JP2011096893A - Nitride semiconductor light emitting element, and method of manufacturing nitride semiconductor light emitting element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a nitride semiconductor light emitting element having a light emitting layer with superior light emission characteristics. <P>SOLUTION: The nitride semiconductor light emitting element includes a substrate, an n-type nitride semiconductor layer formed on the substrate, the light emitting layer formed on the n-type nitride semiconductor layer, and a p-type nitride semiconductor layer formed on the light emitting layer. The n-type nitride semiconductor layer includes a first n-type nitride semiconductor layer, an intermediate layer, and a second n-type nitride semiconductor layer in this order from the side of the substrate. The intermediate layer is made of SiN, the light emitting layer includes In, and in the In in the light emitting layer, a maximum value of a ratio σ of localization of the In, which is calculated by formula (1): E(T)=Em(0 to 10)-αT<SP>2</SP>/(T+β)-σ/(k<SB>B</SB>T), is ≤50 meV (in the formula (1), E(T) is a band gap of the light emitting layer at an arbitrary absolute temperature, Em (0 to 10) is a band gap of the light emitting layer at an absolute temperature of 0 to 10K, α and β are Varshni's fitting parameters, T is an absolute temperature (K), and k<SB>B</SB>is a Boltzmann constant). <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a nitride semiconductor light-emitting device and a method for manufacturing the same, and more particularly to a nitride semiconductor light-emitting device with improved light-emitting characteristics of a light-emitting layer and a method for manufacturing the same.

  Sapphire is widely used as a substrate constituting a nitride semiconductor light emitting device. However, sapphire has a drawback that threading dislocations are formed in the nitride semiconductor due to the high lattice mismatch rate between sapphire and nitride semiconductor when a nitride semiconductor is formed thereon.

  Thus, threading dislocations are formed in the nitride semiconductor, particularly the n-type nitride semiconductor layer, so that the light emitting layer formed on the n-type nitride semiconductor layer contains point defects or emits light. There is a problem that the crystallinity of the light emitting layer is deteriorated such that In constituting the layer is aggregated. In addition, the formation of threading dislocations in the light emitting layer causes carrier recombination in the region of the light emitting layer, which may become a non-light emitting region.

  As an attempt to solve such a problem, a technique in which a low-temperature buffer layer is formed on a substrate made of sapphire and then a nitride semiconductor is formed on the low-temperature buffer layer is well known. By forming the low-temperature buffer layer in this manner, the lattice mismatch between sapphire and the n-type nitride semiconductor layer tends to be relaxed, and threading dislocations formed in the light emitting layer can be reduced.

However, even if a low-temperature buffer layer is formed on the substrate, it has been confirmed that threading dislocations of approximately 1 × 10 ⁸ or more per 1 cm ² enter at the initial stage of growing a nitride semiconductor, Reduction was required. In order to meet such a requirement, Patent Document 1 discloses a technique for forming an intermediate layer made of SiN in a part of each layer of a nitride semiconductor.

JP 2002-43233 A

  Although forming an intermediate layer made of SiN inside a nitride semiconductor as in Patent Document 1 tends to make it difficult for threading dislocations to occur in the light emitting layer, the light emitting layer still has insufficient light emission characteristics, and particularly emits light. The current situation is that improvement of the luminous efficiency of the layer is required.

  The present invention has been made in view of the above-described situation, and a nitride in which the light-emitting characteristics of the light-emitting layer are improved by reducing the threading dislocation density of the n-type nitride semiconductor layer serving as the base of the light-emitting layer. A semiconductor light emitting device is provided.

  The nitride semiconductor light emitting device of the present invention is formed on a substrate, an n-type nitride semiconductor layer formed on the substrate, a light emitting layer formed on the n type nitride semiconductor layer, and the light emitting layer. The n-type nitride semiconductor layer includes a first n-type nitride semiconductor layer, an intermediate layer, and a second n-type nitride semiconductor layer from the substrate side. In order, the intermediate layer is made of SiN, the light emitting layer contains In, and the maximum value of In localization energy σ calculated by the following formula (1) is 50 meV or less. It is characterized by. The maximum value of the In localization energy σ is preferably 30 meV or less.

