JPH10256600A - Semiconductor light emitting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a light emitting device having high light emission efficiency and excellent electric characteristics without lowering film quality and capable of suppressing light absorption in a window layer to the utmost in a semiconductor light emitting device in which a light emitting layer formation part is formed with an AlGaInP compound semiconductor and there is used as the window layer one comprising a laminate structure of a semiconductor layer having higher carrier concentration and a GaP layer having greater band gap energy. SOLUTION: The present device includes a substrate 1, a light emitting layer formation part 11 which comprises an AlGaInP compound semiconductor and in which an n-type layer and a p-type layer are laminated to form a light emitting layer on the substrate 1, and a window layer 7 provided out a surface side of the light emitting layer formation part 11. Herein, the window layer 7 comprises a laminate structure of a greater carrier concentration semiconductor layer 7a and large band gap energy semiconductor layer 7c, and a buffer layer 7b is provided between both layers for moderating lattice distortion of both layers.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention
The present invention relates to a visible light semiconductor light emitting device using a GaInP-based compound semiconductor and having a window layer having a stacked structure of a semiconductor layer having a high carrier concentration and a semiconductor layer having a large band gap energy on a light emitting surface side. More specifically, the present invention relates to a semiconductor light emitting device that improves the film quality of a semiconductor crystal layer of a window layer and suppresses light absorption to improve electrical characteristics such as luminous efficiency.

[0002]

2. Description of the Related Art A conventional visible light semiconductor light emitting device has a structure as shown in FIG. 3, for example, using an AlGaInP-based compound semiconductor material for a light emitting layer forming portion. That is, in FIG. 3, an n-type cladding layer 22 made of, for example, an n-type AlGaInP-based semiconductor material, a non-doped AlGaInP-based composition having a band gap energy smaller than that of the cladding layer are formed on a semiconductor substrate 21 made of an n-type GaAs. Active layer 23 made of a semiconductor material of
A p-type cladding layer 24 made of a p-type AlGaInP-based semiconductor material is epitaxially grown to form a light emitting layer forming portion 29 having a double hetero junction structure.
Further, an AlGaAs-based compound semiconductor layer 25a is formed on the surface thereof.
And a p-type window layer (current diffusion layer) 25 composed of a GaP layer 25b and a GaP layer 25b are sequentially epitaxially grown. A p-side electrode 27 is formed on the surface of the window layer 25, and an n-side electrode 28 is formed on the back side of the semiconductor substrate 21. It is constituted by being formed of an Au-Ge-Ni alloy or the like.

In the light emitting device having this structure, light from the surface side of the stacked semiconductor layers, that is, light from the p-side electrode 27 side is used, and the p-side electrode 27 for blocking light is formed with an area as small as possible. On the other hand, in order to emit light by confining carriers in the active layer 23 sandwiched between the cladding layers 22 and 24, it is desirable that the current be distributed uniformly throughout the light emitting layer. Therefore, the window layer 25 is provided so that the current spreads over the entire chip.
The window layer 25 desirably diffuses current and does not absorb light emitted from the active layer 23. When the window layer 25 is made of GaP, which is a material having a large band gap energy, as shown in FIG. In order to spread the current as much as possible, the AlGaAs-based compound semiconductor layer 25a having a high carrier concentration and the GaP layer 25b having a small carrier absorption but a large band gap energy and a small light absorption are formed by a laminated structure. Sometimes.

[0004]

In a conventional semiconductor light emitting device having the structure shown in FIG. 3, a GaAs substrate and an AlGaI
Lattice matching with an nP-based compound semiconductor (lattice constant: 5.653 °) is performed by a mixed crystal ratio of (AlGa) and In. Further, lattice matching with an AlGaAs-based compound semiconductor is achieved. Is not matched with 5.451 °). For this reason, the film quality of the window layer made of GaP is deteriorated, the electric resistance is increased, the operating voltage is increased, or the electric current is not sufficiently diffused, and the electric characteristics such as the luminous efficiency are reduced. There's a problem.

Further, even if the GaP layer has a large band gap energy, it absorbs light emitted from the light emitting layer to some extent, and is not completely transparent to visible light.

The present invention has been made in order to solve such a problem. A light emitting layer forming portion is formed of an AlGaInP compound semiconductor, a semiconductor layer having a high carrier concentration as a window layer and a GaP having a large band gap energy. It is an object of the present invention to provide a semiconductor light emitting device using a window layer having a layered structure with a layer and having high luminous efficiency and excellent electric characteristics without deteriorating the film quality of the window layer.

