JP2011134967A - Semiconductor light emitting element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a long-wavelength semiconductor light emitting element that uses a GaAs substrate without requiring complicate design with respect to a semiconductor light emitting element. <P>SOLUTION: The GaAs substrate has thereupon a first conductivity type semiconductor layer, a light emitting layer having a heterojunction of at least one Ge<SB>1-x</SB>Si<SB>x</SB>layer (where 0≤x≤0.5) and at least one In<SB>1-y</SB>Ga<SB>y</SB>As layer (where 0≤y≤0.7), and a second conductivity type semiconductor layer having the opposite conductivity type from that of the first conductivity type semiconductor layer. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a semiconductor light emitting device, for example, a 1.5 μm wavelength semiconductor light emitting device having a type II quantum well structure formed on a GaAs substrate.

  Currently, an InGaAsP / InP semiconductor laser is used as a long wavelength light source having a wavelength of 1.3 μm or more in an optical communication system. However, since an InP substrate is more expensive than a GaAs substrate and it is difficult to manufacture a large-area wafer, it is desired to form a long wavelength light emitting element having a wavelength of 1.3 μm or more on the GaAs substrate.

  A general light-emitting element has a structure in which a material layer that emits light is sandwiched by a material having a larger band gap than that layer and a carrier is confined, such as a quantum well or a quantum dot. Conventionally, in a light emitting device using a GaAs substrate, a type I quantum well structure capable of confining both carriers of electrons and holes in the same layer has been used.

  As a type I quantum well structure formed on this GaAs substrate, InGaAs is generally used as a light emitting layer. However, since InGaAs is a lattice-mismatched material having a larger lattice constant than GaAs, if a light-emitting layer having a high In composition and a thick film thickness is formed in order to increase the wave length, the accumulated strain becomes too large. As a result, there was a problem in increasing the wavelength of 1.3 μm or more in order to deteriorate the crystallinity.

  As a configuration that enables longer wavelengths, a type II quantum well structure that confines only electrons or holes has been proposed. There is GaSb that can form a type II quantum well structure by combining with GaAs, but the lattice constant is larger than that of GaAs as in InGaAs.

  As a result, compressive strain accumulated monotonously with the increase in the number of quantum well layers, and thus a GaAs / GaSb quantum well structure could not be formed on the GaAs substrate. For the above reasons, it has been impossible to form a light emitting element having a long wavelength on a GaAs substrate using only a III-V group compound semiconductor.

  Therefore, a 1.3 μm band light-emitting structure using a group IV semiconductor has been proposed. For example, an element that emits light with a Ge layer using a GaAs / Ge superlattice structure using Ge that is substantially lattice-matched with GaAs has been proposed. (For example, refer to Patent Document 1).

Japanese Patent Laid-Open No. 08-070154

  However, Ge itself is an indirect transition type semiconductor with low luminous efficiency. Therefore, in order to improve luminous efficiency, the Ge layer is thinned and the ground level of the conduction band is made a direct transition band (Γ point) by the quantum effect. There is a problem that a complicated design is required.

  Accordingly, an object of the present invention is to realize a long wavelength light emitting device using a GaAs substrate without requiring a complicated design.

From one aspect to be disclosed, a GaAs substrate, a first conductive semiconductor layer provided on the GaAs substrate, and at least _one Ge _1-x Si _x layer provided on the first conductive semiconductor layer ( However, a light emitting layer having a heterojunction between 0 ≦ x ≦ 0.5) and at least _one In _1-y Ga _y As layer (where 0 ≦ y ≦ 0.7) is provided on the light emitting layer. In addition, a semiconductor light emitting device is provided, comprising a second conductivity type semiconductor layer having a conductivity type opposite to the first conductivity type semiconductor layer.

  According to the disclosed semiconductor light emitting device, a long wavelength light emitting device having a wavelength of 1.5 μm or the like can be formed on a GaAs substrate without requiring a complicated design.

