JPH04253381A - Semiconductor light emitting element and manufacture thereof - Google Patents

Abstract

PURPOSE:To obtain a semiconductor light emitting element which can perform a multicolor high intensity light emission by a single substrate by forming two or more light emitting layers of (In-Ga-Al-P) series mixed crystal which can be independently biased on the same semiconductor substrate. CONSTITUTION:A first clad layer 2, a first active layer 3, a second clad layer 4, a second active layer 5, and a third clad layer 6 containing compositions as shown in a table, are sequentially epitaxially grown in this order on a compound semiconductor substrate 1 made, for example, of n-type GaAs. Here, a composition (y) is so set to 0<=y<=0.2 that the layer 3 is formed as a red light emitting layer of an emitting light wavelength of about 620-670nm, and a composition (w) is so set to 0.35<=w<=0.6 that the layer 5 is formed as a green light emitting layer of an emitting light wavelength of about 550-575nm. The composition ratio of the layers is so set as to satisfy relations of y<=x, w,y<=z,w<=y.

Description

[Detailed description of the invention]

[Object of the invention]

0002

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a compact semiconductor light emitting device capable of emitting multicolor light with high brightness, and a method for manufacturing the same.

0003

[Prior Art] Light-emitting diodes (LEDs) are light sources for displays that utilize their high brightness characteristics, such as information display boards for indoors and in station premises, road display information boards used outdoors, stop lamps for automobiles, traffic lights, etc. Also, due to its fast response speed, it is used as a light source for optical communications using plastic fibers, and is widely used in various fields.

[0004] As such a light emitting diode, red L
ED and green LED are the basics, and G is the red LED.
AAsP red LEDs or GaAlAs red LEDs are often used, and nitrogen-doped GaP green LEDs are often used as green LEDs. In addition, other display colors such as yellow are obtained by mixing these two colors.

The brightness of each LED is about 300 (mcd) for GaAsP red LEDs, and 500 mcd for GaAlAs red LEDs with SH (single hetero) structure.
(mcd), GaA in DH (double hetero) structure
The ultra-high brightness of the lAs substrate is about 3000 (mcd), while the GaP (N-doped) green LED is about 500 mcd.
(mcd) degree has been obtained.

As described above, the direct transition type GaAlAs red LED has a brightness of 1 (cd) or more, but the indirect transition type GaP green LED has a maximum brightness of only about 500 (mcd). Not obtained. For this reason, green LEDs cannot function satisfactorily as an outdoor display light source that requires a brightness of 1 (cd) or more due to insufficient brightness, making it difficult to use them. Furthermore, even in the case of a multicolor display light source using a mixture of red and green, its use outdoors is restricted because the brightness of the green LED is insufficient. As described above, the range of use of green LEDs is limited.

On the other hand, both red LED and green LED
When obtaining light emission of two or more colors using
Since semiconductor chips with EDs formed are housed in the same package, the cost is significantly higher than in the case of a single color, and the manufacturing cost of a module-type display light source made by arranging a large number of LEDs also increases. I will do it.

On the other hand, GaP red L on one chip
A multicolor light-emitting element that formed both an ED and a GaP green LED and was able to emit two-color light was disclosed in Japanese Patent Laid-Open No. 57-79687.
It is disclosed in the publication No. However, in this multicolor light emitting device, the brightness of the GaP red LED is 100 (mcd
) can only be obtained. Therefore, as mentioned above,
It was difficult to use it as an outdoor display light source, and its range of use was limited.

[0009]

[Problem to be solved by the invention] As explained above,
Conventional green LEDs have had problems such as limited use due to insufficient brightness. Furthermore, green L
Similar problems have also occurred in multicolor LEDs using ED.

Furthermore, in the case of realizing multicolor light emission, chips on which red and green LEDs are formed are combined, resulting in an increase in the size and cost of the structure.

[0011] On the other hand, in the case of a configuration in which multicolor light emission is achieved with a single chip, the use thereof is limited due to insufficient brightness, as described above.

[0012] As described above, conventional light emitting diodes have not been able to satisfy both the requirements of one chip and high brightness multicolor light emission.

