JP2012174876A - Semiconductor light-emitting element and method for manufacturing semiconductor light-emitting element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the concentration of oxygen mixed into a reflection layer, and enhance the reliability of a semiconductor light-emitting element.SOLUTION: In a semiconductor light-emitting element 1 which includes a substrate, a buffer layer 20 provided on the substrate, a reflection layer 30 formed by laminating a plurality of pairs of low refractive index layers and high refractive index layers on the buffer layer 20, and a light-emitting layer 40 formed by laminating a first clad layer, an active layer and a second clad layer on the reflection layer 30, the buffer layer 20 includes an oxygen adsorption layer.

Description

  The present invention relates to a semiconductor light emitting device and a method for manufacturing the semiconductor light emitting device, and more particularly to a semiconductor light emitting device having a reflective layer in which a plurality of pairs of low refractive index layers and high refractive index layers are stacked and a method for manufacturing the semiconductor light emitting devices. .

In recent years, in the manufacturing process of semiconductor light emitting devices such as light emitting diodes (LEDs), a technology for growing high quality crystals such as AlGaInP and GaN based on metal-organic vapor phase epitaxy (MOVPE) method. With the development, high brightness LEDs such as blue, green, orange, yellow, and red can be manufactured.

Since the high quality crystal as described above can be grown, the internal efficiency of the semiconductor light emitting device is approaching the theoretical limit value. However, the light extraction efficiency from the semiconductor light emitting device is still low, and it is important to improve the light extraction efficiency. Therefore, for example, a reflective layer in which a plurality of pairs of low refractive index layers and high refractive index layers are stacked is provided below the light emitting layer that has a light emitting function by laminating a plurality of epitaxial layers, and light directed toward the semiconductor substrate side. Is reflected by light interference to the light extraction surface side of the upper surface of the semiconductor light emitting element. For example, Patent Document 1 discloses an n-type light reflection layer using an Al _x Ga _1-x As layer (0 ≦ X ≦ 1) for some or all materials. A GaAs layer is used as an n-type buffer layer below the n-type light reflection layer.

  The buffer layer is provided as a base for forming a desired semiconductor epitaxial layer on the buffer layer by taking in and suppressing impurities such as Si adhering to the surface of the semiconductor substrate or impurities remaining in the furnace for epitaxial growth. .

Japanese Patent No. 4123235

  However, in a semiconductor light emitting device including the above-described structure, there are cases where phenomena such as a decrease in light emission intensity and a decrease in light emission intensity may be observed and sufficient reliability may not be obtained. . The present inventors have found that in a semiconductor light emitting device in which such a phenomenon is observed, high-concentration oxygen is mixed in a reflective layer included in the device.

  An object of the present invention is to provide a semiconductor light-emitting device and a method for manufacturing the semiconductor light-emitting device that can reduce the oxygen concentration mixed in the reflective layer and improve the reliability.

  According to the first aspect of the present invention, a buffer layer provided on the substrate, a reflective layer provided by laminating a plurality of pairs of low refractive index layers and high refractive index layers on the buffer layer, and the reflection And a light emitting layer provided by laminating a first cladding layer, an active layer, and a second cladding layer on the layer, wherein the buffer layer includes a semiconductor light emitting device including an oxygen adsorption layer.

According to the second aspect of the present invention, the oxygen adsorption layer includes the Al _X Ga _1-X As layer (provided that 0.6 ≦ X ≦ 1) having a layer thickness of 75 nm or more and 200 nm or less. The semiconductor light-emitting device described in 1. is provided.

According to a third aspect of the present invention, the oxygen adsorption layer has a layer thickness of 75 nm or more and 200 nm or less, and graded Al _{X in} which the Al composition ratio X gradually decreases from the substrate side toward the reflective layer side. A semiconductor light-emitting element according to the first aspect including a Ga _1-X As layer (provided that 0.6 ≦ X ≦ 1) is provided.

According to a fourth aspect of the present invention, there is provided the semiconductor light emitting element according to the first to third aspects, wherein the oxygen concentration in the reflective layer is 4.0 × 10 ¹⁸ cm ⁻³ or less.