E (T) = Em (0~10 ) -αT 2 / (T + β) -σ / (k B T) (1) formula, however, the constants in equation (1), is shown below.

E (T): band gap of the light emitting layer at an arbitrary absolute temperature Em (0-10): band gap of the light emitting layer at an absolute temperature of 0 K to 10 K α, β: Varshni's fitting parameters
T: Absolute temperature (K)
k _B : Boltzmann constant It is preferable that the light emitting layer has a peak wavelength of light emission at 430 nm or more and 480 nm or less. The threading dislocation density of the n-type nitride semiconductor layer is preferably 5 × 10 ⁷ / cm ² or less.

  The method for manufacturing a nitride semiconductor light emitting device of the present invention includes a step of forming an n-type nitride semiconductor layer on a substrate, a step of forming a light emitting layer on the n-type nitride semiconductor layer, and a step of forming on the light emitting layer. a step of forming a p-type nitride semiconductor layer, wherein the step of forming the light emitting layer is performed at a pressure of 400 mbar or less by metal organic vapor phase epitaxy. It is preferable to include a step of supplying an In precursor after the step of forming the light emitting layer.

  The present invention has the effect of enhancing the light emission characteristics of the nitride semiconductor light emitting device by having the above-described configuration.

It is typical sectional drawing which shows an example of the nitride semiconductor light-emitting device of this invention. It is typical sectional drawing which shows an example of the nitride semiconductor light-emitting device of this invention.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. The configurations shown in the drawings and the following description are merely examples, and the scope of the present invention is not limited to those shown in the drawings and the following description. In the drawings of the present invention, the same reference numerals represent the same or corresponding parts. In the drawings of the present application, the dimensional relationships such as length, width, and thickness are appropriately changed for clarity and simplification of the drawings and do not represent actual dimensional relationships.

<Nitride semiconductor light emitting device>
Hereinafter, the nitride semiconductor light emitting device of the present embodiment will be described with reference to FIG. FIG. 1 is a schematic cross-sectional view showing a preferred example of the nitride semiconductor light emitting device of the present invention. As shown in FIG. 1, the nitride semiconductor light emitting device of the present embodiment includes a substrate 1, an n-type nitride semiconductor layer 10 formed on the substrate 1, and an n-type nitride semiconductor layer 10. The n-type nitride semiconductor layer 10 includes the first n-type nitride semiconductor layer 2, the intermediate layer, and the light-emitting layer 5 formed and the p-type nitride semiconductor layer 6 formed on the light-emitting layer 5. 3 and the second n-type nitride semiconductor layer 4 in this order from the substrate 1 side, and the intermediate layer 3 is made of SiN. A p-side translucent electrode layer 7 is formed on the p-type nitride semiconductor layer 6.

Here, the first n-type nitride semiconductor layer 2, the second n-type nitride semiconductor layer 4, the light emitting layer 5, and the p-type nitride semiconductor layer 6 are all formed of a nitride semiconductor. However, such a nitride semiconductor typically means a semiconductor represented by Al _x Ga _y In _1-xy N (x and y are both 0 or more and 1 or less), but is not limited thereto. It is not a thing but what added arbitrary elements for n-type-izing or p-type-izing is included.

(substrate)
In the present embodiment, as the substrate 1, an insulating substrate such as sapphire, or a conductive substrate such as GaN, SiC, ZnO or the like can be used. Such a substrate 1 is not necessarily limited to a planar substrate, and a substrate having irregularities formed on the surface of the substrate 1 may be used.