Another object of the present invention is to provide a semiconductor light emitting device having a high external luminous efficiency, which is a ratio of light that can be extracted to the outside while minimizing light absorption in a window layer.

[0008]

A semiconductor light emitting device according to the present invention comprises a substrate and an AlGaInP substrate provided on the substrate.
A light-emitting layer forming part comprising a compound semiconductor, wherein an n-type layer and a p-type layer are stacked to form a light-emitting layer, and a window light-emitting layer provided on a surface side of the light-emitting layer forming part; The window layer has a laminated structure of a semiconductor layer having a high carrier concentration and a semiconductor layer having a large band gap energy, and a buffer layer for relaxing lattice distortion of both layers is provided between the two layers.

Here, the AlGaInP-based compound semiconductor is expressed in the form of (Al _x Ga _{1 -x} ) _0.51 In _0.49 P,
It means the material when the value of x varies between 0 and 1. Note that the mixed crystal ratio of (Al _x Ga _1-x ) and In is set to 0.1.
51 and 0.49 mean that the ratio is such that it is lattice-matched with a semiconductor substrate such as GaAs on which an AlGaInP-based compound semiconductor is laminated.

[0010] Since the buffer layer is inserted between the semiconductor layer having a high carrier concentration and the semiconductor layer having a high band gap energy, no strain is accumulated due to a difference in lattice constant in the laminated structure of the window layer. Since the strain at the interface due to the difference in the constant is reduced, the film quality of the window layer is improved, and the electrical characteristics of the light emitting element are improved.

Specifically, the semiconductor layer having a high carrier concentration is an AlGaAs-based compound semiconductor layer or an AlGa
In the InP-based compound semiconductor layer, the semiconductor layer having a large band gap energy may be a GaP layer, and the buffer layer may be a GaInP-based compound semiconductor layer. here,
An AlGaAs-based compound semiconductor means that the mixed crystal ratio of Al and Ga can be variously changed, and a GaInP-based compound semiconductor means that the mixed crystal ratio of Ga and P can be variously changed. The same applies to other compound semiconductors.

Another embodiment of the semiconductor light-emitting device of the present invention is a light-emitting layer forming a light-emitting layer provided on the substrate and made of an AlGaInP-based compound semiconductor and having an n-type layer and a p-type layer laminated to form a light-emitting layer. And a window layer provided on the surface side of the light emitting layer forming portion, wherein the window layer has a laminated structure of a semiconductor layer having a large carrier concentration and a semiconductor layer having a large band gap energy. The semiconductor layer having a large band gap energy is made of (Al _x G) such as an AlGaP-based compound semiconductor.
a _1-x ) _1-z In _z P (0 ≦ x ≦ 1, 0 ≦ z <0.4)
9) It is made of a compound semiconductor. As the semiconductor layer having a high carrier concentration, for example, an AlGaAs-based compound semiconductor layer or an AlGaInP-based compound semiconductor layer is used.

By using the above-mentioned material as the semiconductor layer having a large band gap energy, the band gap energy is larger than that of the GaP layer, light absorption can be suppressed, and external luminous efficiency is improved.

By providing a GaP layer on the surface side of the semiconductor layer having a large band gap energy,
The electrical characteristics due to the contact with the side electrode do not lower than the conventional structure.

[0015]

Next, a semiconductor light emitting device of the present invention will be described with reference to the drawings.

The semiconductor light emitting device of the present invention has an n-type GaAs substrate 1 as shown in FIG.
A light emitting layer forming portion 11 made of an AlGaInP-based compound semiconductor and forming a light emitting layer is deposited thereon, and has a stacked structure of a semiconductor layer 7a having a high carrier concentration, a buffer layer 7b, and a semiconductor layer 7c having a large band gap energy on the surface. A p-type window layer 7 is provided.
A side electrode 8 is formed, and an n-side electrode 9 is provided on the back surface of the GaAs substrate 1 to form a light emitting element chip. That is, in the present invention, a buffer layer 7b having a lattice constant intermediate between the semiconductor layer 7a having a large carrier concentration of the window layer 7 and the semiconductor layer 7c having a large band gap energy is interposed between the semiconductor layer 7a and the semiconductor layer 7c having a large band gap energy. The strain between the two layers based on the difference in lattice constant is reduced.

