.1, 0 ≦ y ≦ 1, 0 ≦ z on the substrate) ≦ 0.1, p + contact layer having a composition of x + y + z = 1) is a group III nitride semiconductor light emitting device, wherein the p-type contact layer is a first p-type contact containing Mg A group III nitride semiconductor comprising: a layer first layer; and a first p-type contact layer second layer having a lower Mg content concentration than the first p-type contact layer first layer. Light emitting element [5] The p-type contact layer is formed by laminating a first p-type contact layer and a second p-type contact layer, and Mg is added to the first p-type contact layer in the second p-type contact layer. [4] characterized in that it is contained at a higher concentration than Placing of the group III nitride semiconductor light-emitting device.
[6] A lamp comprising the group III nitride semiconductor light-emitting device according to any one of [4] and [5].
[7] An electronic device in which the lamp according to [6] is incorporated.
[8] A mechanical apparatus in which the electronic device according to [7] is incorporated.

According to the method for manufacturing a group III nitride semiconductor light emitting device of the present invention, the flow rate of the carrier gas when supplying the dopant gas in the step of forming the p-type contact layer by the MOCVD method of intermittently supplying the dopant gas. Is reduced, the total flow rates of the carrier gas, the source gas, and the dopant gas during the formation of the p-type contact layer are kept constant. For this reason, the fluctuation | variation of the pressure in a growth chamber at the time of supplying dopant gas intermittently can be prevented. For this reason, even if the number of layers of the undoped film and the doped film is increased, the flow rate of the dopant gas does not change and the timing of supplying the dopant gas does not change. As a result, a film that is not doped with a dopant and a film that is doped with a dopant can be uniformly laminated.
Usually, when the p-type contact layer is doped with Mg, the crystallinity is deteriorated. However, since the film not doped with the dopant and the doped film can be uniformly laminated, the crystallinity is reduced between the doped films. A good undoped layer is inserted. Thereby, the crystallinity of the p-type contact layer can be increased and the carrier concentration can be increased as compared with the case where Mg is continuously doped. As a result, a reduction in VF and an improvement in light emission output of the group III nitride semiconductor light emitting device can be realized.

FIG. 1 is a schematic cross-sectional view showing an example of a group III nitride semiconductor light emitting device manufactured using the method for manufacturing a group III nitride semiconductor light emitting device of the present invention. FIG. 2 is a schematic cross-sectional view for explaining a process for manufacturing the group III nitride semiconductor light-emitting device shown in FIG. FIG. 3 is a graph illustrating a method for manufacturing a group III nitride semiconductor light emitting device according to an embodiment of the present invention. FIG. 4 is a graph illustrating the acceptor concentration of a group III nitride semiconductor light emitting device manufactured using the method for manufacturing a group III nitride semiconductor light emitting device of the present invention. FIG. 5 is a schematic cross-sectional view showing an example of a lamp including the group III nitride semiconductor light-emitting device shown in FIG.

  Hereinafter, the group III nitride semiconductor light emitting device 1 of the present invention will be described in detail with reference to FIG. Note that the drawings referred to in the following description may show the characteristic portions in an enlarged manner for the sake of convenience, and the dimensional ratios of the respective components are not always the same as the actual ones. In addition, the materials, dimensions, and the like exemplified in the following description are examples, and the present invention is not limited to them, and can be appropriately changed and implemented without changing the gist thereof.

FIG. 1 is a schematic cross-sectional view showing an example of a group III nitride semiconductor light emitting device 1 of the present invention.
A group III nitride semiconductor light emitting device 1 according to this embodiment shown in FIG. 1 includes a substrate 11, a laminated semiconductor layer 20 laminated on the substrate 11, and a translucent electrode 15 laminated on the upper surface of the laminated semiconductor layer 20. A p-type bonding pad electrode 16 laminated on the translucent electrode 15, and an n-type electrode 17 laminated on the exposed surface 20 a of the laminated semiconductor layer 20.

In the laminated semiconductor layer 20, at least the n-type semiconductor layer 12, the light emitting layer 13, and the p-type semiconductor layer 14 are laminated in this order from the substrate 11 side. Further, as shown in FIG. 1, the n-type semiconductor layer 12, the light emitting layer 13, and the p-type semiconductor layer 14 are partially removed by means such as etching, and the n-type semiconductor layer 12 is removed from the removed portions. A part of is exposed. An n-type electrode 17 is stacked on the exposed surface 20 a of the n-type semiconductor layer 12.
A translucent electrode 15 and a p-type bonding pad electrode 16 are stacked on the upper surface of the p-type semiconductor layer 14. The translucent electrode 15 and the p-type bonding pad electrode 16 constitute a p-type electrode 18.

As a semiconductor constituting the n-type semiconductor layer 12, the light emitting layer 13, and the p-type semiconductor layer 14, a group III nitride semiconductor is preferably used, and a gallium nitride compound semiconductor is more preferably used. As the gallium nitride compound semiconductor constituting the n-type semiconductor layer 12, the light emitting layer 13, and the p-type semiconductor layer 14 in the present invention, a general formula Al _x Ga _y In _z N (0 ≦ x ≦ 1, 0 ≦ y ≦ 1) is used. , 0 ≦ z ≦ 1, x + y + z = 1) can be used without any limitation.

The group III nitride semiconductor light-emitting device 1 of the present embodiment is configured such that light can be emitted from the light-emitting layer 13 constituting the stacked semiconductor layer 20 by passing a current between the p-type electrode 18 and the n-type electrode 17. This is a face-up mount type light emitting element that extracts light from the light emitting layer 13 from the side where the p type bonding pad electrode 16 is formed. The group III nitride semiconductor light emitting device of the present invention may be a flip chip type light emitting device.
Hereinafter, each configuration will be described in detail.

<Substrate 11>
As the substrate 11, for example, a substrate made of sapphire, SiC, silicon, GaN, germanium, zinc oxide, or the like can be used. Among the above substrates, it is particularly preferable to use a sapphire substrate having a c-plane as a main surface. Further, at least a regular uneven shape may be provided on the main surface side of the substrate 11. In addition, a bonded substrate may be used.

(Buffer layer 21)
The buffer layer 21 works 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, for example, the sapphire (0001) C surface of the substrate 11. is there. By providing the buffer layer 21, the base layer 22 having good crystallinity can be stacked on the buffer layer 21.

The buffer layer 21 is particularly preferably made of single crystal Al _x Ga _1-x N (0 ≦ x ≦ 1), but is made of polycrystalline Al _x Ga _1-x N (0 ≦ x ≦ 1). It doesn't matter.
The buffer layer 21 can be, for example, made of polycrystalline Al _x Ga _1-x N (0 ≦ x ≦ 1) and having a thickness of 0.01 μm to 0.5 μm. If the thickness of the buffer layer 21 is less than 0.01 μm, the buffer layer 21 may not be able to alleviate the difference in lattice constant between the substrate 11 and the base layer 22. Further, when the thickness of the buffer layer 21 exceeds 0.5 μm, the film forming process time of the buffer layer 21 becomes long and the productivity is lowered although the function as the buffer layer 21 is not changed. There's a problem.

  The buffer layer 21 may have a polycrystalline structure or a single crystal structure. When the buffer layer 21 having such a polycrystalline structure or a single crystal structure is formed on the substrate 11 by the MOCVD method or the sputtering method, the buffer function of the buffer layer 21 works effectively. The group III nitride semiconductor thus formed becomes a crystal film having good orientation and crystallinity.

(Underlayer 22)
As the underlayer 22, it is particularly preferable to use Al _x Ga _1-x N (0 ≦ x <1) because the underlayer 22 with good crystallinity can be formed. However, Al _x Ga _y In _z N (0 ≦ x ≦ 1, 0 ≦ y ≦ 1, 0 ≦ z ≦ 1, x + y + z = 1) may be used.
The film thickness of the underlayer 22 is preferably 0.1 μm or more, more preferably 0.5 μm or more, and most preferably 1 μm or more. The underlayer (Al _x Ga _1-x N layer) 22 is formed with a film thickness of 1 μm or more, whereby the crystallinity is improved. Moreover, it is preferable that the film thickness of the base layer 22 is 10 μm or less from the viewpoint of downsizing the group III nitride semiconductor light emitting device and shortening the formation time.

  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.

<Laminated semiconductor layer 20>
(N-type semiconductor layer 12)
The n-type semiconductor layer 12 is further composed of an n-contact layer (first n-type semiconductor layer) 12a and an n-clad layer (second n-type semiconductor layer) 12b formed in a first step described later.

(N contact layer 12a)
The n contact layer 12a is a layer for providing the n-type electrode 17, and an exposed surface 20a for providing the n-type electrode 17 is formed as shown in FIG.
The thickness of the n contact layer 12a is preferably 0.5 to 5 μm, and more preferably 2 to 4 μm. When the film thickness of the n contact layer 12a is within the above range, the crystallinity of the n contact layer 12a is favorably maintained.

The n-contact layer 12a is preferably composed of an Al _x Ga _1-x N layer (0 ≦ x <1, preferably 0 ≦ x ≦ 0.5, more preferably 0 ≦ x ≦ 0.1), This layer is doped with n-type impurities (impurities). Further, it is preferable that the n-type impurity is contained in the n-contact layer 12a at a concentration of 1 × 10 ¹⁷ to 1 × 10 ²⁰ / cm ³ , preferably 1 × 10 ¹⁸ to 1 × 10 ¹⁹ / cm ³ . When the n-type impurity is contained in the n-contact layer 12a at a concentration within this range, the width of the barrier between the n-contact layer 12a and the n-type electrode 17 is narrowed, and a tunnel current is likely to be generated. Therefore, the contact resistance between the n contact layer 12a and the n-type electrode 17 can be lowered. The n-type impurity used for the n-contact layer 12a is not particularly limited, and examples thereof include Si, Ge, and Sn. Si and Ge are preferable, and Si is most preferable. In the present embodiment, Si of about 5 × 10 ¹⁸ / cm ³ is contained as an n-type impurity (impurity).

(N-cladding layer 12b)
The n-clad layer 12b has a function of relaxing crystal lattice mismatch between the n-contact layer 12a and the light-emitting layer 13. The n-clad layer 12b is a layer for injecting carriers into the light emitting layer 13 and confining carriers.

  The n-clad layer 12b can be formed of AlGaN, GaN, GaInN, or the like. In the specification, the composition ratio of each element may be omitted and described as AlGaN or GaInN. When the n-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 structure of the n-clad layer 12b may be either a single layer structure or a superlattice structure. The film thickness of the n-clad layer 12b is preferably 5 nm to 500 nm. If the film thickness of the n-clad layer 12b is within the above range, the crystal lattice mismatch between the n-contact layer 12a and the light-emitting layer 13 can be sufficiently relaxed. Can be confined.

On the other hand, if the film thickness of the n-clad layer 12b is less than 5 nm, it is not preferable because the crystal lattice mismatch between the n-contact layer 12a and the light-emitting layer 13 cannot be sufficiently relaxed.
On the other hand, when the thickness of the n-clad layer 12b exceeds 500 nm, the series resistance increases, so that VF increases. Further, the productivity of the n-clad layer 12b is lowered, which is not preferable.

  In this embodiment, the n-clad layer 12b may be a single layer, but consists of 10 pairs (20 layers) to 40 pairs (80 layers) by repeatedly growing two thin film layers having different compositions. A superlattice structure is preferred. In the case where the n-clad layer 12b has a superlattice structure, if the number of thin film layers is 20 or more, the crystal lattice mismatch between the n-contact layer 12a and the light-emitting layer 13 is more effectively reduced. Therefore, the effect of improving the output of the group III nitride semiconductor light emitting device 1 becomes more remarkable. However, if the number of stacked thin film layers exceeds 80, the series resistance increases, so that VF increases. Further, the productivity of the n-clad layer 12b is lowered, which is not preferable.

<Light emitting layer 13>
The light emitting layer 13 has a multiple quantum well structure in which a plurality of barrier layers 13a and well layers 13b are alternately stacked. The number of stacked layers in the multiple quantum well structure is preferably 3 to 10 layers, more preferably 4 to 7 layers.

(Well layer 13b)
The thickness of the well layer 13b is preferably in the range of 1.5 nm to 5 nm. When the film thickness of the well layer 13b is within the above range, a higher light emission output can be obtained.
The well layer 13b is preferably a gallium nitride compound semiconductor containing In. A gallium nitride compound semiconductor containing In is preferable because it emits strong light in the blue wavelength region. The well layer 13b can be doped with impurities. Moreover, it is preferable to use Si as an impurity in this embodiment. The dope amount is preferably about 1 × 10 ¹⁶ cm ⁻³ to 1 × 10 ¹⁷ cm ⁻³ .

(Barrier layer 13a)
The thickness of the barrier layer 13a is preferably in the range of 2 nm or more and less than 10 nm. 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 of the barrier layer 13a is too thick, a drive voltage rises and light emission falls. For this reason, the film thickness of the barrier layer 13a is more preferably 7 nm or less.
In addition to GaN and AlGaN, the barrier layer 13a can be formed of InGaN having a smaller In ratio than InGaN constituting the well layer. Among these, GaN is preferable. Further, the barrier layer 13a can be doped with impurities. Si is preferably used as an impurity in the present embodiment. The dope amount is preferably about 1 × 10 ¹⁷ cm ⁻³ to 1 × 10 ¹⁸ cm ⁻³ .

<P-type semiconductor layer 14>
The p-type semiconductor layer 14 is usually composed of a p-type cladding layer 14a and a p-type contact layer 14b.

(P-type cladding layer 14a)
In the present embodiment, the p-type cladding layer 14 a is formed on the light emitting layer 13. The p-type cladding layer 14a is a layer for confining carriers in the light emitting layer 13 and injecting carriers. The p-type cladding layer 14a is not particularly limited as long as it has a composition larger than the band gap energy of the light emitting layer 13 and can confine carriers in the light emitting layer 13, but Al _x Ga _1-x N (0 ≦ x ≦ 0.4) is preferable. When the p-type cladding layer 14a is made of such AlGaN, it is preferable in terms of confining carriers in the light emitting layer 13.

The film thickness of the p-type cladding layer 14a is not particularly limited, but is preferably 1 to 400 nm, and more preferably 5 to 100 nm. The p-type doping concentration of the p-type cladding layer 14a is preferably 1 × 10 ¹⁸ to 1 × 10 ²¹ / cm ³ , more preferably 1 × 10 ¹⁹ to 1 × 10 ²⁰ / cm ³ . When the p-type dope concentration is in the above range, a good p-type crystal can be obtained without reducing the crystallinity. The p-type cladding layer 14a may have a superlattice structure in which thin films are stacked a plurality of times, or may have a single layer structure with a constant composition.
The growth rate of the p-type cladding layer 14a is preferably slower than the growth rate of the p-contact layer. The growth rate of the p-type cladding layer 14a is preferably in the range of 2 nm / min to 10 nm / min, more preferably 3 nm / min to 8 nm / min. When the growth rate of the p-type cladding layer 14a is less than 2 nm / min, productivity is lowered, which is not preferable. On the other hand, if the growth rate of the p-type cladding layer 14a exceeds 10 nm / min, the crystallinity of the AlGaN crystal is lowered, which is not preferable.

(P-type contact layer 14b)
As shown in FIG. 1, the p-type contact layer 14b of the present embodiment is formed by laminating a first p-type contact layer 14c and a second p-type contact layer 14d.

The first p-type contact layer 14c has a structure in which the first p-type contact layer first layer 14c ₁ and the first p-type contact layer second layer 14c ₂ is formed by alternately stacked. The first p-type contact layer first layer 14c _1, which is an impurity Mg is contained at a higher concentration than the first p-type contact layer second layer 14c _2.
The first p-type contact layer 14c, respectively to the plane of the surface and the transparent electrode 15 side of the p-type cladding layer 14a side, a first p-type contact layer first layer 14c ₁ are disposed. Thereby, the luminous efficiency of the group III nitride semiconductor light emitting device 1 can be increased. In particular, the first p-type contact layer first layer 14c ₁ arranged closest to the translucent electrode 15 also has a function of blocking the diffusion of impurities from the first p-type contact layer 14c.

