JPH01208885A - Semiconductor light emitting device - Google Patents

Abstract

PURPOSE:To effectively perform the function of a semiconductor laser by forming P-type, N-type buried layers at an interval from the surface of a semiconductor substrate, and forming first and second electrodes on the surface. CONSTITUTION:A clad layer 22, an optically active layer 23 and further a clad layer 24 are sequentially laminated and formed by epitaxial growth on a substrate 21. Here, the refractive indices of the layers 22, 24 are smaller than the optical refractive index of the layer 23. P-type and N-type buried layers 25, 26 are formed at both sides of the layer 23. Electrodes 27, 28 are formed on the layers 25, 26. An insulating film 29 is so formed on the layer 24 as to electrically isolate the electrodes 27, 28. With the thus configuration, the function of a semiconductor laser can be effectively performed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a semiconductor light emitting device constituting an embedded semiconductor laser, which can be effectively applied particularly to optical integrated circuits.

[Prior Art] A semiconductor laser is often constructed integrally with an integrated circuit or the like, and a buried type (BH) laser is used as such a semiconductor laser.

FIG. 4 shows the structure of a conventionally known buried type semiconductor laser. For example, an n-type semiconductor substrate 11, an n-type buried layer 12, an n-type buried layer 13,
The photoactive layer 14 is formed so as to be surrounded by these buried layers. The n-type buried layer 13 is set on the surface of the substrate 11, and the surface of the n-type buried layer 13 is covered with an insulating layer 15.

Further, a cladding layer 16 is laminated on the photoactive layer 14, and a cap layer 17 is formed on the surface side of the cladding layer IB.
A first electrode 18 is formed via the first electrode 18 .

Then, the second electrode 19 is formed on the back surface of the semiconductor substrate 11.

That is, in the semiconductor laser configured in this way, the two electrodes 18 and 19 are respectively connected to the semiconductor substrate 1.
1 is arranged and formed on both sides of the paper.

Therefore, when this semiconductor laser is monolithically integrated with other circuit elements, in order to connect the second electrode 19 formed on the back side of the substrate 11 to the other integrally integrated circuit elements. will require complex manufacturing processes.

[Problems to be Solved by the Invention] The present invention has been made in view of the above-mentioned points, and a pair of electrodes are both formed on one surface of a substrate, so that they can be easily integrated with other circuit elements. It is an object of the present invention to provide an embedded semiconductor light emitting device that can be configured as follows.

[Means for Solving the Problems] That is, in the semiconductor light emitting device according to the present invention,
P-type and n-type first and second buried layers are formed separated from each other at a distance from the surface of the semiconductor substrate, and the first and second buried layers are formed on the surface of each of the buried layers. 2 electrodes are formed. The first and second buried layers are connected by a photoactive layer, and both sides of the photoactive layer are sandwiched between cladding layers having a smaller optical refractive index than the photoactive layer.

[Function] In the semiconductor light emitting device configured as described above, current flows in a horizontal direction parallel to the surface of the semiconductor substrate, and the pair of electrodes is integrated by being formed on the surface of the substrate. This makes it easier to Therefore, it is effective for integrating and integrating semiconductor lasers with various semiconductor circuit elements.

[Embodiments of the invention] Hereinafter, one embodiment of the present invention will be described with reference to the drawings.

Figure 1 shows the cross-sectional configuration of a semiconductor laser.
A semi-insulating substrate is used as the base substrate 21, and when other circuit elements are integrated with this substrate 21, the electrical connection between this semiconductor laser and other circuit elements (for example, photodiode, FET, etc.) is separation became easy.

On such a substrate 21, a cladding layer 22, a photoactive layer 23, and a cladding layer 2 are formed by epitaxial growth.
4 are sequentially laminated. Here, the cladding layer 22.2
4, its optical refractive index is smaller than that of the photoactive layer 23.

P-type and n-type buried layers 25 and 26 are formed on both sides of the photoactive layer 23, respectively, and electrodes 27 and 28 are formed on the surfaces of these buried layers 25 and 2B, respectively. Letting it be formed. An insulating film 29 is formed on the surface of the cladding layer 24 so as to electrically isolate the electrodes 27 and 28 .

The structure of the semiconductor laser constructed in this way will be further explained according to its manufacturing process. First, as shown in FIG.
A cladding layer 22 is formed by epitaxially growing GaAs, and GaAs is roughly grown on this cladding layer 22.
The photoactive layer 2 is formed by epitaxially growing s.
form 3. Then, A is further applied on this photoactive layer 28.
I! Cladding layer 2 is formed by epitaxially growing GaAs.
4 to form a laminated structure in which the photoactive layer 23 is sandwiched between the cladding layers 22 and 24.

In this way the cladding layer 22,24 and the photoactive layer 2
3 is formed on the substrate 21, an insulating film 29 for striping is formed at the center of the cladding layer 24 on the front side, as shown in FIG. 2B. After the insulating film 29 is formed in this way, as shown in FIG. An etching mask 30 is formed so as to partially include the etching.

Here, silicon nitride, silicon oxide, and the like are used as materials constituting the insulating film 29 and the mask 30, respectively, so as to provide selectivity when removing the mask 30 by etching.

Once the etching mask 30 is formed in this manner, etching is performed using this mask 30 and the insulating film 29 as an etching mask to form a filling notch 31 as shown in the second diagram.