As the semiconductor layer 7a having a high carrier concentration, an AlGaAs compound semiconductor or AlGaInP
-Based compound semiconductor is used and the carrier concentration is 1 × 10 ¹⁸
It is formed at a thickness of about 1-5 μm at about 1 × 10 ²⁰ cm ⁻³ . These semiconductors can be sufficiently doped with impurities to increase the carrier concentration. AlGaIn
The P-based compound semiconductor is a semiconductor of the same type as the semiconductor layer of the light emitting layer forming part 11, but the light emitting layer forming part 11 cannot increase the carrier concentration too much due to luminous efficiency. Is provided separately. In this case, a composition having a higher band gap energy by increasing the ratio of Al than the cladding layer of the light emitting layer forming portion 11 may be used, or the same ratio may be used.

Semiconductor having a large band gap energy
As the layer 7c, a GaP layer similar to the conventional one or a GaP layer described later
(Al_xGa_1-x)_1-zIn_zP (0 ≦ x ≦ 1, 0 ≦ z
<0.49) A compound semiconductor is used, and the carrier concentration is
1 × 10¹⁶~ 1 × 10¹⁹ cm ^-3About 0.1 ~ 20μ
The thickness is about m. The buffer layer 7b is made of GaAs
AlGaAs or A with lattice constant matched with s substrate 1
Lattice constant of lGaInP-based compound semiconductor 5.653Å
And the semiconductor layer 7c having a large band gap energy.
Lattice constant of the GaP layer with a lattice constant of 5.451 °
Is used. For example, a GaInP layer (grating
Constant is 5.491Å) and the carrier concentration is 1 × 1
0¹⁶~ 1 × 10¹⁹cm^-3About 0.1 to 20 μm
It is provided in the thickness of.

The light emitting layer forming section 11 is made of an AlGaInP compound semiconductor and has a carrier concentration of 1 × 10 ¹⁷ to 1 × 10 ^17.
An n-type cladding layer ^{3 of} about 10 ¹⁹ cm ^-3 and a thickness of about 0.1 to 2 μm, and an AlGaInP-based compound semiconductor which is non-doped and has a composition in which the band gap energy is smaller than that of the cladding layer, is 0.1 to 2 μm. An active layer 4 having a thickness of about 10 nm and a carrier concentration of 1 × 10
It is about ¹⁶ to 1 × 10 ¹⁹ cm ^−3, has a thickness of about 0.1 to 2 μm, and has a laminated structure of an n-type cladding layer 3 and a p-type cladding layer 5 made of an AlGaInP-based compound semiconductor having the same composition. . These light emitting layer forming portions 11 may be stacked on the GaAs substrate 1 via a buffer layer (not shown). In that case, the buffer layer is made of n-type GaAs.
And a carrier concentration of about 1 × 10 ¹⁷ to 1 × 10 ¹⁹ cm ^{−3 with} a thickness of about 0.1 to 2 μm.

Au-Ti is applied to the surface of the window layer 7 described above.
A p-side electrode 8 made of an alloy or an Au-Zn-Ni alloy is provided, and an n-side electrode 9 made of an Au-Ge-Ni alloy is provided on the back surface of the GaAs substrate 1. Note that Zn is 2 × 10 ¹⁹ cm between the window layer 7 and the p-side electrode 8.
G doped to a carrier concentration of about ^-3
a contact layer (not shown) made of aAs
In some cases, the thickness may be about 0.2 μm.

In order to manufacture such a semiconductor light emitting device, for example, an n-type GaAs substrate 1 is placed in an MOCVD apparatus, and a reaction gas of triethylgallium (hereinafter referred to as TEG) is used.
) Or trimethylgallium (hereinafter, referred to as TMG), arsine (hereinafter, referred to as AsH ₃ ), and H ₂ Se, which is a dopant gas for Se, are introduced together with hydrogen (H ₂ ) as a carrier gas, and epitaxial growth is performed at about 500 to 800 ° C. Then, a buffer layer (not shown) made of n-type GaAs doped with Se so as to have a carrier concentration of about 1 × 10 ¹⁸ cm ⁻³ is formed to a thickness of about 0.1 μm.
Next, phosphine (hereinafter, referred to as PH ₃ ) is substituted for AsH ₃ , and trimethylaluminum (hereinafter, referred to as TM)
A) and trimethylindium (hereinafter referred to as TMI).
n) and an n-type carrier concentration of 1 × 10 ¹⁷
１1 × 10 ¹⁹ cm ⁻³ , for example (Al _0.7 G
a _0.3 ) _0.51 In _0.49 P n-type cladding layer 3 of about 0.5 μm, TMA of the reaction gas is reduced to increase TEG or TMG, and for example, non-doped (Al _0.25
The active layer 4 made of Ga _0.75 ) _0.51 In _0.49 P has a thickness of 0.5 μm.
about m, a reaction gas similar to that of the n-type cladding layer 3, and H ₂ S
In place of e, dimethyl zinc (DMZn) as a dopant gas for Zn is introduced to reduce the carrier concentration to 1 × 10 ¹⁶
(Al _0.7 Ga _0.3 ) _0.51 In of ~ 1 × 10 ¹⁹ cm ^-3
_A p-type cladding layer 5 made of _0.49 P is epitaxially grown to about 0.5 μm.