The first p-type contact layer 14c is made of Al _x Ga _1-x N (0 ≦ x ≦ 0.4), and maintains good crystallinity and good ohmic contact with the p ohmic electrode. This is preferable.
The composition of the first p-type contact layer first layer 14 c ₁ and the first p-type contact layer second layer 14 c ₂ is such that the band gap energy of the first p-type contact layer 14 c is larger than the band gap energy of the light emitting layer 13. It is preferable that the composition be such that

Specifically, the first p-type contact layer first layer 14c ₁ has the same composition as the first p-type contact layer second layer 14c ₂ (a composition of Al _x Ga _1-x N (x is 0 ≦ x ≦ 0 4)), and the more preferable range of the composition ratio x is 0 ≦ x ≦ 0.2, and the most preferable range is 0 ≦ x ≦ 0.1. The smaller the value of x, the better.
The first p-type contact layer first layer 14c ₁ contains Mg as a dopant. The dopant concentration in the first p-type contact layer first layer 14c ₁ is preferably in the range of 5 × 10 ^{18 to} 5 × 10 ²⁰ cm ⁻³ , and more preferably in the range of 1 × 10 ¹⁹ to 1 × 10 ²⁰ cm ^−3. The range of 1 × 10 ^{19 to} 5 × 10 ¹⁹ cm ⁻³ is most preferable. Also, the dopant concentration of the first p-type contact layer first layer 14c ₁ that constitutes the p-type contact layer 14b is preferably constant. Since the dopant concentration of each first p-type contact layer first layer 14c ₁ is constant, the dopant distribution of the p-type contact layer 14b can be made constant.

The first p-type contact layer second layer 14c ₂ has the same composition as the first p-type contact layer first layer 14c ₁ (composition of Al _x Ga _1-x N (x is 0 ≦ x ≦ 0.4)). In addition, the more preferable range of the composition ratio x is 0 ≦ x ≦ 0.2, and the most preferable range is 0 ≦ x ≦ 0.1. Since the crystallinity of the first p-type contact layer second layer 14c A high proportion of the _second Al first p-type contact layer second layer 14c ₂ is reduced, as the upper limit of the above composition ratio x 0.4 The following is preferable, and the value is preferably as small as possible.

Further, Mg concentration of the first p-type contact layer second layer 14c ₂ is lower than the first p-type contact layer first layer 14c _1, and particularly preferably contains no Mg. When the first p-type contact layer second layer 14c ₂ is made of an AlGaInN-based semiconductor that does not contain a dopant, the crystallinity of the first p-type contact layer second layer 14c ₂ is increased. For this reason, the crystallinity of the entire p-type contact layer 14b is improved, and the drive voltage can be reduced.

The first p-type contact layer first layer 14c ₁ and the first p-type contact layer second layer 14c ₂ of the thickness is preferably not more than respectively 10 nm, more preferably 6nm or less, it is 4nm or less Is more preferable, and the range of 1 nm to 2.5 nm is most preferable. When the first p-type contact layer first layer 14c ₁ and the first p-type contact layer second layer 14c ₂ each thickness exceeds 10 nm, it becomes a layer containing many crystal defects, which is undesirable.

In the first p-type contact layer 14c, the number of pairs of the first p-type contact layer first layer 14c ₁ and the first p-type contact layer second layer 14c ₂ is preferably at least 1 pair to be alternately stacked, also 5 More preferably, it is a pair or more. By the number of pairs of the first p-type contact layer first layer 14c ₁ and the first p-type contact layer second layer 14c ₂ which are stacked in this alternate is 5 or more pairs, the carrier density of the entire p-type contact layer 14b Can be increased. As a result, a large number of holes can be injected into the light emitting layer 13, and the high output of the group III nitride semiconductor light emitting device 1 can be realized.

Further, in the present invention, the number of pairs of the first p-type contact layer first layer 14c ₁ that is layered on the first p-type contact layer second layer 14c ₂ alternately, productivity, in view of the reverse current inhibiting Therefore, it is desirable that it is within 20 pairs.
The first p-type contact layer 14c ₁ is provided on the surface closest to the translucent electrode 15 in the first p-type contact layer 14c. That, p-type cladding layer 14a side, respectively to the plane of the surface and the transparent electrode 15 side of the first p-type contact layer first layer 14c ₁ of the first p-type contact layer 14c is disposed.

A second p-type contact layer 14d may be formed on the first p-type contact layer 14c for the purpose of reducing contact resistance with the translucent electrode 15. The second p-type contact layer 14d preferably contains a higher concentration of Mg than the first p-type contact layer 14c, and is particularly about 1 × 10 ²⁰ / cm ^{3 to} 5 × 10 ²⁰ / cm ³ . It is preferably contained in a concentration. Here, the higher concentration than the first p-type contact layer 14c, that higher than the average concentration of Mg in the first p-type contact layer first layer 14c ₁ and the second p-type contact layer first layer 14c ₂ It is.
The second p-type contact layer 14d, as in the first p-type contact layer 14c, a second p-type contact layer first layer 14d ₁ of Mg is contained, the second p-type contact layer first layer 14d _A plurality of second p-type contact layer second layers 14d ₂ having a Mg content concentration lower than ₁ may be alternately stacked. The second p-type contact layer 14d ₁ is provided on the surface closest to the translucent electrode 15 in the second p-type contact layer 14d. That is, the first p-type contact layer 14c side, respectively to the plane of the surface and the transparent electrode 15 side, the second p-type contact layer first layer 14d ₁ of the second p-type contact layer 14d is disposed.

When the p-type contact layer 14b has a two-layer structure including the first p-type contact layer 14c and the second p-type contact layer 14d, the total thickness of the p-type contact layer 14b is not particularly limited. It is preferable that it is 10-500 nm, More preferably, it is 50-200 nm. The thickness of the p-type contact layer 14b within this range is preferable in terms of light emission output. The thickness of the second p-type contact layer 14d in the entire p-type contact layer 14b is preferably about 6% to 40% of the entire p-type contact layer 14b.
The p-type contact layer 14b is preferably formed at a growth rate higher than that of the p-type cladding layer 14a, more preferably formed at a growth rate twice or more that of the p-type cladding layer 14a. It is particularly preferable that the film is formed at the above growth rate.
The p-type contact layer 14b is preferably formed at a formation rate of 10 nm / min to 30 nm / min, particularly preferably formed at a formation rate of 15 nm / min to 25 nm / min. preferable. When the growth rate of the p-type contact layer 14b is less than 10 nm / min, it is difficult for the p-type contact layer 14b to contain a high-concentration dopant, and when it is 30 nm / min or more, the crystallinity of the p-type contact layer 14b decreases. Therefore, it is not preferable.

<N-type electrode 17>
The n-type electrode 17 also serves as a bonding pad, and is formed so as to be in contact with the n-type semiconductor layer 12 (n-contact layer 12a) of the laminated semiconductor layer 20. Therefore, when forming the n-type electrode 17, at least a part of the p-semiconductor layer 14 and the light-emitting layer 13 is removed to expose the n-type semiconductor layer 12, and on the exposed surface 20 a of the n-type semiconductor layer 12. An n-type electrode 17 also serving as a bonding pad is formed. As the n-type 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.

(Translucent electrode 15)
The translucent electrode 15 is laminated on the p-type semiconductor layer 14 and preferably has a small contact resistance with the p-type semiconductor layer 14. The translucent electrode 15 is preferably excellent in light transmissivity in order to efficiently extract light from the light emitting layer 13 to the outside of the group III nitride semiconductor light emitting device 1. In addition, the translucent electrode 15 preferably has excellent conductivity in order to diffuse current uniformly over the entire surface of the p-type semiconductor layer 14.

As a constituent material of the translucent electrode 15, any one of conductive oxide containing any one of In, Zn, Al, Ga, Ti, Bi, Mg, W, and Ce, zinc sulfide, or chromium sulfide is used. A translucent conductive material selected from the group consisting of: As the conductive oxide, ITO (indium tin oxide (In ₂ O ₃ —SnO ₂ )), IZO (indium zinc oxide (In ₂ O ₃ —ZnO)), AZO (aluminum zinc oxide (ZnO—Al ₂ O)) ₃ )), GZO (gallium zinc oxide (ZnO—Ga ₂ O ₃ )), fluorine-doped tin oxide, titanium oxide and the like.

  Moreover, the structure of the translucent electrode 15 may be any structure including a conventionally known structure. The translucent electrode 15 may be formed so as to cover almost the entire surface of the p-type semiconductor layer 14, or may be formed in a lattice shape or a tree shape with a gap.

(P-type bonding pad electrode 16)
The p-type bonding pad electrode 16 also serves as a bonding pad, and is laminated on the translucent electrode 15. As the p-type bonding pad electrode 16, 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.

  Further, the electrode area of the p-type bonding pad electrode 16 is as large as possible, but the bonding operation is easy, but it prevents the emission of light emission. Specifically, it is preferably slightly larger than the diameter of the bonding ball, and generally has a circular shape with a diameter of 100 μm.

