JP3361964B2 - Semiconductor light emitting device and method of manufacturing the same - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a structure of a semiconductor light emitting device such as a light emitting diode (LED) or a semiconductor laser using a compound semiconductor material and a method for manufacturing the same, and particularly to a semiconductor light emitting device made of a gallium nitride (GaN) based semiconductor. It relates to a device and a manufacturing method thereof.

[0002]

2. Description of the Related Art GaN-based semiconductors such as In _x Al _y Ga _1-xy N are capable of highly efficient radiative recombination because their optical transition type (energy diagram) is a direct transition type.
In addition, its transition energy is as wide as 2-6.2 eV, green,
It is being developed as a high-efficiency light emitting device material such as a short-wavelength semiconductor laser of green-blue, blue to ultraviolet or the like or a high-luminance short-wavelength LED.

In _x Al _y Ga which is a quaternary semiconductor
_1-xy N is a binary semiconductor, GaN,
It is composed of a combination of AIN and InN, and among these, GaN has been particularly actively developed. Since GaN has a high melting point of 1700 ° C. or higher, and the equilibrium vapor pressure of nitrogen at the growth temperature is extremely high, it is difficult to control the stoichiometric composition (stoichiometry) and it is difficult to grow a bulk single crystal. . Therefore, at present, the hydride vapor phase epitaxy (HVPE) method and the metalorganic vapor phase epitaxy (MOCV) are used for the single crystal growth.
Method D) is mainly used. Recently, especially MO
The growth method using the CVD method is actively developed, and Ga
In _x Ga _1-x N or Al with N mixed with In or Al
_A ternary mixed crystal of yGa1 _-yN has been obtained. These Ga
The use of a heterojunction structure composed of a plurality of combinations of N-based materials makes it possible to improve the luminous efficiency. Double hetero (D) is especially effective for confining injected carriers and light.
H) By forming the structure, a high-luminance short-wavelength LED and a short-wavelength LD can be realized.

[0004]

When manufacturing a current injection type light emitting device, since a pn junction is basically used, a p type and n type are formed.
It is important to control the conduction type for forming the type semiconductor region.
In a GaN-based semiconductor, n-type conductivity type control can be relatively easily performed by using Si as an impurity material. However, it is generally difficult to control the conductivity type of the p-type semiconductor region. That is, although Mg or Zn is mainly used as an acceptor impurity for p-type, these impurities have a low activation rate due to their deep levels, and in addition, as a source gas in the growth by the MOCVD method. It is believed that this is due to inactivation by atomic hydrogen that is a decomposition product of the used ammonia (NH ₃ ) (JA Van Vechten,
et al. Jpn. J. Appl. Phys. 31
(1992) 3662).

That is, when the Mg-doped GaN layer is grown by the MOCVD method or the like, after the Mg-doped GaN layer is laminated, the substrate temperature is lowered to room temperature (at this time, in order to control the stoichiometry, that is, N from the grown layer is increased). It is general to continue supplying the NH ₃ gas, which is the group 5 element source gas, so that there is no dissociation of hydrogen, but), then atomic hydrogen H is taken into the growth layer, and this H inactivates the acceptor. It is known that the Mg-doped GaN layer has a high resistance in order to achieve high resistance. For example, Mg is 1 × 10 ²⁰
In the case of a cm ^-3 doped GaN layer, the H impurity concentration of this GaN layer is 5 × 10 ¹⁹ cm ^-3, which is 10 times or more the incorporation of H as compared with the undoped and n-type GaN layers grown under the same conditions. It is common for this to happen.

On the other hand, electron beam irradiation (H. Amano, et al. Jp.
n. J. Appl. Phys. 28 (1989) L21
12) and heat treatment (S. Nakamura, et al.
Jpn. J. Appl. Phys. 31 (1992) 1
It has been found that the activation rate is improved by carrying out step 258), and the possibility of realizing a high-efficiency light emitting device is spreading, but there is a problem that a complicated process such as electron beam irradiation or heat treatment is required to be added. . Further, in the case of electron beam irradiation, there is also a problem that an expensive electron beam irradiation device is required and the product cost increases.

Further, in order to realize a highly efficient LED element, high light extraction efficiency is required, and for this purpose, G
it is necessary to realize a special structure such as used in a _x Al _1-x As and GaP light emitting element. Specifically, it has a structure with a low electric resistivity, a thick film and a transparent layer for light emission, to expand the light emission area inside the element and to extract light to the outside of the element without being shielded by electrodes. is there. However, with a GaN-based material, it is difficult to obtain a low-resistance crystal, especially in the p-type, and the deterioration of the surface morphology due to doping with a high impurity density becomes more remarkable as the film thickness increases. Therefore, for the GaN-based LED, a method of forming a current confinement structure using an oxide film to prevent light shielding at the electrode in order to improve the light extraction efficiency has been proposed, but an additional step of forming an oxide film is required. However, there is a problem that the process becomes complicated.

As described above, in the conventional GaN-based light emitting device, in order to achieve high light extraction efficiency, a special process for activating the acceptor and a complicated device forming process such as formation of an oxide film are required. Was becoming. Since the addition of these complicated steps and processes has a great influence on the reproducibility and reliability of the device characteristics, there have been serious problems such as an increase in product cost and a decrease in yield.

The present invention has been made in view of the above circumstances, and an object of the present invention is to simplify the device forming process in forming a GaN-based light emitting device and to have high reproducibility and reliability of characteristics. It is to provide a high-brightness light emitting device and a manufacturing method thereof.

More specifically, it is possible to activate acceptor impurities without using a special treatment such as electron beam irradiation or heat treatment, and to provide a structure of a light emitting device having a high light extraction efficiency, and It is an object to provide a simple manufacturing method.

In particular, an object of the present invention is to realize a light emitting device made of a GaN-based semiconductor having a simple structure, which can easily control the p-type conductivity type and obtain high luminous efficiency.

[0012]

In order to achieve the above object, a light emitting device according to the present invention has a general formula of In _x Al _y G 2.
_1. A semiconductor light emitting device having a laminated structure of a GaN-based semiconductor represented by a _1-xy N (0 ≦ x, y ≦ 1), wherein the laminated structure is n for injecting electrons and holes into a light emitting region. The first feature is that the semiconductor device includes at least a p-type semiconductor region and a p-type semiconductor region, and an n-type cap layer is formed on the p-type semiconductor region.

More specifically, in a light emitting device structure in which a p-type GaN-based semiconductor layer is formed on an n-type GaN-based semiconductor (In _x Al _y Ga _1-xy N) layer, this p-type G
The first feature is that the cap layer made of an n-type GaN-based semiconductor is formed on the aN-based semiconductor layer. A pn junction may be formed between the p-type semiconductor layer and the n-type semiconductor layer, or a pin junction may be formed between the p-type semiconductor layer and the n-type semiconductor layer by sandwiching the undoped semiconductor layer serving as the i-layer. . Further, a buffer layer or an undoped or n ⁻ type semiconductor layer may be formed between the n type semiconductor layer and the substrate in order to improve surface morphology and crystallinity. The buffer layer may be n-type or p-type. Further, it may be a homojunction, a single hetero (SH) structure, or a double hetero (DH) structure.