According to the fifth aspect of the present invention, a buffer layer, a reflective layer composed of a low refractive index layer and a high refractive index layer, a first cladding layer, an active layer, and a second cladding are formed on the substrate using a vapor deposition method. In the method for manufacturing a semiconductor light emitting device, in which a light emitting layer comprising a layer is grown, the buffer layer includes an oxygen adsorption layer, and the oxygen adsorption layer is represented by a molar ratio of a group V source gas and a group III source gas. / III ratio is 30 or more and 150 or less, growth temperature is 580 ° C. or more and 650 ° C. or less, and any one of Al _X Ga _1-X As (where 0 <X <1), AlAs, AlGaInP, AlInP, AlGaP, AlAsP Or by reducing the V / III ratio and lowering the growth temperature, GaAs, InGaP, InP, GaP, InGaAs, InGaAsP, GaAsP, and InAsP. A method of manufacturing a semiconductor light emitting device is provided that is grown to include any composition.

  According to the present invention, it is possible to reduce the oxygen concentration mixed in the reflective layer and improve the reliability of the semiconductor light emitting device.

It is sectional drawing which shows the semiconductor light-emitting device based on one Embodiment of this invention. It is sectional drawing which shows the manufacturing process of the semiconductor light-emitting device concerning one Embodiment of this invention. It is sectional drawing which shows the semiconductor light-emitting device which concerns on the modification of one Embodiment of this invention. It is a graph which shows the oxygen concentration in the reflection layer which the semiconductor light-emitting device concerning the Example of this invention has. 3 is a graph showing reliability of a semiconductor light emitting device according to an example of the present invention.

<One Embodiment of the Present Invention>
Hereinafter, a semiconductor light emitting device and a method for manufacturing the semiconductor light emitting device according to an embodiment of the present invention will be described.

(1) Structure of Semiconductor Light Emitting Element A semiconductor light emitting element according to an embodiment of the present invention has a reflective layer in which a plurality of semiconductors including, for example, aluminum (Al) is stacked. As described above, in such a semiconductor light-emitting element, there is a case where the luminescence intensity decreases with time as the operating time is continued and the use time becomes longer. A high concentration of oxygen was found in the reflective layer. According to the present inventors, it has been clarified that oxygen is mixed into the reflective layer when the reflective layer is epitaxially grown, for example, by the MOVPE method.

The present inventors have found that by providing an oxygen adsorption layer in the buffer layer, the oxygen concentration mixed in the reflective layer can be reduced and the reliability of the semiconductor light emitting device can be improved. Hereinafter, the structure of the semiconductor light emitting device of this embodiment including the oxygen adsorption layer in the buffer layer will be described with reference to FIG.
Will be described. FIG. 1 is a cross-sectional view showing a semiconductor light emitting device 1 according to this embodiment.

As shown in FIG. 1, the semiconductor light emitting device 1 includes, for example, an n-type GaAs substrate 10 and an n-type AlGaAs buffer layer 20 provided on the n-type GaAs substrate 10. The buffer layer 20 includes an n-type GaAs layer 20b as an underlayer and an n-type Al _X Ga _1-X As layer 20a as an oxygen adsorption layer. That is, the buffer layer 20 is provided with an n-type GaAs layer 20b having an Al composition ratio X = 0 on the substrate side, and an n-type Al _X Ga _1-X As layer 20a having a predetermined Al composition ratio X is provided on the upper layer portion. It has a two-layer structure. The Al composition ratio X of the n-type Al _X Ga _1-X As layer 20a is 0 <X <1, more preferably 0.6 ≦ X ≦ 0.8. The layer thickness of the n-type Al _X Ga _1-X As layer 20a is not less than 75 nm and not more than 200 nm.
Thus, by providing the buffer layer 20 with the n-type Al _X Ga _1-X As layer 20a having a predetermined Al composition ratio X, when the reflective layer 30 described later is epitaxially grown by the MOVPE method, the MOVPE Oxygen in the atmosphere in the apparatus can be reduced.