(Protective film layer)
The protective film layer (not shown) includes the upper surface and side surfaces of the translucent electrode 15, the exposed surface 20a of the n-type semiconductor layer 12, the side surfaces of the light-emitting layer 13 and the p-type semiconductor layer 14, the n-type electrodes 17 and p as required. It is formed so as to cover the side surface and the peripheral portion of the mold bonding pad electrode 16. By forming the protective film layer, it is possible to prevent moisture and the like from entering the group III nitride semiconductor light emitting device 1 and to suppress the deterioration of the group III nitride semiconductor light emitting device 1.
As the protective film layer, it is preferable to use an insulating material having a transmittance of 80% or more at a wavelength in the range of 300 to 550 nm. For example, silicon oxide (SiO ₂ ), aluminum oxide (Al ₂ O ₃ ), niobium oxide (Nb ₂ O ₅ ), tantalum oxide (Ta ₂ O ₅ ), silicon nitride (Si ₃ N ₄ ), aluminum nitride (AlN), or the like can be used. Among these, SiO ₂ and Al ₂ O ₃ are more preferable because a dense film can be easily formed by CVD film formation.

According to the group III nitride semiconductor light-emitting device 1 of the present embodiment, the first p-type contact layer 14c is, the first p-type contact layer first layer 14c _1, than the first p-type contact layer first layer 14c ₁ since also a laminated structure of the lower first p-type contact layer second layer 14c ₂ of Mg concentration, and the first layer 14c ₁ high Mg concentration first p-type contact layer, high crystallinity first p-type contact layer A second layer 14c ₂ is formed. For this reason, it is possible to increase the Mg concentration while keeping the crystallinity of the entire p-type contact layer 14b high. Thereby, the drive voltage fall of the group III nitride semiconductor light-emitting device 1 is realizable.
Further, since each first p-type contact layer dopant concentration of the second layer 14c ₂ is constant, the carrier concentration of the entire p-type contact layer 14b is uniform. As a result, it becomes possible to inject a large number of holes into the light emitting layer 13 and increase the output of the group III nitride semiconductor light emitting device 1.

Further, p-type cladding layer 14a side, respectively to the plane of the surface and the transparent electrode 15 side of the first p-type contact layer first layer 14c ₁ of the first p-type contact layer 14c is disposed. Thereby, the luminous efficiency of the group III nitride semiconductor light emitting device 1 can be increased. In particular, the first p-type contact layer first layer 14c ₁ arranged closest to the translucent electrode 15 also has a function of blocking the diffusion of impurities from the first p-type contact layer 14c.

  Further, since the crystallinity of the entire p-type contact layer 14b is kept high, the translucent electrode 15 having high crystallinity is formed on the p-type contact layer 14b. As described above, the driving voltage of the group III nitride semiconductor light emitting device 1 can be reduced. In addition, the light emission output of the group III nitride semiconductor light emitting device 1 can be improved.

  Further, the p-type contact layer 14b has a two-layer structure including a first p-type contact layer 14c and a second p-type contact layer 14d having a higher Mg concentration than the first p-type contact layer 14c. Of the type contact layer 14b, a portion (second p-type contact layer 14d) in contact with the translucent electrode 15 can contain Mg at a high concentration. Therefore, the drive voltage of the group III nitride semiconductor light emitting device 1 can be reduced. In addition, the light emission output of the group III nitride semiconductor light emitting device 1 can be further improved.

Hereinafter, the manufacturing method of the group III nitride semiconductor light-emitting device 1 will be described in detail with reference to the drawings as appropriate.
The drawings referred to in the following description are for explaining the present invention, and the size, thickness, dimensions, etc. of the respective parts shown in the figure are the dimensional relationships of the actual group III nitride semiconductor light-emitting element 1. Is different.

In the manufacturing method of the group III nitride semiconductor light emitting device 1 of the present invention shown in FIG. 1, as an example, first, the laminated semiconductor layer 20 shown in FIG. 2 is manufactured. The method for manufacturing the laminated semiconductor layer 20 includes a buffer layer 21, a base layer 22, a first n-type semiconductor layer (n contact layer) 12 a, a second n-type semiconductor layer (n clad layer) 12 b on the substrate 11, and a light emitting layer. 13 and a p-type semiconductor layer 14 are sequentially stacked.
Hereafter, each process is demonstrated in detail using FIG.

First, for example, a substrate 11 made of sapphire or the like is prepared.
Next, the substrate 11 is placed in a growth chamber of an MOCVD apparatus (first metal organic chemical vapor deposition apparatus), and a buffer layer 21 is formed on the substrate 11 by MOCVD. Alternatively, the buffer layer 21 may be formed by sputtering, and then the substrate 11 may be moved into the growth chamber of the MOCVD apparatus to form the underlayer 22.

  As an example, the buffer layer 21 made of AlN may be formed on the substrate 11 made of sapphire or the like by using an RF sputtering method, and the base layer 22 may be sequentially laminated on the substrate in the growth chamber of the MOCVD apparatus.

The underlayer 22 is preferably formed with a film thickness of 0.1 μm or more, more preferably 0.5 μm or more, and most preferably 1 μm or more. The contact layer 12 with good crystallinity is more easily obtained when the thickness is increased. In addition, from the viewpoint of downsizing the group III nitride semiconductor light emitting device and shortening the formation time, the thickness of the underlayer 22 is preferably 10 μm or less.
In order to improve the crystallinity of the underlayer 22, it is desirable that the underlayer 22 is not doped with impurities.

Next, an n contact layer (first n-type semiconductor layer) 12 a is stacked on the substrate having the base layer 22. The n-type contact layer 12a may be formed by the MOCVD method.
When growing the n-contact layer 12a, it is preferable to set the temperature of the substrate 11 in the range of 1000 ° C. to 1200 ° C. in a hydrogen atmosphere.
Further, as a raw material for growing the n-contact layer 12a, an organic metal raw material of a group III metal such as trimethyl gallium (TMG) or triethyl gallium (TEG) and a nitrogen raw material such as ammonia (NH ₃ ) are used. A group III nitride semiconductor layer is deposited on the buffer layer. The pressure in the growth chamber of the MOCVD apparatus is preferably 15 to 80 kPa.

Next, the n clad layer 12b is formed on the n contact layer 12a. Here, in the step of forming the n-clad layer 12b having a superlattice structure, the n-side first layer made of a group III nitride semiconductor having a thickness of 10 nm or less and the III-layer having a composition different from that of the n-side first layer are 10 nm or less. An n-side second layer made of a group nitride semiconductor is repeatedly stacked alternately 20 to 80 layers. The n-side first layer and / or the n-side second layer is preferably made of a gallium nitride compound semiconductor containing In.
The n-clad layer 12b is preferably formed with a film thickness of 5 nm to 500 nm.
Further, the carrier gas used when growing the n-clad layer 12b may be only nitrogen gas or a mixed gas of hydrogen gas and nitrogen gas.

As a raw material for growing the n-clad layer 12b, for example, trimethylgallium (TMG) or triethylgallium (TEG) can be used as a Ga source. Trimethylaluminum (TMA) or triethylaluminum (TEA) can be used as the Al source.
Further, trimethylindium (TMI) or triethylindium (TEI) can be used as the In source. In addition, ammonia (NH ₃ ), hydrazine (N ₂ H ₄ ), or the like can be used as an N source that is a group V raw material. Moreover, as an n-type impurity (dopant) raw material, for example, monosilane (SiH ₄ ) or disilane (Si ₂ H ₆ ), which is a Si raw material, can be used.

Next, the light emitting layer 13 having a multiple quantum well structure is formed. First, the well layers 13b and the barrier layers 13a are alternately and repeatedly stacked. At this time, the layers are stacked so that the barrier layer 13a is disposed on the n-type semiconductor layer 12 side and the p-type semiconductor layer 14 side.
The composition and film thickness of the well layer 13b and the barrier layer 13a can be appropriately set so as to have a predetermined emission wavelength. Moreover, the substrate temperature at the time of making the light emitting layer 13 grow can be 600-900 degreeC, and nitrogen gas is used as carrier gas.

  Next, a p-type cladding layer 14 a is formed on the light emitting layer 13. When the p-type cladding layer 14a is a layer including a superlattice structure, a p-side first layer made of a group III nitride semiconductor having a thickness of 10 nm or less and a film having a composition different from that of the p-side first layer are used. A p-side second layer made of a group III nitride semiconductor having a thickness of 10 nm or less may be alternately and repeatedly stacked. Hydrogen gas is used as a carrier gas when forming the p-type cladding layer 14a.