More specifically, the p-type GaN-based semiconductor layer of the present invention is a GaN-based semiconductor containing an acceptor impurity such as Mg or Zn, and n is formed on the p-type semiconductor layer.
Firstly, a cap layer having electrical characteristics of the mold is laminated.
It is a feature of. The cap layer is In _u Al _v Ga _1-uv N
It is preferable to form (0 <u, v <1). More preferably, the semiconductor light emitting device is configured by using the cap layer in the current confinement structure.

FIG. 2A shows a secondary ion mass spectrometer (SIM) for the laminated structure of the first feature of the present invention shown in FIG.
The impurity density profile of Mg measured in the depth direction from the uppermost layer of the n-type cap 305 using S) is shown. n
The impurity profile of Mg in the type cap layer 305 is 2 when the growth interruption time between the n-type cap layer 305 and the p-type semiconductor layer 304 indicated by the solid line is 1 second and when the growth interruption time indicated by the broken line is 30 seconds. Shows the street. Here, “growth interruption” refers to a step of flowing only a specific gas while keeping the substrate temperature at the growth temperature. As can be seen from FIG. 2 (a), Mg at the stacking interface was changed by the growth interruption step.
A steep impurity density profile of is obtained. Figure 2
(B) shows the dependence of the impurity density of H in the p-type semiconductor layer 304 on the thickness of the n-type cap layer. It can be seen that when the thickness of the n-type cap layer 305 is 1 μm or more, the H impurity density is 5 × 10 ¹⁸ cm ⁻³ . FIG. 2B also shows the impurity concentration of H in the case of the structure in which the n-type cap layer, which is found in the conventional GaN-based light emitting device, is not laminated. The impurity density of H in the prior art shown by a circle is 5 ×
It is 10 ¹⁹ cm ⁻³ , and it is known that the p-type GaN layer has 10 times or more H incorporation as compared with the undoped and n-type GaN layers grown under the same growth condition.
On the other hand, in the n-type cap structure of the first feature of the present invention, as apparent from FIG.
The impurity concentration of H in 04 is undoped or n-type Ga
It has dropped to a value equivalent to that of the N layer. n-type cap layer 3
05 or the impurity density of the p-type semiconductor layer 304 is changed, the thickness of the n-type cap layer becomes 0.
If it is 1 μm or more, the uptake of H may be suppressed in some cases. However, if the thickness of the n-type cap layer is 1 μm or more, the uptake of H can be reliably suppressed. As will be described later, n
Impurity density of the type cap layer 305 and the p-type semiconductor layer 304, thickness of the n-type cap layer 305, p-type semiconductor layer 30
The four parameters of the growth interruption condition between the No. 4 and the n-type cap layer 305 are related to each other, and the present invention has the greatest feature in finding the optimum condition. After the continuous growth of the structure shown in FIG.
When the electrical characteristics of the Mg-doped GaN layer 304 were measured by removing the aN cap layer 305, p-type (1 × 10 ¹⁸ cm ⁻³ ) characteristics were obtained with low resistance (resistivity 1 Ω-cm). That is, according to the first feature of the present invention, the activation rate of the p-type GaN-based semiconductor layer 304 is equivalent to that obtained when the conventional Mg-doped GaN layer is activated (lowered in resistance) by thermal annealing. You can get it without. The impurity density of H contained in both crystals was also the same as that obtained by thermal annealing as shown in FIG. Therefore, by adopting the laminated structure of the first feature of the present invention shown in FIG. 1 or 3, it is possible to suppress the incorporation of H into the Mg-doped layer, and to carry out activation treatment such as thermal annealing or electron beam irradiation. The p-type GaN layer can be obtained without adding a special step. Once the H incorporation can be suppressed, the n-type cap layer 305 may be removed thereafter. In FIG. 3, the n-type cap layer 3 is initially formed on the entire upper surface of the p-type cladding layer 304.
No. 05 was formed, but thereafter the n-type cap layer 305
It is a structure in which a part of is removed selectively. As described above, even if a part of the n-type cap layer 305 is removed in the subsequent step, the effect of increasing the activation rate of the acceptor is the same, and the profile of the impurity density in the p-type conductivity type can be controlled well.

A second feature of the present invention relates to a method for manufacturing a GaN-based semiconductor light emitting device. Specifically, a semiconductor light emitting device that emits light of a predetermined wavelength by a laminated structure including an n-type GaN-based semiconductor layer and a p-type GaN-based semiconductor layer,
In contact with the p-type GaN-based semiconductor layer, n-type In _u Al _v G
a _1-uv N (0 <u, v <1) as a cap layer 1
This is to include at least a step of growing to a thickness of μm or more.

According to the second feature of the present invention, n-type In _{u is used} in the series of vapor phase epitaxial growth steps.
The activation rate of the acceptor can be improved and the resistance of the p-type GaN-based semiconductor layer can be reduced only by making a simple improvement of forming the Al _v Ga _{1 -uv} N cap layer. As a result, the luminous efficiency of the semiconductor light emitting device is improved.

According to the second feature of the present invention, it is not necessary to add a complicated and time-consuming special process. As a result, the device fabrication process can be simplified when lowering the resistance of the p-type GaN-based semiconductor layer, which increases the manufacturing yield and improves the productivity. Further, since the product can be manufactured in a short time, the substantial production cost is reduced and the industrial value is great. In particular, the use of the n-type In _u Al _v Ga _{1 -uv} N cap layer improves the etching selectivity with respect to the base of the cap layer, so that the cap layer can be easily processed. By setting the thickness of the cap layer to 1 μm or more, the activation rate of acceptor impurities in the p-type GaN-based semiconductor layer that is the base of the cap layer can be increased.

A third feature of the present invention relates to a method for manufacturing a GaN-based semiconductor light emitting device. Specifically, an n-type clad layer, an active layer, a p-type clad layer, and an n-type In _u Al _v G
This is a manufacturing method including at least a step of continuously growing a laminated structure including an a _{1 -u- v} N cap layer (0 <u, v <1) in this order in the same growth chamber. n-type In _u Al _v
The Ga _1-uv N layer has a thickness of 1 μm or more. Here, "continuously" means that the growth of each layer is "without exposing to the atmosphere in the middle". That is, it is a concept that the above-mentioned "growth interruption" that stops the supply of a part of the source gas may be included. Rather, in the present invention, "growth interruption" is preferably included as one step of continuous growth.

According to the third aspect of the present invention, the activation rate of the acceptor is increased by forming an n-type In _u Al _v Ga _{1 -uv} N cap layer in a series of continuous vapor phase epitaxial growth steps. Can be improved,
The resistance of the p-type cladding layer is lowered. As a result, the luminous efficiency of the semiconductor light emitting device is improved. Further, since the current constriction structure can be easily realized by using the laminated structure formed by continuous epitaxial growth, the luminous efficiency is further improved. Further, according to the third feature of the present invention, since the device forming process can be simplified, the manufacturing yield is increased and the productivity is improved. Since the product can be manufactured in a shorter time, the substantial production cost is reduced. Especially crystalline n-type In _u Al
_{Since the v} Ga _1-uv N cap layer is used, subsequent processing is easy even if the thickness is 1 μm or more, and the activation rate of acceptor impurities can be more surely improved.

In particular, the MOCVD method is preferable as the growth method in the third aspect of the present invention, and at this time, on the p-type GaN-based semiconductor layer containing acceptor impurities such as Mg,
"Growth interruption" by supplying only NH ₃ gas and carrier gas
It is desirable to continuously grow a cap layer made of n-type In _u Al _v Ga _{1 -uv} N through the steps.

The fourth feature of the present invention relates to a method of manufacturing a GaN-based semiconductor device. Specifically, an n-type GaN-based semiconductor layer and a p-type Ga are provided on a predetermined substrate such as a sapphire substrate.
A laminated structure composed of N-based semiconductor layers and the like is grown by a vapor phase epitaxial growth method, and after forming the uppermost layer of the laminated structure, TM
This is to stop the supply of the group ₃ element source gas such as G and the group 5 element source gas such as NH ₃ and lower the substrate temperature from the growth temperature to room temperature in the carrier gas atmosphere. As the carrier gas at this time, an inert gas such as N ₂ , Ar, or He is preferable, and in consideration of the change in the stoichiometric composition associated with the dissociation (revaporation) of N, a carrier gas containing N ₂ or N ₂ is particularly preferable. Is preferred.

From the viewpoint of avoiding the complexity of the operation at the time of lowering the substrate temperature, it is preferable that the carrier gas at the time of vapor phase epitaxial growth is the same inert gas as that at the time of lowering the temperature. By setting an inert gas atmosphere at the time of temperature reduction, atomic hydrogen decomposed by NH ₃ as in the prior art is not taken into the epitaxial growth layer, and the activation rate of acceptor impurities is increased.

A fifth feature of the present invention is that a laminated structure including an n-type GaN-based semiconductor layer, a p-type GaN-based semiconductor layer, and the like is formed on a substrate such as a sapphire substrate so that the total thickness is finally required. Is grown in a vapor phase epitaxial growth method so as to be thicker than that, and is performed in hydrogen (H ₂ ) or a carrier gas containing hydrogen when the substrate temperature is lowered from the growth temperature to room temperature, and vapor phase etching of the uppermost layer of the laminated structure is performed. And finally obtain an epitaxial growth layer having a desired film thickness. By lowering the temperature of the substrate while vapor-phase etching, the incorporation of atomic hydrogen (H) into the epitaxial growth layer is suppressed, and the activation rate of acceptor impurities is improved.

[0025]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings.

(First Embodiment) First, a GaN-based semiconductor (I), which is the basic technique of the first embodiment of the present invention, will be described.
For _{n x Al y Ga 1-xy} N) stacking technology describing the GaN continuous growth as an example.

FIG. 1 is a sectional view of a laminated structure of a GaN-based semiconductor according to the basic technique of the first embodiment of the present invention.
In the figure, 301 is a sapphire (Al ₂ O ₃ ) substrate, and Si-doped n-type on one main surface of the sapphire substrate 301.
-Type GaN layer 302, Mg-doped p-type GaN layer 304,
Si-doped n-type GaN layer (n-type cap layer) 305,
Are sequentially stacked. The growth of these layers is MOCVD
By using a vapor phase epitaxial growth method such as a vapor deposition method, and ammonia (NH ₃ ) as a Group 5 element source gas, TMG (Ga (CH ₃ ) ₃ ) and TEG (G as a Group 3 element source gas.
a (C ₂ H ₅ ) ₃ ) or the like, biscyclopentadienyl magnesium (Cp ₂ Mg), monosilane (SiH ₄ ) or the like as a dopant gas, and a mixed gas of H ₂ / N ₂ as an atmosphere gas (carrier gas) Etc. may be used. The film thickness of each layer is as follows. n-type GaN layer 302 ··· 2.0 μm p-type GaN layer 304 ··· 1.0 μm n-type GaN layer 305 ··· 1.0 μm For example, Cp ₂ M is used as a dopant gas for the p-type GaN layer.
When g is used and Mg is used as the acceptor impurity, it is difficult to obtain a steep Mg profile at the crystal interface due to the memory effect of the Mg raw material (Cp ₂ Mg). That is, when another layer is continuously grown on the Mg-doped p-type GaN layer 304, the upper layer is also doped with Mg, which makes it difficult to grow the n-type layer on the p-type layer. In the present invention, in order to prevent the memory effect of Mg, the Mg raw material (Cp ₂ Mg) is supplied separately from other raw materials through a separate pipe, and “growth interruption” at the interface with the n-type layer 305 growing thereon. I do. The “growth interruption” may be performed for about 1 to 10 minutes while flowing only NH ₃ gas and carrier gas and maintaining the substrate temperature at the growth temperature.

In order to suppress the memory effect of Mg and increase the activation rate of Mg which is the object of the present invention, the impurity density of Mg (acceptor impurity) in the p-type GaN layer 304, n The impurity density of Si (donor impurity) in the cap layer 305, the thickness of the n cap layer 305,
And it is necessary to optimize the conditions for growth interruption.

The upper limits of the doping amounts of Mg and Si exist in relation to the surface morphology of the doping layer. For example, when the Mg and Si impurity densities in the GaN crystal exceed 2 × 10 ²⁰ and 5 × 10 ¹⁹ cm ⁻³ , respectively, the surface morphology becomes rough, which is desirable when the steepness of the interface is taken into consideration. Disappear. Also, G
The electrical activation rates of Mg and Si in the aN crystal are 10% and ≧ 90%, respectively. Therefore, particularly in Mg doping, high-concentration Mg doping is required in order to increase the p-type carrier density. From these relationships, in the present invention, the impurity concentration of Mg in the p-type GaN layer is substantially 1 × 10 ²⁰ cm ⁻³ . “Substantially” does not need to be exactly 1 × 10 ²⁰ cm ⁻³ , but 5 × 10 ¹⁹ 〜
This means that there is no problem even if there is a slight increase or decrease within the range of 1.5 × 10 ²⁰ cm ^-3 . That is, it may be understood as the same meaning as the maximum impurity density at which the surface morphology is not roughened.

FIG. 2A shows the p-type Ga in the structure of FIG.
9 shows an impurity density profile in the film thickness direction of Mg by SIMS when the N layer 103 has an Mg impurity density of 1 × 10 ²⁰ cm ⁻³ . FIG. 2A shows the results under the two growth interruption conditions. It can be seen that the Mg impurity density in the n-type cap layer 305 changes due to the Mg memory effect depending on the growth interruption conditions. That is, the solid line shows the growth interruption time at the interface with the n-type cap layer 305 at 1 second, and the broken line shows the growth interruption time at 30 seconds. In this growth interruption, only the carrier gas and the NH ₃ gas are supplied as described above, and the substrate temperature is kept at the growth temperature. As shown in FIG. 2A, it is understood that the memory effect of Mg can be reduced by prolonging the growth interruption time. As a result of repeating further experiments, it was found that the effect was gradually increased by the growth interruption for 30 seconds or more and then saturated. It was also found that when the growth was interrupted for 30 minutes or more, the desorption of N from the crystal became remarkable, and the surface morphology when the n-type cap layer 305 was grown was remarkably roughened. Therefore, the growth interruption time in the present invention is preferably a relatively long time of less than 30 minutes. Further, in order to bring out the effect of this structure, it is necessary to make the cap layer 305 n-type as described above. Therefore, depending on the situation of the memory effect of Mg, the Si doping amount in the n-type cap layer 305 and the cap layer 305 may be changed. It is necessary to adjust the film thickness. For example, under the growth interruption condition of 30 seconds shown in FIG. 2A, considering the above-mentioned electrical activation rates of Mg and Si, the impurity density of Si is 1 ×.
The condition can be realized by setting it to 10 ¹⁸ cm ⁻³ or more. Further, considering the surface morphology roughness due to the high concentration doping of Mg and Si, it is possible to sufficiently satisfy the condition by setting the Si impurity density of the n cap layer to 2 × 10 ^{18 to} 5 × 10 ¹⁹ cm ⁻³ .

