JP2901823B2 - Light emitting diode - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light emitting diode used for display and transmission.

[0002]

2. Description of the Related Art In a light emitting diode (LED), it is very important to effectively extract internally generated light to the outside, that is, to improve external emission efficiency. Because, L
Since the refractive index of the semiconductor constituting the ED is extremely high, the critical angle at which the light is totally reflected at the light exit surface is reduced. When the light exit surface is flat, only light having a limited angle within the critical angle is emitted to the outside. Because it does not.

[0003] Conventionally, there is a light emitting diode shown in FIG. 18 for improving the above-mentioned external emission efficiency. This light-emitting diode allows a current to flow from the electrode 8 to the p-type AlGaAs substrate 1 via the p ⁺ -type layers 4Q and 3Q and the p-type AlGaAs layer 2, and from the substrate 1 to the p-type AlGaAs layer 2. A current is applied to the electrode 7 via the n-type AlGaAs light emitting layer 3 and the n ⁺ -type AlGaAs cap layer 4. Then, the light emitting layer 3 is caused to emit light by the current and light is extracted from the substrate 1 to the outside. In FIG. 18, Q is a peripheral portion, P is a central portion, 6 is a SiO ₂ film, and 5 is a groove.

In this light emitting diode, the light emitting surface of the substrate 1 is formed in a dome shape, and the light emitting region is limited to a central portion P facing the center of the dome shaped light emitting surface. Light is incident on the surface substantially perpendicularly, and light can be effectively extracted to the outside.

[0005] The light emitting diode is manufactured as follows. Referring to FIG. 18 upside down, first, p
On a p-type AlGaAs substrate 1, a p-type AlGaAs layer 2 and an n-type A
An lGaAs light emitting layer 3 and an n ⁺ type GaAs cap layer 4 are formed in this order. Subsequently, by diffusing Zn into the peripheral portion Q,
The light emitting layer 3 and the cap layer 4 in the peripheral portion Q are changed to p ⁺ -type conductivity to form p ⁺ -type layers 3Q and 4Q. further,
A groove 5 is formed between the peripheral portion Q and the central portion P, and the groove 5 is covered with a SiO ₂ film 6. Then, the electrodes 7 and 8 are formed on the surfaces of the central portion P and the peripheral portion Q. Thereafter, the substrate is divided into chip units as shown in FIG. 18, and the substrate 1 is polished for each chip to make the light emitting surface into a dome shape.

[0006]

Incidentally, in the above-mentioned conventional light emitting diode, in order to extract the light generated by the light emitting layer 3 to the outside, the light must pass through the substrate 1. Therefore, the wavelength is shorter than the absorption edge of the substrate 1,
When light that cannot pass through the substrate 1 is to be extracted to the outside, both the light emitting surface and the light emitting layer 3 are provided below the substrate 1 in FIG. 18 so that the light emitting surface and the light emitting layer 3 do not sandwich the substrate 1. You need to do that. However, in this case, in the structure shown in FIG. 18, the light emitting area is limited by the groove 5, so that the light emitting surface is formed in a convex shape, and the light emitting area is limited to the central portion of the light emitting surface. However, there is a problem that the external emission efficiency cannot be improved.

Accordingly, an object of the present invention is to extract light to the outside without passing through the substrate, to set the emission wavelength regardless of the light absorption region of the substrate, and to improve the efficiency of light emission to the outside. It is an object of the present invention to provide a light emitting diode which can be used.

[0008]

According to a first aspect of the present invention, there is provided a light emitting diode comprising a semiconductor substrate of a first conductivity type and a semiconductor layer of at least a first conductivity type. A light emitting diode that emits light generated near the interface between the semiconductor layer of the first conductivity type and the semiconductor layer of the second conductivity type to the outside from the semiconductor layer of the second conductivity type. The cross section of the semiconductor layer of the second conductivity type cut on a plane perpendicular to the surface of the substrate has a convex shape, and the surface pattern viewed from above the convex shape has a stripe shape. Between the semiconductor layer of the first conductivity type and the semiconductor substrate of the first conductivity type.
A current blocking layer having an opening is provided in a region facing the center of the conductive semiconductor layer.

According to a second aspect of the present invention, in the light emitting diode according to the first aspect, an opening of the current blocking layer is provided along a center axis of the stripe pattern.

According to a third aspect of the present invention, at least a first conductive type semiconductor layer and a second conductive type semiconductor layer are formed on a first conductive type semiconductor substrate.
A light emitting diode in which conductive semiconductor layers are sequentially stacked, and light generated near an interface between the first conductive semiconductor layer and the second conductive semiconductor layer is emitted from the second conductive semiconductor layer to the outside. And forming the second conductive type semiconductor layer in a convex shape so that a cross section obtained by cutting the second conductive type semiconductor layer in a plane perpendicular to the surface of the substrate has a convex shape;
A current blocking layer having an opening in a region opposed to the center of the convex second conductive type semiconductor layer is provided between the second conductive type semiconductor layer and the first conductive type semiconductor substrate. ,
The convex second conductivity type semiconductor layer has a surface pattern viewed from above, a primary branch stripe from a pad portion of a surface electrode, a primary branch stripe to a secondary branch stripe from the primary branch stripe, and a second secondary stripe. A multi-stage branch tree branch in which at least a tertiary branch stripe branches from the next branch stripe;
An opening of the current blocking layer is provided at least in a region opposed to the center of the tip of the branch of the multi-tiered surface pattern.

According to a fourth aspect of the present invention, in the light emitting diode according to the first or second aspect, the current blocking layer is provided between the first conductive type semiconductor substrate and the interface. It is characterized in that it is a type semiconductor layer or a high resistance semiconductor layer.

According to a fifth aspect of the present invention, in the light emitting diode according to the first or second aspect, a plurality of second conductivity type semiconductor layers are provided on the interface, and the current blocking layer is formed of the plurality of second conductivity type semiconductor layers. It is a first conductivity type semiconductor layer or a high resistance semiconductor layer provided between the second conductivity type semiconductor layers.

According to a sixth aspect of the present invention, in the light emitting diode of the third aspect, the current blocking layer is provided between the first conductivity type semiconductor substrate and the interface. Or a high-resistance semiconductor layer.

According to a seventh aspect of the present invention, in the light emitting diode according to the third aspect, a plurality of second light emitting diodes are provided on the interface.
A conductive semiconductor layer is provided, and the current blocking layer is a first conductive semiconductor layer or a high resistance semiconductor layer provided between the plurality of second conductive semiconductor layers.

The invention according to claim 8 is a semiconductor device having at least a first conductivity type semiconductor layer and a second conductivity type semiconductor layer on a first conductivity type semiconductor substrate.
Conductive first and second semiconductor layers are sequentially stacked, and the first
A light emitting diode which emits light generated near the interface between the conductive semiconductor layer and the second conductive semiconductor layer to the outside from the second conductive second semiconductor layer, the light emitting diode being a plane perpendicular to the surface of the substrate. The second semiconductor layer of the second conductivity type is formed in a convex shape so that the cross section obtained by cutting the second semiconductor layer of the second conductivity type is formed in a convex shape, and the first semiconductor layer of the second conductivity type and the second semiconductor layer are formed. A first conductive type semiconductor layer or a high resistance semiconductor layer between the first conductive type semiconductor layer and the second conductive type second conductive type semiconductor layer.
A current blocking layer having an opening in a region facing the center of the semiconductor layer; and a current injection layer having an opening communicating with the opening is provided between the current blocking layer and the second semiconductor layer. An electrode is provided on the current injection layer exposed from the second semiconductor layer.

According to a ninth aspect of the present invention, in the light emitting diode according to the eighth aspect, the opening of the current injection layer and the opening of the current blocking layer are continuous.

According to a tenth aspect of the present invention, in the light emitting diode according to the eighth or ninth aspect, the current injection layer includes a lower layer in contact with the current blocking layer, and an upper layer formed on the lower layer. Including, the band gap of the upper layer,
The band gap is an intermediate value between the band gap of the lower layer and the band gap of the second semiconductor layer of the second conductivity type.

According to an eleventh aspect of the present invention, in the light emitting diode according to the tenth aspect, the upper layer of the current injection layer is removed at a peripheral portion of the second semiconductor layer of the second conductivity type having a convex shape, The electrode is provided on the lower layer of the current injection layer exposed thereby.