1 is a conceptual cross-sectional view of a semiconductor light emitting device according to an embodiment of the present invention. 1 is a band diagram of a semiconductor light emitting device according to an embodiment of the present invention. Is an illustration of a Ga composition ratio y dependence of the difference Delta] E _c1 and indirect conduction band energy of the direct transition conduction band energy and Ge of InGaAs. A Si composition ratio x dependency of illustration of the valence band energy difference Delta] E _v. It is an illustration of the Al composition ratio dependency of the conduction band energy difference Delta] E _c2 of the GeSi layer and the AlGaAs layer. It is a band diagram of a superlattice structure. It is a notional cross section of the light emitting diode of Example 1 of the present invention. It is a conceptual sectional drawing of the light emitting diode of Example 2 of this invention. It is explanatory drawing of the manufacturing process to the middle of the surface emitting laser of Example 3 of this invention. It is explanatory drawing of the manufacturing process to the middle after FIG. 9 of the surface emitting laser of Example 3 of this invention. It is explanatory drawing of the manufacturing process after FIG. 10 of the surface emitting laser of Example 3 of this invention. It is a conceptual sectional view perpendicular to the optical axis of the ridge type edge emitting laser of Example 4 of the present invention.

Here, with reference to FIG. 1 thru | or FIG. 6, the semiconductor light-emitting device of embodiment of this invention is demonstrated. FIG. 1 is a conceptual cross-sectional view of a semiconductor light emitting device according to an embodiment of the present invention. A first conductive semiconductor layer 2, a light emitting layer 3, and a second conductive semiconductor layer 4 are sequentially stacked on a GaAs substrate 1. Formed by. The second conductivity type semiconductor layer 4 and the first conductivity type semiconductor layer 2 are of opposite conductivity types. Further, the light-emitting layer 3 is at least one layer of _{Ge 1-x} Si x layer 5 (where, 0 ≦ x ≦ 0.5) and at least one layer of _In 1-y _Ga y As layer 6 (where, 0 ≦ y ≦ 0. 7) and a heterojunction.

FIG. 2 is a band diagram of the semiconductor light emitting device according to the embodiment of the present invention. As a result of intensive studies by the present inventor, as shown in the figure, the lowest energy of the conduction band is the In _1-y Ga _y As layer 6 (direct transition band: Γ point), and the highest energy of the valence band is Ge _1-x. It has been found that the Si _x layer 5 may be obtained. At this time, the light emission transition is performed by recombination of electrons confined in the In _1-y Ga _y As layer 6 and holes confined in the Ge _1-x Si _x layer 5, so that the conventional InGaAs layer The emission wavelength can be increased compared to a quantum well structure using only a single layer.

For electrons confined in _In 1-y _Ga y As layer _{6, In} 1-y _Ga y energy Γ point of As layer 6 is L points of an indirect transition band of _{Ge 1-x} Si x layer 5 Energy Need to be lower. In order to satisfy all the GeSi layers, the range of the Ga composition ratio y of the InGaAs layer may be obtained for the Ge layer having the lowest conduction band energy in GeSi.

FIG. 3 is an explanatory diagram of the dependence of the difference ΔEc1 between the direct transition conduction band energy of InGaAs and the indirect transition conduction band energy of Ge on the Ga composition ratio y. Here, the energy difference ΔE _c1 is expressed as ΔE _c1 = E _c1. (Γ _InGaAs ) -E _c1 (L _Ge )
Define in. If the value Delta] E _c of the vertical axis is _negative, the electrons are confined in _{an In} 1-y _Ga y As _layer, the _{an In} 1-y _Ga y As layer of Ga composition ratio y them with 0 ≦ y ≦ 0.7 It ’s fine.

Next, in order to confine holes in the Ge _1-x Si _x layer, the Si composition ratio x of the Ge _1-x Si _x layer with respect to InAs having the highest valence band energy in the InGaAs layer. Find the range.

FIG. 4 is an explanatory diagram of the dependence of the valence band energy difference on the Si composition ratio x. Here, the valence band energy difference ΔE _v is expressed as follows:
ΔE _v = E _v (GeSi) −E _v (InAs)
Define in. If positive value _{E v} of the vertical _axis, since the hole is confined in the _{Ge 1-x} Si _{x layer,} if the _{Ge 1-x} Si _x layer of Si composition ratio x between 0 ≦ x ≦ 0.5 good.

The first conductive type semiconductor layer 2 and the second conductive type semiconductor layer 4 have a valence band energy lower than that of the Ge _1-x Si _x layer 5 and have a conduction band energy of In _1-y Ga. it is preferable to use a larger semiconductor than the conduction band energy of the _y As layer 6. For example, AlGaAs may be used, whereby the first conductive semiconductor layer 2 and the second conductive semiconductor layer 4 can be prevented from acting as a light absorption layer for the emission wavelength of the light emitting layer 3, and It functions as an energy barrier layer and a cladding layer.