(N-type nitride semiconductor layer)
The n-type nitride semiconductor layer 10 of the present embodiment is characterized in that the intermediate layer 3 made of SiN is sandwiched between the first n-type nitride semiconductor layer 2 and the second n-type nitride semiconductor layer 4. . As the intermediate layer 3 is sandwiched between the n-type nitride semiconductor layers 10 in this way, the threading dislocations formed in the first n-type nitride semiconductor layer 2 are bent in the lateral direction and stopped at the intermediate layer 3. By forming the second n-type nitride semiconductor layer 4 on the intermediate layer 3 through a nucleation process, the threading dislocation density of the n-type nitride semiconductor layer 10 can be reduced. Thus, by reducing the threading dislocation density of the n-type nitride semiconductor layer 10, the light emission efficiency of the light emitting layer 5 formed immediately thereon can be increased.

The threading dislocation density of the n-type nitride semiconductor layer 10 is preferably 5 × 10 ⁷ / cm ² or less, and the threading dislocation density of the second n-type nitride semiconductor layer 4 is 5 × 10 ⁷ / cm ^2. The following is more preferable. By having such threading dislocation density, the light emission efficiency of the light emitting layer 5 formed on the second n-type nitride semiconductor layer 4 can be increased. Here, the threading dislocation density of the n-type nitride semiconductor layer 10 can be confirmed by observing the density of dark spots by using cathodoluminescence (CL) measurement.

  Here, the “threading dislocation density of the n-type nitride semiconductor layer 10” means the threading dislocation density in the vicinity of the uppermost surface of the n-type nitride semiconductor layer 10.

  In the present invention, the “n-type nitride semiconductor layer” includes not only a nitride semiconductor doped with an n-type impurity but also an undoped nitride semiconductor. This is because when the nitride semiconductor is undoped, it generally exhibits n-type conductivity.

(1) First n-type nitride semiconductor layer The first n-type nitride semiconductor layer 2 is not limited to a single layer but may be a laminate of a plurality of layers. As such a first n-type nitride semiconductor layer 2, for example, a low-temperature buffer layer, an AlN buffer layer, an undoped layer, an n-type doped layer, or the like can be used. Among these, an AlN buffer layer and an undoped GaN layer can be used. Preferably it consists of. Moreover, Si, Ge, etc. can be used as the n-type dopant introduced into the nitride semiconductor. Among these, from the viewpoint of reducing the resistivity of the first n-type nitride semiconductor layer 2, when the first n-type nitride semiconductor layer 2 is a single layer, GaN, AlGaN, InAlGaN, or InGaN is used. It can be used and may contain Si or an undoped layer. Further, when the first n-type nitride semiconductor layer 2 has a plurality of layers, a stacked structure such as InGaN / GaN, InGaN / AlGaN, AlGaN / GaN, or InGaN / InGaN may be used.

(2) Intermediate layer The intermediate layer 3 is made of SiN. By forming the intermediate layer 3 in this manner, threading dislocations in the second n-type nitride semiconductor layer 4 formed thereafter can be reduced, and the light emission characteristics of the light emitting layer can be improved. .

(3) Second n-type nitride semiconductor layer The second n-type nitride semiconductor layer 4 is not limited to a single layer but may be a laminate of a plurality of layers. Such second n-type nitride semiconductor layer 4 may include, for example, any one of an undoped layer, an n-type doped layer, and a nitride semiconductor layer containing In. Among these, the second n-type nitride semiconductor layer 4 is preferably composed of an n-type GaN layer and an undoped GaN layer from the viewpoint of improving lattice matching with the light emitting layer 5.

(Light emitting layer)
In the present invention, the light emitting layer 5 preferably includes a barrier layer made of GaN and a well layer made of a nitride semiconductor containing In. The thickness of the well layer varies depending on the wavelength at which the well layer emits light, but is preferably in the range of 2 to 20 nm. As the crystal quality of the n-type nitride semiconductor layer 10 increases, The layer thickness can be increased. The structure of the light emitting layer 5 is not limited to the quantum structure, and may be any of a single well structure, a multiple well structure, a multiple quantum well structure, and the like.

When the light emitting layer 5 includes a plurality of well layers, at least one well layer functions as a light emitting layer. Such a well layer is preferably made of In _q Ga _{1 -q} N (0 <q <1).

