JPH0992878A - Semiconductor light emitting device and manufacturing method thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a semiconductor light emitting device excellent in efficiency of outputting emitted light and a manufacturing method thereof. SOLUTION: A multilayer body 3 is formed by depositing an AlGaAs double heterojunction layer 2 on a p-type GaAs substrate 1. A multilayer body 5 is formed by forming a plurality of recessed portions 4 of generally spherical shape on the surface of an n-type AlGaAs clad layer 2 by photolithography and etching. The multilayer body 5 is dipped into an ammonia-hydrogen peroxide aqueous solution to dissolve and remove the substrate 1, thereby forming a compound epitaxial layer body 6. Electrodes 7 and 8 are formed on the surfaces of the compound epitaxial layer body 6, respectively. Thereafter, the obtained substrate is divided by dicing to thereby make semiconductor light emitting device pellets 10. A semiconductor light emitting device is manufactured by using one of the pellets 10.

Description

Detailed Description of the Invention

[0001]

The present invention relates to a semiconductor light emitting device and a method for manufacturing the same.

[0002]

2. Description of the Related Art A method of manufacturing a semiconductor light emitting device which has been generally adopted conventionally will be described by taking an AlGaAs light emitting device as an example. 14A to 14F are cross-sectional views showing an example of a method of manufacturing the semiconductor light emitting device in the order of steps.
Mirror-polished surface 5 of p-type GaAs substrate 51 [FIG. 14 (a)]
Composite epitaxial layer 5 constituting a light emitting device on 1a
2, that is, an AlGaAs double heterojunction structure composed of a p-type AlGaAs clad layer 52a (thickness: about 70 μm), a p-type AlGaAs active layer 52b (thickness: about 1 μm) and an n-type AlGaAs clad layer 52c (thickness: about 130 μm) The layer 52 is deposited by a liquid phase epitaxial growth method to obtain a laminated body 53 [FIG. 14 (b)].

By removing the substrate 51 from this laminated body 53 by an appropriate method, one surface of the composite epitaxial layered body 5 has a flat mirror surface 54 corresponding to the mirror-polished surface 51a.
5 is obtained [FIG. 14 (c)]. Electrodes 56 and 57 are formed on both surfaces of the composite epitaxial layer body 55 by a conventional method [FIG. 14 (d)] and then divided by dicing to obtain semiconductor light emitting device pellets 60, 60 ,. (E)].

The semiconductor light emitting device pellet 60 obtained by the above manufacturing method is replaced with a conductive adhesive (for example, silver paste) 61.
Then, the semiconductor light emitting element 65 is obtained by fixing it to the support (frame) 62 by means of wire bonding and then molding it with a sealing material 63 such as epoxy resin [FIG. 14 (f)].

It is well known that the brightness (external output) of a semiconductor light emitting element is generally determined by the internal luminous efficiency and the external extraction efficiency of the emitted light. It is also known that the internal light emission efficiency mainly depends on the quality of the crystal material forming the light emitting element, and the external extraction efficiency largely depends on the structure and shape of the light emitting element pellet.

Since the compound semiconductor crystal forming the light emitting element (light emitting element pellet) has a very large refractive index of 3 or more, when the emitted light is taken out to the outside, a critical angle (epoxy resin) is formed on the surface of the compound semiconductor crystal. 20 for mold
Light incident at an angle of more than a few degrees is totally reflected and cannot be extracted to the outside. As described above, the large refractive index of the compound semiconductor crystal is a major cause of a decrease in the extraction efficiency to the outside. Therefore, in the light emitting element pellet having a shape as shown in FIG. 14E, the emitted light has a large total reflection rate on the surface of the light emitting element pellet, and the emitted light cannot be efficiently extracted to the outside.

Therefore, as a technique for improving the external extraction efficiency, the shape of the upper part of the light emitting element pellet is formed into a spherical convex shape, or the top surface and / or side surface of the light emitting element pellet is made into a surface having fine irregularities, and the micro Various techniques have been proposed and adopted for reducing the proportion of total reflection, such as a lens.