FIG. 5 is an explanatory view of the Al composition ratio dependence of the conduction band energy difference ΔE _c2 between the GeSi layer and the AlGaAs layer. Ge and Ge _0.9 so that the Al composition ratio is in the range where AlGaAs is in direct transition. The case of Si _0.1 is shown. Here, the conduction band energy difference ΔE _c2 is expressed as
ΔE _c2 = E _c2 (Γ _AlGaAs ) −E _c2 (Γ _GeSi )
Define in. If the value ΔE _{c on the} vertical axis is positive, the Ge _1-x Si _x layer does not serve as a barrier against electrons injected from the AlGaAs layer, and electrons are injected well. Note that InGaAs does not become a barrier to holes at all composition ratios of AlGaAs.

Although omitted in FIG. 1, a light confinement layer (SCH layer) may be provided between at least one of the first conductive semiconductor layer 2 and the second conductive semiconductor layer 4 and the light emitting layer 3. . The optical confinement layer has a conduction band energy higher than the Ge _1-x Si _x layer 5 direct transition conduction band energy (Γ point), and a valence band energy higher than that of the In _1-y Ga _y As layer 6. A lower semiconductor, for example, AlGaAs. Further, the band gap of the optical confinement layer is set to be equal to or smaller than the band gaps of the first conductive semiconductor layer 2 and the second conductive semiconductor layer 4.

Further, the light-emitting layer 3, as described above, at least one layer of _{Ge 1-x} Si x layer 5 (0 ≦ x ≦ 0.5) and at least one layer of _In 1-y _Ga y As layer 6 (0 ≦ y ≦ 0.7). Preferably, a multiple quantum well structure or a superlattice structure in which thin Ge _1-x Si _x layers 5 and In _1-y Ga _y As layers 6 are alternately stacked is desirable. In the case of a multiple quantum well structure or a superlattice structure, any one may be stacked first, and the number of stacked layers may be either n: n or n: n-1.

  FIG. 6 is a band diagram of a superlattice structure. When the thickness of each layer is made thinner than that of a multiple quantum well structure to form a superlattice structure, GeSi layers and InGaAs layers are quantum mechanically coupled. And the overlap of the density of states of electrons and holes increases. As a result, luminescent recombination occurs in the entire light emitting layer, and light is emitted more efficiently.

When the light emitting layer 3 has a superlattice structure, it is more preferable from the viewpoint of crystallinity to reduce the average strain ε _{av of the} light emitting layer represented by the following formula.
_{ε av = (ε GeSi × t} GeSi G + ε InGaAs × t InGaAs) / (t GeSi + t InGaAs)
Here, each ε is a strain with respect to the GaAs substrate, and each t is a film thickness. Since ε _InGaAs takes negative values for all compositions and ε _GeSi can take positive values, the average strain ε _av can be reduced by adjusting the film thickness of InGaAs and GeSi. .

Incidentally, the amount of strain of each material with respect to GaAs is
GaAs: ε _GaAs = 0
InAs: ε _InAs = −0.066
_{In 0.8 Ga 0.2 As: ε In0.8Ga0.2As} = -0.053
Ge: ε _Ge = −0.001
Si: ε _Si = 0.046
_{Ge 0.9 Si 0.1: ε Ge0.9Si0.1 =} 0.004
It becomes.

  The semiconductor light emitting element may be a light emitting diode (LED) or a semiconductor laser (LD). When a semiconductor laser is used, a surface along the stacking direction may be a Fabry-Perot surface, and a striped ridge may be provided as necessary. Alternatively, a surface emitting laser may be provided by providing a distributed Bragg reflector (DBR) made of a III-V group compound semiconductor above and below the stacking direction.

  By adopting the above configuration, it is possible to form a semiconductor light emitting element that emits light at a wavelength longer than 1.3 μm using a GaAs substrate that is large in diameter and inexpensive compared to the InP substrate.

  Based on the above, a semiconductor light-emitting diode according to Example 1 of the present invention will now be described with reference to FIG. FIG. 7 is a conceptual cross-sectional view of the light-emitting diode according to the first embodiment of the present invention. The n-type GaAs buffer layer 12 having a thickness of 100 to 300 nm, the multiple quantum well layer 13 and the thickness are formed on the n-type GaAs substrate 11. A p-type GaAs layer 14 having a thickness of 100 to 300 nm is sequentially stacked. An n-side electrode 17 is formed on the back surface of the n-type GaAs substrate 11, and a p-side electrode 18 is formed on the surface of the p-type GaAs layer 14. As a film forming method, molecular beam epitaxy or MOCVD method is used.

