JP3242910B2 - Semiconductor light emitting device - Google Patents

Description

The present invention relates to a semiconductor light emitting device, and more particularly to a semiconductor light emitting device using an InGaAlP-based material.

(Prior Art) In recent years, various light emitting diodes (semiconductor light emitting devices) using a direct transition type compound semiconductor material have been developed.
In particular, light-emitting diodes using InGaAlP-based materials are 580 mm
(Yellow) to 690 mm (red), it emits light and emits light by direct transition, so it is expected as a highly efficient light source.

A structure shown in FIG. 3 is known as an example of this type of light emitting diode. That is, the n-GaAs substrate 80
A buffer layer 81, an n-InGaAlP cladding layer 82, an undoped InGaP active layer 83 and a p-InGaAlP cladding layer 84 are grown and formed, and a p-InGaP intermediate band gap layer 85 and p-GaAs The contact layer 86 is formed by growth. Then, a p-side electrode 87 is formed on the contact layer 86, and an n-side electrode 88 is formed on the back surface of the substrate 80.

By the way, in the structure as shown in FIG.
To obtain high luminous efficiency by confining carriers sufficiently, the Al composition of the cladding layers 82 and 84 must be increased.
However, in the p-cladding layer, generally, when the Al composition is increased, the carrier concentration cannot be increased.
In the configuration shown in the figure, the carrier concentration of the p-cladding layer 84 is low. For this reason, the current injected from the electrode 87 is injected into the active layer 83 almost without spreading in the p-cladding layer 84, and the light emitting region is only the region 91 of the active layer 83 immediately below the electrode 87. .

In this case, light 93 extracted from the light emitting region 91 in the upper surface direction
Is the active layer without being absorbed by the cladding layer 84.
It has a wavelength corresponding to the band gap at 83. on the other hand,
Because of the double hetero structure, light emitted from the light emitting region 91 becomes light 94 that is guided through the active layer 83 and exits from the end face.
The end face light 94 has a longer wavelength than the light 93 extracted from the upper surface because the end face light 94 receives light absorption in the active layer 83. For this reason, the light 94 emitted from the end face has been removed as unnecessary light.
That is, in the conventional light emitting diode, waste light is radiated from the end face, and this is a factor that causes a decrease in light extraction efficiency.

(Problems to be Solved by the Invention) As described above, in a conventional semiconductor light emitting device having a double heterostructure portion, a light emitting region is provided immediately below an electrode on a light extraction side, and light emitted from an end face receives light absorption in an active layer. The wavelength differs from the light extracted from the upper surface (light extraction surface).
For this reason, it is necessary to remove the light emitted from the end face, and this has been a factor that causes a decrease in light extraction efficiency.

The present invention has been made in consideration of the above circumstances, and aims to eliminate a decrease in light extraction efficiency due to a difference in emission wavelength of light from the light extraction surface and light from the end surface, An object of the present invention is to provide a semiconductor light emitting device capable of improving light extraction efficiency.

[Structure of the Invention] (Means for Solving the Problems) The gist of the present invention is to make the wavelength of light emitted from the end face of the double heterostructure part the same as the light emitted from the top face, and to activate the double heterostructure part. The object is to improve the light extraction efficiency by extracting light emitted from the layer from both the upper surface and the end surface.

That is, the present invention provides a semiconductor light emitting device in which an active layer made of an InGaAlP-based material is sandwiched between cladding layers on a semiconductor substrate, and a first electrode is provided at least in an end face region on the double hetero structure. And a region where the first electrode does not exist is provided in a part other than the end surface region, and a second electrode is provided on the back surface of the semiconductor substrate.

(Operation) According to the present invention, since the first electrode is formed on the end surface region, a light emitting region is also formed on the end surface region, and light emitted from the light emitting region on this end surface absorbs light absorbed by the active layer. It is not affected and has the same wavelength as the light emerging from the top surface. Therefore, it is not necessary to remove the light emitted from the end surface, and by extracting this light together with the light emitted from the upper surface, it is possible to improve the light extraction efficiency.