Then, an n-type buried layer 25 is formed in the notch 31 by epitaxial growth as shown in FIG. 2E.

Once the n-type buried layer 25 has been formed in this way, only the mask 30 is selectively etched away, and as shown in FIG. An etching mask 32 is formed by partially including the etching. This mask 32 is made of the same material as the mask 30. Then, etching is performed in this state to form a notch 33 as shown in FIG. 2G, and an n-type buried layer 2B is formed in the notch 33 by epitaxial growth as shown in FIG. 2H. .

After the n-type buried layer 2B is formed in this way, the mask 32 is removed by etching, and the n-type buried layer 2B is etched away.
By forming electrode layers on the surfaces of the n-type buried layer 5 and the n-type buried layer 26, a semiconductor laser as shown in FIG. 1 is completed.

When integrating such a semiconductor laser, since a mirror cannot be formed by cleavage, the mirror is formed by etching or a diffraction grating is used.

A semiconductor laser configured as described above is optically similar to a refractive index guided BH laser, that is, in terms of refractive index distribution, but its electrical configuration, for example, the state in which current flows, is essentially the same. There is a difference.

Generally, a BH (buried type) laser has a refractive index distribution not only in the vertical direction but also in the horizontal direction. For example, the optical refractive index of the photoactive layer 23 is made larger than the optical refractive index of any of the cladding layers 22, 24 and the buried layer 28. By setting such an optical layer refractive index distribution, the transverse mode, which is one of the oscillation modes of light, is stabilized.

Specifically, a photoactive layer 23 is built in that is cut off for modes other than the fundamental mode, and such stabilization means ensure that bends in optical output and current characteristics are removed. This improves the quality of the generated laser light.

While maintaining these characteristics of an embedded laser,
Furthermore, in order to make a semiconductor laser suitable for integration, the first condition is that all electrodes are formed on the upper surface and that electrical isolation is facilitated, and that the threshold current is kept small. The second condition is to ensure that both conditions are satisfied.

In this regard, considering the semiconductor laser shown in the above embodiment, the first condition is satisfied because the first and second electrodes 27 and 28 are both formed on the upper surface. In addition, in the conventional buried laser shown in FIG. It is designed to block current flowing through other parts. On the other hand, in the semiconductor laser of the embodiment shown in FIG. 1, current is injected into the photoactive layer 23 from the lateral direction. The current injection area becomes extremely small. Therefore, compared to the conventional buried laser shown in FIG. 4, the threshold value can be lowered sufficiently, making the semiconductor laser suitable for integration.

In addition to the materials shown in the description of the embodiments, materials constituting this semiconductor laser include, for example, G as the substrate 2I.
In addition to using As, for example, when GaAs is used as the substrate 21, A, I! as the cladding layer 22, 24, etc. Ga In P may be used, and InGaP may also be used as the material for the photoactive layer 23 . Further, for example, GaAs may be used as the substrate 21, InGBAsP mixed crystal may be used as the cladding layer 22, 24, and InGaAsP mixed crystal, which has a smaller optical refractive index than the cladding layer, may be used as the material for the photoactive layer 23. You can. Furthermore, the substrate 21 and the cladding layers 22 and 24 may be made of the same material.

That is, when the semi-insulating substrate 21 is made of ero-P as shown in FIG. 3, the cladding layer 22
and 24 are made of the same <InP, and in this case, the photoactive layer 23 sandwiched between the cladding layers 22 and 24 is made of InGaAsP.

As described above, the present invention is not limited to the materials described in the examples, but any material can be used as long as the optical refractive index of the material of the photoactive layer can be set smaller than the optical refractive index of the material of the cladding layer. It may be made of such materials.

[Effects of the Invention] As described above, according to the semiconductor light emitting device according to the present invention,
Since the first and second electrodes were able to be formed on the surface of the substrate, it is possible to achieve great effects when integrated with other circuit elements, and the function as a semiconductor laser is effective. You will be able to perform effectively.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing a cross-sectional structure for explaining a semiconductor laser according to an embodiment of the present invention, FIGS. 2A to 2H are diagrams showing the steps of manufacturing the semiconductor laser, and FIG. FIG. 4 is a sectional configuration diagram illustrating another embodiment of the present invention, and FIG. 4 is a sectional configuration diagram illustrating a conventional embedded laser. 21... Substrate (semi-insulating), 22.24... Cladding layer, 23... Photoactive layer, 25... P-type buried layer, 26... N-type buried layer, 27.28... ··electrode,
29...Insulating film. Applicant's agent Patent attorney Takehiko Suzue P:S1 Figure 4 Figure 2 Figure 2 A Figure 2 B ζ°S2 Figure C Figure 2 D g2 Figure E ・ Figure 2 F 02 Figure G Building 2 Figure H Engraving Figure 3

Claims (1)

[Claims] P-type and n-type first and second buried layers formed at intervals from the surface of a semiconductor substrate, and surfaces of the first and second buried layers, respectively. In the department,
first and second electrodes formed to be insulated and separated from each other; a photoactive layer formed to connect the first and second buried layers; and the photoactive layer. cladding layers are provided on both sides of the layer to sandwich the photoactive layer, and the optical refractive index of the cladding layer is set to be lower than the optical refractive index of the photoactive layer. A semiconductor light emitting device characterized by: