JP2003347578A - Semiconductor light emitting element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a semiconductor light emitting element which can provide higher external quantum efficiency by reducing an absorption rate by a substrate of the light emitted from a light emitting layer. <P>SOLUTION: For example, on a semiconductor substrate 1, a semiconductor laminating portion 10, consisting of a compound semiconductor including a light emitting layer forming portion 9 where an n-type clad layer 2 and a p-type clad layer 4 are laminated, is provided. At least a part of the external circumference in the interface side in contact with the semiconductor laminating portion 10 among the semiconductor substrate 1 is cut away and thereby a cut-away portion 1a is formed. <P>COPYRIGHT: (C)2004,JPO

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor light emitting device which uses a compound semiconductor material such as AlGaAs or InGaAlP and is used for a display panel or an LED panel. More specifically, the present invention relates to a semiconductor light emitting device having improved efficiency of extracting light to the outside.

[0002]

2. Description of the Related Art A conventional semiconductor light emitting device using an InGaAlP-based compound semiconductor is, for example, as shown in FIG.
An n-type cladding layer 2 made of an aAlP-based semiconductor material, an active layer 3 made of a non-doped InGaAlP-based semiconductor material having a composition smaller in band gap energy than the cladding layer, and a p-type cladding layer 4 made of a p-type InGaAlP-based semiconductor material Each of them is epitaxially grown to form a light emitting layer forming portion 9 having a double hetero junction structure.
A window layer 5 made of an AlGaAs-based semiconductor material is provided on the front surface side, and a p-side electrode 8 is provided on a part of the surface thereof via a contact layer 6 made of p-type GaAs, and n is provided on the back surface side of the semiconductor substrate 1. The side electrodes 7 are each Au
It is provided by a Ge / Ni alloy or the like, and is chipped from a wafer.

[0003]

In the conventional structure, FIG.
As shown in (2), the light emitted from the light emitting layer is not only light traveling to the upper surface but also travels in four directions to the substrate side. However, since the GaAs substrate absorbs light that emits visible light or infrared light, the light reflected on the substrate side is very small (see FIG. 3).
The light directed to the substrate side hardly travels to the light emitting surface side (the upper surface side in FIG. 3) and cannot be used effectively.

On the other hand, in order to solve such a problem, a multilayer reflective layer (DBR) having a different refractive index (not shown) is formed on the semiconductor substrate 1 and a light emitting layer forming section 9 is grown thereon. As a result, the reflection layer is interposed between the semiconductor substrate 1 and light having a desired wavelength is reflected toward the upper surface before entering the semiconductor substrate 1 by light traveling toward the semiconductor substrate 1, and light is emitted from the front surface side. An LED chip having a structure for extracting a large amount of light is also considered. However, when the reflective layer is generally designed to have a high reflectance, the lattice constant differs from that of the semiconductor substrate.
The mismatch ratio is large, many defects occur in the reflective layer, the light cannot be completely reflected, and the light transmitted to the semiconductor substrate side is absorbed by the semiconductor substrate, resulting in a small external quantum efficiency. Often it does not improve.

The present invention has been made in order to solve such a problem, and it is possible to increase the external quantum efficiency by reducing the rate at which light emitted from a light emitting layer is absorbed by a semiconductor substrate. It is an object to provide a light-emitting element.

[0006]

A semiconductor light emitting device according to the present invention comprises a semiconductor substrate and a light emitting layer laminated on the semiconductor substrate and having at least an n-type layer and a p-type layer laminated to form a light emitting layer. The semiconductor substrate includes a semiconductor laminated portion including a formation portion, and the semiconductor substrate has a notched portion in which an outer peripheral portion on an interface side in contact with the semiconductor stacked portion is at least partially omitted.

[0007] Here, the outer peripheral portion means the outer periphery of the device when a large number of devices are manufactured on a wafer and each device is formed into one device (chip), and at least a part thereof covers the entire periphery of the outer periphery. It is not limited to the case where the outer peripheral portion has the cutout portion, but also includes the case where the outer peripheral portion has the cutout portion, for example, the case where the opposing sides have the cutout portion only.