Further, a dopant gas DMZn is introduced.
While reacting gas, TEG or TMG, TMA and A
sH_ThreeAnd the carrier concentration is 1 × 10¹⁷~ 1 × 10¹⁹
cm ^-3About 10 μm of p-type AlGaAs layer 7a
Grow to a degree. Further, the reaction gas is transferred to TMIn and TEG.
Or TMG and PH_ThreeAnd replace the p-type GaInP layer 7b with
About 0.001 to 0.1 μm, the reaction gas is TEG or T
MG and PH_ThreeAnd change the p-type GaP layer 7c to 0.0.
The layers are laminated with a thickness of about 01 to 0.1 μm. And overall
Forming a window layer 7 having a thickness of about 0.1 to 20 μm;
You. Further, if necessary, T
EG or TMG and AsH_ThreeAnd DMZn
As a result, the carrier concentration becomes 2 × 10¹⁹cm^-3G of degree
a contact layer (not shown) made of aAs
A film having a thickness of about 0.2 μm is formed.

An Au—Ti alloy or an Au—Z alloy is formed on the upper and lower surfaces of the substrate thus epitaxially grown.
An upper electrode (p-side electrode) 8 made of an n-Ni alloy or the like and a lower electrode (n-side electrode) 9 made of an Au-Ge-Ni alloy or the like are formed, and diced into chips.

According to the present invention, a buffer layer made of a GaInP layer is interposed between a semiconductor layer made of an AlGaAs-based or AlGaInP-based compound semiconductor and having a high carrier concentration and a semiconductor layer made of GaP and having a high band gap energy. Thus, a window layer is formed. The lattice constant of the GaInP layer is located in the middle between the two layers adjacent on both sides, and relaxes the strain based on the difference in lattice constant between the two. As a result, even in a semiconductor light emitting element in which the window layer has a stacked structure of a semiconductor layer having a high carrier concentration and a semiconductor layer having a high band gap energy, the strain at the interface between the semiconductor layers is relaxed and the film quality of the window layer is reduced. Without this, a semiconductor light emitting device having high luminous efficiency is obtained. On the other hand, this buffer layer has an intermediate property between the layers on both sides in carrier concentration and band gap energy, and does not hinder light emission.

FIG. 2 is an explanatory sectional view of a window layer 7 for explaining another embodiment of the semiconductor light emitting device of the present invention. In this example, by using a material having a larger band gap energy than that of GaP, external light emission efficiency, which is a ratio of light that can be extracted to the outside while further reducing light absorption in the window layer, is improved. That is, as shown in FIG. 2A, as a semiconductor material having a large band gap energy, Al
For example, in a GaP-based compound semiconductor, the composition of In is made smaller than the value (0.49) that lattice-matches with GaAs, and the band gap energy is increased (Al _x Ga _1-x ) _1-z I.
An _nzP (0 ≦ x ≦ 1, 0 ≦ z <0.49) compound semiconductor is used. These semiconductor layers have a larger band gap energy than GaP and can further suppress light absorption. Such a semiconductor having a large band gap energy generally cannot have a very high carrier concentration. Therefore, it is preferable to interpose the semiconductor layer 7a having a high carrier concentration on the light emitting layer forming portion 11 side as described above. . As the semiconductor layer 7a having a high carrier concentration, an AlGaAs-based compound semiconductor similar to that described above or an AlGaInP-based compound semiconductor having a high carrier concentration is used. Although not shown in FIG. 2, it is preferable that a buffer layer for relaxing lattice distortion is interposed between the two layers as shown in FIG.