[0008]

By the above-mentioned technique for improving the external extraction efficiency, the total reflection ratio of the emitted light on the surface of the compound semiconductor crystal constituting the light emitting element is reduced and the light is incident on the crystal surface. Light can now be efficiently extracted to the outside. However, the light emitting layer which constitutes the light emitting element (in the case of the light emitting element of FIG.
Since the aAs active layer 52b) also serves as an absorption layer for emitted light, light emitted toward the lower part of the light emitting element is emitted from the lower surface of the light emitting element (conductive adhesive layer fixing the light emitting element pellet). Although it becomes reflected light that is reflected and goes upward, most of the light that is incident on the light emitting layer that also serves as the absorbing layer is internally absorbed by this light emitting layer (cannot reach the crystal surface), There is a problem that the emitted light cannot be efficiently extracted to the outside.

The present invention has been made in view of the above-mentioned problems, and an object thereof is to provide a semiconductor light emitting device in which internal absorption of emitted light is reduced to further enhance external extraction efficiency, and a method for manufacturing the same. It is in.

[0010]

A light emitting device according to the present invention is characterized in that the lower surface (support fixing surface) of a semiconductor light emitting device pellet is a surface having a single or a plurality of substantially spherical recesses. Further, in the above light-emitting element, by making the upper surface (the surface opposite to the support-fixing surface) and / or the side surface of the light-emitting element pellet a surface with reduced total reflection, the extraction efficiency to the outside is further improved.

As a concrete example of the total reflection reducing surface,
Examples of the upper surface include a surface having a single or a plurality of substantially spherical projections, a surface having fine irregularities, and a side surface having a surface having fine irregularities. AlGaAs is mentioned as a specific example of the crystal material of the composite epitaxial layer body constituting the semiconductor light emitting device pellet, and p-type AlGa is a specific example of the composite epitaxial layer body.
As clad layer, AlGaAs active layer and n-type AlGa
An example thereof includes an AlGaAs double heterojunction structure layer composed of an As clad layer.

A first method of manufacturing a light emitting device according to the present invention is a method of depositing a composite epitaxial layer constituting a semiconductor light emitting device on a compound semiconductor substrate by a liquid phase epitaxial growth method to form the substrate and the composite epitaxial layer. A step of forming a laminated body, a step of selectively removing the substrate from the laminated body by etching to form a composite epitaxial layer body, and forming a plurality of substantially spherical concave portions on one surface of the composite epitaxial layer body The method is characterized by including a step and a step of pelletizing the composite epitaxial layer body in which the substantially spherical concave portion is formed into a semiconductor light emitting device pellet.

A step of treating the other surface (the surface on which the substantially spherical recess is not formed) and / or the side surface of the composite epitaxial layer body constituting the semiconductor light emitting device pellet with a chemical solution to form a surface having fine irregularities. It is preferable to add to the first manufacturing method described above. By doing so, the other surface and / or the side surface can be made into a total reflection reducing shape surface.

In a second method for manufacturing a light emitting device according to the present invention, a step of forming a plurality of recesses of a predetermined shape on the surface of a compound semiconductor substrate and a semiconductor device is formed on the recessed surface of the compound semiconductor substrate. A step of depositing a composite epitaxial layer by a liquid phase epitaxial growth method to form a laminate of the substrate and the composite epitaxial layer; and a step of forming a plurality of substantially spherical recesses on the uppermost layer side of the composite epitaxial layer. A step of selectively removing the substrate from the stacked body by etching to form a composite epitaxial layer body in which convex portions corresponding to the concave portions formed in the substrate are formed on the substrate removal surface of the composite epitaxial layer; And a step of pelletizing the composite epitaxial layer body to obtain a semiconductor light emitting device pellet.

As a concrete example of the concave shape formed on the surface of the compound semiconductor substrate, there is a substantially spherical concave shape.
Further, the second manufacturing method described above more preferably includes a step of treating the side surface of the composite epitaxial layer body constituting the semiconductor element light emitting element pellet with a chemical solution to form a surface having fine irregularities.