According to a twelfth aspect of the present invention, in the light emitting diode according to the eighth aspect, the current injection layer is formed on the first layer in contact with the current blocking layer and on the first layer. A second layer, wherein the first layer has an opening that is continuous with the opening of the current blocking layer, and the second layer has an opening that opens over a wider range than the opening of the first layer. It is characterized by having a portion.

According to a thirteenth aspect of the present invention, in the light emitting diode according to the twelfth aspect, the first of the current injection layers is provided.
The layer and the current blocking layer are characterized by being transparent to the emission wavelength at the interface.

According to a fourteenth aspect of the present invention, in the light emitting diode according to any one of the eighth to thirteenth aspects, the convex second conductive type second semiconductor layer has a stripe pattern as viewed from above. Wherein the opening of the current blocking layer is provided along the center axis of the stripe pattern.

[0022]

According to the first aspect of the present invention, only the opening of the current blocking layer allows current to pass therethrough. Therefore, the current blocking layer is provided in a region facing the opening,
A light emitting region near an interface between the first conductivity type semiconductor layer and the second conductivity type semiconductor layer is limited. That is, the current blocking layer limits the light emitting region to the vicinity of the interface in a region facing the center of the second conductivity type semiconductor layer having the convex light emitting surface. Therefore, according to the present invention, the light can be made to approach the vertical incidence on the convex light emission surface, and the efficiency of light emission to the outside can be improved.

Regarding the improvement of the light emission efficiency, the second
The case where the light emitting surface of the conductive semiconductor layer has a dome shape as an example of a convex shape will be described in detail. FIG.
(A) is a ray a, emitted from the center O of the dome-shaped light emitting surface.
The path of b and c is shown. Since each of the light beams a, b, and c is perpendicularly incident on the light exit surface, most of the light emitted upward exits without being refracted or reflected. On the other hand, FIG.
4 shows paths of light rays d, e, and f emitted from a peripheral position A shifted from the position A. The ray e is obliquely incident on the light exit surface and is totally reflected and is not emitted to the outside. The other light beams d and f are also refracted on the surface and the emission direction is bent. As described above, light emitted from the center O of the dome-shaped emission surface has higher external emission efficiency. Specifically, when the internal and external refractive indices of the dome surface are set to 3.1 and 1.5, respectively, the calculated value of the external emission efficiency is 42.5 when only the center O emits light.
%, And 16.4% when the light is uniformly emitted as a whole.
That is, in this case, by limiting the light emitting region to the center, the external emission efficiency is increased by a factor of 2.6. This tendency also holds when the light emitting surface is not a dome shape but a convex shape such as a mesa shape.

According to the invention, light is extracted from the interface on the substrate to the outside through the second conductivity type semiconductor layer on the interface, so that the light generated at the interface is transmitted to the substrate. It can be taken out without passing through, and the emission wavelength can be set regardless of the light absorption region of the substrate.

Further, according to the present invention, light can be emitted from the two light emission surfaces on both the left and right sides of the stripe shape of the second conductive type semiconductor layer having the stripe-shaped surface pattern.

According to the second aspect of the present invention, since the opening of the current blocking layer extends along the center axis of the stripe pattern, the amount of light emitted from the light emission surface having the stripe shape can be increased.

According to the third aspect of the present invention, at each branch tip of the multi-stage resin-like surface pattern of the convex second conductivity type semiconductor layer having a multi-stage tree-like surface pattern, the right and left sides in the branch direction are set. Light can be emitted from three surfaces, the side surface and the front side surface.

According to the fourth and sixth aspects of the present invention, since the current blocking layer is provided below the interface, the current blocking layer blocks light traveling from the interface to the second conductivity type semiconductor layer. Absent.

According to the fifth and seventh aspects, since the current blocking layer having the opening is provided above the interface, the interface and the layer below the interface are formed flat on a flat substrate. it can. Therefore, the quality of the interface can be easily improved.

According to the eighth aspect, the current reaches the interface from the electrode on the current injection layer via the current injection layer, the second conductive type second semiconductor layer and the first semiconductor layer. . The current reaching the interface depends on the first semiconductor layer and the second semiconductor layer.
The current is limited to the current passing through the opening of the current blocking layer between the semiconductor layers. Therefore, the current is reduced to the interface in the region facing the center of the second semiconductor layer, and only the interface in the region emits light. The light generated by the interface is the second light.
The light exits from the convex light exit surface of the semiconductor layer.

As described above, the light emitting region at the interface is the second region.
Light from the light emitting region is limited to a region facing the center of the semiconductor layer, and enters the convex light emitting surface of the second semiconductor layer. Therefore, the incidence of the light on the light emission surface can be made closer to the vertical incidence, and the light emission efficiency can be improved.

Further, since the electrode is provided on the current injection layer exposed from the second semiconductor layer, the electrode does not cover the second semiconductor layer. Therefore, light loss can be reduced and light emission efficiency can be improved as compared with the case where the electrode is formed on the second semiconductor layer.

Further, since light is extracted outside without passing through the substrate, the emission wavelength can be set regardless of the light absorption region of the substrate.

According to the ninth aspect, since the opening of the current injection layer and the opening of the current blocking layer are continuous, the opening of the current injection layer and the opening of the current blocking layer are continuous. Can be simultaneously formed, which simplifies the manufacturing process.

According to a tenth aspect, the current injection layer includes an upper layer and a lower layer, and the band gap of the upper layer is the same as the band gap of the lower layer and the second gap of the second conductivity type.
Since the value is an intermediate value with respect to the band gap of the semiconductor layer, the electric resistance between the current injection layer and the second semiconductor layer can be reduced.

According to the eleventh aspect, since the electrode is provided on the lower layer of the current injection layer exposed from the second semiconductor layer having the convex shape, the electrode is provided between the current injection layer and the electrode. Can be reduced in electric resistance.

According to the twelfth aspect, since the second layer of the current injection layer has an opening wider than the opening of the first layer, the second layer has passed through the opening of the first layer. Light is not blocked by the second layer. Therefore, light emission efficiency is improved.

According to the thirteenth aspect, the first layer of the current injection layer and the current blocking layer are transparent with respect to the emission wavelength at the interface, and thus do not block light generated at the interface. Therefore, light emission efficiency is improved.

According to the fourteenth aspect of the present invention, the two light-emitting surfaces on both the left and right sides of the stripe shape of the second semiconductor layer of the second conductivity type having the stripe-shaped surface pattern and the stripe shape are formed. Light can be emitted from the upper surface.

[0040]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the light emitting diode of the present invention will be described in detail with reference to embodiments.

FIGS. 1A to 1C show the AlGaI of the first embodiment.
FIG. 2 is a cross-sectional view illustrating a manufacturing process of the nP-based LED, and FIG.
FIG. 2A is a plan view corresponding to FIG. 1A, and FIG.
FIG. 2 is a plan view corresponding to FIG. In the following description, the _{(Al y Ga 1-y)} 0.5 In 0.5 P AlGaInP,
AlInP the Al _0.5 In _0.5 P, GaInP the Ga _0.5 In _0.5 P
Abbreviated.

First, the manufacturing process for manufacturing the LED of the above embodiment will be described. As shown in FIG. 1A, an n-type GaAs current blocking layer 11 is formed on a p-type GaAs substrate 10, and the current blocking layer 11 is partially removed to form an opening 12. FIG. 2A is a plan view corresponding to FIG.
FIG. 1A is a sectional view taken along line AA of FIG.

Next, as shown in FIG. 1B, p-type AlGa
InP (y = 0.7) cladding layer 13 and undoped AlGaI
nP (y = 0.5) light emitting layer 14 and n-type AlGaInP (y = 0.
7) A cladding layer 15 and an n-type GaAs contact layer 16 are sequentially formed on the entire surface. Thereafter, a surface electrode 17 is formed on the contact layer 16, and a back electrode 18 is formed on the lower surface of the substrate 10.

Next, a resist pattern is formed on the surface electrode 17 by photolithography, the surface electrode 17 is etched with a first etchant, and the n-type GaAs contact layer 16 and the n-type AlGaI are etched with a second etchant.
By etching the nP cladding layer 15, the n-type AlGaInP cladding layer 15 is formed into a mesa shape as shown in FIG. As shown in FIG. 1C, the cladding layer 15 is formed such that the opening 12 of the current blocking layer 11 faces the center of the mesa-shaped cladding layer 15.
Is etched. FIG. 2B is a plan view of the LED shown in FIG. FIG. 1C is a sectional view taken along the line BB of FIG.
It is.