  Here, for example, the p-type cladding layer 14a is formed by supplying a source gas containing at least an Al, Ga source and a nitrogen source and a dopant gas containing an Mg source. The growth rate of the p-type cladding layer 14a at this time is slower than the growth rate of the p-type contact layer 14b, for example, 5.1 nm / min.

  Next, a p-type contact layer 14b is formed on the p-type cladding layer 14a. Hereinafter, details of the process of forming the p-type contact layer 14b will be described.

First, before forming the p-type contact layer 14b, it is preferable to supply a dopant gas containing an Mg source to the surface of the p-type cladding layer 14a in advance at a first flow rate. Specifically, the substrate 11 formed up to the p-type cladding layer 14a is placed in the reaction chamber of the MOCVD apparatus, and a dopant gas containing an Mg source is supplied at a first flow rate while the substrate 11 is heated.
As such a dopant gas, biscyclopentadienyl magnesium (Cp ₂ Mg) or the like can be used.

  As this 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 not less than the lower limit of the above range, the amount of Mg supplied to the p-type contact layer 14b will not be insufficient. For this reason, the carrier concentration at the interface of the p-type contact layer / p-cladding layer can be increased, and VF can be decreased. In addition, since the carrier concentration at the interface of the p-type contact layer / p-cladding layer can be increased, the Mg uptake at the initial growth stage of the p-type contact layer 14b can be stabilized. Moreover, if the 1st flow rate is below the upper limit of the said range, the fall of the crystal quality by containing Mg excessively can be suppressed. Thereby, the fall of light emission output can be prevented.

  The time for which the dopant gas is allowed to flow at the first flow rate is preferably 3 seconds to 120 seconds, and more preferably 5 to 60 seconds. The flow time when the dopant gas is flowed at a large flow rate may be short, and the flow time when the flow rate is small 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 temperature of the substrate 11 is 1300 ° C. or less, more preferably 1200 ° C. or less, and most preferably 1100 ° C. or less. By setting the lower limit of the temperature of the substrate 11 as described above, it is possible to stabilize the Mg uptake at the initial stage of growth of the p-type contact layer 14b. Moreover, damage to the light emitting layer 13 can be reduced by setting the upper limit of the temperature of the substrate 11 as described above.

Next, the first p-type contact layer 14c is formed on the p-type cladding layer 14a.
Forming a first p-type contact layer 14c includes forming a first p-type contact layer first layer 14c ₁ by MOCVD, low Mg concentration than the first p-type contact layer first layer 14c ₁ By alternately repeating the step of forming the first p-type contact layer second layer 14c ₂ , the first p-type contact layer first layer 14c ₁ and the first p-type contact layer second layer 14c ₂ are alternately formed. A structure in which a plurality of layers are stacked is formed.

FIG. 3 shows a procedure of supplying a dopant gas (for example, Cp ₂ Mg) including the Mg source and supplying a source gas (for example, TMG) including the Ga source of the p-type contact layer 14b according to the present embodiment. It is a figure explaining. The horizontal axis in FIG. 3 is time, and the vertical axis is the gas flow rate.

First, for example, by supplying a source gas containing at least hydrogen (H ₂ ), a Ga source and a nitrogen source as a carrier gas, and a dopant gas having a second flow rate lower than the first flow rate by MOCVD. to form a first p-type contact layer first layer 14c ₁ on p-type cladding layer 14a. At this time, it is important to keep the total flow rate of the carrier gas, the source gas, and the dopant gas constant. Further, by supplying the gas under such a condition, the first p-type contact layer first layer 14c ₁ is faster than the growth rate of the p-type cladding layer 14a, is formed at a growth rate of 20 nm / min.
Here, for example, a carrier gas and a raw material gas and the dopant gas was supplied for 30 seconds, for example, to form the first p-type contact layer first layer 14c ₁ having a thickness of 10nm made of GaN.

For example, the second flow rate is preferably in the range of 50 to 750 sccm, more preferably in the range of 70 to 650 sccm, and most preferably in the range of 80 to 500 sccm. If the second flow rate is less than the lower limit of the above range, without first p-type contact layer dopant concentration of the first layer 14c ₁ is insufficient, it increases the carrier concentration of the p-type contact layer 14b. The second flow rate is equal to or less than the upper limit of the above range, it is prevented that the Mg concentration of the first p-type contact layer first layer 14c in ₁ becomes excessive. For this reason, the crystallinity of the p-type contact layer 14b is improved, and the driving voltage of the group III nitride semiconductor light emitting device 1 can be lowered.
If the second flow rate is the same as or higher than the first flow rate, the carrier concentration of the p-type contact layer 14b in the region close to the p-type cladding layer 14a becomes insufficient. As a result, the driving voltage of the group III nitride semiconductor light-emitting device 1 increases and the light emission output decreases, which is not preferable.
Further, it is preferable to appropriately adjust the second flow rate so that the Mg concentration of the first p-type contact layer first layer 14c ₁ is 5 × 10 ^{18 to} 5 × 10 ²⁰ cm ⁻³ .

Next, a first p-type contact layer second layer 14c ₂ on the first p-type contact layer first layer 14c _1.
First, the supply of the dopant gas containing the Mg source is stopped, and in this state, the carrier gas and the source gas used in the first p-type contact layer first layer 14c ₁ forming process are continuously supplied. In this case, the total flow rate of the gas, so that the same as the total flow rate of the first p-type contact layer first layer gas during 14c ₁ formed to adjust the flow rate of the carrier gas.
Accordingly, the first p-type contact layer second layer 14c ₂ is formed at a growth rate of, for example, 20 nm / min.

Here, for example, a carrier gas, a raw material gas was supplied for 15 seconds to form a first p-type contact layer second layer 14c ₂ having a thickness of 5 nm.
Further, the lower limit of the temperature for forming the first p-type contact layer second layer 14c _2, for example, as the temperature of the substrate 11, 600 ° C. or higher, more preferably 700 ° C. or higher, and most preferably 800 ° C. or higher. The upper limit of the first p-type formation temperature of the contact layer the second layer 14c _2, as the temperature of the substrate 11, 1300 ° C. or less, more preferably 1200 ° C. or less, and most preferably 1100 ° C. or less. The lower limit of the forming temperature by a as described above, the crystallinity of the first p-type contact layer second layer 14c 2 _b is increased, thereby improving the light emission characteristics. 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.

The temperature during the deposition of the first p-type contact layer second layer 14c ₂ may be may differ from the temperature at the time of the first p-type contact layer first layer 14c ₁ deposition, but the same preferable. By making the temperature at the time of film formation the same, it is not necessary to provide an extra stabilization waiting time. This is effective in shortening the process.
In particular, in the present invention, the first p-type contact layer first layer 14c ₁ and the first p-type contact layer second layer 14c ₂ are composed of the same Al _x Ga _1-x N (x is 0 ≦ x ≦ 0.4). Therefore, the temperature of the substrate 11 in the step of forming the p-type cladding layer 14 is set to the step of forming the first p-type contact layer first layer 14c ₁ and the step of forming the first p-type contact layer second layer 14c ₂ . Can always be constant. This eliminates the time required for changing and stabilizing the temperature of the substrate 11 and shortens the process.
By the above, the first p-type contact layer first layer 14c ₁ same composition as, and a low Mg content concentration than the first p-type contact layer first layer 14c ₁ first p-type contact layer second layer 14c ₂ is formed.

Thereafter, the first p-type contact layer first layer 14c ₁ forming step and the first p-type contact layer second are performed by intermittently supplying the dopant gas while the source gas and the carrier gas are continuously supplied. The layer 14c ₂ formation step is further repeated.

At this time, in each first p-type contact layer first layer 14c ₁ forming step, each first p-type contact layer second layer 14c ₂ forming step is carried out by the carrier gas flow rate by the amount of the second flow rate dopant gas. It is preferable that the total flow rate of the carrier gas, the source gas, and the dopant gas in the entire process of forming the p-type contact layer 14b is kept constant. Thus, it is possible to prevent by the supply of the dopant gas for forming the respective first p-type contact layer first layer 14c _1, the pressure fluctuations in the growth chamber.
Thus, by equalizing the first p-type contact layer first layer 14c ₁ formed total gas flow rates of the total flow rate of the first p-type contact layer second layer 14c ₂ formed of a gas during, p-type The crystal quality of the contact layer 14c is improved.

In addition, it is preferable that the flow rate (second flow rate) of the dopant gas in each first p-type contact layer first layer 14c ₁ forming step is always constant. Thus, it is possible to make the dopant concentration of the plurality of first p-type contact layer first layer 14c ₁ that constitutes the p-type contact layer 14b is constant. Therefore, the distribution of dopant in the p-type contact layer 14b can be made constant.