In the first and second light emitting device manufacturing methods according to the present invention, GaAs is a specific example of the crystal material of the compound semiconductor substrate, and AlGaAs is a crystal material of the composite epitaxial layer. A specific example of the composite epitaxial layer is p-type AlGa.
As clad layer, AlGaAs active layer and n-type AlGa
An example thereof includes an AlGaAs double heterojunction structure layer composed of an As clad layer.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of a semiconductor light emitting device and a method of manufacturing the same according to the present invention will be described with reference to the drawings. Embodiment 1 FIG. 1 (f) is a sectional view of a semiconductor light emitting element pellet used in a semiconductor light emitting element, and FIGS. 1 (a) to 1 (f) are sectional views showing the manufacturing method in the order of steps.

On the mirror-polished surface 1a of the p-type GaAs substrate 1 [FIG. 1 (a)], the composite epitaxial layer 2 constituting the light emitting element, that is, the p-type AlGaAs clad layer 2a (thickness: about 70 μm), p-type AlGaAs activity. Layer 2b (thickness about 1
μm) and the n-type AlGaAs clad layer 2c (thickness of about 1
An AlGaAs double heterojunction structure layer 2 having a thickness of 30 μm) is deposited by a liquid phase epitaxial growth method to obtain a laminate 3 (FIG. 1B). On the surface of the n-type AlGaAs cladding layer 2c of the composite epitaxial layer,
A plurality of substantially spherical recesses 4 are formed by ordinary photolithography and etching using a bromine / methanol solution to obtain a laminate 5 (FIG. 1 (c)).

Next, the laminate 5 is dipped in an aqueous solution of ammonia / hydrogen peroxide to selectively dissolve and remove the substrate 1 to form the concave portion having the substantially spherical shape as shown in FIG. 1 (d). A composite epitaxial layer body 6 in which a plurality of 4 are formed on the surface of the n-type AlGaAs cladding layer 2c is obtained. On the p-type AlGaAs cladding layer 2a and the n-type AlGaAs cladding layer 2c of this composite epitaxial layer body 6,
After forming the p-side electrode 7 and the n-side electrode 8 by a conventional method [FIG. 1 (e)], they are divided by dicing to obtain semiconductor light emitting device pellets 10, 10 ,.
(F)]. The semiconductor light emitting device pellet 1 shown in FIG.
No. 0 has a single substantially spherical concave portion on the lower surface of the pellet 10, and this concave portion forming surface serves as a support fixing surface.

As a semiconductor light emitting device pellet obtained by a variation of the above manufacturing method, there is, for example, one shown in FIGS. The semiconductor light emitting device pellet 70 shown in FIG.
A plurality of substantially spherical recesses are formed on the lower surface thereof. The semiconductor light emitting device pellet 71 shown in FIG. 3 and the semiconductor light emitting device pellet 72 shown in FIG. 4 are the pellet 10 (FIG. 1) and the pellet 70 (respectively). 2) top surface,
The side surface is immersed in hydrofluoric acid to form the surface 9 having fine irregularities, that is, a surface with reduced total reflection.

Embodiment 2 FIG. 5 (g) is a sectional view of a semiconductor light emitting device pellet used in a semiconductor light emitting device, and FIGS. 5 (a) to 5 (g) are sectional views showing the manufacturing method in the order of steps. is there. A plurality of substantially spherical recesses 12 are formed in the mirror-polished surface 11a of the p-type GaAs substrate 11 [FIG. 5 (a)] [FIG. 5 (b)]. For that purpose, the mirror-polished surface 11a is etched using a conventional photolithography method and a bromine-methanol solution. FIG.
As shown in (c), the composite epitaxial layer 13, that is, p-type AlGa, is formed on the recess forming surface 11 a of the substrate 11.
As clad layer 13a (thickness: about 120 μm), p-type Al
GaAs active layer 13b (thickness: about 1 μm) and n-type AlG
An AlGaAs double heterojunction structure layer 13 composed of an aAs clad layer (thickness: about 120 μm) is deposited to obtain a laminated body 14.