As described above, in the above embodiment, the n-type AlGaInP clad layer 15 is formed in a mesa shape, and the opening 12 of the current blocking layer 11 is formed in a region facing the center of the mesa-shaped clad layer 15. Was formed. Therefore,
The light-emitting region of the light-emitting layer 14 can be limited to a region facing the center of the mesa-shaped clad layer 15. Therefore, the light generated by the light emitting layer 14 can be made closer to the vertical incidence on the light emitting surface 15a of the mesa-shaped cladding layer 15. Therefore, the light can be prevented from being refracted or reflected by the light exit surface 15a, and the light exit efficiency can be improved. Also,
Since the light generated by the light emitting layer 14 is extracted to the outside without passing through the substrate 10, the emission wavelength can be set regardless of the light absorption region of the substrate 10. Further, the current blocking layer 11 of the above embodiment also has a function of suppressing invalid light emission immediately below the surface electrode pad portion 17P of the surface electrode 17 shown in FIG.

In the above embodiment, the current blocking layer 1
1. The etching of the cladding layer 15 and the contact layer 16 may be wet etching or RIBE (reactive ion beam etching).

In the above embodiment, the cladding layer 1
Etching 5 is performed on the undoped AlGaInP light emitting layer 1
Although stopped just before step 4, the light emitting layer 14 may be etched. Further, the above etching may reach the p-type AlGaInP cladding layer 13.

In the above embodiment, not only the cladding layer 15 from which light is emitted, but also the n-type G
Although the aAs contact layer 16 is also formed into a mesa shape, the contact layer 1 which is an opaque layer provided for improving electrical characteristics is formed.
The light emitting efficiency can be improved by forming only the cladding layer 15 into a mesa shape without having to form the mesa shape of the cladding layer 6.

The above embodiment is a basic configuration example of an LED, and the n-type GaAs current blocking layer 11 of the above embodiment is an example.
Between the p-type AlGaInP cladding layer 13 and the p-type Ga
Crystallinity and electrical characteristics may be improved by forming an As buffer layer and a p-type GaInP intermediate bandgap layer. Further, an n-type GaInP intermediate band gap layer may be formed between the n-type AlGaInP cladding layer 15 and the n-type GaAs contact layer 16 to improve electrical characteristics.

The front electrode 17 and / or the back electrode 18 are formed of the cladding layer 15 and the contact layer 16.
May be formed after mesa etching.

In the above embodiment, AuGe is used as the material of the surface electrode 17, but other n-type ohmic electrodes may be used. Although AuZn is used as the material of the back electrode 18, other p-type ohmic electrodes may be used.

The conductivity type of the substrate 10 may be n-type or p-type. However, when the conductivity type of the substrate 10 is n-type, the current blocking layer 11 must be p-type, so that the current blocking layer 11 is more optimal than when the current blocking layer 11 is n-type. It is necessary to increase the thickness.

In the above embodiment, each of the semiconductor layers 11 and
13 to 16 were formed by MOCVD (metalorganic vapor phase epitaxy), but the above semiconductor layers were formed by MBE (molecular beam epitaxy), VPE (vapor phase epitaxy) or LPE (liquid phase epitaxy). May be formed.

The pn junction of the above embodiment may be formed during crystal growth, or may be formed by diffusing a dopant after crystal growth.

In the above embodiment, the junction at the interface of the light emitting layer 14 is a double hetero junction, but the junction may be a single hetero junction or a homo junction.

The light emitting layer 14 and the cladding layer 1
The materials 3 and 15 are not limited to AlGaInP, but include AlGaAs, GaAsP, GaP, AlGaN, and InGaA.
A group III-V compound semiconductor such as sP may be used.
It may be a II-VI compound semiconductor such as CdSeTe or a chalcopyrite semiconductor such as CuAlSSe or CuGaSSe. The material of the substrate 10 is
It is not limited to GaAs, but may be GaP, InP, sapphire, or the like. Further, the substrate 10 may be opaque or transparent to light having an emission wavelength.

Next, a second embodiment is shown in FIGS. FIG. 3 is a sectional view taken along line CC of FIG. 4B, which is a plan view.

Referring to FIG. 3, the LED of the second embodiment will be described.
Will be described. First, p-type AlInP and p-type AlGaInP (y = 0.6) are formed on a p-type GaAs substrate 30.
Are alternately laminated, and a reflective layer 31 which is an alternate multilayer film and an n-type AlInP current blocking layer 32 are sequentially formed. Next, n-type A
An opening 33 is formed in the lInP current blocking layer 32. The opening 33 is arranged so as to face the center of the tip of the multi-stage branch mesa shape manufactured in a later step. FIG. 4A shows a plan view of this manufacturing stage.

Next, the p-type AlGaInP (y = 0.7) cladding layer 34 and the undoped AlGaInP (y = 0.5)
5, an n-type AlGaInP (y = 0.7) cladding layer 36 and an n-type GaAs contact layer 37 are sequentially formed on the entire surface. next,
A front electrode 38 is formed on the contact layer 37, and a back electrode 39 is formed on the lower surface of the substrate 30.

Next, a resist pattern is formed on the surface electrode 38 by photolithography, the surface electrode 38 is etched by a first etchant, and the n-type GaAs contact layer 37 and the n-type AlGaI are etched by a second etchant.
The nP cladding layer 36 is etched. Thus, FIG.
As shown in the figure, the cladding layer 36 is formed in a mesa shape.

As shown in FIG. 4B, which is a plan view, the mesa-shaped protrusion 40 including the cladding layer 36 is
From the pad portion 38a of the first branch 51a, 51b, 51c, 51d
Has branched. Each of the first branches 51a to 51d branches into three second branches. For example, from the first branch 51a, the second branches 52a, 52b, 5
2c is branched. Further, three third branches are branched from each second branch. For example, the third branch 53a, 53b, 53c branches from the second branch 52b. As described above, in the above-described embodiment, the mesa-shaped convex portion 40 including the clad layer 36 has a dendritic shape having multiple branches.

According to the above-described embodiment, similarly to the first embodiment, the light generated by the light emitting layer 35 can be made to approach normal incidence to the light emitting surface 36a of the mesa-shaped cladding layer 36, Light emission efficiency to the outside can be improved.

In addition, according to the above embodiment, the cladding layer 36 at the tip of each branch has a front side surface, a left side surface, and a right side surface with respect to the branching direction, as shown at Z in FIG. 4B. Light can be emitted from three side surfaces. Therefore, according to the above embodiment, a large number of branch tip portions shown in the Z portion of FIG. 4B can be easily formed, and the light emission efficiency can be particularly improved.

In the above embodiment, since the multilayer reflective film 31 is formed on the substrate 30, the light emitting layer 35
Light traveling toward zero can be reflected by the multilayer reflective film 31 and emitted from the light exit surface 36a of the cladding layer 36.

The current blocking layer 32 is made of AlGaIn
It is made of AlInP, which has a larger band gap than P,
Since the light emission wavelength of the lGaInP light emitting layer 35 is made transparent, the light traveling from the light emitting layer 55 to the multilayer reflective film 31 is not blocked by the current blocking layer 32.

The second embodiment can be modified in the same manner as the first embodiment.

Next, the ZnCdSe-based LE of the third embodiment
D is shown in FIG. This embodiment is formed as follows. First, on the n-type GaAs substrate 60 by MBE method, undoped and n-type ZnSSe buffer layer 61 and the n-type ZnSe cladding layer _{62 Zn 1-x Cd x Se} (x = 0.2) strained quantum well active layer 63 p-type ZnSe first cladding layer 64 and n
A type ZnSe current blocking layer 65 is formed in order. Next, n
An opening 71 is formed by partially removing the type ZnSe current blocking layer 65 by etching. The opening 71 is formed in a region facing the center of the mesa-shaped portion 70 to be formed in a later step.

Next, the p-type ZnSe second cladding layer 66 and p-type ZnSe
A type GaAs contact layer 67 is formed in order. And
A front electrode 68 is formed on the contact layer 67, and a back electrode 69 is formed on the lower surface of the substrate 60.