FIG. 2B shows the relationship between the film thickness of the n-type cap layer 305 and the impurity concentration of H in the Mg-doped GaN layer 304. Here, the n-type cap layer 305
The impurity density of Si therein is 5 × 10 ¹⁸ cm ⁻³ , and the impurity density of Mg in the Mg-doped GaN layer 304 is 1 × 10 ²⁰ cm 3.
^-3 . In FIG. 2B, the result when the n-type cap layer 305 in the prior art is not provided is also indicated by a circle. That is, after stacking the Mg-doped GaN layer 304, the substrate temperature is lowered to room temperature without forming the n-type cap layer 305 (at this time, N which is a group 5 source gas N so that N is not dissociated from the growth layer).
When H ₃ gas is continuously supplied), the impurity density of H is 5 × 10 ¹⁹ cm ⁻³ . On the other hand, when the n-type cap layer is formed, the impurity concentration of H decreases as the thickness of the n-type cap layer 305 increases, and the thickness of the n-type cap layer 305 is reduced to 1
It can be seen that, when the thickness is μm, the incorporation of H is lowered to 5 × 10 ¹⁸ cm ⁻³ , and even if the thickness of the n-type cap layer 305 is increased, it is saturated at this value. This 5 × 10 ¹⁸ c
The incorporation of H of m ⁻³ is equivalent to the value during growth of the undoped or n-type doped GaN layer. Further, the structure shown in FIG. 1 is continuously epitaxially grown, and then the upper n-type GaN cap layer 305 is removed to remove M.
When the electrical characteristics of the g-doped GaN layer were measured, it showed low resistance (resistivity 1 Ω-cm) and p-type (1 × 10 ¹⁸ cm ⁻³ ). This characteristic is similar to Mg-doped G in the conventional technique.
This is the same as when the aN layer is activated (lowered in resistance) by thermal annealing. Further, the impurity densities of H contained in both crystals are also the same. Therefore, by using the n-type cap structure as shown in FIG.
The incorporation of H into the doped layer can be suppressed, and a p-type GaN layer having a high activation rate, that is, a low resistance, can be obtained without performing a special activation treatment such as thermal annealing or electron beam irradiation. The foregoing is the case for the composition x = y = 0, can of course be more generally applied to the laminated structure of _{In x Al y Ga 1-xy} N.

FIG. 3 (a) is a cross-sectional structural view showing the outline of an LED using a GaN-based material according to the first embodiment of the present invention, and FIG. 3 (b) is a bird's eye view thereof. The LED structure on the sapphire substrate _{301 In x Al y Ga 1-} x -y N
Layer, a GaN layer, and an In _x Ga _1-x N layer are laminated, and the respective film thicknesses are as shown below.

N-type In _x Al _y Ga _{1-x -y} N (0 ≦ x, y ≦ 1) buffer layer 331 ··· 50 nm undoped (or n ⁻ type) GaN layer 332 ··· 0.5 μm n-type GaN cladding layer 302 ··· 4.0 μm undoped In _x Ga _1-x N active layer 303 ··· 0.1 μm p-type GaN cladding layer 304 ··· 0.5 μm n-type GaN cap layer 305 ... 0.1 μm where the n-type GaN cap layer 305 is formed on a part of the upper portion of the p-type GaN cladding layer 304, and the upper portion of the n-type GaN cap layer 305 and the p-type without the cap layer 305 are formed. On top of the GaN cladding layer 304, a thin film metal (conductive light transmission film) layer 306 which becomes a transparent electrode layer which can transmit light is formed. N-side electrode 307 for current injection
And the p-side electrode 308 are part of the surface of the n-type GaN cladding layer 302 and the n-type GaN cap layer 305, respectively.
Is formed on a part of the surface of the thin film metal layer 306 located above. The n-type In _x Al _y Ga _1-xy N buffer layer 331 is composed of the sapphire substrate 301 and the epitaxial growth layers 332, 303, 304, 305 formed thereon.
Is a layer for alleviating the lattice mismatch between and. Buffer layer 331, may be a p-type _{In x Al y Ga 1-xy} N layer. The layer 332 is preferably undoped, but if the impurity density is lower than that of the upper n-type GaN cladding layer 302, a certain effect can be obtained. That is, by forming the undoped or low impurity density GaN layer 332, even if the impurity density of the n-type GaN cladding layer 302 formed thereon is increased, the surface morphology can be prevented from being roughened. For example, the buffer layer 33
When the n-type GaN layer is grown directly on the Si substrate 1, the impurity concentration of Si is about 5 × 10 ¹⁹ cm ^−3, which is a threshold value for preventing the surface morphology from being roughened.
By forming the ⁻ type GaN layer 332, the n type impurity density can be increased to 8 × 10 ¹⁹ cm ⁻³ .

The n-type GaN cap layer 305 of the present invention has a p-type GaN cladding layer 304 during the manufacturing process.
Thicker than the final design film thickness (1.0 μm) on the entire upper surface of
It prevents the inactivation of Mg that is formed and serves as an acceptor. However, finally, as shown in FIGS. 3A and 3B, the n-type GaN cap layer 305 is formed only on a part of the upper portion of the p-type GaN cladding layer 304 and functions as a current blocking layer. Further, its thickness is smaller than that immediately after the epitaxial growth. That is, this n
It is also an excellent feature of the present invention that the current confinement structure can be formed using the type GaN cap layer 305. That is, the p-side electrode 308 formed on the upper surface of the device prevents light extraction, and the current injection directly under the p-side electrode 308 results in a reactive current that does not contribute to external light emission. This is because this ineffective component can be reduced and the luminous efficiency as a whole can be improved. In the conventional structure, after epitaxial growth, C
An oxide film (SiO ₂ film) or the like was deposited using a VD furnace or the like, and this oxide film or the like was formed as a current block layer to reduce this reactive current. However, in the structure according to the present invention, n-type Ga is used.
The N cap layer 305 can be used as it is as the current confinement layer. CVD of SiO ₂ as in the prior art
In order to perform the above, a pretreatment process such as cleaning of the substrate is naturally required, and an increase in one process will result in an additional increase in several processes. Therefore, according to the present invention, the process can be simplified, and an excellent current injection / light extraction structure can be easily formed in a short time.