[0008] With this structure, of the light emitted from the light emitting layer forming portion, the light in the direction of the missing portion comes into contact with the atmosphere having a small refractive index, and the refractive index of the air is higher than the refractive index of the semiconductor substrate. Light is easily reflected because it is much smaller, and even when it is not reflected, light is emitted to the outside and is not absorbed by the substrate, but is reflected in a desired direction by a reflecting member provided around the semiconductor chip. Efficiency can be increased.

Further, even when a reflective layer is formed at the interface between the substrate and the semiconductor laminated portion, the light transmitted to the reflective layer in the direction of the missing portion among the light transmitted through the reflective layer is similarly absorbed by the semiconductor substrate. Instead, light is reflected or emitted directly, and the external quantum efficiency can be increased.

[0010]

Next, a semiconductor light emitting device of the present invention will be described with reference to the drawings. A semiconductor light emitting device according to the present invention has, for example, an n-type layer (n-type cladding layer) on a semiconductor substrate 1 as shown in FIG. A) a semiconductor laminated portion 10 of a compound semiconductor including a light emitting layer forming portion 9 on which a p-type layer (p-type cladding layer) 4 is laminated, and an interface side of the semiconductor substrate 1 which contacts the semiconductor laminated portion 10 At least a part of the outer peripheral portion is missing to form a missing portion 1a.

As the semiconductor substrate 1, AlGaAs or I
In order to grow a semiconductor laminated portion composed of nGaAlP, Ga
As is generally used. In this case, since the light is absorbed, the effect of the present invention is great. However, even in the case of a substrate made of a light-transmitting material such as GaP, there is an effect in extracting light upward. Further, the semiconductor substrate 1 may be either p-type or n-type, and is determined by the relationship with the semiconductor laminated portion 10 grown on the semiconductor substrate 1. Further, when a buffer layer made of the same material as the semiconductor substrate 1 described later is provided on the semiconductor substrate 1, the buffer layer is also included in a part of the semiconductor substrate 1.

A feature of the present invention is that the semiconductor substrate 1 has at least a part of the outer peripheral portion on the interface side with the semiconductor laminated portion 10 which is missing to form a missing portion 1a. The missing portion 1a is formed, for example, by forming a semiconductor laminated portion 10 described later in a wafer state, and removing the semiconductor laminated portion 10 in an element isolation region which is divided into chips after forming electrodes by etching or the like until the semiconductor substrate 1 is exposed. Then, the semiconductor substrate 1 is formed by using an etching solution that etches the semiconductor substrate 1 without etching the semiconductor laminated portion 10. This etching is performed by using an etching method such as isotropic wet etching for etching in the lateral direction, and utilizing the side etching. It is preferable that the side etching amount is large because the region absorbed by the semiconductor substrate 1 is reduced.
Since the contact surface with 0 also decreases, the operating voltage starts to increase, or the semiconductor laminated portion 10 cannot be held, so that the side etching is actually performed on the contact region up to half or less.

In the element isolation, a region other than the element isolation region is covered with a resist or the like, and the element isolation region is etched by wet etching until it reaches the semiconductor substrate 1.
The element isolation etchant is suitable for etching the semiconductor laminated portion 10 and may be any liquid that can selectively etch the semiconductor substrate 1.
When the semiconductor substrate 1 is made of GaAs and the semiconductor substrate 1 is made of GaAs, an aqueous solution of hydrochloric acid or the like is used.
When 0 is an AlGaAs-based material and the substrate 1 is GaAs, a mixed solution of sulfuric acid or tartaric acid with an aqueous hydrogen peroxide solution, an aqueous hydrochloric acid solution, or the like is used. By using such an etchant, the semiconductor substrate 1 and the semiconductor laminated portion 10
Etching stops at the interface with, and element isolation becomes possible.

On the other hand, element isolation can be performed not only by wet etching but also by dry etching or half dicing. Also in this case, the dry etching or the dicing groove
Adjust to reach

An etching solution used for forming the missing portion 1a after element isolation is suitable for etching the semiconductor substrate 1, and can selectively etch the semiconductor laminated portion 10.
In addition, the etching is performed not only in the vertical direction but also in the lateral direction with respect to the material of the semiconductor substrate 1.
For example, when the semiconductor laminated portion 10 is made of an InGaAlP-based material and the semiconductor substrate 1 is made of GaAs, a material obtained by adding an aqueous solution of hydrogen peroxide to an aqueous ammonia solution or an aqueous sodium hydroxide solution so as to obtain an etching selectivity between them is used. And
The semiconductor substrate 1 is made of an AlGaAs-based material.
Is GaAs, the semiconductor laminated portion 10 is made of InGaAs.
This is the same as in the case of the IP-based material. By using such an etching solution, only the semiconductor substrate 1 is etched without etching the semiconductor laminated portion 10, and is etched in the vertical direction of the semiconductor substrate 1 and simultaneously with the side etching in the horizontal direction. It is possible to form a state in which a part of the semiconductor substrate 1 below the semiconductor lamination portion 10 is missing.

In the example shown in FIG. 1, the missing portion of the outer peripheral portion is formed over the entire outer periphery. However, even if the missing portion 1a is not formed over the entire outer periphery. ,
For example, the effect can be obtained even if the cutout portion 1a is formed only in the outer peripheral portion on two opposite sides having a short planar shape, such as a cutout portion. However, it is preferable that the number of the missing portions 1a is large because the light absorption is reduced.

In the example shown in FIG. 1, the light emitting layer forming portion 9 has a double hetero structure in which the active layer 3 is sandwiched between the n-type cladding layer 2 and the p-type cladding layer 4 made of a material having a larger band gap. For example, an InGaAlP-based material is mainly used to obtain red light, and an AlGaAs-based material is mainly used to obtain infrared light. The growth of the light-emitting layer forming portion 9 may be made to have a necessary composition (e.g., changing the Al composition ratio or doping with a dopant) depending on the emission wavelength of the target device, or the like.
Grow to the required thickness.

Here, the InGaAlP-based material is referred to as InGaAlP-based material.
_0.49 (Ga _1−x Al _x ) _{0.51 Represents} a material when the value of x varies between 0 and 1 in the form of P. Note that the mixed crystal ratios of In and (Al _x Ga _1-x ) of 0.49 and 0.51 are determined by Ga on which the InGaAlP-based material is laminated.
AlGaAs-based material means a ratio that is lattice-matched to a semiconductor substrate such as As, and Al _y Ga _1-y As
, And means a material when the value of y varies between 0 and 1.

As a specific example, for example, InGaAl
In the case of a P-based compound semiconductor, In_0.49(Ga
_0.25Al_0.75)_0.51Made of P and doped with Se
Carrier concentration is 1 × 10¹⁷~ 1 × 10¹⁹cm^-3Degree, thickness
An n-type cladding layer 2 having a thickness of about 0.1 to 2 μm;
_0.49(Ga_0.8Al_0.2)_0.51Made of P, non-doped
The active layer 3 having a thickness of about 0.1 to 2 μm and Zn
And the carrier concentration is 1 × 10¹⁶~ 1 × 10¹⁹cm^-3
About 0.1 μm to 2 μm in thickness, and the n-type cladding layer 2
Made of an InGaAlP-based compound semiconductor having the same composition as
It is formed by a laminated structure with the shaped cladding layer 4. on the other hand,
When made of an AlGaAs-based compound semiconductor,
_0.7Ga_0.3Made of As, doped with Se and carrier
Concentration is 1 × 10 ¹⁷~ 1 × 10¹⁹cm^-3About 0.3mm thick.
An n-type cladding layer 2 of about 1 to 2 μm;_0.2Ga_0.8
Made of As, non-doped with a thickness of about 0.1 to 2 μm
Active layer 3 and a Zn-doped carrier concentration of 1 ×
10¹⁶~ 1 × 10¹⁹cm^-3About 0.1 to 2 μm in thickness
AlGaAs based on the same composition as the n-type cladding layer 2
Layered structure with compound semiconductor p-type cladding layer 4
Formed.