In this case, the multi-quantum well layer 13 includes three layers of Ge _0.9 Si _0.1 layer 15 having a thickness of, for example, 17 nm and In _0.8 Ga _0.2 As having a thickness of, for example, 1.8 nm. The layers 16 are formed by alternately stacking two layers. Here, the strain ratio is adjusted so that the average strain ε _av becomes 0 by adjusting the composition ratio and the film thickness.

Thus, in Example 1 of the present invention, the multiple quantum well layer 13 is formed by the Ge _0.9 Si _0.1 layer 15 and the In _0.8 Ga _0.2 As layer 16. Even if a GaAs substrate is used, light emission in the 1.55 μm band is possible.

Next, with reference to FIG. 8, the light emitting diode of Example 2 of this invention is demonstrated. FIG. 8 is a conceptual cross-sectional view of the light-emitting diode according to Example 2 of the present invention, in which an n-type Al _0.3 Ga _0.7 As buffer layer 22 having a thickness of 100 to 300 nm is formed on an n-type GaAs substrate 21. For example, an i-type Al _0.3 Ga _0.7 As light confinement layer 23 having a thickness of 30 nm, a superlattice light-emitting layer 24, and an i-type Al _0.3 Ga _0.7 As light confinement layer having a thickness of 30 nm, for example. 25 and a p-type Al _0.3 Ga _0.7 As layer 26 having a thickness of 100 to 300 nm are sequentially stacked. An n-side electrode 29 is formed on the back surface of the n-type GaAs substrate 21, and a p-side electrode 30 is formed on the surface of the p-type Al _0.3 Ga _0.7 As layer 26. For example, a p-type GaAs contact layer may be provided on the p-type Al _0.3 Ga _0.7 As layer 26. As a film forming method, molecular beam epitaxy or MOCVD is used.

In this case, the superlattice light-emitting layer 24 has a Ge _0.9 Si _0.1 layer 27 having a thickness of, for example, 2 nm and an In _0.5 Ga _0.5 As layer 28 having a thickness of, for example, 1 nm alternately. It is formed by stacking 20 layers.

Thus, in Example 2 of the present invention, the superlattice light-emitting layer 24 is formed by the Ge _0.9 Si _0.1 layer 27 and the In _0.5 Ga _0.5 As layer 28. Luminescent recombination occurs in the entire superlattice light emitting layer, and light is emitted with higher efficiency. Further, since the superlattice light emitting layer 24 is sandwiched between Al _0.3 Ga _0.7 As layers, light confinement is performed well. Laser oscillation is also possible by forming a Fabry-Perot resonator by cleavage.

  Next, a surface emitting laser according to Example 3 of the present invention will be described with reference to FIGS. FIGS. 9 to 11 are explanatory views of the manufacturing process of the surface emitting laser according to the third embodiment of the present invention. First, as shown in FIG. 9A, for example, an n-type GaAs using a molecular beam epitaxy method is used. On the substrate 31, the lower DBR mirror layer 32 is formed by alternately stacking n-type GaAs layers 33 and n-type AlGaAs layers 34, for example, 35 cycles or more at a growth temperature of 600 ° C. to 700 ° C.

The lower DBR mirror layer 32 may be alternately stacked with a thickness of an optical distance that is ¼ of the wavelength λ desired to reflect a film having a different refractive index. For example, the n-type AlGaAs layer 34 is made of Al _0.3 Ga _0.7 As having a thickness of, for example, 120 nm doped with Si of 1 × 10 ¹⁸ cm ⁻³ , and the n-type GaAs layer 33 has Si of 1 × 10 6. For example, GaAs with a thickness of 115 nm doped with ¹⁸ cm ⁻³ is used.

  Subsequently, an i-type GaAs layer 35 having a thickness of, for example, 50 nm, a multiple quantum well layer 36, and an i-type GaAs layer 39 having a thickness of, for example, 50 nm are formed on the lower DBR mirror layer 32 at a growth temperature of 600 ° C. to 700 ° C. Are sequentially deposited.

In this case, the multi-quantum well layer 36 includes six Ge _0.9 Si _0.1 layers 37 having a thickness of, for example, 21 nm, and In _0.8 Ga _0.2 As having a thickness of, for example, 1.8 nm. The layers 38 are formed by alternately stacking five layers. In this case as well, the distortion is compensated so that the average strain ε _av becomes 0 by adjusting the composition ratio and the film thickness.

  Subsequently, an i-type GaAs layer / multiple quantum well is grown by growing an i-type AlAs layer 40 having a thickness of, for example, 10 nm as a current confinement layer on the i-type GaAs layer 39 at a growth temperature of 500 ° C. to 600 ° C. A resonator layer composed of layer / i-type GaAs layer / i-type AlAs layer is formed.

  Subsequently, the upper DBR mirror layer 41 is formed by alternately stacking the p-type GaAs layer 42 and the p-type AlGaAs layer 43 on the i-type AlAs layer 40 for, for example, 35 periods or more at a growth temperature of 600 ° C. to 700 ° C.

The upper DBR mirror layer 41 uses, for example, Al _0.3 Ga _0.7 As having a thickness of 120 nm, for example, doped with 1 × 10 ¹⁸ cm ⁻³ of Be as the p-type AlGaAs layer 43. As the p-type GaAs layer 42, GaAs having a thickness of, for example, 115 nm doped with 1 × 10 ¹⁸ cm ⁻³ of Be is used.

  Next, as shown in FIG. 9B, using the resist pattern (not shown) as a mask, the upper DBR mirror layer 41 to the i-type GaAs layer 35 are etched to form a cylindrical mesa having a diameter of 20 μm, for example. To do.

  Next, as shown in FIG. 10C, for example, the exposed end face of the i-type AlAs layer 40 is locally oxidized in a heated water vapor atmosphere heated to 450 ° C. to form a current confining oxide film 44. At this time, the exposed end portions of other layers not containing Al are not oxidized much.

Next, as shown in FIG. 10D, for example, a protective oxide film 45 is formed by depositing a SiO ₂ film to a thickness of 200 nm. As the protective oxide film 45, a SiN film or a Si ON film may be used instead of the SiO ₂ film.

  Next, as shown in FIG. 11E, the protective oxide film 45 deposited on the top of the mesa is selectively removed using a resist pattern (not shown) as a mask.

  Finally, as shown in FIG. 11 (f), an n-side electrode 46 is formed on the back surface of the n-type GaAs substrate 31 by lithography and vapor deposition, and an annular p-side electrode 47 is formed on the top of the mesa. Thus, the surface emitting laser according to Example 3 of the present invention is completed.

  Thus, in Example 3 of the present invention, a long wavelength surface emitting laser using a GaAs substrate can be realized by using a GeSi / InGaAs multiple quantum well layer and providing a DBR mirror.

Next, a ridge-type edge emitting laser according to Example 4 of the present invention will be described with reference to FIG. FIG. 12 is a conceptual cross-sectional view perpendicular to the optical axis of the ridge-type edge emitting laser according to Example 4 of the present invention. First, for example, an n-type AlGaAs cladding layer 52 is grown on an n-type GaAs substrate 51 having a (100) plane as a main surface by using molecular beam epitaxy at a growth temperature of 600 ° C. to 700 ° C. In this case, the n-type AlGaAs cladding layer 52 is, for example, Al _0.3 Ga _0.7 As having a thickness of 500 nm to 1500 nm doped with Si of 1 × 10 ¹⁸ cm ⁻³ .

  Subsequently, an i-type AlGaAs optical confinement layer 53 having a thickness of, for example, 30 nm and an Al composition ratio of 0.3 is formed on the n-type AlGaAs cladding layer 52.

Subsequently, a multiple quantum well layer 54 is grown on the i-type AlGaAs optical confinement layer 53. The multi-quantum well layer 54 has, for example, three Ge _0.9 Si _0.1 layers 55 having a thickness of, for example, 17 nm, and a thickness of, for example, 1.8 nm, as in the first embodiment. Two In _0.8 Ga _0.2 As layers 56 are alternately stacked.

