KR20170066365A - Semiconductor light-emitting element - Google Patents

Abstract

The present invention provides a semiconductor light emitting device having a quantum well active layer composed of a well layer and a barrier layer, wherein the semiconductor light emitting device has an emission wavelength of 585 nm or more and 605 nm or less and the well layer has a composition formula (Al _x Ga _{1 - x) y in 1 - y P} (0 <x≤0.06, made of a compound semiconductor of 0 <y <1), the barrier layer, composition formula _{(Al m Ga 1 -m) n} in 1 - n P (0 Lt; m < 1, 0 < n &lt; 1). Thereby, a semiconductor light emitting element which can obtain a high luminous efficiency in a short wavelength region (yellow light emission) while using an active layer of a quantum well structure is provided.

Description

Technical Field [0001] The present invention relates to a semiconductor light-

The present invention relates to a semiconductor light emitting device using a compound semiconductor material.

The AlGaInP-based material has the largest direct transition band gap among III-V compound semiconductor mixed crystals excluding nitride, and is used as a light emitting device material of 500 to 600 nm band. Particularly, a light emitting device having a light emitting portion made of AlGaInP lattice-matched with a GaAs substrate can emit light with high luminance as compared with a conventional material using an indirect transition material such as GaP or GaAsP.

However, even in the case of a light emitting device having a light emitting portion made of AlGaInP, the light emitting efficiency in a short wavelength region (yellow light emission) was not necessarily sufficient.

(1) the difference in energy gap between the active layer and the cladding layer becomes small, so that the constraint of the carrier becomes insufficient; and (2) the Al composition of the active layer becomes high. Therefore, (3) the energy band structure approaches from the direct deformation type to the indirect deformation type, and so on.

In order to solve these problems, in Patent Document 1, the active layer has a quantum well structure of 80 to 200 layers, and the Al composition in the barrier layer is larger than 0.5 (that is, the composition formula is (Al _x Ga _{1 -x} ) _{1 - y} In _y P (0.5 < x &lt; / = 1) is used to suppress carrier overflow and obtain high luminescence efficiency.

Patent Document 2 discloses a quantum well structure in which a lattice strain is introduced into an active layer (that is, a quantum well structure including a well layer having tensile strain or compressive strain and a strain relaxation barrier layer having strain opposite to that of the well layer) A method of reducing the Al composition in the active layer and obtaining a high luminescence efficiency is disclosed.

Japanese Patent Application Laid-Open No. 2008-192790 Japanese Patent Application Laid-Open No. 8-088404

As described above, a method disclosed in Patent Document 1 or Patent Document 2 has been proposed in order to suppress a decrease in luminous efficiency in a short wavelength region.

However, in the method disclosed in Patent Document 1, the overflow of the carriers can be suppressed, but the Al composition in the active layer is increased, which causes a problem that the luminous efficiency is lowered.

Further, in the method disclosed in Patent Document 2, even if a strain reducing layer is used, there is a problem that luminescence efficiency can not be necessarily obtained because the lattice defects in crystals caused by deformation are increased.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and it is an object of the present invention to provide a semiconductor light emitting device which can obtain a high luminous efficiency in a short wavelength region (yellow light emission) while using an active layer of a quantum well structure.

In order to achieve the above object, the present invention provides a semiconductor light emitting device having a quantum well active layer composed of a well layer and a barrier layer, wherein the semiconductor light emitting device has an emission wavelength of 585 nm or more and 605 nm or less, composition formula of _{(Al x Ga 1 -x) y} in 1 -y P (0 <x≤0.06, 0 <y <1) is made of a compound semiconductor, wherein the barrier layer, composition formula _{(Al m Ga 1-m)} n And a compound semiconductor of In _1-n P (0? M? 1, 0 <n <1).

As described above, by making the Al composition of the well layer made of the AlGaInP compound semiconductor constituting the quantum well active layer equal to or less than 0.06, the average Al composition of the quantum well active layer can be made small, And high luminous efficiency in a short wavelength region (yellow light emission) can be obtained.