Further, in the first p-type contact layer 14c forming step, the number of pairs of the first p-type contact layer first layer 14c ₁ and the first p-type contact layer second layer 14c ₂ is 1 is preferably at least pairs and 5 pairs More preferably, the above is used. By setting the number of pairs to 5 or more, the carrier concentration of the entire p-type contact layer 14b can be increased. Further, the number of pairs of the first p-type contact layer first layer 14c ₁ and the first p-type contact layer second layer 14c _2, from the viewpoint of reverse current suppression, is desirably within 20 pairs.
Then, after forming a first p-type contact layer first layer 14c ₁ the pair of the first p-type contact layer second layer 14c _2, and finally form the first p-type contact layer first layer 14c _1. Thus, the first p-type contact layer 14c is formed.

  The growth rate of the p-type contact layer 14b is preferably faster than the growth rate of the p-clad layer 14a, preferably 2 times or more, more preferably 3 times or more the growth rate of the p-type cladding layer 14a. Specifically, the growth rate of the p-type contact layer 14b is preferably 10 nm / min to 30 nm / min, and particularly preferably 15 nm / min to 25 nm / min. When the growth rate of the p-type contact layer 14b is less than 10 nm / min, it is difficult to contain a high-concentration dopant in the p-type contact layer 14b, and when it is 30 nm / min or more, the crystallinity of the p-type contact layer 14b decreases. Therefore, it is not preferable.

Thereafter, Mg is contained on the first p-type contact layer 14c at a concentration of about 1 × 10 ²⁰ / cm ^{3 to} 5 × 10 ²⁰ / cm ³ , and the Mg concentration is higher than that of the first p-type contact layer 14c. It is preferable to form the second p-type contact layer 14d.

Second p-type contact layer 14d forming step, similarly to the first p-type contact layer 14c forming step, the second p-type contact layer first layer is higher Mg concentration than the second p-type contact layer second layer 14d ₂ The step of forming 14d ₁ and the step of forming the second p-type contact layer second layer 14d ₂ are alternately repeated, and the second p-type contact layer first layer 14d ₁ and the second p-type contact layer second layer 14d ₂ are alternately stacked, and the second p-type contact layer first is formed on the surface of the second p-type contact layer 14d on the first p-type contact layer 14c side and the surface on the translucent electrode 15 side, respectively. It is desirable to form a structure in which the layer 14d ₁ is disposed.

First, on the first p-type contact layer 14c, to form a second p-type contact layer first layer 14d ₁ containing Mg.
Next, a second p-type contact layer second layer 14d ₂ having a dopant concentration lower than that of the second p-type contact layer first layer 14d _{1 is formed} on the second p-type contact layer first layer 14d ₁ . At this time, the second p-type contact layer second layer 14d _2, it is preferable not to contain a dopant. Then, after forming the second p-type contact layer first layer 14d ₁ a pair of the second p-type contact layer second layer 14d _2, and finally forming a second p-type contact layer first layer 14d _1. Thus, the second p-type contact layer 14d is formed.

  As described above, when the p-type contact layer 14b has a two-layer structure including the first p-type contact layer 14c and the second p-type contact layer 14d, the film thickness of the entire p-type contact layer 14b is particularly Although not limited, it is preferable that it is 10-500 nm, More preferably, it is 50-200 nm. When the film thickness of the p-type contact layer 14b is within this range, it is preferable in terms of a decrease in VF of the group III nitride semiconductor light emitting device 1 and an improvement in light emission output. The thickness of the second p-type contact layer 14d in the entire p-type contact layer 14b is preferably about 6% to 40% of the entire p-type contact layer 14b.

As a result, Mg can be contained at a high concentration in the portion (p-type contact upper layer) in contact with the translucent electrode 15 and the surface thereof can be formed flat. As a result, the VF of the group III nitride semiconductor light emitting device 1 can be lowered and the light emission output can be further improved.
As described above, the laminated semiconductor layer 20 shown in FIG. 2 is manufactured.
Thereafter, the translucent electrode 15 is laminated on the p-type semiconductor layer 14 of the laminated semiconductor layer 20, and the translucent electrode 15 other than the predetermined region is removed by, for example, a generally known photolithography technique.

Subsequently, patterning is performed by a photolithography technique, for example, and a part of the laminated semiconductor layer 20 in a predetermined region is etched. By this etching, a part of the n contact layer 12a is exposed, and then the n-type electrode 17 is formed on the exposed surface 20a.
Thereafter, a p-type bonding pad electrode 16 is formed on the translucent electrode 15.
As described above, the group III nitride semiconductor light emitting device 1 shown in FIG. 1 is manufactured.

  According to the manufacturing method of the group III nitride semiconductor light emitting device 1 of the present embodiment, the carrier is used when supplying the dopant gas in the step of forming the p-type contact layer 14b by the MOCVD method of intermittently supplying the dopant gas. By reducing the gas flow rate, the total flow rates of the carrier gas, the source gas, and the dopant gas during the formation of the p-type contact layer 14b can be kept constant. For this reason, the fluctuation | variation of the pressure in a growth chamber at the time of supplying dopant gas intermittently can be prevented.

Therefore, even if many as the first p-type contact layer first layer 14c ₁ number of stacked first p-type contact layer second layer 14c _2, the dopant gas flow rate variation and a, the timing of supplying the dopant gas Misalignment does not occur. Therefore, it is possible to the first p-type contact layer first layer 14c _1, uniformly stacking a first p-type contact layer second layer 14c _2.

  FIG. 4 shows a p-type contact layer 14b formed by the method for manufacturing a group III nitride semiconductor light-emitting device 1 of this embodiment and a p-type contact layer formed by a conventional method for manufacturing a group III nitride semiconductor light-emitting device. It is the graph which showed the acceptor density | concentration of the depth direction. The horizontal axis in FIG. 4 indicates the depth from the outermost surface (translucent electrode 15 side), and the vertical axis indicates the acceptor concentration. According to the present invention, a P-type contact layer having a high electrical activation ratio and a low resistance is obtained, reflecting high-quality crystallinity, as compared with the prior art.

  As shown in FIG. 4, the p-type contact layer 14b formed by the manufacturing method of this embodiment has a higher acceptor concentration than the p-type contact layer formed by the conventional method. Further, even if the distance in the depth direction from the translucent electrode 15 side is increased, the decrease in acceptor concentration can be suppressed. Therefore, compared with the conventional manufacturing method, the p-type contact layer 14b with uniform dopant concentration distribution can be formed.

  As described above, according to this embodiment, the p-type contact layer 14b having high crystallinity and uniform dopant concentration distribution can be formed. As a result, the VF of the group III nitride semiconductor light emitting device 1 can be reduced and the light emission output can be improved.

  Further, by supplying a dopant gas containing an Mg source at the first flow rate to the surface of the p-type cladding layer 14a, the amount of Mg supplied to the p-type contact layer 14b is not insufficient. For this reason, the carrier concentration of the p-type contact layer 14b can be increased. In addition, it is possible to stabilize the Mg uptake at the initial growth stage of the p-type contact layer 14b.

Further, in the step of forming a p-type contact layer 14b, finally by forming the first p-type contact layer first layer 14c _1, the first p-type contact layer 14c, the surface of the p-type cladding layer 14a side and each face of the transparent electrode 15 side, the first p-type contact layer first layer 14c ₁ are disposed. As a result, the VF of the group III nitride semiconductor light emitting device 1 can be reduced and the light emission output can be improved.

Moreover, by making the flow rate of the dopant gas constant in each first p-type contact layer first layer 14c ₁ formation step, the plurality of first p-type contact layer first layers 14c ₁ constituting the p-type contact layer 14b The dopant concentration can be made constant. Therefore, the distribution of dopant in the p-type contact layer 14b can be made constant. As described above, the VF of the group III nitride semiconductor light-emitting element 1 can be reduced and the light emission output can be improved.

  Further, the p-type contact layer 14b has a two-layer structure including a first p-type contact layer 14c and a second p-type contact layer 14d having a Mg concentration higher than that of the first p-type contact layer 14c. A portion of the contact layer 14b that is in contact with the translucent electrode 15 (second p-type contact layer 14d) can contain Mg at a high concentration, and the surface thereof can be formed flat. Therefore, the VF of the group III nitride semiconductor light emitting device 1 can be reduced and the light emission output can be improved.