In the semiconductor light emitting device 1, for example, a reflective layer 30 using an n-type Al _Y Ga _1-Y As layer (0 ≦ Y ≦ 1) is provided on part or all of the buffer layer 20. More specifically, the reflective layer 30 includes an n-type Al _Y Ga _1-Y As layer as a low refractive index layer where Y <1, and an n-type AlAs layer as a high refractive index layer where Y = 1. A plurality of pairs are stacked. A light emitting layer provided on the reflective layer 30 by laminating an n-type AlGaInP cladding layer 41 as a first cladding layer, an undoped AlGaInP active layer 42 as an active layer, and a p-type AlGaInP cladding layer 43 as a second cladding layer. 40.

As described above, when the reflective layer 30 includes the low refractive index layer and the high refractive index layer, when a part of the light having a predetermined wavelength generated in the undoped AlGaInP active layer 42 enters the reflective layer 30, Optical interference can be caused between the low refractive index layer and the high refractive index layer, and incident light can be reflected. That is, the reflective layer 30 functions as a distributed Bragg reflector (DBR) for light of a predetermined wavelength. The wavelength of light to be reflected can be selected by setting the refractive index and thickness of each of the low refractive index layer and the high refractive index layer. The refractive indexes of the low refractive index layer and the high refractive index layer can be changed by changing the composition ratio Y of the n-type Al _Y Ga _{1 -Y} As layer, for example.

In addition, the composition ratio of the buffer layer formed on the substrate may be determined so as to achieve homoepitaxial growth with respect to the substrate. For example, if it is on the n-type GaAs substrate 10, it is formed from an n-type GaAs layer. In addition, the oxygen adsorption layer may be formed so that the oxygen concentration in the reflective layer 30 is 4.0 × 10 ¹⁸ cm ⁻³ or less.

  In addition, the semiconductor light emitting element 1 includes, for example, a p-type AlGaInP layer 50 as a connection layer provided on the light-emitting layer 40 and a p-type GaP layer 60 as a current spreading layer provided on the p-type AlGaInP layer 50. . Further, the semiconductor light emitting device 1 includes a surface electrode 71 provided by laminating, for example, gold / beryllium (AuBe) alloy, nickel (Ni), gold (Au) on the p-type GaP layer 60, and the n-type GaAs substrate 10. And a back electrode 72 provided by laminating, for example, a gold / germanium (AuGe) alloy, Ni, or Au, on the entire surface opposite to the surface on which each of the layers is formed.

(2) Manufacturing Method of Semiconductor Light Emitting Element Next, a manufacturing method of the semiconductor light emitting element 1 according to an embodiment of the present invention will be described.

(Epitaxial wafer production)
First, a plurality of epitaxial layers from the buffer layer 20 to the p-type GaP layer 60 shown in FIG. 1 are stacked on the n-type GaAs substrate 10 by the MOVPE method to manufacture an epitaxial wafer having a predetermined emission wavelength.

Specifically, the n-type GaAs substrate 10 is loaded and installed in the MOVPE apparatus, and a predetermined source gas is supplied at a predetermined flow rate while maintaining the growth pressure and growth temperature at predetermined values. As the source gas, for example, an organic metal gas such as trimethylgallium (TMGa) or triethylgallium (TEGa) is used as a gallium (Ga) source. Further, for example, an organic metal gas such as trimethylaluminum (TMAl) is used for an aluminum (Al) source and trimethylindium (TMIn) is used for an indium (In) source. Further, arsenic (As) source uses arsenic (AsH ₃ ) or the like, and phosphorus (P) source uses hydride gas such as phosphine (PH ₃ ). At this time, the ratio (quotient) in which the number of moles of the group III source gas such as TMGa and TMAl is the denominator and the number of moles of the group V source gas such as AsH ₃ and PH ₃ is the numerator, that is, the V / III ratio, Set to a predetermined value.

Moreover, the addition of the conductivity determining impurity for determining the conductivity type of each layer is performed by adding a predetermined additive source gas to the source gas, for example. For example, selenium (Se) is used as the n-type conductivity determining impurity. In order to add Se, an additive source gas such as hydrogen selenide (H ₂ Se) is used. In addition, as the p-type conductivity determining impurity, for example, zinc (Zn) is used. In order to add Zn, for example, an additive material gas such as diethyl zinc (DEZn) is used.