At this time, it is preferable that the total thickness of the quantum well active layer is 200 nm or more and 300 nm or less.

When the total film thickness of the quantum well active layer is 200 nm or more, it is possible to suppress the decrease in the light emitting efficiency due to the carrier overflow. In addition, when the total thickness of the quantum well active layer is 300 nm or less, it is possible to prevent an increase in manufacturing time and material cost and an increase in manufacturing cost.

As described above, according to the semiconductor light emitting device of the present invention, a high luminous efficiency in a short wavelength region (yellow light emission) can be obtained while using an active layer of a quantum well structure.

1 is a schematic cross-sectional view showing an example of an embodiment of the semiconductor light emitting device of the present invention.
2 is a process sectional view showing a manufacturing flow used for manufacturing the semiconductor light emitting device of the present invention.
3 is a graph showing the relationship between the total film thickness of the quantum well active layer and the luminous efficiency.
4 is a graph showing the relationship between the light emission wavelength and the light emission efficiency in the examples and comparative examples.

Hereinafter, the present invention will be described in detail with reference to the drawings as an example of the embodiment, but the present invention is not limited thereto.

As described above, a plurality of methods using an active layer of a quantum well structure have been proposed in order to suppress a decrease in the light emission efficiency in a short wavelength region of the semiconductor light emitting device. In any of the methods, in a short wavelength region (yellow light emission) There was room for improvement in that high luminous efficiency was obtained.

Thus, the inventors of the present invention have conducted intensive studies on a semiconductor light emitting device which can obtain a high luminous efficiency in a short wavelength region (yellow light emission) while using an active layer of a quantum well structure.

As a result, when the Al composition of the well layer made of the AlGaInP-based compound semiconductor constituting the quantum well active layer is 0.06 or less, the average Al composition of the quantum well active layer can be made small, Can be reduced, and a high luminescence efficiency can be obtained in a short wavelength region (yellow light emission). Thus, the present invention has been completed.

First, an embodiment of the semiconductor light emitting device of the present invention will be described with reference to Fig.

The semiconductor light emitting device 10 of the present invention shown in Fig. 1 has a light emitting portion 19 having a quantum well active layer 14. The quantum well active layer 14 is formed by alternately stacking the well layer 16 and the barrier layer 15. Well layer 16 has a composition formula _{(Al x Ga 1 -x) y} In 1 - y P (0 <x≤0.06, 0 <y <1) is made of AlGaInP-i, the barrier layer 15 is expressed by a composition formula ( _{Al m Ga 1 -m) n in} 1 - n P ( composed of i-AlGaInP of 0≤m≤1, 0 <n <1) . The emission wavelength of the semiconductor light emitting element 10 is 585 nm or more and 605 nm or less. For example, by changing the film thickness of the well layer 16 of the quantum well active layer 14, a desired wavelength can be set within the above range.

The light emitting portion 19 includes a first conductive type current spreading layer 12, a first conductive type cladding layer 13, a quantum well active layer 14, a second conductive type cladding layer 17, And a conductive type current spreading layer (18). The first conductive type current spreading layer 12, the first conductive type cladding layer 13, the second conductive type cladding layer 17 and the second conductive type current diffusion layer 18 are formed of, for example, Al _{x Ga 1 -x) y in 1 -} y p (0≤x≤1, 0 <y <1) of the p-AlGaInP layer, the composition formula _{(Al x Ga 1 -x) y} in 1 -y p (0≤x≤ 1, 0 <y <1) of the p-AlGaInP layer, the composition formula _{(Al x Ga 1 -x) y} in 1 - y P (0≤x≤1, 0 <y <1) of n-AlGaInP layer, n- GaP layer.

On the light emitting portion 19, for example, a p-type first ohmic wire electrode 11 and a pad electrode (not shown) are provided.