The present invention has been made in view of the above, and its purpose is to provide a semiconductor light emitting device and a method for manufacturing the same that can achieve multicolor high luminance light emission with a single substrate. It is in.

[Configuration of the invention]

[0015]

[Means for Solving the Problems] In order to achieve the above object, the present invention provides light-emitting layers of (In-Ga-Al-P) mixed crystal that can be independently biased on the same semiconductor substrate. , is composed of at least two layers.

[0016]

[Function] With the above structure, the present invention realizes direct transition type light emission within a predetermined emission wavelength range by changing the composition ratio of the mixed crystal, improves lattice matching between the substrate and the mixed crystal layer, and produces a high-quality mixed crystal. I'm trying to get a membrane.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Examples of the present invention will be described below with reference to the drawings.

FIG. 1 is a diagram showing a cross-sectional structure of an embodiment of a semiconductor light emitting device according to the present invention. The light emitting element of the example shown in the figure realizes two-color light emission of red light and green light emission on the same substrate.

In FIG. 1, the impurity concentration is 1×1018
A first cladding layer 2, a first active layer 3, and a second The cladding layer 4, the second active layer 5, and the third cladding layer 6 are epitaxially grown in this order by, for example, MOCVD. Note that each layer may be epitaxially grown using the MBE method.

[0020]

[Table 1]

In the composition shown in Table 1 of each growth layer, the composition ratios x, y, z, w, and v are set as shown below. First, the composition ratio y of the first active layer 3 is 62
In order to obtain a red light-emitting layer with an emission wavelength of approximately 0 to 670 (nm), O≦y≦0.2, and the composition ratio w is such that the second active layer 5 has an emission wavelength of approximately 550 to 575 (nm). In order to obtain a green light-emitting layer, the w is set to 0.35≦w≦0.6. In addition, the composition ratio of each layer is y≦x, w,
It is set so that the relationships shown by y≦z and w≦v are satisfied.

[0022] With such a composition ratio, the forbidden band width of each of the active layers 3 and 5 serving as a light emitting layer is smaller than the forbidden band width of both cladding layers sandwiching each active layer 3 and 5. , a double heterojunction is formed at both end faces of each active layer.

[0023] Second cladding layer 4, second active layer 5, third
An ohmic region 7 for applying a voltage to the second cladding layer 4 is formed in a part of the cladding layer 6 by selectively diffusing Zn as a P-type impurity. A predetermined voltage is applied to the second active layer 5 at the boundary between the ohmic region 7 where Zn is selectively diffused and the region where Zn is not diffused, and reaches the second cladding layer 4 so as to emit green light. Grooves 8 are formed by dry etching or wet etching, and the second active layer 5, which emits green light, and the ohmic region 7 are electrically isolated reliably.

Ohmic electrodes 9 and 10 made of Au-Ge are formed on one side of the substrate 1 and the third cladding layer 6, and an ohmic electrode 11 made of Au-Zn is formed on one side of the ohmic region 7. is formed.

In such a structure, In-Ga-A
By changing the Al composition ratio, the l-P quaternary mixed crystal becomes a direct transition type in the red to green emission range, and the lattice matching with GaAs of the substrate 1 is extremely good, resulting in a high-quality grown film. can get.

Therefore, for example, when the composition ratio of the quaternary mixed crystal layer is set to about x=z=v=0.7, y=0.13, w=0.4, the electrode 9 side is (-), The electrode 11 side is (+
) When a current is applied between the electrodes 9 and 11 by applying a voltage with a polarity such that When a voltage with a polarity such that the electrode 10 side is (-) and the electrode 11 side is (+) is applied and a current is passed between the electrodes 10 and 11, a high brightness of 1 (cd) or more is generated in the second active layer 5. So 5
Green light emission with an emission wavelength of about 60 (nm) is obtained.

Furthermore, by appropriately adjusting the value of the current flowing through each active layer, it becomes possible to obtain high-intensity light emission of any color tone within the red to green light emission range from each active layer.