In the example shown in FIG. 1, for example, p-type Al _z Ga _{1 -z} As is formed on the p-type cladding layer 4 of the light emitting layer forming section 9.
(0.5 ≦ z ≦ 0.8) 1 to 1
A contact layer 6 made of, for example, p-type GaAs only on the lower side of the p-side electrode 8.
Are laminated to form the semiconductor laminated portion 10.

Although not shown in the example of FIG.
Between the semiconductor cladding layer 2 and the semiconductor substrate 1, 5 to 40 semiconductor layers having different refractive indices are alternately formed with a thickness of λ / (4n) (λ is an emission wavelength and n is a refractive index of the semiconductor layer). A reflective layer (DBR), which is laminated to a certain degree, may be inserted, or a buffer layer may be inserted. An n-type window layer can also be formed on the semiconductor substrate 1 side of the n-type cladding layer 2 with the same composition as the window layer 5. The reflective layer (DBR)
It is obtained by a layer having a band gap larger than that of the active layer or the substrate, for example, a laminated structure in which Al of AlGaAs is changed in composition. The buffer layer is made of the same material as the semiconductor substrate 1 or a layer capable of reducing lattice mismatch between the semiconductor substrate 1 and a layer on the semiconductor substrate 1, for example, the semiconductor laminated portion 10 is made of an InGaAlP-based compound. Is GaA
s, GaAs, InGaP, InGaAlP
When the semiconductor compound and the semiconductor laminated portion 10 are AlGaAs-based materials and the semiconductor substrate 1 is GaAs, GaAs or AlGa
As-based compounds are conceivable.

A p-side electrode 8 made of Au-Be / Ni / Ti / Au or the like is formed on the contact layer 6 on the front surface side of the semiconductor laminated portion 10, and Au-Ge / Ni / Au is formed on the back surface side of the semiconductor substrate 1.
The chip is formed in a state where the n-side electrodes 7 made of, for example, are provided.

To manufacture such an LED chip,
For example, as shown in FIG.
The substrate 1 is placed in an MOCVD (metal organic chemical vapor deposition) apparatus, and triethylgallium (hereinafter, referred to as TEG), trimethylaluminum (hereinafter, referred to as TMA), trimethylindium (hereinafter, referred to as TMIn), and phosphine (hereinafter, referred to as reaction gas) are used. , PH ₃ ) and H ₂ Se as an n-type dopant gas are introduced together with hydrogen (H ₂ ) as a carrier gas, and epitaxially grown at about 500 to 700 ° C. to have a carrier concentration of 1 × 10 ¹⁶ to 1 × 10 6.
In _0.49 (Ga _0.25 Al _0.75 ) _0.51 P of about ¹⁹ cm ^-3
An n-type cladding layer 2 of about 0.5 μm is epitaxially grown. Then, the TMA of the reaction gas was reduced and T
EG is increased to, for example, undoped In _0.49 (Ga
_0.8 Al _0.2 ) _{0.51 The} active layer 3 made of P is about 0.5 μm, and the same reactive gas as that of the n-type cladding layer 12 is used. The dopant gas is dimethyl zinc (DMZn). ^A p-type cladding layer 4 made of, for example, In _0.49 (Ga _0.25 Al _0.75 ) _0.51 P of about ¹⁷ to 1 × 10 ¹⁹ cm ^{−3 is} about 1 μm, and the p-type carrier concentration is 1 × 10 ¹⁷ to 1 × 10 ²⁰ cm ^{−. About 3} Al
_A p-type window layer 5 made of _0.7 Ga _0.3 As and a p-type contact layer 6 made of, for example, GaAs having a p-type carrier concentration of about 1 × 10 ¹⁷ to 1 × 10 ²⁰ cm ⁻³ are grown. Form. Then, a metal Au-Ti alloy, Au-Zn / Ni alloy, Au-Be / Ni alloy, or the like for an electrode is formed on the substrate 1, and the metal film for the electrode is patterned as shown in FIG. To form a p-side electrode 8, and using the p-side electrode 8 as a mask, a portion of the p-type contact layer 6 not covered with the p-side electrode 8 is removed by etching, and the p-type contact layer 6 is patterned.