  Hereinafter, the growth method of each layer will be described with reference to FIG. FIG. 2 is a cross-sectional view showing a manufacturing process of the semiconductor light emitting device 1.

First, as shown in FIG. 2A, for example, an n-type AlGaAs buffer layer 20 is grown on an n-type GaAs substrate 10. That is, an n-type GaAs layer 20b is grown as a base in the buffer layer 20, and an n-type Al _x Ga _1-x As layer 20a is grown in the upper layer portion. At this time, the flow rate ratio of each source gas is adjusted to control 0 <X <1, more preferably 0.6 ≦ X ≦ 0.8. The V / III ratio is, for example, 30 or more and 150 or less, and the growth temperature is
For example, the temperature is set to 580 ° C. or higher and 650 ° C. or lower.

Moisture or the like may be brought into the MOVPE apparatus when mounting parts or carrying a substrate into the apparatus, and oxygen (O ₂ ) exists in the atmosphere in the apparatus. For example, in a conventional semiconductor light emitting device in which only an n-type GaAs layer is provided as a buffer layer, oxygen in the atmosphere in the device contains, for example, n-type Al _Y containing Al which is a component that easily binds to oxygen when the reflective layer is grown. It was easy to be taken into a reflective layer composed of a Ga _1-Y As layer, an n-type AlAs layer, or the like. When high concentration oxygen is mixed in an epitaxial layer such as a reflective layer, the crystallinity of the epitaxial layer is impaired. As a result, the quality of the reflective layer and the like deteriorates, and a predetermined reflectance cannot be obtained. In addition, oxygen becomes a non-radiative recombination center and decreases luminous efficiency. For this reason, the light emission intensity of the semiconductor light emitting device has decreased over time, and the reliability of the semiconductor light emitting device may not be obtained.

However, in the present embodiment, when the buffer layer 20 is grown before the reflective layer 30 is grown, the n-type Al _X Ga _1-X As layer 20a is grown as the oxygen adsorption layer. Oxygen in the atmosphere is taken into the n-type Al _x Ga _1-x As layer 20a. Therefore, the oxygen concentration in the atmosphere can be reduced before the reflective layer 30 is grown. At this time, in order to improve the oxygen adsorption effect, it is preferable that the n-type Al _x Ga _1-x As layer 20a as the oxygen adsorption layer has a high Al composition ratio.

Next, as shown in FIG. 2B, the reflective layer 30 is grown on the buffer layer 20. The reflective layer 30 is formed, for example, by stacking a plurality of pairs of n-type Al _Y Ga _1-Y As layers (Y <1) as low refractive index layers and n-type AlAs layers (Y = 1) as high refractive index layers. Provided. The composition ratio of the n-type Al _Y Ga _1-Y As layer is controlled by adjusting the flow rate ratio of the respective source gases.

In the present embodiment, by growing the n-type Al _X Ga _1-X As layer 20a, the oxygen concentration in the atmosphere in the MOVPE apparatus is reduced in advance before the reflective layer 30 is grown. Thereby, mixing of oxygen into the reflective layer 30 is suppressed, and the oxygen concentration in the reflective layer 30 can be, for example, 4.0 × 10 ¹⁸ cm ⁻³ or less.

  Subsequently, as illustrated in FIG. 2C, the light emitting layer 40 is grown on the reflective layer 30. The light emitting layer 40 is provided by stacking an n-type AlGaInP cladding layer 41 as a first cladding layer, an undoped AlGaInP active layer 42 as an active layer, and a p-type AlGaInP cladding layer 43 as a second cladding layer.

  Next, a p-type AlGaInP layer 50 as a connection layer is grown on the light emitting layer 40, and a p-type GaP layer 60 as a current spreading layer is grown on the p-type AlGaInP layer 50.

  As described above, an epitaxial wafer having a predetermined emission wavelength is manufactured.