(Examples) Hereinafter, details of the present invention will be described with reference to the illustrated examples.

FIG. 1 is a view for explaining a schematic configuration of a semiconductor light emitting device according to a first embodiment of the present invention, where (a) is a cross-sectional view showing a reference example, and (b) and (c) show the embodiments. It is sectional drawing which shows an example.

In FIG. 1A, reference numeral 10 denotes an n-GaAs substrate, on which an n-GaAs buffer layer 11, n-In _0.5 (Ga _0.3 Al
_0.7 ) _0.5 P clad layer 12, In _0.5 (Ga _0.8 Al _0.2 ) _0.5 P active layer 13, p-In _0.5 (Ga _0.3 Al _0.7 ) _0.5 P clad layer 14 is grown and formed. A p-In _0.5 Ga _0.5 P intermediate band gap layer 15 and a p-Ga
As contact layer 16 is formed by growth. Then, a p-side electrode (first electrode) 17 is formed on the contact layer 16,
An n-side electrode (second electrode) 18 is formed on the lower surface (back surface) of the substrate 10.

In order to realize the structure shown in FIG. 1, the contact layer 16 is epitaxially grown on the substrate 10 and the p-side electrode 17 is formed. Then, the contact layer 16 and the intermediate band gap layer 15 are selectively etched by RIE or the like. do it. In the figure, reference numeral 21 denotes a light-emitting region in the center, 22 denotes a light-emitting region in the end surface region, 23 denotes light emitted from the light extraction surface on the upper surface, and 24 denotes light emitted from the end surface.

With such a configuration, since the light emitting region 22 is formed in the end surface region together with the light emitting region 21 in the central portion, the end surface outgoing light 24 is also emitted without being absorbed by the active layer 13.
Therefore, the end face outgoing light 24 has the same emission wavelength as the top face outgoing light 23. Therefore, the end face outgoing light
There is no need to remove 24, and the light extraction efficiency can be improved. In the conventional structure, the intermediate band gap layer 14, the contact layer 15, and the p-side electrode 1
There are advantages such as realization with a simple configuration in which only 7 is added.

FIG. 1 (b) is basically the same as FIG. 1 (a), except that the region where the p-side electrode 17 is formed is
Is formed in the shape of a mesa partway. With such a configuration, the end face outgoing light 24 and the top face outgoing light 23 have the same wavelength, and the solid angle with respect to the top surface in the light emitting region 21 is widened, so that the light extraction efficiency can be further improved.

FIG. 1C is basically the same as FIG. 1A, except that the region where the p-side electrode 17 is formed is
Up to a mesa shape. In such a configuration, the upper surface emitting light 23 is formed by reflected light of the end surface emitting light 24 from the active layer 13 formed in a mesa shape. In other words, the end face emission light 24 and the top emission light 23 have the same emission wavelength,
The active layer 13 is formed in a mesa shape, and light emitted from the mesa end face is reflected by another mesa-shaped crystal and emitted, so that the light extraction efficiency can be further improved.

In the first embodiment, the buffer layer 11 is formed of n-Ga
AlAs or n-In _0.5 Ga _0.5 P, intermediate band gap layer 15
Even if is p-GaAlAs, the same effect as above can be obtained.
The active layer 13 may be p-type or n-type InGaAlP, or may be InGaP.

FIG. 2 is a view for explaining a schematic configuration of a semiconductor light emitting device according to a second embodiment of the present invention, where (a) is a cross-sectional view showing a reference example, and (b) and (c) show the embodiments. It is sectional drawing which shows an example.