Next, in order to perform division for each element, FIG.
As shown in FIG. 2C, the area other than the element isolation region is covered with a resist film 11 by using a photolithography technique, and the isolation region is exposed to a mixture of hydrochloric acid and water at a ratio of 2: 1 at room temperature for about 3 minutes (rate). The semiconductor substrate 1 is dew-condensed by etching (0.6 μm / min).

Further, etching is performed continuously at room temperature for about 20 minutes (at a rate of about 2 μm / min) using, for example, a mixed solution of ammonia water, hydrogen peroxide solution, and water at a ratio of 1:10:10, so that the vertical direction is about 40 μm. By etching, about 40 μm is also etched in the lateral direction, and as shown in FIG. 2D, a width of about 80 μm on both sides is missing at the outer peripheral portion on the interface side in contact with the semiconductor laminated portion 10. A state can be formed. Note that if the p-type contact layer 6 is made of GaAs when the etching is performed after the resist film 11 is stripped, the etching is performed at the same time. When element isolation is performed by dicing, it is necessary to cover the area other than the element isolation region with the resist film 11 by a photoresist step or the like after dicing.

Thereafter, after the resist film covering the element is peeled off, Au-Ge / Ni is coated on the entire back surface of the semiconductor substrate 1.
An n-side electrode 7 is formed by forming a film of an alloy or the like, and is diced to form a chip.
An ED chip is obtained.

In the above-described example, the light emitting layer forming portion is formed by using the non-doped active layer as an n-type having a band gap larger than that of the non-doped active layer.
Although the example of the double hetero structure sandwiched between the n-type cladding layers has been described, a pn junction structure in which the p-type layer and the n-type layer are directly bonded may be used. The conductivity type is a p-type semiconductor substrate,
The conductivity type of each semiconductor layer described above may be reversed.

[0028]

According to the present invention, of the light emitted from the light emitting layer of the semiconductor laminated portion, the light in the direction of the missing portion comes into contact with air having a small refractive index, and the light is easily reflected.
Even when the light is not reflected, light is emitted to the outside and is hardly absorbed by the substrate, and can be effectively used by being reflected by the external reflection member, so that the external quantum efficiency can be increased.
That is, conventionally, light traveling in the direction of the semiconductor substrate is mostly absorbed by the semiconductor substrate because the band gap of the semiconductor substrate is smaller than the band gap of the light emitting layer, whereas in the present invention, By removing a part of the semiconductor substrate, light emitted from the missing portion does not absorb light, and the refractive index of air is smaller than that of the semiconductor substrate. The amount of light reflected at the interface between the substrate and the semiconductor laminated portion increases, and light can be extracted effectively.

[Brief description of the drawings]

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

FIG. 2 is a process explanatory view of a method for manufacturing the semiconductor light emitting device of FIG.

FIG. 3 is a view for explaining light extraction by a cross-sectional structure of a conventional LED chip.

[Explanation of symbols]

1 semiconductor substrate 2 N-type layer (n-type cladding layer) 3 Active layer 4 p-type layer (p-type cladding layer) 9 Light emitting layer forming part 10 Semiconductor lamination section

Continuation of front page    (72) Inventor Nobuaki Oguro             21 Ryosan-cho, Saiin-mizozaki-cho, Ukyo-ku, Kyoto-shi             In the formula company F term (reference) 5F041 AA03 CA04 CA12 CA34 CA35                       CA36 CA49 CA53 CA57 CA65                       CA74 CA76 CA85 CB11 CB15                       CB36 FF01

Claims (1)

[Claims] 1. A semiconductor substrate, and at least an n-type layer and a p-layer laminated on the semiconductor substrate to form a light emitting layer.
A semiconductor laminated portion including a light emitting layer forming portion on which a shape layer is laminated, wherein the semiconductor substrate has a cutout portion in which an outer peripheral portion on an interface side in contact with the semiconductor laminated portion is at least partially cut off Light emitting element.