N-type AlGa of composite epitaxial layer 13
A plurality of substantially spherical concave portions 15 are formed on the surface of the As clad layer 13c by a conventional photolithography and etching using a bromine-methanol solution, and the laminate 1 is formed.
4a is obtained [FIG. 5 (d)]. Next, the laminated body 14a is immersed in an aqueous solution of ammonia / hydrogen peroxide to selectively dissolve and remove the substrate 11 to form a substantially spherical surface formed on the substrate 11 as shown in FIG. 5 (e). Shaped recess 12
A composite epitaxial layer body 17 having a plurality of substantially spherical convex portions 16 having a shape corresponding to the above is formed on the substrate removal surface. After forming electrodes 18 and 19 on both surfaces of the composite epitaxial layer body 17 [FIG. 5 (f)], the semiconductor light emitting element pellets 20, 20, ... Are divided by dicing.
Is obtained [FIG. 5 (g)]. This semiconductor light emitting device pellet 2
0 has a single substantially spherical convex portion and a substantially spherical concave portion on the upper and lower surfaces of the pellet 20, respectively, and the lower surface having the concave portion serves as the support fixing surface.

Embodiment 3 FIG. 6 (g) is a sectional view of a semiconductor light emitting device pellet used in a semiconductor light emitting device, and FIGS. 6 (a) to 6 (g) are sectional views showing the manufacturing method in the order of steps. is there. In the manufacturing method according to this embodiment, in the process shown in FIG. 6B (corresponding to FIG. 5B of the second embodiment), the mirror-polished surface 31a of the p-type GaAs substrate 31 [FIG. Was etched using a conventional photolithography method and a bromine-methanol solution to form a large number of substantially spherical recesses 32 (FIG. 6B) smaller than those in the second embodiment. The same as Form 2. 6 (a)-(g)
Corresponds to FIGS. 2A to 2G, respectively.

Therefore, the semiconductor light emitting device pellet 40 manufactured by the manufacturing method according to the third embodiment [see FIG.
(G)] is the same as the semiconductor light emitting device pellet 20 according to the second embodiment except that the upper surface thereof is a surface having a plurality of substantially spherical convex portions corresponding to the substantially spherical concave portions 32 of the substrate. The shape. In FIG. 6, 33 is a composite epitaxial layer, 33a is a p-type AlGaAs cladding layer, 33b is a p-type AlGaAs active layer, and 33c is an n-type A.
lGaAs clad layer, 34 and 34a are laminated bodies, 35
Is a substantially spherical concave portion, 36 is a substantially spherical convex portion, 37 is a composite epitaxial layer body, 38 and 39 are electrodes, and 40 is a semiconductor light emitting element pellet.

Similar to the case of the first embodiment, as the semiconductor light emitting device pellet obtained by the modified examples of the manufacturing method of the second and third embodiments, for example, the semiconductor light emitting device pellet 73 shown in FIGS. There is ~ 78.

According to the semiconductor light emitting device of the present invention, since the lower surface (support fixing surface) of the semiconductor light emitting device pellet is a surface having a substantially spherical concave portion, the light emitted from the semiconductor light emitting device is higher than that of the conventional semiconductor light emitting device. Can be taken out more efficiently. This will be specifically described with reference to FIG. FIG. 13 is a cross-sectional view (schematic diagram) of a semiconductor light emitting device manufactured using the semiconductor light emitting device pellet 10 obtained by the manufacturing method of the first embodiment. In the figure, 45 is a conductive adhesive (for example, silver paste), and 46 is a support (schematic diagram).

In the figure, a solid line L ₁ with an arrow indicates an optical path of light, which is downward in the drawing, of light emitted by the semiconductor light emitting device according to the present invention. A broken line L ₂ with an arrow indicates that the lower surface of the semiconductor light emitting device pellet is a flat surface (in the figure,
Of the light emitted from the conventional semiconductor light emitting element, which is indicated by the one-dot chain line M), the optical path of the light directed downward in the drawing is shown. However, in these cases, the radiation angle θ of the downward light is the same.

The semiconductor light emitting device pellets are fixed to the support through a conductive fixing agent layer such as a silver paste having a high reflectance. Therefore, the support fixing surface (lower surface) of the pellets serves as a reflecting mirror. Carry.

As can be seen from FIG. 13, in the conventional semiconductor light emitting device, since the lower surface of the light emitting device is a plane mirror, the light directed downward is reflected by this plane mirror and the light emitting layer (p-type in FIG. 13). The incidence rate on the AlGaAs active layer 2b) is very large [L ₂ ]. Since this light emitting layer also serves as an absorption layer for emitted light, most of the light incident on the light emitting layer is internally absorbed by this light emitting layer, and the emitted light cannot be efficiently extracted to the outside.