Next, a resist pattern is formed on the surface electrode 68 by photolithography, the surface electrode 68 is etched with a first etchant, and the p-type GaAs contact layer 67 and the p-type ZnSe second layer are etched with a second etchant. The cladding layer 66 is etched. By this etching, the second clad layer 66 is formed into a mesa shape, and a mesa-shaped portion 70 including the second clad layer 66 is formed.

According to the above embodiment, the following effect can be obtained in addition to the light emission efficiency improving effect similar to that of the first embodiment. That is, in the above embodiment, since the current blocking layer 65 having the opening 71 is formed on the light emitting layer 63, the light emitting layer 63 and the semiconductor layer below the light emitting layer 63 are continuously formed on the substrate 60 flat. The light emitting layer 63 of good quality can be easily obtained.

In the third embodiment, the structure in which the current blocking layer is formed on the light emitting layer is employed for the ZnCdSe LED, but the above structure may be applied to the AlGaInP LED. Conversely, the structures of the first and second embodiments in which the current blocking layer is formed below the light emitting layer may be adopted for a ZnCdSe LED.

In the above embodiment, the mesa-shaped portion 7
Although the surface pattern of No. 0 has the same stripe mesa shape as in the first embodiment, the surface pattern of the mesa-shaped portion 70 may have the same multi-stage branch mesa shape as in the second embodiment.

Further, other points of the third embodiment can be changed in the same manner as those of the first and second embodiments. For example, a reflection film can be formed below the light emitting layer to improve the external emission efficiency.

The following changes are also possible. That is, the substrate material may be ZnSe or the like other than GaAs, and may be opaque or transparent with respect to the emission wavelength.

The light emitting layer 63 is composed of Zn _1-x Cd _x Se (x =
0.2), but the value of x is not particularly limited. For example, x =
It may be set to 0 and the light emitting layer 63 may be made of ZnSe. Further, the light emitting layer may have, for example, a ZnSe / ZnCdSe multiple quantum well structure.

Further, instead of the n-type ZnSSe buffer layer 61, an n-type InGaAs buffer layer may be used.
It may be a type ZnS / ZnSe strained superlattice layer.

The semiconductor layers 61 to 66 are formed by MBE.
Formed by molecular beam epitaxy (MOCVD)
(Organic metal vapor phase epitaxy), VPB (vapor phase epitaxy) or LPE (liquid phase epitaxy). Also, pn
The junction may be formed during crystal growth, or may be formed by diffusing a dopant after crystal growth.

Next, FIG. 6 shows the AlGaA according to the fourth embodiment.
1 shows a cross section of an s-based LED. FIG. 7 shows the surface of the fourth embodiment.

The manufacturing process of the fourth embodiment will be described below. First, an n-type current blocking layer 81 is formed on a p-type GaAs substrate 80 by the LPE method (liquid phase growth method).
An opening 89 as a current path is provided by etching away the center of 1. Subsequently, a p-type AlGaAs cladding layer 82, a p-type GaAs active layer 83, an n-type AlGaAs cladding layer 84, and an n-type GaAs cap layer 85 are sequentially formed by the LPE method. At this time, in the LPE method, the thickness of the n-type AlGaAs cladding layer 84 was made very thick to 100 μm, taking advantage of the fact that the growth of a thick film was easy.

Next, the surface electrode 8 is formed on the cap layer 85.
After the formation of 6, the surface is etched from the surface to form a conical convex portion 88. The convex-shaped portion 88 includes a convex-shaped n-type cladding layer 84. Next, the wafer formed as described above is wrapped from the back surface of the substrate 80 to reduce the overall thickness of the wafer to 200 μm. Thereafter, a back electrode 87 is formed on the lower surface of the substrate 80.

Next, the wafer is divided into chips of about 200 μm square. FIG. 7 shows the surface of the chip thus manufactured.

According to the fourth embodiment, the following effect is obtained in addition to the effect of improving the external light emission efficiency similar to that of the first embodiment. That is, in the above embodiment, since only one conical convex portion 88 is provided, light emitted from one convex shape portion is different from the case where a plurality of convex shape portions are provided. There is no obstruction by the convex shaped part. Therefore, light loss is further reduced, and the efficiency of light emission to the outside can be further improved.

The single convex-shaped portion shown in the above embodiment is
It may be formed by the LPE method, the MOCVD method or the MBE method. In the case of forming by the MOCVD method or the MBE method, for example, if the size of the chip itself is reduced, the thickness of the cladding layer can be reduced, and the chip can be easily manufactured.

The fourth embodiment can be modified as shown in the other embodiments. For example, changes such as reversing the n-type and p-type, arranging the current blocking layer on the light emitting layer, and providing a semiconductor multilayer reflective film layer under the light emitting layer are possible. Further, the material for forming each semiconductor layer can be the material shown in the first embodiment. In particular, GaAsP, GaP, or InG
It is preferable to grow a semiconductor layer made of aAsP or the like on a substrate made of GaAs, GaP, InP, or the like by an LPE method or the like.

Next, a fifth embodiment is shown in FIG. This fifth
The embodiment is an AlGaInP-based LED. FIG. 9 (B)
2 shows a surface of the LED as viewed from above. FIG.
FIG. 3B is a sectional view taken along line AA of FIG.

First, the present embodiment will be described while sequentially describing the steps of the process of manufacturing the embodiment.

First, on an n-type GaAs substrate 90, an n-type GaAs
InP intermediate band gap layer 91 and n-type AlGaInP (y
= 0.7) cladding layer 92 and undoped AlGaInP (y
= 0.5) a light emitting layer 93, a p-type AlGaInP (y = 0.7) first cladding layer 94, an n-type GaAs current blocking layer 95,
A type GaAs contact layer 96 and a p-type GaInP intermediate band gap layer 97 are sequentially formed on the entire surface. Current blocking layer 95
Contact layer 96 which is two p-type layers formed on
And the intermediate band gap layer 97 constitute a current injection layer.

Next, a resist pattern is formed on the p-type GaInP intermediate band gap layer 97 by photolithography, and the p-type GaInP intermediate band gap layer 97 is formed.
Then, the p-type GaAs contact layer 96 and the n-type GaAs current blocking layer 95 are sequentially etched to form an opening 101. The opening 101 is an opening that communicates the intermediate band gap layer 97, the contact layer 96, and the current blocking layer 95. FIG. 9A shows a surface pattern viewed from above at this manufacturing stage.

Next, a p-type AlGaInP (y = 0.7) second cladding layer 98 is formed on the surface where the opening 101 is formed.

Next, the p-type AlGaInP second cladding layer 9
8, a resist pattern is formed by photolithography, and a p-type AlGaInP second cladding layer 98 and p-type AlGaInP
The mesa-shaped portion 102 is formed by etching the GaInP intermediate band gap layer 97. Further, the p-type GaAs around the mesa-shaped portion 102 is formed by the etching.
The contact layer 96 is exposed. The mesa-shaped part 102
Is formed so as to face the opening 101.

Thereafter, a surface electrode 99 is vapor-deposited on the entire surface from above, and then the surface electrode 99 vapor-deposited on the mesa-shaped portion 102 is removed by etching so that the surface electrode 99 is vapor-deposited except on the p-type GaAs contact layer 96. The removed surface electrode 99 is removed. Further, a back electrode 100 is deposited on the lower surface of the substrate 90.

The current path of the light emitting diode of the fifth embodiment will be described. The current path on the p-type semiconductor side is shown by a dotted line in FIG. The current flows from the surface electrode 99 to the p-type GaAs contact layer 96. Thereafter, the current is changed to n-type Ga
It does not flow to the As current blocking layer 95 but flows to the p-type AlGaInP second cladding layer 98 via the p-type GaInP intermediate band gap layer 97. The current flows from here through the opening 101 into the p-type AlGaInP first cladding layer 94, and reaches the undoped AlGaInP light emitting layer 93 immediately below, to emit light.

As described above, this AlGaInP-based LED
Since the p-type contact layer 96 is exposed around the mesa-shaped portion 102 and the surface electrode 99 is formed on the exposed portion of the contact layer 96 during the etching for forming the mesa-shaped portion 102, There is no need to form an electrode on top. Therefore, according to the fifth embodiment, light can be effectively emitted also from the upper portion of the mesa-shaped portion 102.

According to the above embodiment, the LED surface is processed into a mesa shape, the second clad layer 98 is formed into a mesa-shaped convex shape, and the current blocking layer 95 is provided.
Since the light-emitting layer 93 emits light only in a region facing the center of the mesa-shaped portion 102, the external emission efficiency of light can be further improved.

In the above embodiment, the current blocking layer 95, the contact layer 96 and the band gap layer 97 constituting the current injection layer can be formed simultaneously, and the formation of the opening 101 allows the current blocking layer 95 and the current Since the injection layer can be simultaneously opened, the manufacturing process can be simplified.

This embodiment may be modified as follows.

The method of etching the semiconductor layers 95, 96, 97, 98 may be wet etching or RIBE (reactive ion beam etching).

The material of the n-type current blocking layer 95 is GaAs which absorbs the emission wavelength. However, AlGaAs in the indirect transition region which is weakly absorbing at the emission wavelength, or AlGaInP (y = 0.7) or AlInP, in which case the light absorption loss can be reduced.

Although the p-type contact layer 96 (the lower layer of the current injection layer) is made of GaAs that absorbs the emission wavelength, it is made of AlGaAs in an indirect transition region that is weakly absorbing at the emission wavelength, or transparent at the emission wavelength. It may be AlGaInP (y = 0.7) or AlInP, which can reduce light absorption loss. However, GaAs has the lowest contact resistance to the surface electrode 99 among the above materials.

An n-type GaAs buffer layer may be formed between the n-type GaAs substrate 90 and the n-type GaInP intermediate band gap layer 91 in order to improve the crystallinity of the semiconductor layers 91 to 97.

Further, the material of the p-type intermediate band gap layer 97 may be AlGaAs as well as GaInP, and the intermediate band gap layer 97 may not be formed.
Generally, the intermediate band gap layer is composed of two semiconductors.
(In the case of this embodiment, GaAs (contact layer 96) and AlGa
When the difference in band gap of InP (the second cladding layer 98) is large, a kind of electric resistance is generated at the interface, and therefore it is inserted to reduce the electric resistance.

In the above embodiment, AuZn was used as the material of the surface electrode 99, but other p-side ohmic electrodes may be used. Although AuGe is used as the material of the back electrode 100, another n-side ohmic electrode may be used.

As a method for patterning the surface electrode 99, a photolithography method in which a resist is patterned after the entire surface is vapor-deposited and then etched, or a metal mask having an opening corresponding to an electrode forming portion is formed by vapor deposition. Metal mask method.

The pattern of the surface electrode 99 is as follows.
It is not necessary to cover the entire exposed region of the p-type GaAs contact layer 96. For example, the exposed region may be provided only in a wide exposed portion (pad for wire bonding) in the center of FIG.

The conductivity type of the substrate 90 may be n-type or p-type. When the conductivity type of the substrate 90 is n-type,
It is necessary to make the current blocking layer 95 p-type. When the current blocking layer 95 is of the p-type, the optimum thickness of the current blocking layer 95 is larger than in the case of the n-type.

In the above embodiment, each of the semiconductor layers 91 to 91
98 was formed by MOCVD (metal organic chemical vapor deposition), but may be formed by MBE (molecular beam epitaxy), VPE (vapor phase), or LPE (liquid phase). .

The junction at the interface of the light emitting layer 93 is not limited to the double hetero junction, but may be a single hetero junction or a homo junction.

The material of the LED cladding layer is AlGa.
It is not limited to InP but AlGaAs, GaAsP, G
It may be a III-V group compound semiconductor such as aP, AlGaN, InGaAsP, etc., and ZnCdSSe, ZnCdSeTe.
Or a chalcopyrite-based semiconductor such as CuAlSSe or CuGaSSe. The substrate material is GaAs
The present invention is not limited to this, and may be GaP, InP, sapphire, or the like, and may be opaque or transparent with respect to the emission wavelength.

Next, FIG. 10 shows a sixth embodiment. The sixth embodiment is an AlGaInP LED. FIG. 10 is a cross-sectional view taken along line BB in FIG. 11B showing the surface of this embodiment viewed from above.

First, this embodiment will be described in accordance with the manufacturing process.

On a p-type GaAs substrate 110, a p-type GaInP intermediate band gap layer 111, p-type AlInP and p-type AlGa
Reflective layer 112 composed of alternating multilayer films of InP (y = 0.5)
A p-type AlGaInP (y = 0.7) cladding layer 113; an undoped AlGaInP (y = 0.4) light-emitting layer 114;
lGaInP (y = 0.7) First cladding layer 115, p-type Al
GaInP (y = 0.7) current blocking layer 116 and n-type AlGaIn
A P (y = 0.7) third cladding layer 117, an n-type AlGaAs intermediate band gap layer 118, and an n-type GaAs contact layer 119 are sequentially formed on the entire surface. The three n-type layers (the third cladding layer 117, the intermediate band gap layer 118, and the contact layer 119) formed on the current blocking layer 116 constitute a current injection layer.

Next, a first resist pattern is formed on the n-type GaAs contact layer 119 by photolithography, and the n-type GaAs contact layer 119 and the n-type AlGa
The As intermediate band gap layer 118 is sequentially etched. The opening 124 is formed by this etching.

Next, a second resist pattern is formed again by photolithography on the surface where the opening 124 has been formed, and the n-type AlGaInP third cladding layer 117 is formed.
Then, the p-type AlGaInP current blocking layer 116 is etched. By this etching, an opening 123 having an opening diameter smaller than the opening 124 is formed. FIG. 11A shows a surface pattern of the opening 123.

Next, an n-type AlGaInP (y = 0.7) second cladding layer 120 is formed on the surface where the openings 123 and 124 are formed.

Next, the n-type AlGaInP second cladding layer 1
A third resist pattern is formed on the second clad layer 20 by photolithography.
0 is etched until the n-type GaAs contact layer 119 is exposed. Thereby, the conical convex portion 125 is formed.
To form The convex-shaped portion 125 is formed such that the central portion of the conical convex-shaped portion 125 faces the opening 123.

After that, the surface electrode 121 is formed on the exposed portion of the n-type GaAs contact layer 119 around the convex shape portion 125, and the back electrode 122 is formed on the entire back surface of the substrate 110.

A current path of the light emitting diode of the sixth embodiment will be described. For convenience of explanation, the electron path (in the direction opposite to the current path) on the n-type semiconductor layer side is shown by a dotted line in FIG. Electrons are supplied from the surface electrode 121 to the n-type GaAs contact layer 119 and the n-type AlGaAs intermediate band gap layer 1.
Through 18, it flows to the n-type AlGaInP third cladding layer 117. Thereafter, the electrons do not flow to the p-type AlGaInP current blocking layer 116 but flow to the n-type AlGaInP second cladding layer 120. Further, the electrons flow into the n-type AlGaInP first cladding layer 115 through the second cladding layer 60 in the opening 123 of the current blocking layer 116, and the undoped AlGaIP immediately below the first cladding layer 115.
Light reaches the nP light emitting layer 114 to emit light. Thus, the above L
In the ED, the light emitting layer 114 facing the center of the conical convex portion 125 selectively emits light.

As described above, the AlGaInP of this embodiment
In the system LED, the surface electrode 121 has a conical convex portion 12.
5, the light can be effectively extracted from the upper surface of the conical convex portion 125 because it is disposed around the convex shape portion 125 instead of the upper surface.

Further, in the above embodiment, the current blocking layer 116 controls the current path, so that the conical convex portion 12 is formed.
5 is made to emit light only in the light emitting layer 114 in a region opposed to the central portion of the second cladding layer 120 included in the convex shape portion 125.
Becomes an incident angle close to normal incidence with respect to the light exit surface of Therefore, the external emission efficiency of light can be improved.

Further, in the above embodiment, the current blocking layer 116 is used.
In addition, the contact layer 119, the intermediate band gap layer 118, and the third cladding layer 117 constituting the current injection layer can be simultaneously formed, so that the manufacturing process is simplified.