The difference between the example of FIG. 2A and the example of FIG.
That is, the relationship between p and n is reversed. That is, the p-GaAs substrate 30
The p-In _0.5 Ga _0.5 P intermediate band gap layer 35, p-In
_0.5 (Ga _0.3 Al _0.7 ) _0.5 P cladding layer 32, In _0.5 (Ga _0.8 Al
_0.2 ) _0.5 P active layer 33 and n-In _0.5 (Ga _0.3 Al _0.7 ) _0.5 P
A cladding layer 34 is formed, and an n-GaAs contact layer 36 is grown and formed on the central portion and the end face region of the cladding layer 34. Then, an n-side electrode 37 is formed on the contact layer 36, and a p-side electrode 38 is formed on the lower surface of the substrate 10. In the drawing, reference numeral 41 denotes a light-emitting region in the center, 42 denotes a light-emitting region in the end surface region, 43 denotes light emitted from the light extraction surface on the upper surface, and 43 denotes light emitted from the end surface.

In such a configuration, since the light emitting region 42 is formed in the end face region, the end face light 44 and the top face light 43 have the same emission wavelength, and the end face light 44 is removed as in the conventional example. You don't have to. Therefore, similarly to the first embodiment, the light extraction efficiency can be improved.

FIGS. 2 (b) and 2 (c) are improvements of FIG. 2 (a), and are basically the same as FIGS. 1 (b) and 1 (c) except that the relationship between p and n is reversed. It is a structure of. Even with such a configuration, the same effects as in the first embodiment can be obtained. In the second embodiment, the same effects as described above can be obtained even if the intermediate band gap layer 35 is made of p-GaAs or p-GaAlAs, and the active layer 33 is made of p-type or n-type InGaAlP or InGaP.

The present invention is not limited to the above-described embodiments, and can be implemented with various modifications without departing from the scope of the invention.

[Effects of the Invention] As described in detail above, according to the present invention, by forming the light emitting region in the active layer of the double hetero structure portion in the end face region, the light emitted from the end face is the same as the light emitted from the upper surface. It can be used without removing the light emitted from the end face, and it is possible to realize a semiconductor light emitting device with high light extraction efficiency.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a schematic configuration of a semiconductor light emitting device according to a first embodiment of the present invention, FIG. 2 is a sectional view showing a schematic configuration of a second embodiment of the present invention, and FIG. FIG. 4 is an element structure sectional view for describing a problem of the semiconductor light emitting element of FIG. 10,30 ... GaAs substrate, 11 ... n-GaAs buffer layer, 12,14,32,34 ... InGaAlP cladding layer, 13,33 ... InGaAlP active layer, 15,35 ... InGaP intermediate band gap layer, 16,36 ... GaAs contact layer, 17,37 ... First electrode, 18,38 ... Second electrode, 21,41 ... Central light emitting region, 22,42 ... End face light emitting region , 23,43 ... top-side emission light, 24,44 ... end-side emission light.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-1-231379 (JP, A) JP-A-1-243483 (JP, A) JP-A-58-46685 (JP, A) JP-A-48-48 66384 (JP, A) JP-A-2-298083 (JP, A) JP-A-62-245687 (JP, A) JP-A-56-29382 (JP, A) JP-A-54-42989 (JP, A) JP-A-52-114289 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01L 33/00

Claims (2)

(57) [Claims] 2. A semiconductor light emitting device comprising: a semiconductor substrate having a double heterostructure portion in which an active layer made of an InGaAlP-based material is sandwiched by cladding layers; A first electrode, a second electrode on the back side of the semiconductor substrate, and the double heterostructure portion is selectively disposed from the first electrode side to the middle of the cladding layer on the first electrode side of the active layer. The region where the first electrode is formed is formed in a mesa shape, and the upper surface emission light and the end surface emission light from the region where the first electrode does not exist other than the central region and the peripheral region are formed. A semiconductor light-emitting device, wherein both are taken out. 2. A semiconductor light emitting device in which a double heterostructure portion in which an active layer made of an InGaAlP-based material is sandwiched between cladding layers is formed on a semiconductor substrate. A first electrode, a second electrode on the back side of the semiconductor substrate, and selectively extending the double heterostructure part from the first electrode side to a middle of the cladding layer on the second electrode side of the active layer. The region where the first electrode is formed is formed in a mesa shape, and the upper surface emission light and the end surface emission light from the region where the first electrode does not exist other than the central region and the peripheral region are formed. A semiconductor light-emitting device, wherein both are taken out.