(Formation of electrodes)
After the epitaxial wafer on which each layer is formed as described above is unloaded from the MOVPE apparatus, electrodes are formed on the upper and lower surfaces (front and back surfaces) of the epitaxial wafer as shown in FIG. That is, for example, a photoresist pattern is formed on the p-type GaP layer 60 by a photolithography process using a mask aligner or the like. Subsequently, for example, AuBe alloy, Ni, and Au are vapor-deposited in this order by a vacuum vapor deposition method. After vapor deposition, the photoresist pattern is removed by a lift-off method to form, for example, a substantially circular surface electrode 71 for each element. Each surface electrode 71 is arranged on the p-type GaP layer 60 in, for example, a matrix. In the drawing shown in FIG. 2D, one of the plurality of surface electrodes 71 arranged in a matrix is shown.

Next, AuGe alloy, Ni, and Au are vapor-deposited in this order on the back surface of the epitaxial wafer, that is, on the entire surface opposite to the epitaxial layer forming surface of the n-type GaAs substrate 10 in this order, and the back electrode 72 Form. Thereafter, in the alloy process, the epitaxial wafer on which the electrodes 71 and 72 are formed is heated to 400 ° C. for 5 minutes in, for example, a nitrogen (N ₂ ) gas atmosphere to alloy the electrodes 71 and 72.

  Subsequently, the wafer on which the electrodes 71 and 72 are formed is diced into, for example, a substantially rectangular shape so that each of the plurality of formed surface electrodes 71 is located in the center, and the semiconductor light emitting device shown in FIG. Obtain multiple 1s. Thus, the semiconductor light emitting device 1 according to this embodiment is manufactured.

(Semiconductor light emitting device mounting)
Thereafter, the cut out semiconductor light emitting element 1 is mounted. That is, a plurality of individual semiconductor light emitting devices 1 cut out by dicing are mounted on, for example, a TO-18 stem, die bonded, and then wire bonded.

(3) Effects According to One Embodiment of the Present Invention According to the present embodiment, one or more effects shown below can be obtained.

(A) According to this embodiment, a plurality of pairs of an n-type Al _Y Ga _1-Y As layer as a low refractive index layer and an n-type AlAs layer as a high refractive index layer are stacked on the buffer layer 20. The buffer layer 20 includes an n-type Al _X Ga _1-X As layer 20a. Thereby, oxygen in the atmosphere in the MOVPE apparatus can be taken into the n-type Al _X Ga _1-X As layer 20a, and the oxygen concentration in the atmosphere can be reduced before the reflective layer 30 is epitaxially grown. Therefore, the oxygen concentration mixed in the reflective layer 30 can be reduced, and the reliability of the semiconductor light emitting element 1 can be improved.

(B) According to the present embodiment, the oxygen adsorption layer is the n-type Al _X Ga _1-X As layer 20a. By including Al, which is a material that easily adsorbs oxygen, in the oxygen adsorbing layer, an effect of adsorbing oxygen can be obtained and the oxygen concentration in the atmosphere can be reduced.

Here, an n-type Al _X Ga _1-X As layer having an Al composition ratio X = 1 having a higher oxygen adsorption effect, that is, an n-type AlAs layer or the like can be used as the oxygen adsorption layer. than n-type AlAs you are concerned, it is preferable to use the Al X _Ga 1-X _as a more stable material oxygen adsorption layer, thereby, the semiconductor light emitting element 1 can be obtained which more stable.

(C) Further, according to the present embodiment, the oxygen concentration in the reflective layer 30 is reduced to 4.0 × 10 ¹⁸ cm ⁻³ or less by reducing the oxygen concentration in the atmosphere before the growth of the reflective layer 30. can do. Thereby, the long-term stability and reliability of the semiconductor light emitting device 1 can be improved.

(4) Semiconductor Light Emitting Element According to Modification of One Embodiment of the Invention Next, a semiconductor light emitting element according to a modification of the above-described embodiment will be described with reference to FIG. FIG. 3 is a cross-sectional view showing a semiconductor light emitting device 2 according to this modification. Also in the semiconductor light emitting device 2, the n-type AlGaAs buffer layer 21 includes an oxygen adsorption layer, but the oxygen adsorption layer according to this modification has a layer thickness of 75 nm to 200 nm, for example, 100 nm, and is from the n-type GaAs substrate 10. The n-type graded Al _X Ga _1-X As layer 21a is configured such that the Al composition ratio X gradually decreases toward the reflective layer 30 side. However, the range in which the Al composition ratio X is changed is 0 ≦ X ≦ 1, more preferably 0.6 ≦ X ≦ 1, and still more preferably 0.6 ≦ X ≦ 0.8.