In the sixth embodiment, the current blocking layer 1
16 and the third cladding layer 117 thereover are made of AlGaInP (y = 0.7) transparent to the emission wavelength, so that the current blocking layer 116 and the third Light that passes through the three cladding layers 117 and travels obliquely upward is present. Therefore, in the sixth embodiment, unlike the fifth embodiment, the opening is formed in two stages, and the opening 123 and the opening 124 having a larger opening diameter than the opening 123 are provided. Is a layer that absorbs
The type GaAs contact layer 119 and the n-type AlGaAs intermediate band gap layer 118 are removed around the opening 123 so that the transmitted light is not absorbed by the intermediate band gap layer 118 and the contact layer 119. Therefore, in the sixth embodiment, the external emission efficiency of light can be particularly improved. Further, in the sixth embodiment, since the multilayer reflective film 112 is formed between the light emitting layer 114 and the substrate 110, light reflected toward the substrate 110 is reflected by the reflective film 112, and the reflected light is reflected. Can be effectively extracted from the light emitting surface of the second cladding layer 120.

In the sixth embodiment, the current blocking layer 11
6 is formed into the pattern shown in FIG. 11A, so that the light emitting layer 1 facing the central portion of the conical convex portion 125 is formed.
14 and the surface pattern of the conical convex portion 125 viewed from above is shown in FIG.
As shown in FIG. 1 (B), the convex shape portion 125 is
It has a conical shape with missing peaks.

Therefore, the conical convex portion 125 shown in the present embodiment emits light from the upper surface and all the side surfaces, so that the stripe-shaped mesa shape from which light is emitted from the upper surface and the two left and right side surfaces. Fifth Example (FIG. 9)
As compared with (A), the external emission efficiency can be further increased. The surface pattern of the convex-shaped portion viewed from above may be a polygon other than a circle, such as a triangle, a quadrangle, a hexagon, and an octagon, or a substantially polygon in which those corners are rounded. And so on.

The sixth embodiment can be modified as described below.

The material of the n-type intermediate band gap layer 118 may be AlGaAs, GaInP, or the like. Also,
The intermediate band gap layer 118 may be omitted.

In the sixth embodiment, the material of the p-type current blocking layer 116 is AlGaInP, which transmits the emission wavelength. However, the material may be AlInP or AlGaAs, which is an indirect transition region having low absorption to the emission wavelength. You may.

In the sixth embodiment, the material of the n-type third cladding layer 117 (the lower layer of the current injection layer) is AlGaInP, which transmits the emission wavelength. The transition region may be made of AlGaAs or the like.

The sixth embodiment can be modified in the same manner as the modification described in the fifth embodiment.

Next, FIG. 13 shows a seventh embodiment. The seventh embodiment is a ZnCdSe LED.

The seventh embodiment will be described while sequentially explaining the manufacturing steps. First, on an n-type GaAs substrate 130, M
By the BE method, the n-type ZnSSe buffer layer 131, the n-type ZnSe cladding layer 132, and the undoped Zn _1-x Cd _x Se
(x = 0.2) strained quantum well light emitting layer 133, p-type ZnSe first cladding layer 134, and n-type ZnSe current blocking layer 135
And a p-type ZnSe third cladding layer 136 is formed in order.
Next, the n-type ZnSe current blocking layer 135 and the p-type ZnSe third cladding layer 136 are partially etched away to form the opening 1
41 is formed. The p-type third cladding layer 136 formed on the n-type current blocking layer 135 constitutes a current injection layer.

Next, a p-type ZnSe second cladding layer 137 is formed by MBE. Next, the p-type ZnSe second cladding layer 137 is processed by a method described later to form a dome-shaped portion 140 composed of the second cladding layer 137.
In forming the dome-shaped portion 140, the third cladding layer 136 around the dome-shaped portion 140 is exposed.

Next, a front surface electrode 138 is formed on the exposed p-type ZnSe third cladding layer 136, and a back surface electrode 139 is formed on the entire back surface of the substrate 130.

Here, a method of manufacturing the dome-shaped portion 140 will be described in detail with reference to the schematic sectional view of FIG. First, the cladding surface 160 of the second cladding layer 137
A positive resist is applied thereon, and a photomask on which a circular light-shielding pattern is drawn is exposed apart from the positive resist. As a result, the light goes around the circular pattern of the photomask, and the light intensity decreases as approaching the center of the circle. Therefore, when the positive resist is developed, the resist pattern 15 is thick at the center and thin at the periphery.
1 can be formed. Next, using the resist pattern 151 as a mask, the second cladding layer 137 is etched by the RIBE method (reactive ion beam etching method). The etching rate of this etching is lower than that of the resist pattern 151, and the second clad layer 1
Since the resist pattern 151 is faster than the resist pattern 37, the resist pattern 151 becomes the resist pattern 152 and the surface shape of the second cladding layer 137 becomes convex 162 during the etching. When the resist pattern 152 is completely removed, the surface shape of the second cladding layer 137 becomes
A dome-shaped surface shape 163 is obtained.

The arrangement pattern of the dome shape 163 on the LED surface is the same as the arrangement pattern of the conical convex portions 125 in FIG. 11B.

According to the seventh embodiment, the surface of the light emitting surface of the second cladding layer 137 has a dome shape, and the light emitting surface has a substantially spherical shape. Therefore, in the seventh embodiment, the incidence of light on the light exit surface can be made even closer to the vertical incidence as compared with the fifth and sixth embodiments in which the light exit surface has a conical shape. Efficiency can be further improved.

The seventh embodiment can be modified as follows.

In the seventh embodiment, the surface electrode 138 is
The p-type ZnSe third cladding layer 136 is directly contacted, and the p-type GaAs contact layer is not provided in the middle, simply because the manufacturing technique is inexperienced. Therefore, it is desirable to provide the above-mentioned contact layer in order to lower the contact resistance.

The material of the substrate 130 is Z in addition to GaAs.
It may be nSe or the like, and may be opaque or transparent with respect to the emission wavelength. The conductivity type of the substrate 130 may be n-type or p-type.

The light emitting layer 133 is composed of Zn _1-x Cd _x Se (x =
0.2), but the value of x is not particularly limited. For example, x = 0
Of ZnSe. Further, the light emitting layer 133 may have, for example, a ZnSe / ZnCdSe multiple quantum well structure.

The n-type ZnSSe buffer layer 131 has n
An InGaAs buffer layer may be used, and n-type ZnS / Z
It may be an nSe strained superlattice layer.

Each of the semiconductor layers 131 to 137 is formed by MBE.
Formed by molecular beam epitaxy (MOCVD)
(Organic metal vapor phase epitaxy), VPE (vapor phase epitaxy) or LPE (liquid phase epitaxy).
Further, the pn junction may be formed during crystal growth, or may be formed by diffusing a dopant after crystal growth.

Further, with respect to other points of the seventh embodiment, the same changes as those shown in the fifth and sixth embodiments can be made. For example, a reflection film can be formed under the light emitting layer to improve the external emission efficiency.

Conversely, the dome-shaped cladding layer shown in this embodiment may be applied to the fifth and sixth embodiments, and may be applied to an eighth embodiment described later.

Next, an eighth embodiment is shown in FIG. The eighth embodiment is an AlGaAs LED.

The eighth embodiment will be described while explaining the manufacturing steps. First, LPE is placed on an n-type GaAs substrate 200.
N-type AlGaAs cladding layer 201 by a liquid phase growth method.
, A p-type GaAs light emitting layer 202, a p-type AlGaAs first cladding layer 203, and an n-type AlGaAs current blocking layer 204.
And a p-type AlGaAs contact layer 205 are sequentially formed. The p-type layer 205 formed on the n-type current blocking layer 204 constitutes a current injection layer.

Next, the p-type AlGaAs contact layer 205
Then, an opening 231 is formed by etching away a part of the n-type AlGaAs current blocking layer 204. Next, p-type Al
The GaAs second cladding layer 206 is formed by the LPE method. In particular, the layer thickness of the p-type AlGaAs second cladding layer 206 is made extremely thick at 100 μm, taking advantage of the fact that the thick film can be easily grown by the LPE method.

Next, the p-type AlGaAs second cladding layer 20
6 is etched to form a conical convex portion 232. In addition, the above-mentioned etching causes the above-mentioned convex-shaped portion 2 to be formed.
The p-type AlGaAs contact layer 205 is exposed around 32, and a surface electrode 207 is formed on the exposed contact layer 205. After that, the wafer is
Is wrapped from the back surface to a total thickness of 200 μm, and a back electrode 208 is formed on the entire back surface. Next, the wafer is divided into chips of about 200 μm square. FIG. 15 shows the surface of this chip viewed from above.