On the other hand, in the semiconductor light emitting device according to the present invention, since the lower surface of the light emitting device is a convex mirror, the light traveling downward (in FIG. 13, the emission angle θ of the light is the same as the conventional example). The proportion of light reflected by the convex mirror and entering the side surface of the light emitting element without entering the light emitting layer increases [L
₁ ]. Since the light incident on the side surface of the light emitting element can be extracted to the outside, in the semiconductor light emitting element according to the present invention,
The emitted light can be extracted to the outside more efficiently than the conventional one.

[0031]

As is apparent from the above description, according to the semiconductor light emitting device of the present invention, the emitted light from the light emitting layer to the lower surface (toward the support fixing surface) can be efficiently extracted to the outside. The efficiency of extracting the emitted light to the outside can be increased, and the brightness (external output) of the semiconductor light emitting element can be extremely increased. Further, according to the manufacturing method of the present invention, the semiconductor light emitting device can be manufactured accurately and with high yield.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a semiconductor light emitting device pellet according to a first embodiment of the present invention and a cross-sectional view showing a manufacturing method thereof in the order of steps.

FIG. 2 is a cross-sectional view of a semiconductor element pellet obtained by a modification of the manufacturing method according to the first embodiment of the present invention.

FIG. 3 is a cross-sectional view of a semiconductor element pellet obtained by a modification of the manufacturing method according to the first embodiment of the present invention.

FIG. 4 is a sectional view of a semiconductor element pellet obtained by a modification of the manufacturing method according to the first embodiment of the present invention.

FIG. 5 is a cross-sectional view of a semiconductor light emitting device pellet according to a second embodiment of the present invention and a cross-sectional view showing the manufacturing method thereof in the order of steps.

FIG. 6 is a cross-sectional view of a semiconductor light emitting device pellet according to a third embodiment of the present invention and a cross-sectional view showing a manufacturing method thereof in the order of steps.

FIG. 7 is a cross-sectional view of a semiconductor element obtained by a modification of the manufacturing method according to the second embodiment of the present invention.

FIG. 8 is a sectional view of a semiconductor element obtained by a modification of the manufacturing method according to the second embodiment of the present invention.

FIG. 9 is a sectional view of a semiconductor element obtained by a modification of the manufacturing method according to the second embodiment of the present invention.

FIG. 10 is a sectional view of a semiconductor device obtained by a modification of the manufacturing method according to the third embodiment of the present invention.

FIG. 11 is a cross-sectional view of a semiconductor element obtained by a modification of the manufacturing method according to the third embodiment of the present invention.

FIG. 12 is a cross-sectional view of a semiconductor device obtained by a modification of the manufacturing method according to the third embodiment of the present invention.

FIG. 13 is a cross-sectional view showing, in comparison, the optical paths of emitted light in a semiconductor light emitting device according to the present invention and a conventional semiconductor light emitting device.

FIG. 14 is a sectional view showing an example of a conventional semiconductor light emitting device,
FIG. 5A is a cross-sectional view showing an example of a manufacturing method thereof in the order of steps.

[Explanation of symbols]

1, 11, 31, 51 p-type GaAs substrate 1a, 11a, 31a, 51a mirror-polished surface 2, 13, 33, 52 composite epitaxial layer 2a, 13a, 33a, 52a p-type AlGaAs cladding layer 2b, 13b, 33b, 52b p-type AlGaAs active layer 2c, 13c, 33c, 52c n-type AlGaAs clad layer 3, 5, 14, 14a, 34, 34a, 53 laminated body 4, 15, 35 substantially spherical recess (composite epitaxial layer) 6, 17 , 37, 55 composite epitaxial layer body 7, 8, 18, 19, 38, 39, 56, 57 electrode 9 surface having fine unevenness 10, 20, 40, 60, 70, 71, 72 semiconductor light emitting device pellet 73, 74, 75, 76, 77, 78 Semiconductor light emitting element pellet 12, 32 Substantially spherical recess (substrate) 16, 36 The convex portion of surface shape (composite epitaxial layer body) 45,61 conductive binder 46,62 support (frame) 63 sealing material 65 semiconductor light-emitting element

Claims (17)