Since In _q Ga _{1 -q} N constituting the well layer is thermodynamically unstable, spinodal decomposition occurs and In is localized. In particular, the thicker the well layer, the greater the tendency for In to localize. However, In localization ends in the initial process of spinodal decomposition and In does not separate to the spinodal point. It is considered.

  The localization ratio of In in the light emitting layer can be expressed as the localization energy σ by measuring the temperature dependence of the band gap and using the Varshni approximation law of the following formula (1).

E (T) = Em (0~10 ) -αT 2 / (T + β) -σ / (k B T) (1) formula, however, the constants in equation (1), is shown below.

E (T): Band gap of the light emitting layer at an arbitrary absolute temperature α, β: Varshni's fitting parameters
T: Absolute temperature (K)
k _B : Boltzmann constant In the light emitting layer used in the nitride semiconductor light emitting device of the present invention, the localization energy σ calculated by the equation (1) varies depending on the current density, but the maximum value is 50 meV or less. It is characterized by that. Thus, when the maximum value of the localization energy σ is 50 meV or less, the half-value width of the light emitted from the light emitting layer can be made 30 nm or less, and thus the light emission characteristics of the light emitting layer can be improved.

  Such localization energy σ is preferably 30 meV or less. By reducing the localization energy in this way, the light emission characteristics of the light emitting layer can be enhanced and the threading transition formed in the n-type nitride semiconductor layer 10 can be reduced.

  Here, Em (0 to 10) in the formula (1) means the band gap of the light emitting layer at an absolute temperature of 0K to 10K, and the band gap of the light emitting layer at an absolute temperature of 0K to 10K is A value calculated by measuring the band gap of the light emitting layer when the temperature of the light emitting layer is 4.2 K using a cryostat is adopted. In addition, α and β in Varshni's fitting parameters vary depending on the material of the light emitting layer.

  The light emitting layer 5 preferably has a peak wavelength of light emission at 430 nm or more and 480 nm or less. When the peak wavelength of light emission of the light emitting layer 5 is less than 430 nm, since the In concentration is low, In segregation hardly occurs in the first place, and the effect brought about by the present invention is not necessarily required. On the other hand, if the peak wavelength of light emission of the light emitting layer 5 exceeds 480 nm, the crystal quality of the light emitting layer 5 is remarkably deteriorated and it is difficult to form a practical one.

(P-type nitride semiconductor layer)
In the present invention, the p-type nitride semiconductor layer 6 may be either a single layer or a plurality of layers, and GaN, AlGaN, InAlGaN, or InGaN doped with a p-type impurity can be used. An undoped material may be used. When the p-type nitride semiconductor layer 6 has a plurality of layers, a stacked structure such as InGaN / GaN, InGaN / AlGaN, AlGaN / GaN, or InGaN / InGaN may be used.

  The thickness of such p-type nitride semiconductor layer 6 is preferably 1500 nm or less. When the thickness of the p-type nitride semiconductor layer 6 exceeds 1500 nm, the light emitting layer 5 is exposed to heat at a high temperature for a long time, and there is a possibility that the non-light emitting region due to thermal degradation of the light emitting layer 5 may increase. .

(P-side translucent electrode layer)
In the present invention, the p-side translucent electrode layer 7 is in contact with the p-type nitride semiconductor layer 6 and functions as a translucent electrode. The material used for the p-side translucent electrode layer 7 is not particularly limited, and any material can be used. From the viewpoint of the function as a current diffusion layer, transparency, etc., indium tin oxide It is preferable to use (ITO: indium tin oxide).

(P electrode, n electrode)
In the present invention, the p electrode and the n electrode are provided for connection to the outside. A conventionally well-known thing can be employ | adopted for such a p electrode and n electrode, for example, Ti, Al, Au etc. can be used. Further, the p-electrode and the n-electrode are not limited to a single layer structure, and may have a multilayer structure.