Next, a method of manufacturing the GaN-based LED according to the first embodiment of the present invention shown in FIG. 3 will be described with reference to FIGS. 3 and 4 (a).
This will be described with reference to (c).

(A) MO-on the sapphire substrate 301
As shown in FIG. 4A, a thickness of 50 n is obtained by using the CVD method or the like.
m n-type In _x Al _y Ga _1-xy N buffer layer 331,
Undoped (or n ⁻ type) GaN layer 3 having a thickness of 0.5 μm
32, an n-type GaN cladding layer 302 having a thickness of 4.0 μm,
Undoped In _x Ga _1-x N layer 30 having a thickness of 0.1 μm
3. A p-type GaN cladding layer 304 having a thickness of 0.5 μm and an n-type GaN cap layer 305 having a thickness of 1.0 μm are continuously grown. For example, a reduced pressure C of a high frequency (RF) induction heating system
In a VD furnace or an atmospheric pressure CVD furnace, a Group 3 element source gas such as an organometallic compound and a Group 5 element source gas such as ammonia (NH ₃ ) may be introduced and grown at a predetermined temperature. Specifically, at a substrate temperature of 850 ° C. to 1200 ° C., Ga (CH ₃ ) ₃ , In (C
H ₃ ) ₃ , Al (CH ₃ ) ₃ and NH ₃ may be used as the Group 5 element source gas. Usually, these source gases are introduced together with a carrier gas such as hydrogen or nitrogen. The growth pressure may be, for example, about 1 k to 100 kPa. In this way, n-type _{In x Al y Ga 1-xy} N performs continuous growth of the gallium nitride based semiconductor to the buffer layer 331~n type GaN cap layer 305, middle component ratio of each of the reaction gas in the growth By switching (or completely stopping the supply of some source gases), In _X Al _y Ga
The composition of each layer of _1-xy N, GaN, or In _x Ga _1-x N is adjusted. Especially after growing the p-type GaN cladding layer 304,
Only the carrier gas and NH ₃ are supplied, “growth interruption” is performed for 1 to 20 minutes while keeping the substrate temperature at the temperature growth temperature, and then the n-type cap layer is grown. Further, in order to add impurities, SiH ₄ or CP ₂ Mg or the like is appropriately introduced to control the n-type and p-type predetermined impurity densities.

(B) Next, the n-type buffer layer 33 is formed on top of it.
The sapphire substrate 301 on which the 1 to n-type cap layers 305 are continuously deposited is taken out from the CVD furnace, and the thickness of the n-type GaN cap layer 305 is set to 0.1 μm by etching or CMP (chemical mechanical polishing). Thin to thickness.
Then, as shown in FIG. 4B, the n-type GaN cladding layer 3 is formed.
A U groove 333 reaching 02 is formed, and a part of the n-type GaN cap layer 305 is patterned as shown in FIG. 4B. The U groove 333 is a groove for later forming the n-side electrode 307 on the bottom thereof. The shape of FIG. 4B can be realized by a well-known photolithography technique and etching technique such as RIE.

(C) Subsequently, a transparent electrode layer 306 such as a metal thin film or an ITO film is deposited by sputtering, vacuum deposition, CVD method or the like, and patterned by photolithography technique as shown in FIG. 4 (c). For patterning, any liftoff may be used.

(D) Next, as shown in FIG. 3, an n-side electrode 307 is formed on the bottom of the U groove 333, and an n-type GaN cap layer 305.
On the transparent electrode layer 306 positioned above the p-side electrode 30
8 is formed. The n-side electrode 307 and the p-side electrode 308 may be formed by using the lift-off method. That is, the n-side electrode 3
Cover the area other than the area where 07 is to be formed with photoresist, and
By depositing a metal material such as u, Ti, Al, or Ni by a sputtering method or a vacuum evaporation method and then removing the photoresist, the n-side electrode 307 can be formed only at a predetermined position on the bottom of the U groove 333. The same applies to the p-side electrode.

(E) After the basic structure of the GaN-based LED is completed in this way, a dicing process is performed. That is, a diamond cutter is used to cut on a scribe line that has been previously mesa-etched and cut into a suitable size to obtain a large number of chips. Then, these chips are mounted on a predetermined stem (wire frame), and after wire bonding and molding, the GaN-based LED of the present invention is completed.

The sapphire substrate 301 has a thickness of 60.
˜100 μm is preferable, and yield and device characteristics are improved by selecting this thickness.

The advantage of the manufacturing method according to the first embodiment of the present invention over the prior art is that the process can be simplified as described above. That is, the first aspect of the present invention
According to the embodiment of the present invention, the passivation resulting from the incorporation of H in the p-type GaN cladding layer 304 is improved by the simple process of adding the step of forming the n-type GaN cap layer 305 at the end of the conventional continuous epitaxial growth. Can be suppressed (therefore, there is no substantial increase in the number of steps). This enables remarkable process simplification in that complicated processes such as electron beam irradiation and heat treatment, which are required in the prior art to activate the p-type GaN cladding layer, can be eliminated. In addition, the fact that the current constriction structure can be formed by using the n-type cap layer 305 as described above is also an excellent point of the manufacturing method of the present invention. That is, according to the present invention, in order to realize the current confinement structure, C
It is not necessary to use an additional process such as oxide film formation using the VD method or the sputtering method. Therefore, excellent current injection / light extraction characteristics can be obtained in a simple process.

Using the device structure according to the first embodiment of the present invention, by changing the In composition X of the In _x Ga _{1 -x} N active layer from 0 to 0.6, ultraviolet light to visible light (from purple to Light emission up to the green wavelength can be realized. Since the emitted light can be emitted from the entire surface of the device without the n-type GaN cap layer, LED characteristics with high brightness and high luminous efficiency can be realized.

FIG. 5 is a sectional structural view showing an outline of an LED using a GaN-based material according to a modification of the first embodiment of the present invention. The LED structure _{In x Al y Ga 1-x} -y N layer on a sapphire substrate 301, GaN layer and In _x
It is constituted by stacking Ga _{1 -x} N layers, and the respective film thicknesses are as shown below.

N-type In _x Al _y Ga _{1-x -y} N (0 ≦ x, y ≦ 1) buffer layer 331 ··· 50 nm undoped (or n ⁻ type) GaN layer 332 ··· 0.5 μm n-type GaN cladding layer 302 ··· 4.0 μm undoped In _x Ga _1-x N active layer 303 ··· 0.1 μm p-type GaN cladding layer 304 ··· 0.5 μm n-type In _u Al _v Ga _1-uv N (0 <u, v <1) cap layer 355 ... 0.1 μm where n-type In _u Al _v Ga _1-uv N (0 <u, v <
1) The cap layer (hereinafter referred to as “n-type InAlGaN cap layer”) 355 is a p-type GaN cladding layer 30.
4 and a p-type GaN clad layer 304 formed on a part of the upper part of the n-type InAlGaN cap layer 355 and on which the n-type InAlGaN cap layer 355 is not formed.
A thin-film metal (conductive light-transmitting film) layer 306 serving as a transparent electrode layer capable of transmitting light is formed on the upper part of the. The n-side electrode 307 and the p-side electrode 308 for current injection are part of the surface of the n-type GaN cladding layer 302 and the n-type I, respectively.
It is formed on a part of the surface of the thin film metal layer 306 located above the nAlGaN cap layer 355. N-type I
The n _x Al _y Ga _1-xy N buffer layer 331 is the sapphire substrate 301 and the epitaxial growth layer 3 formed thereon.
32, 303, 304, 305 is a layer for relaxing lattice mismatch with p-type In _x Al _y Ga.
_It may be a _1-xy N layer. That is, the buffer layer 331
The conductivity type of does not matter. The layer 332 is preferably undoped, but is a layer for preventing the surface morphology from being roughened, and may have a lower impurity density than the upper n-type GaN cladding layer 302.