The semiconductor light emitting element 10 further includes a conductive supporting substrate 24, a bonding metal layer 23 provided on the conductive supporting substrate 24, a reflective metal layer 22 provided on the bonding metal layer 23, A transparent oxide film layer 21 provided on the reflective metal layer 22 and an n-type second ohmic wire electrode 20 provided on the transparent oxide film layer 21, and a conductive ohmic electrode 25 are provided on the transparent oxide film layer 21, and the above-described light emitting portion 19 is provided. Further, the first ohmic wire electrode 11 and the second ohmic wire electrode 20 are arranged at positions which do not overlap with each other when viewed from the upper surface, for example.

The total thickness of the quantum well active layer 14 is preferably 200 nm or more and 300 nm or less. 3, the luminous efficiency of the semiconductor light emitting element 10 when the emission wavelength is 585 nm is such that the total film thickness of the quantum well active layer 14 becomes a peak in the range of 200 nm or more and 300 nm or less to be. Here, the luminous efficiency in FIG. 3 is expressed as a ratio when the luminous efficiency when the total thickness of the quantum well active layer 14 is 250 nm is &quot; 1 &quot;.

On the other hand, the characteristic shown in Fig. 3 is that when the total thickness of the quantum well active layer 14 is thinner than 200 nm, the light emitting efficiency is lowered due to the carrier overflow and the total thickness of the quantum well active layer 14 When the thickness is thicker than 300 nm, overflow of the carriers can be suppressed, but self-absorption by the well layer 16 becomes large, and improvement of the luminous efficiency can not be seen.

When the total thickness of the quantum well active layer 14 is 200 nm or more, the decrease in the luminous efficiency due to carrier overflow can be suppressed. When the total thickness of the quantum well active layer 14 is 300 nm or less, It is possible to prevent the manufacturing cost from being increased.

The quantum well active layer 14 is formed by setting the film thickness of the well layer 16 such that the wavelength of light emitted from the semiconductor light emitting element 10 is a desired value and at the same time, (The number of pairs in the case of the well layer n (n is a positive integer) and the barrier layer n + 1 is n) can be adjusted.

The total thickness of the quantum well active layer 14 may be, for example, about 250 nm.

1, since the Al composition of the well layer 16 made of the AlGaInP compound semiconductor constituting the quantum well active layer 14 is 0.06 or less, the quantum well active layer 14 14) can be made smaller. Accordingly, the non-emission center in the quantum well active layer 14 can be reduced, and high luminous efficiency in a short wavelength region (yellow light emission) can be obtained.

Next, an example of a manufacturing method for manufacturing the semiconductor light emitting device of the present invention will be described with reference to FIG. Hereinafter, a case of manufacturing a semiconductor light emitting element having an emission wavelength of 585 nm will be described as an example.

First, as shown in FIG. 2A, a plurality of AlGaInP-based semiconductor laminated structures are formed on a GaAs substrate 26. Specifically, on the n-GaAs substrate 26, for example, p-Ga _{0 . 5} In _{0 .5} P etching stop layer 27 and the contact layer 28 of p-GaAs, the p- _{(Al 0.4 Ga 0.6) 0.5 In} 0.5 P p -type current diffusion layer 12 of a, p-Al _{0. 5} In the _{0 .5} P p-type cladding layer 13, an undoped _{(Al 0. 06 Ga 0.} 94) 0.5 In 0 .5 P well layer 16 (film thickness: 2.7nm) and in the undoped A quantum well active layer 14 made of a (Al _0.6 Ga _0.4 ) _0.5 In _0.5 P barrier layer 15 (film thickness: 7.7 nm), n-Al _{0 . 5.} In the _{0 .5} n-type cladding layer (17), n-type current diffusion layer 18 of the n-GaP of P then sequentially deposited by the MOVPE method (an organometallic vapor growth method). Material used in the MOVPE method, trimethyl gallium (TMGa), triethyl gallium (TEGa), trimethyl aluminum (TMAl), trimethyl indium (TMIn) organometallic compound and aralkyl, such as renal (AsH _3), phosphine (PH ₃ ) Can be used. Furthermore, monosilane (SiH ₄ ) can be used as the raw material for the n-type dopant, and biscyclopentadienyl magnesium (Cp ₂ Mg) can be used as the source for the p-type dopant. As a raw material for the n-type dopant, hydrogen selenide (H ₂ Se), disilane (Si ₂ H ₆ ), diethyl telluride (DETe) or dimethyl tellurium (DMTe) may also be used. Also, dimethyl zinc (DMZn) or diethyl zinc (DEZn) may be used as a material for the p-type dopant.