<Lamp 3>
The lamp 3 of the present embodiment includes the group III nitride semiconductor light emitting device 1 of the present invention, and is a combination of the above group III nitride semiconductor light emitting device 1 and a phosphor. The lamp 3 of the present embodiment can have a configuration well known to those skilled in the art by means well known to those skilled in the art. For example, in the lamp 3 of the present embodiment, a technique for changing the emission color by combining the group III nitride semiconductor light emitting device 1 and the phosphor can be adopted without any limitation.

  FIG. 5 is a schematic cross-sectional view showing an example of a lamp including the group III nitride semiconductor light-emitting element 1 shown in FIG. The lamp 3 shown in FIG. 5 is a cannonball type, and the group III nitride semiconductor light-emitting element 1 shown in FIG. 1 is used. As shown in FIG. 5, the p-type bonding pad electrode 16 of the group III nitride semiconductor light emitting device 1 is connected to one of the two frames 31 and 32 (the frame 31 in FIG. 5) by a wire 33, and the group III The n-type electrode 17 (bonding pad) of the nitride semiconductor light emitting device 1 is connected to the other frame 32 by a wire 34, whereby the group III nitride semiconductor light emitting device 1 is mounted. Further, the periphery of the group III nitride semiconductor light emitting device 1 is sealed with a mold 35 made of a transparent resin.

  Since the lamp 3 of the present embodiment uses the group III nitride semiconductor light emitting device 1 described above, a high light emission output can be obtained.

  In addition, electronic devices such as backlights, mobile phones, displays, various panels, computers, game machines, and lighting incorporating the lamp 3 of the present embodiment, and mechanical devices such as automobiles incorporating such electronic devices. Is provided with the group III nitride semiconductor light-emitting device 1 capable of obtaining a high light emission output. In particular, in a battery-driven electronic device such as a backlight, a mobile phone, a display, a game machine, and an illumination, an excellent product including the group III nitride semiconductor light-emitting element 1 having a low VF and a high light emission output is provided. Is preferable.

Hereinafter, the method for producing a Group III nitride semiconductor light-emitting device of the present invention will be described in more detail with reference to Examples, but the present invention is not limited to these Examples.
( Reference Example 1)
The group III nitride semiconductor light-emitting device 1 shown in FIG. 1 was manufactured by the method described below.
In the group III nitride semiconductor light emitting device 1 of Reference Example 1, a base layer 22 made of undoped GaN having a thickness of 6 μm is formed on a sapphire substrate 11 on which a buffer layer 21 made of AlN is previously formed in the growth chamber of the MOCVD furnace. did. At this time, the substrate temperature in forming the underlayer 22 was 1100 ° C.

Thereafter, an n-contact layer 12 a made of Si-doped n-type GaN having a thickness of 2 μm was formed on the base layer 22. The Si impurity concentration of the n-contact layer 12a was about 5 × 10 ¹⁸ / cm ³ . Further, the substrate temperature when forming the n contact layer 12a was 1080 ° C., and the pressure in the growth chamber was 40 kPa.

Next, an n-cladding layer 12b having a superlattice structure with a thickness of 80 nm was formed on the n-contact layer 12a. 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, a p-type cladding layer 14a was formed.

  Next, a p-type contact layer 14b was formed on the p-type cladding layer 14a. Here, the p-type contact layer 14b was grown under the following growth conditions.

"Growth conditions for p-type contact layer 14b"
First, following each process described above, nitrogen gas (carrier gas) at a flow rate of 50.7 l / min, trimethylgallium (TMG), and ammonia are included on the p-type cladding layer 14a using the same MOCVD apparatus. A source gas and a dopant gas made of biscyclopentadienyl magnesium (Cp ₂ Mg) were continuously supplied for 30 seconds to form a first p-type contact layer first layer 14c ₁ having a thickness of 10 nm. The flow rate (second flow rate) of the dopant gas at this time was 0.30 l / min. Thus, the first p-type contact layer first layer 14c ₁ having an Mg concentration of 5 × 10 ¹⁹ cm ⁻³ was formed.
Next, the source gas was continuously supplied and the dopant gas supply was stopped, and nitrogen gas (carrier gas) at a flow rate of 51.0 l / min was supplied for 15 seconds. Thereby, a first p-type contact layer second layer 14c ₂ having a thickness of 5 nm was formed.

Thereafter, by repeating the above steps, and the first p-type contact layer first layer 14c ₁ of GaN having a composition and a first p-type contact layer second layer 14c ₂ stacked number 12 pairs. Finally, by forming the first p-type contact layer first layer 14c _1, to form a first p-type contact layer 14c.
The total thickness of the p-type contact layer 14b was 180 nm.

Thereafter, a translucent electrode 15 made of ITO having a thickness of 200 nm was formed on the p-type contact layer 14b by a generally known photolithography technique.
Next, etching was performed using a photolithography technique to form an exposed surface 20a of the n contact layer 12a in a desired region, and an n-type electrode 17 having a Ti / Au double layer structure was formed thereon.

Further, on the translucent electrode 15, a p-type bonding pad structure 16 having a three-layer structure composed of a metal reflective layer made of 200 nm Al, a barrier layer made of 80 nm Ti, and a bonding layer made of 1100 nm Au, It formed using the technique of photolithography.
As described above, a Group III nitride semiconductor light-emitting device 1 of Reference Example 1 was obtained.

The characteristics of the Group III nitride semiconductor light-emitting device 1 of Reference Example 1 thus obtained are as follows: forward voltage 20 f, forward voltage Vf = 3.0 V, light emission output Po = 24 mW, reverse current IR (@ 20 V ) = 0.2 μA.

( Reference Example 2)
A first p-type contact layer first layer 14c ₁ and the first p-type contact layer second layer 14c ₂ the number of pairs of the 18 of Reference Example 1, the first p-type contact layer 14c having a thickness of 270 nm (p-type contact The same operation as in Reference Example 1 was performed except that the layer 14b) was formed, and the forward voltage Vf = 2.9 V, the light emission output Po = 24 mW, and the reverse current IR (@ 20 V) = 0.1 μA.

( Reference Example 3)
The number of pairs of the first p-type contact layer first layer 14c ₁ and the first p-type contact layer second layer 14c ₂ of Reference Example 1 and 6, the first p-type contact layer 14c having a thickness of 90 nm (p-type contact The same operation as in Reference Example 1 was performed except that the layer 14b) was formed, and the forward voltage Vf = 3.0 V, the light emission output Po = 25 mW, and the reverse current IR (@ 20 V) = 0.3 μA.

( Reference Example 4)
The flow rate (second flow rate) of the dopant gas of Reference Example 1 is 0.60 l / min, the carrier gas at that time is 50.4 l / min, the total flow rate of these gases is constant, and the first p-type contact The same operation as in Reference Example 1 was performed except that the Mg concentration of the second layer 14c ₂ was set to 8 × 10 ¹⁹ cm ⁻³ , the forward voltage Vf = 3.0 V, the light emission output Po = 23 mW, the reverse current IR (@ 20V) = 0.2 μA.

( Reference Example 5)
The flow rate (second flow rate) of the dopant gas of Reference Example 1 is 0.10 l / min, the carrier gas at that time is 50.9 l / min, the total flow rate of these gases is constant, and the Mg concentration is 2 × 10. ^The same operation as in Reference Example 1 was performed except that the first p-type contact layer first layer 14c ₁ of ¹⁹ cm ⁻³ was formed, and forward voltage Vf = 2.9 V, light emission output Po = 24 mW, reverse current IR (@ 20V) = 0.1 μA.

( Reference Example 6)
After the step of forming the first p-type contact layer 14c of Reference Example 1, while supplying a dopant gas containing an Mg source at a flow rate of 0.90 l / min, an Mg concentration having a composition of Ga _0.99 In _0.01 N The same operation as in Reference Example 1 was performed except that the second p-type contact layer 14d of 1.0 × 10 ²⁰ cm ⁻³ was formed with a film thickness of 30 nm, the forward voltage Vf = 2.9 V, the light emission output Po = It was 24 mW and reverse current IR (@ 20V) = 0.1 μA.

( Reference Example 7)
After the first p-type contact layer 14c forming step of Reference Example 1, while supplying a dopant gas containing an Mg source at a flow rate of 1.20 l / min, an Mg concentration of 2.0 × 10 ²⁰ cm ^{− with a} composition of GaN. ³ except that the second p-type contact layer 14d of ³ is formed to a thickness of 30 nm, the same operation as in Reference Example 6 is performed, and the forward voltage Vf = 2.8 V, the light emission output Po = 24 mW, the reverse current IR (@ 20V) = 0.2 μA.