(Manufacturing method of nitride semiconductor light emitting device)
The method for manufacturing a nitride semiconductor light emitting device of the present invention includes a step of forming an n-type nitride semiconductor layer on a substrate, a step of forming a light emitting layer on the n-type nitride semiconductor layer, and a step of forming on the light emitting layer. including a step of forming a p-type nitride semiconductor layer, wherein the step of forming the light emitting layer is performed at a pressure of 400 mbar or less by metal organic vapor phase epitaxy. Hereafter, each process of the manufacturing method of the nitride semiconductor light-emitting device of this invention is demonstrated.

(Formation of n-type nitride semiconductor layer)
First, the substrate 1 is placed in a metal organic chemical vapor deposition (MOCVD) apparatus. Next, the temperature of the substrate 1 is adjusted to, for example, 1050 ° C., and a group III source gas, a doping gas containing Si, and an ammonia gas are introduced into the MOCVD apparatus using a carrier gas containing nitrogen and hydrogen. Then, the first n-type nitride semiconductor layer 2 is crystal-grown on the substrate 1.

Examples of the group III source gas introduced into the apparatus for forming the first n-type nitride semiconductor layer 2 include TMG ((CH ₃ ) ₃ Ga: trimethyl gallium), TEG ((C ₂ H _{5) 3} Ga: triethyl _{gallium), TMA ((CH 3)} 3 Al: trimethyl _{aluminum), TEA ((C 2 H} 5) 3 Al: _{triethylaluminum), TMI ((CH 3)} 3 In: trimethyl indium), Alternatively, TEI ((C ₂ H ₅ ) ₃ In: triethylindium) or the like can be used. As the doping gas containing Si, may be used, for example SiH ₄ (silane) gas or the like.

  Then, by simultaneously flowing silane gas and ammonia gas into the same reaction furnace, an intermediate layer 3 made of SiN of several nm is formed on the first n-type nitride semiconductor layer 2. Next, the second n-type nitride semiconductor layer 4 is formed on the intermediate layer 3. The source gas introduced when forming the second n-type nitride semiconductor layer 4 can be the same as the source gas used when forming the first n-type nitride semiconductor layer 2. As described above, n-type nitride semiconductor layer 10 is formed on substrate 1.

(Formation of light emitting layer)
Next, the light emitting layer 5 is formed by alternately forming a well layer and a barrier layer containing In on the n-type nitride semiconductor layer 10 in the MOCVD apparatus used for forming the n-type nitride semiconductor layer. Here, the pressure in the MOCVD apparatus in the step of forming the light emitting layer 5 is preferably 400 mbar or less. In this way, by forming the light emitting layer 5 in an environment where the pressure is greatly reduced as compared with the conventional 1000 mbar, the localization energy of In can be reduced, and thus the crystal quality of the n-type nitride semiconductor layer 10 can be reduced. The light emission characteristics of the light emitting layer 5 utilizing the above can be improved. Such crystal growth of the light emitting layer 5 is more preferably 200 mbar or less from the viewpoint of enhancing the light emitting characteristics of the light emitting layer 5.

  As described above, when the pressure in the apparatus during crystal growth is reduced to 400 mbar or less, the detailed mechanism that can reduce the localization energy of In is not clear, but the pressure at the time of forming the light emitting layer is probably not. It is thought that this is caused by an increase in the In migration length due to the decrease.

  As another method for increasing the In migration length, a method of causing an In surfactant effect in the light emitting layer 5 by including a step of supplying an In precursor after forming the light emitting layer can be mentioned. Thus, by supplying the In precursor, the crystal growth on the light emitting layer 5 is interrupted. As a precursor of In, TMI (trimethylindium), TEM (triethylindium), and the like are conceivable. However, the material is not particularly limited to these materials, and any material containing In can be used. However, it is preferable to supply ammonia simultaneously with supplying the In precursor. On the other hand, it is more preferable not to supply the Ga precursor and the Al precursor.

  As a guideline for the supply amount of In when supplying the precursor of In, it is highly possible that the amount of normal supply will adversely affect the crystalline state of the surface of the light-emitting layer 5, so supply it in a smaller amount. Is preferred. Specifically, the molar ratio between the supply amount of In and the supply amount of ammonia when supplying the precursor of In is preferably about 1: 100,000.