Next, as shown in Fig. 2B, a transparent oxide film layer 21 and a second ohmic wire electrode 20 on the n-type side are formed on the surface of the formed n-type current diffusion layer 18 of the semiconductor laminated structure . Specifically, an SiO ₂ film is formed as a transparent oxide film layer 21 by using a plasma CVD (Chemical Vapor Deposition) apparatus, and then an opening is provided by using a photolithography method and an etching method. More specifically, an opening is provided by removing the transparent oxide film layer 21 in a region where no resist pattern is formed by using a fluoric acid etchant as an etching liquid. Then, an AuSi alloy, which is a material for forming the second ohmic wire electrode 20 on the n-type side, is formed in the opening portion by vacuum evaporation.

Next, as shown in Fig. 2 (c), on the transparent oxide film layer 21 and the second ohmic wire electrode 20, an Al layer serving as a reflective layer and an Al layer serving as a barrier layer are formed by vacuum evaporation or sputtering Ti layer, and an Au layer as a bonding layer are sequentially formed. Thus, the reflective metal layer 22 is formed. On the other hand, the reflective metal layer 22 selects a material having a high reflectivity with respect to the wavelength of the light according to the wavelength of the light emitted by the quantum well active layer 14.

Thus, the layered product 29 is produced.

Next, as shown in FIG. 2 (d), on the conductive supporting substrate (for example, the Si substrate) 24, Ti as the contact electrode is formed as the junction metal layer 23 of conductive ohmic, Ni and the Au as a bonding layer are formed by using vacuum deposition method and the supporting substrate 30 is bonded to the layered body 29 to form the supporting substrate 30 and the layered body 29 ) Are mechanically and electrically connected to each other. The bonding of the wafers is carried out by applying a pressure through the jig to the stacked body 29 and the supporting substrate 30 which are superimposed on each other and heating them to a predetermined temperature. The specific bonding conditions are a pressure of 7000 N / m ² and a temperature of 350 ° C for 30 minutes.

Next, as shown in FIG. 2E, the n-GaAs substrate 26 is selectively completely removed from the junction structure 31 using an etchant for GaAs etching to form p-Ga _0.5 In _0.5 The etching stop layer 27 made of P is exposed. As the etchant for GaAs etching, for example, a mixed solution of aqueous ammonia and hydrogen peroxide can be mentioned. Next, the etching stop layer 27 is removed from the junction structure 31 from which the n-GaAs substrate 26 is removed by etching using a predetermined etchant (the contact layer 28 is exposed). When the etching stop layer 27 is formed from a compound semiconductor of an AlGaInP-based material, an etchant containing hydrochloric acid may be used as a predetermined etchant.

Next, as shown in Fig. 2 (f), ohmic electrodes on the p-side are formed at predetermined positions by photolithography and vacuum deposition. The ohmic electrode on the p-side is formed of a first electrode (not shown) and a first ohmic wire electrode 11, and is formed by depositing Ti, AuBe, and Au in this order, for example. In this case, for example, the first ohmic wire electrode 11 is formed at a position that does not overlap with the second ohmic wire electrode 20. Next, using the p-type ohmic electrode as a mask, the contact layer 28 made of p-GaAs is removed by etching. Alternatively, the p-type current diffusion layer 12 may be roughened using the contact layer 28 as a mask. Further, after the contact layer 28 is removed, the p-type current diffusion layer 12 may be roughened using a predetermined etchant.

Next, as shown in Fig. 2 (g), a conductive ohmic electrode 25 is formed on substantially the entire back surface of the conductive supporting substrate 24 by a vacuum evaporation method. The conductive ohmic electrode 25 on the back surface can be formed by, for example, depositing Ti and Au on the bottom surface of the support substrate 24 in this order. Thereafter, an alloying step, which is an alloying step for forming electrical bonding, is performed on each of the ohmic electrodes. As an example of the alloying process, a heat treatment at 400 占 폚 for 5 minutes can be performed in a nitrogen atmosphere as an inert atmosphere. Thus, the bonded structure 32 is fabricated.