( Reference Example 8)
After the step of forming the first p-type contact layer 14c of Reference Example 1, while supplying a dopant gas containing an Mg source at a flow rate of 0.90 l / min, an Mg concentration having a composition of Al _0.01 Ga _0.99 N The same operation as in Reference Example 1 was performed except that the second p-type contact layer 14d of 1.0 × 10 ²⁰ cm ⁻³ was formed with a thickness of 10 nm, the forward voltage Vf = 3.0 V, the light emission output Po = 24 mW, reverse current IR (@ 20 V) = 0.4 μA.

(Example 1 )
Prior to the first p-type contact layer 14c forming step of Reference Example 1, a dopant gas containing an Mg source was supplied to the surface of the p-type cladding layer 14a at a flow rate (first flow rate) of 0.90 l / min. The same operation as in Reference Example 1 was performed, and the forward voltage Vf = 2.9 V, the light emission output Po = 23 mW, and the reverse current IR (@ 20 V) = 0.1 μA.

(Comparative Example 1)
By continuously feeding without changing the flow rate of the dopant gas, except that the formation of the first p-type contact layer 14c made of only the first p-type contact layer first layer 14c _1, similar to that in Reference Example 1 Operation The forward voltage Vf was 3.3 V, the light emission output Po was 20 mW, and the reverse current IR (@ 20 V) was 2.4 μA.

(Comparative Example 2)
In forming the first p-type contact layer first layer 14c _{1 of} Reference Example 1, a carrier gas having a flow rate of 51.0 l / min is supplied to form the first p-type contact layer second layer 14c _2. The same operation as in Reference Example 1 was performed except that the carrier gas having a flow rate of 51.0 l / min was continuously supplied, the forward voltage Vf = 3.4 V, the light emission output Po = 18 mW, the reverse current IR ( @ 20V) = 2.1 μA.

(Comparative Example 3)
In forming the first p-type contact layer first layer 14c _{1 of} Reference Example 1, a carrier gas having a flow rate of 50.7 l / min and a dopant gas having a flow rate of 0.10 l / min were supplied, and an Mg concentration of 3.0 × Except for forming the first p-type contact layer first layer 14c ₁ of 10 ¹⁸ cm ⁻³ and supplying the carrier gas at a flow rate of 51.0 l / min when forming the first p-type contact layer second layer 14c ₂ The same operation as in Reference Example 1 was performed, and the forward voltage Vf = 3.2 V, the light emission output Po = 15 mW, and the reverse current IR (@ 20 V) = 3.5 μA.

(Comparative Example 4)
When the first p-type contact layer first layer 14c _{1 of} Reference Example 1 is formed, a carrier gas having a flow rate of 50.7 l / min and a dopant gas having a flow rate of 0.60 l / min are supplied to form an Mg concentration of 6.0 × Except for forming the first p-type contact layer first layer 14c ₁ of 10 ²⁰ cm ⁻³ and supplying the carrier gas at a flow rate of 51.0 l / min when forming the first p-type contact layer second layer 14c ₂ Performs the same operation as in Reference Example 1, forward voltage Vf = 3.2 V, light emission output Po = 17 mW,
The reverse current IR (@ 20 V) was 5.0 μA.

(Comparative Example 5)
When forming the first p-type contact layer first layer 14c _{1 of} Reference Example 1, a carrier gas having a flow rate of 51.0 l / min and a dopant gas of 0.30 l / min are supplied, and the first p-type contact layer When the second layer 14c _{2 is} formed, a carrier gas having a flow rate of 51.0 l / min is supplied, and the first p-type contact layer first layer 14c ₁ and the first p-type contact layer second layer 14c ₂ The same operation as in Reference Example 1 was performed except that the number of pairs was 30 and the first p-type contact layer 14c (p-type contact layer 14b) having a thickness of 450 nm was formed, and the forward voltage Vf = 3.3V and light emission The output Po was 12 mW, and the reverse current IR (@ 20 V) was 7.0 μA.

(Comparative Example 6)
When forming the first p-type contact layer first layer 14c _{1 of} Reference Example 1, a carrier gas having a flow rate of 51.0 l / min and a dopant gas of 0.30 l / min are supplied, and the first p-type contact layer first It was supplied carrier gas at a flow rate of 51.0l / min during the two-layer 14c ₂ formed. Then, while supplying a dopant gas containing Mg source at a flow rate of 0.10 l / min, a second p-type contact layer 14d having a Mg concentration of 4.0 × 10 ¹⁸ cm ⁻³ and a thickness of 30 nm is formed. in except for forming performs the same operation as in reference example 1, the forward voltage Vf = 3.6V, the light-emitting output Po = 15 mW, was reverse current IR (@ 20V) = 4.2μA.

Table 1 shows the results of forward voltage, light emission output (Po), and reverse current (IR) of the Group III nitride semiconductor light emitting devices of Reference Example 1 to Reference Example 8 , Example 1, and Comparative Examples 1 to 6. Show.
The forward voltage Vf and the light emission output (Po) when the Group III nitride semiconductor light emitting device 1 of the reference example, the example and the comparative example are mounted are measured when the applied current is 20 mA. The reverse current (IR) is a value obtained by measuring the leakage current when 20 V is applied to the light emitting element in the reverse direction.

As shown in Table 1, Reference Example 1 to Reference Example 8, any group III nitride semiconductor light-emitting device 1 of Example 1, a low reverse current (IR), also a relatively low forward voltage obtained It was. In addition, any of the group III nitride semiconductor light emitting devices 1 had a light emission output (Po) of 20 mW or more, high output and low power consumption.

On the other hand, in the group III nitride semiconductor light-emitting device 1 obtained in Comparative Example 1 to Comparative Example 6, Reference Example 1 to Reference Example 8, the light emitting output compared to Example 1 (Po) is lower, forward voltage It was relatively high and the leakage current (reverse current (IR)) was large.

By the above Reference Examples 1 to Example 8, III-nitride semiconductor light emitting device 1 obtained in Example 1, effectively, it was possible to improve the forward voltage and the light emission output. Moreover, it was confirmed that the leakage current was small and a high light emission output was obtained as compared with the Group III nitride semiconductor light emitting device 1 of Comparative Examples 1 to 6.

DESCRIPTION OF SYMBOLS 1 ... Group III nitride semiconductor light emitting element, 3 ... Lamp, 12 ... n-type semiconductor layer, 12a ... n contact layer, 12b ... n clad layer, 13 ... Light emitting layer, 14 ... p-type semiconductor layer, 14a ... p-type clad Layer, 14b ... p-type contact layer, 14c ... first p-type contact layer, 14c ₁ ... first p-type contact layer first layer, 14c ₂ ... first p-type contact layer second layer, 14d ... second p-type Contact layer, 14d ₁ ... second p-type contact layer first layer, 14d ₂ ... second p-type contact layer second layer, 22 ... underlayer

Claims (2)

After sequentially stacking an n-type semiconductor layer, a light emitting layer having a multiple quantum well structure, and a p-type cladding layer on a substrate, a carrier gas and a source gas containing a Ga source and a nitrogen source are continuously supplied, and Mg Al _x Ga _y In _z N (0 ≦ x ≦ 0.1, 0 ≦ y ≦ 1, 0 ≦ z ≦ 0...) Is formed on the p-type cladding layer by an MOCVD method in which a dopant gas containing a source is intermittently supplied. 1. a step of forming a p-type contact layer of x + y + z = 1),
The step of forming the p-type contact layer comprises:
Supplying the dopant gas to the surface of the p-type cladding layer at a first flow rate of 500 to 1500 sccm;
The source gas is continuously supplied, and the dopant gas is intermittently supplied at a second flow rate of 50 to 750 sccm lower than the first flow rate. Forming a contact layer, and reducing the flow rate of the carrier gas when supplying the dopant gas, thereby reducing the carrier gas, the source gas, and the dopant gas during the formation of the p-type contact layer. A method for producing a group III nitride semiconductor light-emitting device, characterized in that the total flow rate is kept constant. The step of forming the p-type contact layer comprises:
Forming a first p-type contact layer on the p-type cladding layer by MOCVD, which continuously supplies the source gas and intermittently supplies the dopant gas;
The source gas is continuously supplied, and the dopant gas is continuously supplied at a higher concentration than in the first p-type contact layer forming step by the MOCVD method, on the first p-type contact layer. The method for producing a group III nitride semiconductor light-emitting device according to claim 1, further comprising: forming a p-type contact layer.

Images