The eighth embodiment has the following effect of improving the light emission efficiency in addition to the effect of improving the light emission efficiency described in the sixth embodiment. That is, since the fifth, sixth, and seventh embodiments have a plurality of convex portions, light emitted from the side surface of one convex portion may be blocked by the other convex portions. On the other hand, since the eighth embodiment has only one convex-shaped portion 232, light emitted from the side surface of one convex-shaped portion is not interrupted by another convex-shaped portion, and there is no loss of light. In particular, the emission efficiency of light to the outside can be particularly improved.

The single convex-shaped portion 232 shown in the eighth embodiment can be formed by using the LPE method,
It may be formed using the VD method or the MBE method. In this case, for example, if the size of the chip itself is reduced, the thickness of the p-type second cladding layer 206 can be reduced.
The convex portion 23 is formed by OCVD or MBE.
2 can be easily formed.

In the eighth embodiment, the modifications shown in the other fifth, sixth, and seventh embodiments can be made.
Therefore, for example, a change such that n-type and p-type are reversed, and a change such as providing a semiconductor multilayer reflective layer below the light-emitting layer are possible. The material of each semiconductor layer can be the same as the material shown in the fifth embodiment.
P or GaP or InGaAsP, etc.
It is suitable to grow on a substrate such as As, GaP, or InP by an LPE method or the like.

Next, a ninth embodiment is shown in FIG. The ninth embodiment is an AlGaInP LED. FIG.
FIG. 17 is a surface view of this embodiment viewed from above.
FIG.

The composition of each layer constituting the ninth embodiment is as follows:
It is the same as the fifth embodiment, and 310 to 31 in FIG.
9 correspond to 90 to 99 in FIG.
2 corresponds to 102. The manufacturing process is the same as that of the fifth embodiment, and the description is omitted.

The ninth embodiment differs from the fifth embodiment in the following points.

The first difference is that the current blocking layer 315 is located only in a region facing the peripheral portion of the mesa shape 332, and is removed in most of the inside of the mesa shape 332. That is, the opening of the current blocking layer is larger than that of the fifth embodiment.

Therefore, in the ninth embodiment, the effect of improving the external emission efficiency by limiting the light emitting region, which is the object of the present invention, is worse than that of the fifth embodiment. However, the area of the light emitting region of the light emitting layer 313 is increased by an amount corresponding to the increase in the opening, and the current density when the same current flows is reduced.
The reliability as a light emitting element can be improved.

The second difference is that the upper portion of the mesa-shaped portion 332 is flat and wide, and the difference in shape between the mesa-shaped portion 332 and the dome shape, which is an ideal convex shape, in terms of external emission efficiency is large. For this reason, the effect of improving the external emission efficiency, which is the object of the present invention, is worse in the ninth embodiment than in the fifth embodiment. However, as shown in FIG. 17, the surface pattern of the mesa-shaped portion 332 is larger than that of the fifth embodiment (see FIG. 9B), so that the fabrication is easy.

The third difference is that, as shown in FIG. 17, the surface electrode 319 has a cross shape extending from the center. In the fifth embodiment (see FIG. 9B), the surface electrode 99 surrounds the periphery of each mesa-shaped portion 102. In the ninth embodiment, the surface electrode 319 surrounds the mesa-shaped portion 332. In other words, the surface electrode 319 is not arranged around the chip. However, the p-type GaAs contact layer 3
16 is conductive, the current is substantially
32 through the p-type GaInP intermediate band gap layer 317 from the entire periphery of the second p-type AlGaInP second cladding layer 318.
Is injected into. As described above, in the ninth embodiment, since the surface electrode 319 is not formed around the chip,
Fabrication is easy.

[0158]

As is apparent from the above description, in order to improve the external emission efficiency of the LED, the invention according to claim 1 has a light emitting surface which is convex and faces the center of the convex. In this case, a current blocking layer having an open region is provided, so that light emission is limited in the vicinity of the interface between the first conductivity type layer and the second conductivity type layer in the convex center facing region.

Therefore, according to the first aspect of the present invention, it is possible to make the light generated at the interface closer to the vertical incidence on the convex light emission surface, and to improve the efficiency of light emission to the outside. Can be.

According to the invention, light is extracted from the interface on the substrate to the outside through the semiconductor layer of the second conductivity type on the interface, so that light generated at the interface passes through the substrate. Without taking out the light, the light emission wavelength can be set regardless of the light absorption region of the substrate.

Further, according to the invention, light can be emitted from the two light emission surfaces on both the left and right sides of the stripe shape of the convex second conductivity type semiconductor layer having the stripe surface pattern.

Further, according to the second aspect of the present invention, since the opening of the current blocking layer extends along the central axis of the stripe pattern, the amount of light emitted from the light emission surface having the stripe shape can be increased.

According to the third aspect, at each branch tip of the multi-stage resin-like surface pattern of the convex second conductivity type semiconductor layer having the multi-stage tree-like surface pattern, the left and right sides in the branch direction are set. Light can be emitted from three surfaces, the side surface and the front side surface.

According to the fourth and sixth aspects of the present invention, since the current blocking layer is provided below the interface, the current blocking layer does not block light traveling from the interface to the second conductivity type semiconductor layer. . Therefore, the efficiency of light emission to the outside can be improved.

According to the fifth and seventh aspects, the current blocking layer having the opening is provided above the interface, so that the interface and the layer below the interface can be formed flat on a flat substrate.
Therefore, the quality of the interface can be easily improved.

According to the present invention, in order to improve the external emission efficiency of the LED, the light emitting surface is made convex, and a current blocking layer having an opening in a region facing the center of the convex is provided. The interface is made to emit light in a limited manner in the convex center facing region, and an exposed portion of the current injection layer is provided around the convex shape, and an electrode is provided in the exposed portion.

Therefore, in the invention according to claim 8, since it is not necessary to dispose an electrode on the upper part of the convex shape, light can be effectively extracted from the upper part of the convex shape, and the external emission efficiency can be improved.

In addition, since the light emitting region is limited to the convex central portion facing region, the incidence of the light on the light emitting surface can be made closer to the vertical incidence. Therefore, it is possible to suppress the ineffective light-emitting component that is totally reflected on the light exit surface, and it is possible to further increase the external light emission efficiency.

Since light is extracted outside without passing through the substrate, the emission wavelength can be set regardless of the light absorption region of the substrate.

According to the ninth aspect, since the opening of the current injection layer and the opening of the current blocking layer are continuous, the opening of the current injection layer and the opening of the current blocking layer are simultaneously formed. Can be formed, and the manufacturing process can be simplified.

According to the tenth aspect, the current injection layer includes an upper layer and a lower layer, and the band gap of the upper layer is the difference between the band gap of the lower layer and the band gap of the second semiconductor layer of the second conductivity type. Since it has an intermediate value, the electric resistance between the current injection layer and the second semiconductor layer can be reduced. Therefore, the current injection efficiency is improved, and the light emission efficiency is improved.

According to the eleventh aspect, the second shape having the convex shape is provided.
Since the electrode is provided on the lower layer of the current injection layer exposed from the semiconductor layer, the electric resistance between the current injection layer and the electrode can be reduced, and the current injection efficiency can be improved.

According to the twelfth aspect, since the second layer of the current injection layer has an opening wider than the opening of the first layer, the light passing through the opening of the first layer is formed. But the second
It is not blocked by layers. Therefore, light emission efficiency is improved.

According to the thirteenth aspect, the first layer of the current injection layer and the current blocking layer are transparent with respect to the emission wavelength at the interface, so that the light generated at the interface is not blocked. Therefore, light emission efficiency is improved.

According to the fourteenth aspect, light is emitted from the two light emission surfaces on both the left and right sides of the stripe shape of the convex second conductivity type semiconductor layer having the stripe surface pattern and the upper surface of the stripe shape. Can be done.

Further, in the above-mentioned invention, ordinary photolithography and etching can be used as a process for forming a convex shape, so that the productivity is extremely excellent. Therefore, the present invention is very useful for increasing the brightness of various LEDs, particularly AlGaInP-based, ZnCdSe-based, and AlGaAs-based LEDs using a GaAs substrate that does not transmit the emission wavelength.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of each step of manufacturing an AlGaIn LED as a first embodiment of a light emitting diode according to the present invention.