In this way, in the above structure, 1(c
d) Since it is possible to emit high-intensity red and green light at the same time, it can be used as a light source for outdoor multicolor display, and the range of use of semiconductor light emitting devices can be expanded. Furthermore, since high-intensity multicolor light emission is realized on the same substrate, it becomes possible to integrate the display light source into a single chip, making it possible to provide an inexpensive and compact display light source.

Next, another embodiment of the present invention will be described.

FIG. 2 is a diagram showing a cross-sectional structure of another embodiment of the semiconductor light emitting device according to the present invention. The light emitting device of the example shown in the figure is characterized by GaA
A first red cladding layer 22, a first red active layer 23, and a second red cladding layer 2 are formed on a compound semiconductor substrate 21 consisting of
4 is formed by epitaxial growth;
The green light-emitting section formed by epitaxially growing the first green cladding layer 25, the first green active layer 26, and the second green cladding layer 27 is formed independently and separately, and the The composition etc. are as shown in Table 2.

[0031]

[Table 2]

Note that the substrate 21 and the second red cladding layer 2
4. On the second green cladding layer 27, an electrode 28 made of Au-Ge and electrodes 29 and 30 made of Au-Zn are formed as ohmic electrodes.

In such a structure, the composition ratios x, y, z, u, v, w in each growth layer are y≦x,
It is set to satisfy the relationship shown by z and v≦w, u. Therefore, the forbidden band width of each of the active layers 23 and 26 that becomes a red or green light emitting layer is smaller than the forbidden band width of both cladding layers sandwiching each active layer 23 and 26, and each active layer A double heterojunction is formed at both end faces of.

Next, one manufacturing method for obtaining the above structure will be explained with reference to manufacturing process cross-sectional diagrams shown in FIGS. 3 to 8.

First, a silicon oxide film (SiO2 film) is formed on the substrate 21 containing about 1×1018 cm−3 of impurities.
31 (FIG. 3).

Next, the first red cladding layer 22, the first red active layer 23, and the second red cladding layer 24 are epitaxially grown in this order by, for example, the MOCVD method to the impurity concentrations and thicknesses shown in Table 2. (Figure 4).

Next, a resist film 32 is selectively formed on the portion of each growth layer formed in the above steps that will become the red light emitting portion (FIG. 5).

Next, each growth layer except the growth layer under the resist film 32 is etched away using an H3 PO4 based etching solution, and then the SiO2 film 31 is etched away.
is removed by etching with an HF-based etching solution. Thereafter, a SiO2 film 3 is deposited on the second red cladding layer 24, which is the top layer of each growth layer formed on the substrate 21.
3 (Fig. 6).

Next, the first green cladding layer 25, the first green active layer 26, and the second green cladding layer 27 are epitaxially grown in this order by, for example, the MOCVD method to the impurity concentrations and thicknesses shown in Table 2. do. After this,
A resist film 34 is selectively formed on the portion of each growth layer formed in the above steps that will become the green light emitting portion (FIG. 7).

Finally, each grown layer and SiO2 film 33 are removed in the same manner as in the step shown in FIG. Thereafter, the resist film 34 is removed, and a red light-emitting section and a green light-emitting section made of the respective growth layers are formed on the substrate 21 in electrically independent and isolated manner (FIG. 8).

In the structure obtained in this way,
Similar to the structure shown in the above-mentioned embodiments, each emission range becomes a direct transition type, and a high-quality grown film can be obtained. For this reason, the Al composition ratio of the quaternary mixed crystal layer, for example, y
= 0.13, when a voltage is applied between the electrode 28 and the electrode 29, 1 (cd) is applied in the first red active layer.
Red light emission with an emission wavelength of about 630 (nm) is obtained with the above high brightness, and when the composition ratio v is set to 0.4 and a voltage is applied between the electrodes 28 and 30, the first green active layer 26 Green light emission with a high luminance of 1 (cd) or more and an emission wavelength of about 560 (nm) can be obtained. In addition, by appropriately adjusting the value of the current flowing through each active layer, it becomes possible to obtain high-intensity light emission of any color in the red to green light emission range from each active layer.

Therefore, even with the light emitting device of this embodiment, the same effects as the above-described light emitting device can be obtained.

Note that the present invention is not limited to the above-mentioned embodiments, and various application examples are possible.