(Formation of p-type nitride semiconductor layer)
In the method for manufacturing the nitride semiconductor light emitting device of the present embodiment, the p-type nitride semiconductor layer 6 is formed on the light emitting layer 5 after the light emitting layer 5 is formed. The p-type nitride semiconductor layer 6 is formed by setting the temperature in the MOCVD apparatus to the temperature of the substrate 1 suitable for crystal growth of the p-type nitride semiconductor layer 6, and then adding a carrier gas containing nitrogen and hydrogen, and III A p-type nitride semiconductor layer 6 is grown on the light emitting layer 5 by introducing a group source gas, a doping gas containing Mg, and an ammonia gas into the MOCVD apparatus.

  Here, the substrate temperature suitable for crystal growth of the p-type nitride semiconductor layer 6 is preferably 950 ° C. or higher and 1300 ° C. or lower when the p-type nitride semiconductor layer 6 is made of GaN or AlGaN. It is more preferable that the temperature is not lower than 1 ° C and not higher than 1100 ° C. Crystal growth of the p-type nitride semiconductor layer 6 at such a temperature can improve the crystallinity of the p-type nitride semiconductor layer 6.

Here, as the doping gas containing Mg, for example, Cp ₂ Mg (cyclopentadienyl magnesium) or (EtCp) ₂ Mg (bisethylcyclopentadienyl magnesium) can be used. Since (EtCp) ₂ Mg is a liquid at normal temperature and pressure, the response when the amount introduced into the MOCVD apparatus is changed is better than Cp ₂ Mg which is solid under the conditions, It is easy to keep the vapor pressure constant.

  Note that as the group III source gas and ammonia gas used for forming the p-type nitride semiconductor layer 6, the same types of gases as in the case of the n-type nitride semiconductor layer 10 and the light emitting layer 5 can be used.

(Formation of p-side translucent electrode layer)
Next, the p-side translucent electrode layer 7 is formed on the p-type nitride semiconductor layer 6 obtained above using a sputtering apparatus.

(P electrode, n electrode)
Next, a p-electrode and an n-electrode are formed. The formation of the p electrode and the n electrode differs depending on the material of the substrate. For example, when an insulating substrate such as sapphire is used, etching is performed from the p-side translucent electrode layer 7 to the second n-type nitride semiconductor layer 4. Do. Then, after exposing a part of the second n-type nitride semiconductor layer 4, an n-electrode is provided on the exposed second n-type nitride semiconductor layer 4 and a p-side translucent electrode layer is provided. A p-electrode is provided on top. And it can supply with electricity by hitting a wire with respect to p electrode and n electrode.

  On the other hand, when a conductive substrate such as GaN is used, the electrode structure is different from that when an insulating substrate is used, but a general structure when a conductive substrate is used can be used. In addition to these electrode structures, a mounting method such as a flip chip structure can also be used.

  EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated in detail, this invention is not limited to these.

  FIG. 2 is a schematic cross-sectional view of the nitride semiconductor light emitting device manufactured in this example. In this example, a nitride semiconductor light emitting device having the configuration shown in FIG. 2 is manufactured.

  First, a sapphire substrate having irregularities formed on the surface is used as the substrate 11, and the substrate 11 is set in a sputtering apparatus. Then, an AlN buffer layer having a thickness of 25 nm is formed on the substrate 11. Thereafter, the substrate 11 is moved into the reactor of the MOCVD apparatus, and an undoped GaN layer having a thickness of 0.8 μm is formed on the AlN buffer layer. Here, the AlN buffer layer and the undoped GaN layer correspond to the first n-type nitride semiconductor layer 12.

Next, silane gas and ammonia gas are simultaneously flowed into the same reaction furnace at a molar ratio of 1: 5 × 10 ⁶ , so that several nm of SiN is deposited on the first n-type nitride semiconductor layer 12. An intermediate layer 13 made of is formed.