The n-type InAlGaN cap layer 355 according to the modification of the first embodiment of the present invention is thicker than the final designed film thickness on the entire upper surface of the p-type GaN clad layer 304 during the manufacturing process. 1.5 μm) formed to prevent inactivation of Mg serving as an acceptor. That is, as shown in FIG. 2B, the InAlGaN cap layer 3 is formed.
By setting the thickness of 55 to 1.0 μm or more, effective prevention of Mg deactivation is achieved. However, finally, as shown in FIG. 5, the n-type InAlGaN cap layer 355 is formed only on a part of the upper portion of the p-type GaN cladding layer 304 and functions as a current blocking layer. Further, its thickness is smaller than that immediately after the epitaxial growth. That is, as in FIG. 3, the n-type InAlGaN cap layer 3 is formed.
55 is used to create a current constriction structure. Therefore, excellent luminous efficiency can be easily achieved.

Next, FIG. 6 shows a method of manufacturing a GaN-based LED according to a modification of the first embodiment of the present invention shown in FIG.
A description will be given using (a) to (c).

(A) MO-on the sapphire substrate 301
As shown in FIG. 6A, a thickness of 50 n is obtained by using the CVD method or the like.
m n-type In _x Al _y Ga _1-xy N buffer layer 331,
Undoped (or n ⁻ type) GaN layer 3 having a thickness of 0.5 μm
32, an n-type GaN cladding layer 302 having a thickness of 4.0 μm,
Undoped In _x Ga _1-x N layer 30 having a thickness of 0.1 μm
3. A 0.5 μm-thick p-type GaN cladding layer 304 and a 1.0 μm-thick n-type InAlGaN cap layer 355 are continuously grown. As described above, the buffer layer 331 may be a p-type In _x Al _y Ga _1-xy N layer, but the n-type is more convenient in consideration of switching of the dopant gas during continuous growth. In this continuous epitaxial growth,
In particular, after growing the p-type GaN clad layer 304, only carrier gas and NH ₃ are supplied, and “growth interruption” is performed for 1 to 20 minutes.
The substrate temperature is kept at the temperature growth temperature, and then the n-type InAlGaN cap layer 355 is grown to a thickness of 1.5 μm.

(B) Next, the n-type buffer layer 33 is formed on top of it.
The sapphire substrate 301 on which the 1-n type InAlGaN cap layer 355 is continuously deposited is taken out from the CVD furnace,
The thickness of the n-type InAlGaN cap layer 355 is set to 0.1 μm by etching or CMP (chemical mechanical polishing).
Thin to m. Then, a U groove 333 reaching the n-type GaN cladding layer 302 is formed as shown in FIG. 6B, and a part of the n-type InAlGaN cap layer 355 is patterned as shown in FIG. 6B. Since InAlGaN with a soft result has a large etching selection ratio with respect to GaN, this patterning can be accurately and easily realized without overetching. The U groove 333 is a groove for later forming the n-side electrode 307 on the bottom thereof. The shape of FIG. 6B can be realized by a well-known photolithography technique and etching technique such as RIE.

The step of forming the transparent electrode layer 306 shown in FIG. 6C and the subsequent step of forming the n-type electrode 307 and the p-type electrode 308 are the same as the steps after FIG. Is omitted.

Although the case of the current confinement structure has been described above, the n-type I after continuous epitaxial growth has been described.
The nAlGaN cap layer 355 may be completely removed. The n-type InAlGaN layer 355 has an In composition u =
If about 0.1, the underlying p-type GaN cladding layer 304
On the other hand, since the etching selection ratio during RIE can be set to about 1: 1,3, overetching can be prevented. It goes without saying that if the composition u is further increased, the selection ratio is further increased. In addition, endpoint monitoring can also be performed by monitoring the reaction product during RIE by infrared spectroscopy, Raman spectroscopy, mass spectrometry, or the like. Since InAlGaN has a soft crystal, it is easy to process and endpoint monitoring is easy. Thus, InAlGaN can be easily removed even if deposited to a thickness of 1 μm or more. Therefore, prevention of Mg inactivation becomes more reliable. Of course, the n-type InAlGaN cap layer 355 having a thickness of 2 μm or more may be deposited.

The first embodiment of the present invention is not limited to the structure including the above modification and the above manufacturing method. That is, the more general In _x Al _y Ga _1-xy N
It can also be applied to a GaN-based LED having a layer and a semiconductor laser. GaN and In as n-type cap layer
Although AlGaN has been described, the same effect can be obtained with other semiconductor materials as long as the electrical characteristics exhibit n-type. In addition, various modifications can be made without departing from the scope of the present invention.

(Second Embodiment) FIG. 7A is a sectional view of a laminated structure of a GaN-based semiconductor according to a second embodiment of the present invention. As shown in FIG. 7A, sapphire (A
An Si 2 -doped n-type GaN layer 302 and a Mg-doped p-type GaN layer 314 are sequentially stacked on one main surface of the (l ₂ O ₃ ) substrate 301. These layers are grown using a vapor phase epitaxial growth method such as MOCVD, and NH ₃ is used as a group 5 element source gas and TM is used as a group 3 element source gas.
G, TEG, etc., Cp ₂ Mg, Si as a dopant gas
H ₂ or the like is used, and H ₂ is used as an atmosphere gas (carrier gas).
A mixed gas of / N ₂ or the like may be used. The substrate temperature during growth is preferably 1050 ° C., for example. The film thickness of each layer is as follows.

N-type GaN layer 302 ··· 2.0 μm p-type GaN layer 314 ··· 1.0 μm After the growth of this laminated structure, a crystal growth layer is formed in the process of lowering the substrate temperature from the growth temperature to room temperature. The atmosphere of the substrate having N
_Set to ₂ . Normally, in the process of lowering the substrate temperature after crystal growth, NH ₃ which is a group 5 source gas is continuously supplied in order to prevent desorption of N from the crystal growth layer, but atomic hydrogen produced by thermal decomposition of this NH ₃ is generated. Are trapped in the crystal during the temperature lowering process and deactivate the acceptor. That is, according to the second embodiment of the present invention, the supply of NH ₃ is stopped when the substrate temperature is lowered to prevent the production of atomic hydrogen, and thus the activation rate of the acceptor can be increased. Actually, from the measurement of the effective carrier density of the Mg-doped GaN layer 314 formed by the method of the second embodiment of the present invention by the CV method, about 10% of the acceptor impurities in the crystal are active. It was confirmed that the activation rate (1%) in the case of using the temperature lowering process in the NH ₃ atmosphere in the prior art was greatly exceeded. When an H ₂ / N ₂ mixed gas is used as a carrier gas during growth, the carrier gas should be adjusted to only N ₂ and the temperature should be lowered at the same time when the supply of the group 3 and group 5 source gases at the end of growth is stopped. Good.
Alternatively, the mixture ratio of H ₂ / N ₂ of the carrier gas is N ₂ 9
It may be N ₂ rich of 0% or more. In this case, it is necessary to consider the etching effect of H ₂ .