For example, as shown in FIG. 9, the structure shown in FIG. 1 has no groove 8, or as shown in FIG. 10, the structure shown in FIG. The selectively diffused ohmic region 7 is not provided, and parts of the second cladding layer 4, second active layer 5, and third cladding layer 6 in the green light emitting part are removed, and a second cladding layer is formed on the top of the first active layer 3. The electrode 11 may be provided through the layer 4. In such a structure, the ohmic region 7 formed by selectively diffusing Zn absorbs some of the red light emitted from the first active layer 3, but since the ohmic region 7 is not formed, Absorption of red light emission is avoided and brightness can be further increased.

Furthermore, two or more active layers serving as light-emitting layers may be formed, and two or more light-emitting regions may be provided. For example, as shown in FIG. 11 or 12, three active layers 41, 42, and 43 are formed as light emitting layers of the quaternary mixed crystal, and the emission wavelength range from red to green is formed in three light emitting regions. Alternatively, the light may be emitted independently at any emission wavelength. In such a case, high-intensity multicolor light emission can be easily achieved.

Furthermore, in the above-mentioned stacked structure of quaternary mixed crystals, the substrate may be of a material that has good lattice matching with the quaternary mixed crystals grown on the substrate and can yield a high-quality grown film. , is not limited to GaAs, and the conductivity type is P.
It may be a type.

Further, the structure of each active layer serving as a light emitting layer may be a single heterostructure or a homojunction structure, and is not limited to a double heterostructure.

On the other hand, between the substrate and the first cladding layer formed on the substrate, a bonding region between the substrate and the first cladding layer is made of GaAs having the same composition and the same conductivity type as the substrate, for example, n-type. A buffer layer may be interposed to improve the crystallinity of and suppress crystal defects.

Further, between the electrode and the cladding layer, a current diffusion layer having the same conductivity type as the cladding layer, low resistance, and transparent to the emission wavelength, for example, an n of about 1×10 18 (cm −3 )
A current diffusion layer made of GaAlAs containing type impurities may be provided. By providing such a current diffusion layer, a current can uniformly flow through the active layer, and uniform light emission in the active layer can be promoted.

[0050]

As explained above, according to the present invention, a plurality of light emitting layers made of (In-Ga-Al-P) mixed crystal are provided on a single semiconductor substrate. A mixed crystal film having good lattice matching with the substrate is formed, making it possible to obtain a high quality mixed crystal film and realizing direct transition type light emission.

As a result, high brightness and multicolor light emission can be achieved by changing the composition and bias of the light emitting layer. Furthermore, since such a light emitting element can be obtained on the same substrate, it becomes possible to form it into a single chip, and it is possible to achieve miniaturization at low cost. Moreover, the above-mentioned effects can expand the range of uses.

[Brief explanation of the drawing]

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

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

3 is a cross-sectional view showing the steps of one manufacturing method for obtaining the structure of the embodiment shown in FIG. 2. FIG.

4 is a cross-sectional view showing the steps of one manufacturing method for obtaining the structure of the embodiment shown in FIG. 2. FIG.

5 is a cross-sectional view showing the steps of one manufacturing method for obtaining the structure of the embodiment shown in FIG. 2. FIG.

6 is a cross-sectional view showing the steps of one manufacturing method for obtaining the structure of the embodiment shown in FIG. 2. FIG.

7 is a cross-sectional view showing the steps of one manufacturing method for obtaining the structure of the embodiment shown in FIG. 2. FIG.

8 is a cross-sectional view showing the steps of one manufacturing method for obtaining the structure of the embodiment shown in FIG. 2. FIG.

FIG. 9 is a diagram showing a cross-sectional structure of another embodiment of the semiconductor light emitting device according to the present invention.

FIG. 10 is a diagram showing a cross-sectional structure of another embodiment of the semiconductor light emitting device according to the present invention.

FIG. 11 is a diagram showing a cross-sectional structure of another embodiment of the semiconductor light emitting device according to the present invention.

FIG. 12 is a diagram showing a cross-sectional structure of another embodiment of the semiconductor light emitting device according to the present invention.