Subsequently, an i-type AlGaAs optical confinement layer 57, a p-type AlGaAs cladding layer 58, and a p-type GaAs contact layer 59 are sequentially grown on the multiple quantum well layer. In this case, the i-type AlGaAs optical confinement layer 57 has an Al _0.3 Ga _0.7 As thickness of 30 nm, for example, and the p-type AlGaAs cladding layer 58 has Be doped 1 × 10 ¹⁸ cm ⁻³ , for example. The thickness is set to Al _0.3 Ga _0.7 As having a thickness of 500 nm to 1000 nm. The p-type GaAs contact layer 59 is, for example, GaAs having a thickness of 10 nm doped with 1 × 10 ¹⁹ cm ^{−3 of} Be.

  Next, a part of the p-type GaAs contact layer 59 to the p-type AlGaAs cladding layer 58 is etched into a stripe shape so that the width becomes, for example, 1.0 μm to 2.5 μm, thereby forming a ridge structure.

  Next, an n-side electrode 60 is formed on the back surface of the n-type GaAs substrate 51, and a p-side electrode 61 is formed on the top surface of the p-type GaAs contact layer 59. Finally, a cavity is formed by cleaving along a plane perpendicular to the extending direction of the ridge, thereby completing the ridge-type edge emitting laser of Example 4 of the present invention.

  Thus, in Example 4 of the present invention, a GeSi / InGaAs multiple quantum well layer is used and a Fabry-Perot resonator is formed by cleavage, so that a long wavelength edge emitting laser using a GaAs substrate is realized. It becomes possible.

1 GaAs substrate 2 first conductivity type semiconductor layer 3 light-emitting layer 4 second conductivity type semiconductor layer 5 _{Ge 1-x} Si x layer 6 _In 1-y _Ga y As layer 11,21,31,51 n-type GaAs substrate 12 n Type GaAs buffer layer 13, 36, 54 multiple quantum well layer 14 p type GaAs layer 15, 27, 37, 55 Ge _0.9 Si _0.1 layer 16, 38, 56 In _0.8 Ga _0.2 As layer 17 , 29, 46, 60 n-side electrode 18, 30, 47, 61 p-side electrode 22 n-type Al _0.3 Ga _0.7 As buffer layer 23, 25 i-type Al _0.3 Ga _0.7 As optical confinement layer 24 superlattice light emitting layer 26 p-type Al _0.3 Ga _0.7 As layer 28 In _0.5 Ga _0.5 As layer 33 n-type GaAs layer 34 n-type AlGaAs layer 32 lower DBR mirror layers 35 and 39 i-type GaAs Layer 40 On i-type AlAs layer 41 Part DBR mirror layer 42 p-type GaAs layer 43 p-type AlGaAs layer 44 current confinement oxide film 45 protective oxide film 52 n-type AlGaAs cladding layer 53 i-type AlGaAs optical confinement layer 57 i-type AlGaAs optical confinement layer 58 p-type AlGaAs cladding layer 59 p-type GaAs contact layer

Claims (5)

A GaAs substrate;
A first conductivity type semiconductor layer provided on the GaAs substrate;
At least _one Ge _1-x Si _x layer provided in the first conductivity type semiconductor layer where 0 ≦ x ≦ 0.5 and at least _one In _1-y Ga _y As layer where 0 ≦ y ≦ A light emitting layer having a heterojunction with 0.7),
A semiconductor light emitting device comprising: a second conductivity type semiconductor layer having a conductivity type opposite to the first conductivity type semiconductor layer provided on the light emitting layer. The energy of the valence band of the first conductivity type semiconductor layer and the second conductivity type semiconductor layer is lower than the energy of the valence band of the Ge _1-x Si _x layer, and the first conductivity type semiconductor layer and the first conductivity type semiconductor layer 2. The semiconductor light emitting device according to claim 1, wherein the energy of the conduction band of the two-conductivity-type semiconductor layer is larger than the energy of the conduction band of the In _1-y Ga _y As layer. Between at least one of the first conductive type semiconductor layer and the second conductive type semiconductor layer and the light emitting layer, a conduction band energy is higher than a direct transition conduction band energy of the Ge _1-x Si _x layer, 3. The semiconductor light emitting element according to claim 1, further comprising an AlGaAs layer having a valence band energy lower than that of the In _1-y Ga _y As layer. 4. The light-emitting layer, any of the _{Ge 1-x} Si _x layer and the _In 1-y _Ga y As claim and having a superlattice structure of alternately laminated layers 1 through claim 3 1 The semiconductor light emitting device according to item. 5. The semiconductor light emitting device according to claim 4, further comprising a distributed Bragg reflection mirror made of a III-V group compound semiconductor above and below the stacking direction of the light emitting layer.

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