That is, when the range of change in the Al composition ratio X is, for example, 1 → 0, the oxygen adsorption layer is changed from n-type AlAs (X = 1) on the n-type GaAs substrate 10 side to n-type GaAs (on the reflective layer 30 side) X = 0), and when the range of change in the Al composition ratio X is 0.8 → 0.6, from the n-type Al _0.8 Ga _0.2 As on the n-type GaAs substrate 10 side. Then, it is changed to n-type Al _0.6 Ga _0.4 As on the reflective layer 30 side.

N-type graded _Al X _{Ga 1-X} As layer 21a as described above, by MOVPE, by gradually grown while changing the flow rate or the like of each raw material gas can be formed. At this time, the flow rate ratio of the source gas is adjusted so that the Al composition ratio X is 0 ≦ X ≦ 1, more preferably 0.6 ≦ X ≦ 1, and further preferably 0.6 ≦ X ≦ 0.8. To do. The V / III ratio is, for example, 30 or more and 150 or less, and the growth temperature is, for example, 580 ° C. or more and 65
0 ° C or less.

  Also in this modification, there exists the same favorable effect as the above-mentioned embodiment.

<Other Embodiments of the Present Invention>
As mentioned above, although embodiment of this invention was described concretely, this invention is not limited to the above-mentioned embodiment, It can change variously in the range which does not deviate from the summary.

For example, in the above-described embodiment, the n-type Al _X Ga _1-X As layer 20a as the oxygen adsorption layer is included in the upper layer portion of the buffer layer 20, but is included in other positions. Also good. For example, it may be configured as n-type GaAs layer / n-type Al _X Ga _1-X As layer (oxygen adsorption layer) / n-type GaAs layer so that the oxygen adsorption layer is included in the middle portion of the buffer layer.

Further, in the above-described embodiment, in the n-type Al _X Ga _1-X As layer 20a, the range of the Al composition ratio X is 0 <X <1, but X = 1, that is, the oxygen adsorption layer is made of AlAs. Layers may be included. The oxygen adsorption layer may be another Al-based epitaxial layer, and may include any composition such as AlGaInP, AlInP, AlGaP, AlAsP, and the like.

Further, in the above-described embodiment, in the n-type Al _X Ga _1-X As layer 20a, the range of the Al composition ratio X is 0 <X <1, but X = 0, that is, the oxygen adsorption layer is made of GaAs. Layers may be included. As described above, when an oxygen adsorption layer having a composition not containing Al is used, the growth conditions of the oxygen adsorption layer are, for example, growth conditions that easily adsorb oxygen such as a low V / III ratio and a low temperature. In addition to this, the oxygen adsorption layer not containing Al may contain any composition such as InGaP, InP, GaP, InGaAs, InGaAsP, GaAsP, InAsP, or the like.

  Further, the conductivity type (n-type, p-type) of the upper and lower cladding layers may be reversed, and the light extraction surface side may be n-type.

In the above-described embodiment, H ₂ Se is used as the n-type additive source gas in forming each layer by the MOVPE method. However, as the n-type additive source gas, disilane (Si ₂ H ₆ ), Monosilane (SiH ₄ ), diethyl tellurium (DETe), dimethyl tellurium (DMTe), and the like can also be used. In addition, although diethyl zinc (DEZn) is used as the p-type additive source gas, dimethyl zinc (DMZn), biscyclopentadienyl magnesium (Cp ₂ Mg), etc. are used as the p-type additive source gas. It can also be used.

  In the above-described embodiment, the surface electrode 71 having a substantially circular shape is formed. In addition, there are various surface electrodes such as a quadrangular shape, a rhombus shape, a polygonal shape, or a shape having a branch-shaped electrode portion. It can be a shape.