Then, using the dicing device having the dicing blade, the junction structure 32 is divided into individual elements (pieces). Thus, a plurality of semiconductor light emitting elements 10 as shown in Fig. 1 are fabricated.

[Example]

Hereinafter, the present invention will be described in more detail with reference to examples and comparative examples, but the present invention is not limited thereto.

(Example)

The semiconductor light emitting element 10 of Fig. 1 was fabricated using the manufacturing method described in Fig.

Here, each layer of the semiconductor light emitting element 10 is as follows.

The p-type current diffusion layer 12 ... p- (Al _0.4 Ga _0.6 ) _0.5 In _0.5 P

The p-type cladding layer 13 ... p-Al _0.5 In _0.5 P

The barrier layer 15 ... i (Al _0.6 Ga _0.4 ) _0.5 In _0.5 P

The well floor (16) ... i (Al _0.06 Ga _0.94 ) _0.5 In _0.5 P

The n-type cladding layer 17 ... n-Al _0.5 In _0.5 P,

n current diffusion layer 18 ... n-GaP,

GaAs substrate 26 ... n-GaAs

Etch stop layer 27 ... p-Ga _0.5 In _0.5 P,

The contact layer 28 ... p-GaAs

However, as shown in Table 1, the Al composition of the well layer 16 was fixed at 0.06 to change the thickness of the well layer 16, and the total thickness of the quantum well active layer 14 was about 250 nm The number of pairs of the well layer 16 and the barrier layer 15 was adjusted so that the emission wavelength of the semiconductor light emitting element 10 was changed in the range of 585 to 605 nm.

The light emitting efficiency of the semiconductor light emitting device fabricated as described above was measured.

Table 1 shows the quantum well active layer structure and the luminous efficiency at each emission wavelength. On the other hand, in Table 1, the luminous efficiency when the emission wavelength is 615 nm is also shown for reference. Here, the luminous efficiency is calculated by the luminous efficiency (%) = the output (mW) / the input power (mW), and the luminous efficiency at the luminous wavelength of 615 nm is represented by "1".

Fig. 4 shows the relationship between the emission wavelength and the luminous efficiency.

(Comparative Example)

A semiconductor light emitting device was fabricated in the same manner as in Example. The Al composition and the film thickness of the well layer 16 were changed as shown in Table 2, and the emission wavelength was changed in the range of 585 to 605 nm.

The light emitting efficiency of the semiconductor light emitting device fabricated as described above was measured in the same manner as in Example.

Table 2 shows the quantum well active layer structure and the luminous efficiency at each emission wavelength. On the other hand, in Table 2, the luminous efficiency when the emission wavelength is 615 nm is shown for reference.

Fig. 4 shows the relationship between the emission wavelength and the luminous efficiency.

As can be seen from Fig. 4, in the range where the emission wavelength is 585 nm or more and 605 nm or less, the luminous efficiency in the example is higher than that in the comparative example.

On the other hand, the present invention is not limited to the above embodiment. The above embodiment is an example, and anything that has substantially the same structure as the technical idea described in the claims of the present invention and exhibits the same operational effects is included in the technical scope of the present invention.

Claims (2)

1. A semiconductor light emitting device having a quantum well active layer composed of a well layer and a barrier layer,
Wherein the semiconductor light emitting device has an emission wavelength of 585 nm or more and 605 nm or less,
The well layer, the composition formula _{(Al x Ga 1 -x) y} In 1 - made of a compound semiconductor of _{y P (0 <x≤0.06, 0} <y <1),
The barrier layer is a composition formula _{(Al m Ga 1 -m) n} In 1 - n P semiconductor light-emitting device which comprises a compound semiconductor (0≤m≤1, 0 <n <1 ). The method according to claim 1,
Wherein the total thickness of the quantum well active layer is 200 nm or more and 300 nm or less.

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