[Explanation of symbols]

1, 21, GaAs substrate 2, 4, 6, 22, 24, 25, 27 cladding layer 3
, 5, 23, 26, 41, 42, 43 active layer 7
Ohmic region

Claims (8)

[Claims] 1. A semiconductor light emitting device comprising at least two independently biasable (In-Ga-Al-P) mixed crystal light emitting layers formed on the same semiconductor substrate. element. 2. The semiconductor light emitting device according to claim 1, wherein each of the light emitting layers emits light at an arbitrary emission wavelength within a predetermined range depending on a mixed crystal composition ratio. 3. An intervening layer having the same conductivity type and composition as the substrate is formed between the substrate and the cladding layer made of the mixed crystal layered on the substrate. 1. The semiconductor light emitting device according to 1. 4. A current diffusion layer for diffusing a current applied to the electrode is formed between an electrode that applies a bias to the light emitting layer and a cladding layer made of the mixed crystal formed in contact with this electrode. 2. The semiconductor light emitting device according to claim 1, wherein the semiconductor light emitting device comprises: 5. A first cladding layer made of an (In-Ga-Al-P)-based mixed crystal of the first conductivity type and a cladding layer of the second conductivity type on one surface of the semiconductor substrate of the first conductivity type. a first light emitting layer made of the same type of mixed crystal; a second cladding layer made of the same type of mixed crystal of a second conductivity type; a second light emitting layer made of the same type of mixed crystal of a second conductivity type; A third cladding layer made of the same type of mixed crystal of one conductivity type is sequentially stacked by a vapor phase epitaxy method, the second cladding layer, the second light emitting layer,
selectively removing the third cladding layer to expose a part of the second cladding layer; A method for manufacturing a semiconductor light emitting device, comprising forming an electrode thereon for applying a bias voltage to the first and second light emitting layers. 6. A first cladding layer made of an (In-Ga-Al-P)-based mixed crystal of the first conductivity type and a cladding layer of the second conductivity type on one surface of the semiconductor substrate of the first conductivity type. a first light emitting layer made of the same type of mixed crystal; a second cladding layer made of the same type of mixed crystal of a second conductivity type; a second light emitting layer made of the same type of mixed crystal of a second conductivity type; A third cladding layer made of the same type of mixed crystal of one conductivity type is sequentially formed by a vapor phase growth method, and by introducing impurities, the second cladding layer, the second light-emitting layer, and the third cladding layer are formed. selectively conductive, and the other surface of the semiconductor substrate, the conductive third cladding layer, and the non-conductive third cladding layer.
A method of manufacturing a semiconductor light emitting device, comprising forming an electrode on the cladding layer of the semiconductor light emitting device to apply a bias voltage to the first and second light emitting layers. 7. The method of manufacturing a semiconductor light emitting device according to claim 6, further comprising the step of forming, by etching, a groove that separates a region into which impurities are introduced and a region into which impurities are not introduced. 8. A first cladding layer made of an (In-Ga-Al-P)-based mixed crystal of the first conductivity type and a cladding layer of the second conductivity type on one surface of the semiconductor substrate of the first conductivity type. A first light-emitting layer made of the same type of mixed crystal and a second cladding layer made of the same type of mixed crystal of a second conductivity type are sequentially laminated by a vapor phase growth method, and each of the laminated layers is selectively removing and coating the remaining second cladding layer;
A third cladding layer made of the same type of mixed crystal of a first conductivity type, a second light emitting layer made of the same type of mixed crystal of a second conductivity type, and a fourth cladding layer of a second conductivity type are sequentially formed in a vapor phase. A laminate consisting of the first and second cladding layers and the first light emitting layer is formed by forming a laminate by a growth method and selectively removing the third and fourth cladding layers and the second light emitting layer formed in a laminate. A laminated structure consisting of a third and fourth cladding layer and a second light emitting layer are formed independently and separately on the semiconductor substrate, and the layered structure consisting of a third and fourth cladding layer and a second light emitting layer is formed independently and separately on the semiconductor substrate. on the second cladding layer and on the fourth cladding layer,
A method for manufacturing a semiconductor light emitting device, comprising forming an electrode for applying a bias voltage to the first and second light emitting layers.