(1) Example 1
Next, Example 1 according to the present invention will be described.
(Epitaxial wafer production)
First, epitaxial wafers having oxygen adsorption layers having different thicknesses from 0 nm to 200 nm (however, no oxygen adsorption layer at 0 mm) were prepared by the same method as in the above-described embodiment. The composition ratio of each layer, the layer thickness, the growth conditions of the MOVPE method, etc. when forming each layer are shown below.

The oxygen adsorption layer was an Al composition ratio X = 0.8 layer, that is, an n-type Al _0.8 Ga _0.2 As layer. In addition, the reflective layer was provided by stacking 20 pairs of an n-type Al _0.4 Ga _0.6 As layer and an n-type AlAs layer as a combination capable of obtaining a large difference in refractive index.

As described above, the epitaxial wafer according to the present example is configured as an epitaxial wafer for red LEDs including an undoped (Al _0.1 Ga _0.9 ) _0.5 In _0.5 P active layer having an emission wavelength of 630 nm band. The

(Formation of electrodes)
Next, a front electrode and a back electrode were formed by the same method as in the above embodiment. At this time, the size of the substantially circular surface electrode was 100 μm in diameter.

Subsequently, dicing is performed on each of the above wafers so that the chip size becomes 9 mil square (1 mil≈25.4 μm) in the same manner as in the above embodiment, and semiconductors having oxygen adsorption layers with different layer thicknesses A plurality of light emitting elements were manufactured. Each semiconductor light emitting element is configured as a red LED having an emission wavelength of 630 nm band.

(Semiconductor light emitting device mounting)
Thereafter, each of the semiconductor light emitting elements was mounted by the same method as in the above embodiment.

(Measurement of oxygen concentration in the reflective layer)
An oxygen adsorption layer made of an n-type Al _0.8 Ga _0.2 As layer with a layer thickness of 0 nm, 50 nm, 75 nm, 100 nm, 150 nm, and 200 nm manufactured as described above (however, there is no oxygen adsorption layer at 0 mm) ) Was measured by secondary ion mass spectrometry (SIMS) for each of the semiconductor light-emitting devices having a). The results are shown in FIG.

FIG. 4 is a graph showing the oxygen concentration in the reflective layer of each semiconductor light emitting device. The horizontal axis in FIG. 4 is the thickness (nm) of the n-type Al _0.8 Ga _0.2 As layer as the oxygen adsorption layer, and the vertical axis in FIG. 4 is the oxygen concentration (cm ⁻³ ) in the reflective layer. ).

As shown in FIG. 4, when the thickness of the n-type Al _0.8 Ga _0.2 As layer is 0 nm and 50 nm, the oxygen concentration in the reflective layer is 5 × 10 ¹⁸ cm ^{−3 to} 6 × 10 ¹⁸ cm. ^-3 or so. On the other hand, the oxygen concentration in the reflective layer when the thickness of the n-type Al _0.8 Ga _0.2 As layer is 75 nm or more is 3 × 10 ¹⁸ cm ^{−3 to} 3.3 × 10 ¹⁸ cm ^−. The value was reduced to about ³ , and the value of the oxygen concentration was substantially stable at a layer thickness of 0 nm to 200 nm.

  From the above results, by providing the oxygen adsorption layer, the oxygen concentration in the reflective layer can be reduced, and in the region where the thickness of the oxygen adsorption layer is 75 nm or more, the oxygen concentration in the reflective layer is low. It was found to be almost stable.

(Reliability test of semiconductor light emitting devices)
Next, the test current If is 50 mA, the test temperature is room temperature, the measurement current is 20 mA, and each of the semiconductor light emitting elements having different oxygen adsorption layer thicknesses is energized, and the energization time is 0 hour (hr), 100 hr, 500 hr, The emission intensity Po at 1000 hr was measured. The results are shown in FIG.
FIG. 5 is a graph showing the reliability of each semiconductor light emitting element. The horizontal axis in FIG. 5 is the energization time (hr). The vertical axis in FIG. 5 represents the emission intensity ΔPo (%) of the semiconductor light emitting device. The light emission intensity (relative light emission intensity) ΔPo (%) represents the light emission intensity Po when the energization time is 0 hr as 100%, and the light emission intensity after 100 hr, 500 hr, and 1000 hr as a percentage. In this example, ΔPo (%) was used as an index representing the reliability of the semiconductor light emitting device.