[Claims] 1. A semiconductor light emitting device, wherein the lower surface (support fixing surface) of the semiconductor light emitting device pellet is a surface having one or a plurality of substantially spherical recesses. 2. The semiconductor light emitting device according to claim 1, wherein the upper surface of the semiconductor light emitting device pellet (the surface opposite to the support fixing surface) has a surface for reducing total reflection. 3. The semiconductor light emitting device according to claim 2, wherein the total reflection reducing shape surface is a surface having one or a plurality of substantially spherical convex portions. 4. The semiconductor light emitting device according to claim 2, wherein the surface with reduced total internal reflection is a surface having fine irregularities. 5. The semiconductor light emitting device according to claim 1, wherein a side surface of the semiconductor light emitting device pellet has a surface having fine irregularities. 6. The semiconductor light emitting device according to claim 1, wherein the crystal material of the composite epitaxial layer body forming the semiconductor light emitting device pellet is AlGaAs. 7. The composite epitaxial layer body is a p-type A
lGaAs clad layer, AlGaAs active layer and n-type A
7. The semiconductor light emitting device according to claim 1, further comprising an AlGaAs double heterojunction structure layer composed of an lGaAs clad layer. 8. A step of depositing a composite epitaxial layer constituting a semiconductor light emitting device on a compound semiconductor substrate by a liquid phase epitaxial growth method to form a laminate of the substrate and the composite epitaxial layer, and from the laminate. A step of selectively removing the substrate by etching to form a composite epitaxial layer body, a step of forming a plurality of substantially spherical concave portions on one surface of the composite epitaxial layer body, and forming the substantially spherical concave portion And a step of pelletizing the composite epitaxial layer body to form a semiconductor light emitting device pellet. 9. The method includes a step of treating the other surface of the composite epitaxial layer body (the surface on which the substantially spherical concave portion is not formed) with a chemical solution to form a surface having fine irregularities. The method for manufacturing a semiconductor light emitting device according to claim 8. 10. The method for manufacturing a semiconductor light emitting device according to claim 8, further comprising a step of treating a side surface of the composite epitaxial layer body with a chemical solution to form a surface having fine irregularities. Method. 11. The crystalline material of the compound semiconductor substrate is G
11. The method for manufacturing a semiconductor light emitting device according to claim 8, wherein the compound epitaxial layer is aAs, and the crystal material of the composite epitaxial layer is AlGaAs. 12. The composite epitaxial layer comprises p-type A
lGaAs clad layer, AlGaAs active layer and n-type A
12. The method for manufacturing a semiconductor light emitting device according to claim 8, further comprising an AlGaAs double heterojunction structure layer composed of an lGaAs clad layer. 13. A step of forming a plurality of recesses having a predetermined shape on the surface of a compound semiconductor substrate, and a composite epitaxial layer constituting a semiconductor light emitting device is deposited on the recessed surface of the compound semiconductor substrate by a liquid phase epitaxial growth method. And forming a laminate of the substrate and the composite epitaxial layer, forming a plurality of substantially spherical recesses on the uppermost layer side of the composite epitaxial layer, selectively the substrate from the laminate A step of removing by etching to form a composite epitaxial layer body in which convex portions corresponding to the concave portions formed in the substrate are formed on the substrate removal surface of the composite epitaxial layer; and the composite epitaxial layer body is pelletized to form semiconductor light emission. A method of manufacturing a semiconductor light emitting device, comprising the step of forming an element pellet. 14. The method for manufacturing a semiconductor light emitting device according to claim 13, wherein the shape of the concave portion formed on the surface of the compound semiconductor substrate is a substantially spherical concave shape. 15. The method of manufacturing a semiconductor light emitting device according to claim 13, further comprising a step of treating a side surface of the composite epitaxial layer body with a chemical solution to form a surface having fine irregularities. Method. 16. The crystalline material of the compound semiconductor substrate is G
16. The method for manufacturing a semiconductor light emitting device according to claim 13, wherein the compound material is aAs, and the crystal material of the composite epitaxial layer is AlGaAs. 17. The composite epitaxial layer is p-type A
lGaAs clad layer, AlGaAs active layer and n-type A
17. The method for manufacturing a semiconductor light emitting device according to claim 13, further comprising an AlGaAs double heterojunction structure layer composed of an lGaAs clad layer.