Thereafter, an undoped GaN layer is formed with a thickness of 2 μm on the intermediate layer 13, and an n-type GaN layer doped with Si at a concentration of 5 × 10 ¹⁸ / cm ³ is formed with a thickness of 3 μm on the undoped GaN layer. Here, the undoped GaN layer and the n-type GaN layer correspond to the second n-type nitride semiconductor layer 14. In this way, an n-type nitride semiconductor layer including the first n-type nitride semiconductor layer 12, the intermediate layer 13, and the second n-type nitride semiconductor layer 14 is formed in this order on the substrate 11.

Next, a well layer made of In _0.15 Ga _0.85 N having a thickness of 5 nm and a barrier layer made of GaN having a thickness of 10 nm are alternately formed on the second n-type nitride semiconductor layer 14 at an arbitrary pressure. The light emitting layer 15 is formed by laminating a total of four layers. Here, since InN has a very high vapor pressure, it is not easily taken into the well layer and is easily adsorbed on the surface of the well layer. And In adsorbed on the surface of the well layer lowers the surface energy and promotes surface migration of the In _0.15 Ga _0.85 N layer. The increase in surface migration tends to improve the light emission characteristics of the light emitting layer 15.

Thereafter, a p-type Al _0.2 Ga _0.8 N layer and a p-type GaN layer are formed in this order on the light emitting layer 15. Here, the p-type Al _0.2 Ga _0.8 N layer and the p-type GaN layer correspond to the p-type nitride semiconductor layer 16. Next, the temperature of the reaction furnace is lowered, and the substrate is taken out from the MOCVD apparatus and placed in the sputtering apparatus. Then, in this sputtering apparatus, the p-side translucent electrode layer 17 made of ITO is formed on the p-type nitride semiconductor layer 16.

  Next, after protecting a desired range from the p-side translucent electrode layer 17 using a photolithography technique, the p-side translucent electrode layer 17 is used using reactive ion etching (RIE). To the n-type GaN layer of the second n-type nitride semiconductor layer, the second n-type nitride semiconductor layer 14 is exposed.

  Then, an n-side pad electrode 19 made of Au / Ti / Al is formed on the exposed second n-type nitride semiconductor layer 14, and Au / Ti / Al is formed on the p-side translucent electrode layer 17. A p-side pad electrode 18 made of Al is formed. Through the above steps, the nitride semiconductor light emitting device of this example can be manufactured.

When n-type nitride semiconductor layers of the nitride semiconductor light emitting device of this example thus fabricated were observed for the density of dark spots using cathodoluminescence (CL) measurement, n-type nitrides were observed. The threading dislocation density of the semiconductor layer is approximately 3 × 10 ⁷ / cm ² .

  Then, the temperature of the light emitting layer of the nitride semiconductor light emitting element of this example is lowered using a cryostat, and the PL (PhotoLuminescence) wavelength is measured while changing the temperature. The PL wavelength at this time corresponds to the energy, and the energy at each temperature. , And the In localization energy of the light emitting layer is 50 meV or less when the In localization energy is calculated by fitting using the equation of Varshni's approximation law. As described above, since the localization energy of In is small, the light emission characteristics of the light emitting layer of this example are good. Note that the values of α and β of the Varshni's fitting parameter are calculated by curve regression of the PL wavelength results at each temperature.

  A nitride semiconductor light emitting device is manufactured by the same method as in Example 1 except that the pressure in the apparatus when crystal growth of the light emitting layer 15 is different from that of the nitride semiconductor light emitting device of Example 1. Specifically, the light-emitting layer is crystal-grown at a pressure of 400 mbar in Example 1, but the light-emitting layer is crystal-grown at a pressure of 200 mbar in this example.

When n-type nitride semiconductor layers of the nitride semiconductor light emitting device of this example thus fabricated were observed for the density of dark spots using cathodoluminescence (CL) measurement, n-type nitrides were observed. The threading dislocation density of the semiconductor layer is approximately 3 × 10 ⁷ / cm ² .