Considering the convenience of the operation of switching and adjusting the carrier gas to N ₂ or N ₂ rich H ₂ / N ₂ mixed gas at the time of lowering the substrate temperature, the n-type GaN layer 3
02, the carrier gas at the time of epitaxial growth of the p-type GaN layer 314 is preferably N ₂ or N ₂ rich H ₂ / N ₂ mixed gas. By setting the carrier gas at the time of epitaxial growth to be an inert gas such as N ₂ , the temperature can be directly transferred to the temperature lowering process, so that the second embodiment of the present invention becomes more effective.

The supply of NH ₃ at the time of lowering the temperature may be stopped at a temperature of 400 ° C. from the substrate temperature at the time of crystal growth. Considering the desorption of N from the crystal, it is preferable to stop at 900 to 400 ° C. More desirable. Furthermore, the amount of atomic hydrogen produced is NH
_Since it depends on the amount of NH ₃ , a small amount of NH ₃ may be added.
Since the desorption of N at the time of temperature decrease can be suppressed if the supply amount is about 10% during crystal growth, the temperature may be decreased in an inert gas atmosphere such as N ₂ to which a small amount of NH ₃ is added.

Further, similarly to the first embodiment, FIG.
As shown in (b), an n-type cap layer 315 may be formed on the p-type GaN layer 314, and the temperature may be lowered from the growth temperature to room temperature in N ₂ or N ₂ -rich carrier gas. As the n-type cap layer 315, it is more preferable to deposit an n-type InAlGaN cap layer to a thickness of 1 μm or more. In addition, after forming an n-type In _x Al _y Ga _1-xy N layer and an undoped (or n ⁻ -type) GaN layer, n-type GaN is formed thereon.
Of course, layer 302 may be formed.

The advantage of the second embodiment of the present invention over the prior art is that the process can be simplified. That is, according to the second embodiment of the present invention, an improvement of the simple process of flowing only N ₂ or N ₂ rich carrier gas at the end of the conventional continuous epitaxial growth and lowering the temperature in the atmosphere of this carrier gas Thus, it is possible to suppress the inactivation due to the incorporation of H in the p-type GaN cladding layer 304 (therefore, the number of steps is not substantially increased). This is due to the p-type Ga in the prior art.
This makes it possible to significantly simplify the process in that complicated processes such as electron beam irradiation and heat treatment required for activation of the N-clad layer can be eliminated.

The second embodiment of the present invention is shown in FIG.
It is not limited to the structures shown in (a) and 7 (b). In FIG. 7B, Ga is used as the n-type cap layer.
Although the N layer 315 is used, the same effect can be obtained by using any other semiconductor material such as n-type InAlGaN described above as long as the electrical characteristics exhibit n-type. The second embodiment of the present invention can be applied not only to the light emitting diode but also to a semiconductor laser. Further, N ₂ and N ₂ -rich H ₂ / N ₂ were used as the atmosphere gas in the temperature lowering process, but other inert gases such as Ar and He, or a mixed gas thereof can also obtain the same effect. In addition, various modifications can be made without departing from the scope of the present invention.

(Third Embodiment) FIG. 8A is a sectional view of a laminated structure of a GaN-based semiconductor according to a third embodiment of the present invention. In FIG. 8A, sapphire (Al
₂ O ₃ ) Si-doped n-type G on one main surface of the substrate 301
The aN layer 302 and the Mg-doped p-type GaN layer 324 are sequentially stacked. These layers are grown using a vapor phase epitaxial growth method such as MOCVD, and NH ₃ is used as a group 5 element source gas, TMG is used as a group 3 element source gas,
Tp, etc. Cp ₂ Mg, SiH ₄ as dopant gas
Etc. using H ₂ / N as an atmosphere gas (carrier gas)
A mixed gas of ₂ or the like may be used. The substrate temperature during growth is preferably 1050 ° C., for example. The film thickness of each layer is as follows.

N-type GaN layer 302 ··· 2.0 μm p-type GaN layer 324 ··· 2.0 μm In the third embodiment of the present invention, the final desired thickness of the p-type GaN layer is 1 Although it is 0.0 μm, the p-type GaN layer 324 is deposited up to 2.0 μm thicker than the desired thickness as shown in FIG. The third embodiment of the present invention is different from the second embodiment in that the atmosphere gas is H ₂ 10% or more H ₂ / N _{2 in the} temperature decreasing process of the substrate temperature after the growth is completed.
It is a mixed gas. If the growth layer is exposed to H ₂ at a high temperature, the film thickness becomes thin due to its etching action, and the crystals disappear if left for a long time. Therefore, in the conventional technique, NH ₃ is simultaneously supplied to suppress the etching effect. However, the supply of NH ₃ is not desirable because atomic hydrogen is produced. Therefore, in the third embodiment of the present invention, the film thickness during growth is set in advance in consideration of the etching effect of H ₂ , so that H ₂ or H ₂ / N ₂ mixed gas having an H ₂ concentration of 10% or more is set. It is possible to lower the temperature in the interior, and eventually suppress the inactivation of the acceptor by atomic hydrogen. That is, the third in the embodiment to stop the supply of NH ₃ during cooling after completion of the crystal growth of the stacked structure shown in FIG. 8 (a) and concentration of H ₂ 10% H of the present invention
_{The 2} / N ₂ mixed gas is supplied and the temperature is lowered at a rate of 50 ° C./min. As a result, as shown in FIG. 8B, the Mg-doped GaN layer 324a is vapor-phase-etched by about 1 μm,
A 1 μm Mg-doped GaN layer 324 remains. In the remaining Mg-doped GaN layer 324b, it has been confirmed that about 8% of the acceptor impurities in the crystal are activated in the measurement of the effective carrier density using the CV method. That is, according to the third embodiment of the present invention, NH _{3 of the related} art is used.
Activation rate (1 when using the cooling process while supplying)
%) Is obtained.

The advantage of the third embodiment of the present invention over the prior art is that the process can be simplified. That is, according to the third embodiment of the present invention, the p-type GaN clad layer 324b is formed by improving the simple process of slightly increasing the laminated film thickness in the conventional continuous epitaxial growth and lowering the temperature in the H ₂ atmosphere. It is possible to suppress the inactivation due to the incorporation of H in (therefore, there is no substantial increase in the number of steps). This enables remarkable process simplification in that complicated processes such as electron beam irradiation and heat treatment, which are required in the prior art to activate the p-type GaN cladding layer, can be eliminated.