FIG. 2B shows that the surface of the semiconductor layer 7c having a large bandgap energy is further reduced by GaP having a smaller bandgap energy but a smaller resistance than that of the semiconductor layer 7c.
A layer 7d is provided. This is for reducing the contact resistance between the p-side electrode 8 and the semiconductor layer, and has the advantage of improving the electrical characteristics.

In each of the above examples, the light emitting layer forming portion 11
However, the active layer 4 is sandwiched between the cladding layers 3 and 5, and the material of the active layer 4 and the cladding layers 3 and 5, for example, the mixed crystal ratio of Al is made different, so that carriers and light are easily confined in the active layer. Although it has a double hetero junction structure in which the active layer 4 is used as a light emitting layer, a pn junction is formed without the active layer 4 and
A structure in which a light emitting layer is formed at the junction may be used.

Further, in the above-described examples, specific examples of the thickness and the carrier concentration are shown using specific semiconductor materials as the respective semiconductor layers constituting the semiconductor light emitting element. It is not limited to.

[0029]

According to the present invention, even when a laminated structure of a semiconductor layer having a large carrier concentration and a semiconductor layer having a large band gap energy is used for a window layer, internal strain due to mismatch of a lattice constant therebetween is obtained. Does not occur.
Therefore, while satisfying both the characteristics of a large carrier concentration and the characteristic of a large band gap energy, a high-quality semiconductor laminated structure can be obtained without distortion at the interface of the semiconductor layers, and a semiconductor light emitting device with high luminous efficiency can be obtained. can get.

As a semiconductor layer having a large band gap energy, (Al _x Ga _{1 -x} ) ₁ -z In _z P (0 ≦ x ≦ 1, 0 ≦ z
<0.49) By using a compound semiconductor, G
Light absorption is lower than that of aP, and the luminous efficiency is further improved.

[Brief description of the drawings]

FIG. 1 is a diagram showing a cross-sectional structure of one embodiment of a semiconductor light emitting device of the present invention.

FIG. 2 is a diagram showing a partial cross-sectional structure of another embodiment of the semiconductor light emitting device of the present invention.

FIG. 3 is a diagram showing a cross-sectional structure of a conventional semiconductor light emitting device.

[Explanation of symbols]

 Reference Signs List 1 substrate 3 n-type cladding layer 4 active layer 5 p-type cladding layer 7 window layer 7a semiconductor layer with high carrier concentration 7b buffer layer 7c semiconductor layer with high band gap energy 7d GaP layer 11 light emitting layer forming section

Claims (5)

[Claims] 1. A substrate, comprising: a substrate;
A semiconductor light-emitting element comprising a light-emitting layer forming portion formed of an InP-based compound semiconductor and forming a light-emitting layer in which an n-type layer and a p-type layer are stacked, and a window layer provided on a surface side of the light-emitting layer forming portion, A semiconductor light emitting device in which the window layer has a stacked structure of a semiconductor layer having a high carrier concentration and a semiconductor layer having a high band gap energy, and a buffer layer for relaxing lattice distortion of both layers is provided between the two layers. 2. The semiconductor layer having a high carrier concentration comprises A
the semiconductor layer having a large band gap energy is a GaP layer, and the buffer layer is a GGaAs-based compound semiconductor layer or an AlGaInP-based compound semiconductor layer.
2. The semiconductor light emitting device according to claim 1, wherein the semiconductor light emitting device is an aInP-based compound semiconductor layer. 3. A substrate and an AlGa provided on the substrate.
A semiconductor light-emitting element comprising a light-emitting layer forming portion formed of an InP-based compound semiconductor and forming a light-emitting layer in which an n-type layer and a p-type layer are stacked, and a window layer provided on a surface side of the light-emitting layer forming portion, The window layer has a laminated structure of a semiconductor layer having a high carrier concentration and a semiconductor layer having a large band gap energy, and the semiconductor layer having a large band gap energy is composed of (Al _x Ga _1-x ) _1-z In.
_A semiconductor light emitting device comprising a zP (0 ≦ x ≦ 1, 0 ≦ z <0.49) compound semiconductor. 4. The semiconductor layer having a high carrier concentration,
4. The semiconductor light emitting device according to claim 3, wherein the semiconductor light emitting device is an AlGaAs-based compound semiconductor layer or an AlGaInP-based compound semiconductor layer. 5. A GaP layer is provided on a surface side of the semiconductor layer having a large band gap energy.
Or the semiconductor light emitting device according to 4.