As shown in FIG. 5, in a semiconductor light emitting device (n mark and ◇ mark in the figure) where the thickness of the n-type Al _0.8 Ga _0.2 As layer is 0 nm and 50 nm, the energization time is increased and the emission intensity is increased. ΔPo continues to decrease. In contrast, a semiconductor light emitting device having an n-type Al _0.8 Ga _0.2 As layer having a thickness of 75 nm or more (in the figure, 75 nm is marked with ♦, 100 nm is marked with ○, 150 nm is marked with □, and 200 nm is marked with ● ), The emission intensity ΔPo, which tended to decrease until the energization time was 100 hr, almost stopped at 500 hr, and remained stable after 500 hr.

From the above results, by setting the oxygen adsorption layer composed of the n-type Al _0.8 Ga _0.2 As layer to 75 nm or more, a stable emission intensity ΔPo can be obtained, and the reliability of the semiconductor light emitting device can be improved. all right.

(2) Example 2
A semiconductor light emitting device having an oxygen adsorption layer in which the Al composition ratio X = 0.6 of the oxygen adsorption layer, that is, the n-type Al _0.6 Ga _0.4 As layer, is measured and tested in the same manner as in Example 1 above. Went against. As a result, although the oxygen concentration in the reflective layer was slightly higher than that in Example 1, as in Example 1 described above, the emission intensity ΔPo was unstable until the layer thickness of the oxygen adsorption layer was 50 nm. A stable emission intensity ΔPo was obtained at 75 nm or more.

1, 2 Semiconductor light emitting device 10 n-type GaAs substrate (substrate)
20, 21 Buffer layer
20a, 21a n-type Al _X Ga _1-X As layer (oxygen adsorption layer)
20b n-type GaAs layer 30 reflective layer 40 light-emitting layer 41 n-type AlGaInP clad layer (first clad layer)
42 Undoped AlGaInP active layer (active layer)
43 p-type AlGaInP cladding layer (second cladding layer)

Claims (5)

A substrate,
A buffer layer provided on the substrate;
A reflective layer provided by laminating a plurality of low refractive index layers and high refractive index layers on the buffer layer;
A light emitting layer provided by laminating a first cladding layer, an active layer, and a second cladding layer on the reflective layer;
The semiconductor light emitting device, wherein the buffer layer includes an oxygen adsorption layer. 2. The semiconductor light emitting element according to claim 1, wherein the oxygen adsorption layer includes an Al _X Ga _1-X As layer (0.6 ≦ X ≦ 1) having a layer thickness of 75 nm to 200 nm. The oxygen adsorption layer is a graded Al _X Ga _1-X As layer (provided that the layer thickness is 0.5 nm or more and 200 nm or less, the Al composition ratio X gradually decreases from the substrate side toward the reflective layer side. The semiconductor light emitting device according to claim 1, wherein 6 ≦ X ≦ 1). 4. The semiconductor light emitting device according to claim 1, wherein an oxygen concentration in the reflective layer is 4.0 × 10 ¹⁸ cm ⁻³ or less. 5. Semiconductor light emission in which a buffer layer, a reflective layer composed of a low refractive index layer and a high refractive index layer, and a light emitting layer composed of a first cladding layer, an active layer, and a second cladding layer are grown on the substrate using vapor phase growth. In the manufacturing method of the element,
The buffer layer includes an oxygen adsorption layer,
The oxygen adsorption layer,
The V / III ratio, which is the molar ratio of the group V source gas to the group III source gas, is set to 30 to 150, the growth temperature is set to 580 ° C. to 650 ° C., and Al _X Ga _1-X As (where 0 <X <1) grown to include any composition of AlAs, AlGaInP, AlInP, AlGaP, AlAsP, or
The V / III ratio is reduced, the growth temperature is lowered, and GaAs, InGaP, InP, G
A method of manufacturing a semiconductor light emitting device, comprising growing a composition containing any one of aP, InGaAs, InGaAsP, GaAsP, and InAsP.

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