The third embodiment of the present invention is shown in FIG.
The structure is not limited to that shown in (b). Figure 3
Similar to (a), n-type In _{x is formed} on the sapphire substrate 301.
Al _y Ga _1-xy N buffer layer or undoped (or n ⁻
It goes without saying that the n-type GaN layer 302 may be formed after the (type) GaN layer is formed. The present invention can be applied to a DH light emitting diode, a semiconductor laser, etc., and various embodiments can be made without departing from the spirit of the present invention.

[0064]

As described above, according to the present invention, the acceptor activation can be performed by simply making a simple improvement in the series of vapor phase epitaxial growth steps without adding a complicated and time-consuming special step. The conversion rate can be improved and the resistance of the p-type semiconductor region is lowered. As a result, the luminous efficiency of the semiconductor light emitting device is improved.

In particular, n-type In _u Al _v Ga _1-uv N (0
<U, v <1) By using the cap layer, it is possible to increase the etching selection ratio with respect to the p-type semiconductor region which is the base of the cap layer, and facilitate endpoint monitoring. Therefore, the cap layer can be made sufficiently thick to a thickness of 1 μm or more, and the activation rate of acceptor impurities can be more reliably improved.

Further, according to the present invention, the current confinement structure can be easily formed, so that the luminous efficiency is further improved.

Further, according to the present invention, since the element forming process can be simplified, the manufacturing yield is increased and the productivity is improved. Further, since the product can be manufactured in a short time, the product can be promptly supplied and the substantial production cost is lowered, so that the industrial value is great.

[Brief description of drawings]

FIG. 1 is a cross-sectional view for explaining a basic technique (principle) of a gallium nitride-based semiconductor light emitting device according to a first embodiment of the present invention.

2A is an impurity density profile of Mg in a film thickness direction by secondary ion mass spectrometry (SIMS) of the laminated structure shown in FIG. 1, and FIG. 2B is an impurity density n of H of FIG.
It is a figure which shows the dependence with respect to the thickness of a cap layer.

FIG. 3 (a) is a cross-sectional view of a gallium nitride based semiconductor LED according to the first embodiment of the present invention, and FIG.
Is a bird's eye view.

FIG. 4 is a diagram illustrating a manufacturing process of the LED of FIG.

FIG. 5 is a cross-sectional view of a gallium nitride based semiconductor LED according to a modified example of the first embodiment of the present invention.

FIG. 6 is a diagram illustrating a manufacturing process of the LED of FIG.

FIG. 7 is a diagram showing a laminated structure according to a second embodiment of the present invention.

FIG. 8 is a diagram showing a laminated structure according to a third embodiment of the present invention.

[Explanation of symbols]

301 Sapphire substrate 302 n-type GaN layer 303 Undoped InGaN active layer 304, 314, 324, 324a, 324b p-type G
aN layer 305, 315 n-type GaN cap layer 306 conductive thin film 307 n-side electrode 308 p-side electrode _{331 In x Al y Ga 1-} xy N buffer layer 332 an undoped (or n ^- -type) GaN layer 333 U groove 355 n-type In _u Al _v Ga _1-uv N (0 <u, v <
1) Cap layer

Continuation of front page (58) Fields surveyed (Int.Cl. ⁷ , DB name) H01L 33/00 H01S 5/00-5/50 JISST file (JOIS)

Claims (12)

(57) [Claims] 1. In _x Al _y Ga _1-xy N (0 ≦ x, y
≦ 1) growing an active layer on the n-type clad layer, and magnesium on the active layer in an amount of 5 × 10 ¹⁹ cm ⁻³
In _x Al _y Ga _1-xy N containing 1.5 × 10 ²⁰ cm ^-3
A step of growing a p-type cladding layer composed of (0 ≦ x, y ≦ 1), and supplying only ammonia (NH ₃ ) gas and carrier gas for 30 seconds or more and 3 minutes or less after the growth of the p-type cladding layer. And a step of continuing the growth, and after the step of stopping the growth, on the p-type cladding layer,
The donor is 2 × 10 ¹⁸ cm ^{−3 to} 5 × 1 with a thickness of 1 μm or more.
N-type In _u Al _v Ga _1-uv N containing 0 ¹⁹ cm ⁻³ (0 <
and a step of growing a cap layer composed of u, v <1). 2. The n-type clad layer, the active layer, the p-type clad layer and the cap layer are formed on a sapphire substrate by MOCVD.
A method for manufacturing the semiconductor light emitting device according to. 3. After the step of growing the cap layer,
3. The method for manufacturing a semiconductor light emitting device according to claim 1, further comprising the step of selectively removing a part of the cap layer to expose the p-type clad layer. 4. The method according to claim 1, further comprising the step of forming a transparent electrode layer on the cap layer.
13. The method for manufacturing a semiconductor light emitting device according to any one of 1. 5. After the step of exposing the p-type clad layer, a part of the exposed p-type clad layer and a part of the active layer are selectively removed to form a part of the n-type clad layer. 4. The method for manufacturing a semiconductor light emitting device according to claim 3, further comprising the step of exposing. 6. The n-type cladding layer, the active layer, the p-type cladding layer and the cap layer are formed by a vapor phase epitaxial growth method using an inert gas as a carrier gas. A method for manufacturing the semiconductor light emitting device according to. 7. After the step of growing the cap layer,
Stop the supply of Group 3 element source gas and Group 5 element source gas,
The method for manufacturing a semiconductor light emitting device according to claim 1, further comprising the step of lowering the substrate temperature from the growth temperature to room temperature in an atmosphere of carrier gas. 8. In _x Al _y Ga _1-xy N (0 ≦ x, y
≦ 1), an n-type clad layer, an active layer above the n-type clad layer, and 5 × 10 ¹⁹ magnesium disposed above the active layer.
cm in the range of ^{-3 ~1.5} × 10 ²⁰ cm ^-3, is added to a constant impurity concentration _{In x Al y Ga 1-xy} N (0 ≦ x,
y ≦ 1), a p-type clad layer, and a donor of 2 × 10 arranged on the p-type clad layer.
^It is added to a constant impurity density in the range of ¹⁸ cm ^{−3 to} 5 × 10 ¹⁹ cm ⁻³ , gradually decreases from the interface with the p-type cladding layer, and 0.3 μm from the interface with the p-type cladding layer.
N _-type made of In _u Al _v Ga _{1 -uv} N (0 <u, v <1) to which magnesium is added, with an impurity density profile of 1.7 × 10 ¹⁸ cm ⁻³ or less. A semiconductor light-emitting device comprising a cap layer. 9. The semiconductor light emitting device according to claim 8, wherein the n-type cap layer is selectively formed on a part of an upper portion of the p-type clad layer. 10. The transparent electrode layer according to claim 9, wherein a transparent electrode layer is formed on the n-type cap layer and on the p-type clad layer in a portion where the n-type cap layer is not formed. Semiconductor light emitting device. 11. The semiconductor light emitting device according to claim 10, wherein a p-side electrode layer is formed on the n-type cap layer so as to sandwich the transparent electrode layer. 12. The semiconductor light emitting device according to claim 8, wherein the n-type cladding layer, the active layer, the p-type cladding layer and the cap layer are laminated on a sapphire substrate.