FIG. 2 is a plan view in each step of the embodiment.

FIG. 3 shows an AlGaInP-based LED according to a second embodiment of the present invention.
FIG.

FIG. 4 is a plan view in each step of the second embodiment.

FIG. 5 is a sectional view of a ZnCdSe-based LED according to a third embodiment of the present invention.

FIG. 6 is a sectional view of an AlGaAs LED according to a fourth embodiment.

FIG. 7 is a plan view of the fourth embodiment.

FIG. 8 shows an AlGaInP system L according to a fifth embodiment of the present invention.
It is sectional drawing of ED.

FIG. 9 is a plan view in each step of the fifth embodiment.

FIG. 10 is a sectional view of an AlGaInP-based LED according to a sixth embodiment of the present invention.

FIG. 11 is a plan view in each step of the sixth embodiment.

FIG. 12 shows a ZnCdSe-based L according to a seventh embodiment of the present invention.
It is explanatory drawing explaining the manufacturing method of ED.

FIG. 13 is a sectional view of the seventh embodiment.

FIG. 14 shows an AlGaAs system L according to an eighth embodiment of the present invention.
It is sectional drawing of ED.

FIG. 15 is a plan view of the eighth embodiment.

FIG. 16 is a sectional view of an AlGaInP-based LED according to a ninth embodiment of the present invention.

FIG. 17 is a plan view of the ninth embodiment.

FIG. 18 is a cross-sectional view of a conventional LED.

FIG. 19 is a diagram showing light paths that differ depending on the angle of incidence of light on the light exit surface.

[Explanation of symbols]

 Reference Signs List 10 p-type GaAs substrate 11 n-type GaAs current blocking layer, 12 opening, 13 p-type AlGaInP clad layer, 14 undoped AlGaInP (y = 0.5) light-emitting layer 15 n-type AlGaInP clad layer 16 n-type GaAs contact layer 17 surface Electrode 18 Back electrode 90 n-type GaAs substrate 91 n-type GaInP intermediate band gap layer 92 n-type AlGaInP (y = 0.7) cladding layer 93 undoped AlGaInP (y = 0.5) light emitting layer 94 p-type AlGaInP (y = 0) .7) First cladding layer 95 n-type GaAs current blocking layer 96 p-type GaAs contact layer (current injection layer) 97 p-type GaInP intermediate band gap layer (current injection layer) 98 p-type AlGaInP (y = 0.7) 2 clad layer 99 front electrode 100 back electrode 101 opening 102 convex (mesa) shape

Continuation of front page (58) Field surveyed (Int. Cl. ⁶ , DB name) H01L 33/00

Claims (14)

(57) [Claims] 1. A semiconductor layer of at least a first conductivity type and a semiconductor layer of a second conductivity type are sequentially laminated on a semiconductor substrate of a first conductivity type, wherein the semiconductor layer of the first conductivity type and the second conductivity type are stacked. A light emitting diode for emitting light generated in the vicinity of the interface between the semiconductor layers of the second conductivity type to the outside from the semiconductor layer of the second conductivity type, wherein a cross section of the semiconductor layer of the second conductivity type cut along a plane perpendicular to the surface of the substrate Is a convex shape, the surface pattern viewed from above the convex shape is a stripe shape, and the second conductive type semiconductor layer is provided between the second conductive type semiconductor layer and the first conductive type semiconductor substrate. A light emitting diode comprising a current blocking layer having an opening in a region facing a center of a conductive semiconductor layer. 2. The light emitting diode according to claim 1, wherein the opening of the current blocking layer is provided along a center axis of the stripe pattern. 3. A semiconductor substrate of a first conductivity type, wherein at least a semiconductor layer of a first conductivity type and a semiconductor layer of a second conductivity type are sequentially laminated, and the semiconductor layer of the first conductivity type and the second conductivity type are stacked. A light emitting diode for emitting light generated in the vicinity of the interface between the semiconductor layers of the second conductivity type to the outside from the semiconductor layer of the second conductivity type, wherein a cross section of the semiconductor layer of the second conductivity type cut along a plane perpendicular to the surface of the substrate The second conductive type semiconductor layer is formed in a convex shape so that the second conductive type semiconductor layer is formed in a convex shape, and the second conductive type semiconductor layer is formed between the second conductive type semiconductor layer and the first conductive type semiconductor substrate. A current blocking layer having an opening in a region opposed to a central portion of the semiconductor layer of the mold; The next branch stripe is the first branch stripe from the first branch stripe. A secondary branch stripe having a multi-stage branch dendritic shape obtained by branching at least a tertiary branch stripe from the secondary branch stripe;
A light-emitting diode, wherein an opening of the current blocking layer is provided at least in a region facing a center of a branch tip of the multi-tiered surface pattern. 4. The light emitting diode according to claim 1, wherein said current blocking layer is provided between said semiconductor substrate of said first conductivity type and said interface. A light emitting diode characterized by having a layer. 5. The light emitting diode according to claim 1, wherein a plurality of second conductivity type semiconductor layers are provided on the interface,
The light emitting diode according to claim 1, wherein the current blocking layer is a first conductive type semiconductor layer or a high resistance semiconductor layer provided between the plurality of second conductive type semiconductor layers. 6. The light emitting diode according to claim 3, wherein the current blocking layer is provided on a second conductive type semiconductor layer or a high resistance semiconductor layer provided between the first conductive type semiconductor substrate and the interface. A light emitting diode, characterized in that: 7. The light emitting diode according to claim 3, wherein a plurality of second conductivity type semiconductor layers are provided on the interface,
The light emitting diode according to claim 1, wherein the current blocking layer is a first conductive type semiconductor layer or a high resistance semiconductor layer provided between the plurality of second conductive type semiconductor layers. 8. A semiconductor substrate of a first conductivity type, wherein at least a semiconductor layer of a first conductivity type and first and second semiconductor layers of a second conductivity type are sequentially laminated, and A light emitting diode that emits light generated in the vicinity of an interface between the second conductivity type semiconductor layers from the second conductivity type second semiconductor layer to the outside, wherein the second conductivity type second semiconductor layer has a plane perpendicular to the substrate surface. The second semiconductor layer of the second conductivity type is formed in a convex shape so that a cross section obtained by cutting the two semiconductor layers is formed in a convex shape, and between the first semiconductor layer and the second semiconductor layer of the second conductivity type, A current blocking layer made of a first conductivity type semiconductor layer or a high resistance semiconductor layer and having an opening in a region opposed to a center of the second semiconductor layer of the second conductivity type having a convex shape; An opening communicating with the opening between the first semiconductor layer and the second semiconductor layer; Current injection layer provided, light emitting diodes, characterized in that a electrode on the current injection layer exposed from the second semiconductor layer. 9. The light emitting diode according to claim 8, wherein the opening of the current injection layer and the opening of the current blocking layer are continuous. 10. The current injection layer includes a lower layer in contact with the current blocking layer, and an upper layer formed on the lower layer, wherein the band gap of the upper layer is equal to the band gap of the lower layer and the second layer. 10. The light emitting diode according to claim 8, wherein the light emitting diode has an intermediate value with a band gap of the conductive second semiconductor layer. 11. An upper layer of the current injection layer is removed at a convex peripheral portion of the second semiconductor layer of the second conductivity type, and the electrode is formed on an exposed lower layer of the current injection layer. The light emitting diode according to claim 10, wherein the light emitting diode is provided. 12. The current injection layer includes a first layer in contact with the current blocking layer, and a second layer formed on the first layer, wherein the first layer is formed of the current blocking layer. 9. An opening according to claim 8, wherein the second layer has an opening which is open over a wider range than the opening of the first layer. Light emitting diode. 13. The light emitting diode according to claim 12, wherein the first layer of the current injection layer and the current blocking layer are transparent to an emission wavelength at an interface. 14. The second semiconductor layer of the second conductivity type having a convex shape has a surface pattern viewed from above in a stripe shape, and an opening of the current blocking layer is set at a center axis of the stripe pattern. 14. The light emitting diode according to claim 8, wherein the light emitting diode is provided along.