  When the localization energy of In is calculated for the light emitting layer of the nitride semiconductor light emitting device of this example, the In localization energy of the light emitting layer is 50 meV or less. As described above, since the localization energy of In is small, the light emission characteristics of the light emitting layer of this example are good.

A nitride semiconductor light emitting device is manufactured by the same method as in Example 1 except that an In precursor is supplied after forming a well layer for the nitride semiconductor light emitting device of Example 1. Specifically, in Example 1, the light emitting layer was crystal-grown by continuously growing the well layer and the barrier layer, but in this example, only TMI and NH ₃ were formed after the well layer was formed. The light emitting layer is crystal-grown with a growth interruption time of supplying the light.

When n-type nitride semiconductor layers of the nitride semiconductor light emitting device of this example thus fabricated were observed for the density of dark spots using cathodoluminescence (CL) measurement, n-type nitrides were observed. The threading dislocation density of the semiconductor layer is approximately 3 × 10 ⁷ / cm ² .

  When the localization energy of In is calculated for the light emitting layer of the nitride semiconductor light emitting device of this example, the In localization energy of the light emitting layer is 30 meV or less. As described above, since the localization energy of In is small, the light emission characteristics of the light emitting layer of this example are good.

  In the present invention, the nitride semiconductor light emitting device having the preferred embodiments described above is not limited to the above, and may have a configuration other than the above.

  Although the embodiments and examples of the present invention have been described as described above, it is also planned from the beginning to appropriately combine the configurations of the above-described embodiments and examples.

  It should be understood that the embodiments and examples disclosed herein are illustrative and non-restrictive in every respect. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  1,11 substrate, 2,12 first n-type nitride semiconductor layer, 3,13 intermediate layer, 4,14 second n-type nitride semiconductor layer, 5,15 light emitting layer, 6,16 p-type nitride Semiconductor layer, 7, 17 p-side translucent electrode layer, 10 n-type nitride semiconductor layer, 18 p-side pad electrode, 19 n-side pad electrode.

Claims (6)

A substrate,
An n-type nitride semiconductor layer formed on the substrate;
A light emitting layer formed on the n-type nitride semiconductor layer;
A p-type nitride semiconductor layer formed on the light emitting layer,
The n-type nitride semiconductor layer includes a first n-type nitride semiconductor layer, an intermediate layer, and a second n-type nitride semiconductor layer in this order from the substrate side,
The intermediate layer is made of SiN,
The light emitting layer includes In;
In the light emitting layer, the maximum value of In localization energy σ calculated by the following equation (1) is 50 meV or less.
E (T) = Em (0~10 ) -αT 2 / (T + β) -σ / (k B T) (1) formula, however, the constants in equation (1), is shown below.
E (T): band gap of the light emitting layer at an arbitrary absolute temperature Em (0-10): band gap of the light emitting layer at an absolute temperature of 0 K to 10 K α, β: Varshni's fitting parameters
T: Absolute temperature (K)
k _B : Boltzmann constant   The nitride semiconductor light emitting device according to claim 1, wherein the maximum value of the localization energy σ of In is 30 meV or less.   The nitride semiconductor light emitting element according to claim 1, wherein the light emitting layer has a peak wavelength of light emission at 430 nm or more and 480 nm or less. The nitride semiconductor light emitting device according to claim 1, wherein the n-type nitride semiconductor layer has a threading dislocation density of 5 × 10 ⁷ / cm ² or less. Forming an n-type nitride semiconductor layer on the substrate;
Forming a light emitting layer on the n-type nitride semiconductor layer;
Forming a p-type nitride semiconductor layer on the light emitting layer,
The step of forming the light emitting layer is a method for manufacturing a nitride semiconductor light emitting device, wherein the step of forming the light emitting layer is performed at a pressure of 400 mbar or less by metal organic chemical vapor deposition.   The method for manufacturing a nitride semiconductor light emitting element according to claim 5, further comprising a step of supplying an In precursor after the step of forming the light emitting layer.

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