JPH02139985A - Optical integrated device and its manufacture - Google Patents

Abstract

PURPOSE:To reduce the degradation of a coupling efficiency caused by light scattering in an optical boundary and improve a light utilization factor and reduce optical noise component by a method wherein, in a coupling part between a light emitting device and the other optical device, a part of the active layer of the other optical device is enlarged. CONSTITUTION:A waveguide device 30a which serves as a waveguide is formed adjacent to a light emitting device 20. A recess 6 is formed in the extension of the first lower cladding layer 2 of the light emitting device 20 at a part adjacent to the light emitting device to form the second lower cladding layer 2a of the waveguide device 30a. The second active layer 7a of the waveguide device 30a is formed on the recess 6 to form an approximately flat surface. In other words, the second active layer 7a has an enlarged thickness in the part adjacent to the light emitting device 20. A second upper cladding layer 8a is formed on the second active layer 7a to form a surface approximately in the same plane as a first upper cladding layer 4. The depth of the recess 6 in the second active layer 7a is not necessarily uniform and may be gradually changed as shown by a broken line.

Description

[Detailed Description of the Invention] [Summary] This invention relates to an optical integrated device in which a plurality of optical elements having semiconductor active layers with different band gaps are integrated, and a method for manufacturing the same. In an integrated device, the decrease in coupling efficiency due to light scattering at the optical interface formed between multiple active layers is reduced, and the light utilization rate is increased.
The purpose of the present invention is to provide an optical integrated device that can reduce optical noise components, and is an optical integrated device in which a light emitting element and other optical elements are integrated on the same substrate. the other optical element has a lower cladding layer of 1, a first active layer formed of a first semiconductor thereon, and a first upper cladding layer thereon; a second lower cladding layer that is an extension of the lower cladding layer of the first active layer and a second semiconductor formed of a second semiconductor having a wider bandgap than the first semiconductor; a second active layer and a second upper cladding layer thereon, the second active layer having a thickness that increases toward the second lower cladding layer at a portion in contact with the first active layer. Configure it as follows.

[Industrial Field of Application] The present invention relates to an optical integrated device and a method for manufacturing the same, and more particularly to an optical integrated device in which a plurality of optical elements having a semiconductor active layer of a particular bandgap are integrated, and a method for manufacturing the same.

In optical communications, when trying to obtain modulated light, a light emitting element such as a semiconductor laser and other optical elements such as a modulator are used. It is convenient to integrate a plurality of these optical elements on the same substrate, and research is being carried out on forming an optical integrated device. °
Generally, the active layer of a light emitting device and the active layer of a modulating device have different band gaps. In such an optical integrated device including a plurality of active layers with different band gaps, it is desired to efficiently couple light from a light emitting element to other optical elements.

[Prior Art] Conventionally, one of the methods for integrating a light emitting element such as a semiconductor laser and an optical modulator is to integrate the active layer of the semiconductor laser and the active layer of the optical modulator on the same plane on the same substrate. They are formed adjacent to each other and shaped into stripes.

FIG. 4 shows an example of an optical integrated device including a semiconductor laser light emitting device 70 and an electroabsorption optical modulation device 80 according to the prior art.
52 is an n-type 1nP lower cladding layer, and 52a is an n-type 1nP lower cladding layer.
An n-type cladding region of the optical modulation device which is an extension of the lower cladding layer 52, 53 is an active layer of a semiconductor laser device made of, for example, InGaASP, and 57 is InGaAsP having a different composition.
54 is an upper cladding layer of a p-type 1nP semiconductor laser device, and 58 is an active layer of a p-type 1nP semiconductor laser device.
The p-type cladding region of the nP light modulation element, 60 is a common n
1llll electrode, and 61 is the pil! of the semiconductor laser device 70.
! The electrode 62 is the p-side electrode of the light modulation element 80. The active layer 57 of the light modulation element 80 transmits the laser light emitted from the active layer 53 of the semiconductor laser element 70 when there is no electric field,
Its composition is selected so that it has a band gap that absorbs light from the active layer 53 when an electric field is applied. For this reason, the active layer 53 of the semiconductor laser device and the active layer 57 of the light modulation device 80 need to have different compositions, and are formed separately. The region where the modulation element is to be formed is removed down to the active layer, and partial epitaxial growth is performed to form the structure of the light modulation element.

[Problems to be Solved by the Invention] In an optical integrated device in which a plurality of active layers with such band gaps are arranged adjacent to each other, an optical interface is formed between the plurality of active layers, and this interface is a barrier to light scattering. Cause.

Therefore, the coupling efficiency between the semiconductor light emitting element and other optical elements decreases, the light utilization rate becomes low, and the optical noise component becomes high.

An object of the present invention is to reduce the reduction in coupling efficiency due to light scattering at the optical interface formed between the plurality of active layers in an optical integrated device in which a plurality of active layers with a wide band gap are arranged adjacently, and to improve the utilization of light. High rate, light 9! An object of the present invention is to provide an optical integrated device that can reduce sound components.

Another object of the present invention is to arrange a plurality of active layers with wide band gaps adjacent to each other, form an optical interface therebetween, and reduce the reduction in coupling efficiency due to light scattering at the optical interface, thereby increasing the light utilization efficiency. An object of the present invention is to provide a method for manufacturing an optical integrated device that can easily manufacture an optical integrated device that can increase the optical noise component and reduce the optical noise component.

[Means for Solving the Problems] FIGS. 1A and 1B show diagrams explaining the principle of the optical integrated device of the present invention. FIG.
FIG. 1B shows an optical integrated device including a light emitting element 20 and a waveguide element 30a.

In FIG. 1(A), a first lower cladding layer 2 is formed on a substrate 1, and a first active layer 3 of a light emitting device 20 is formed on the first lower cladding layer 2.
A first upper cladding layer 4 is formed. The first active layer has a bandgap wavelength λ1 and a refractive index n1, and the upper and lower cladding layers 2.4 are transparent at the wavelength λ1 and have a refractive index smaller than nl. The extended portion of the lower cladding layer 2 has a recess 6 in a portion adjacent to the light emitting element, and forms a second lower cladding layer 2a which is an n-type region of the light modulation element 30. The second active layer 7 of the light modulation element 20 is formed on this,
It has a larger thickness on the recess 6 than on other parts. A second upper cladding layer 8, which is a p-type region of the light modulation element 30, is formed thereon, and forms substantially the same upper plane as the first upper cladding layer 4. The second active layer 7 has a bandgap wavelength λ2 (×λ1) close to λ1 but shorter than λ1, and its refractive index n2 is also different from nl. The cladding layers 2a and 8 above and below the second active layer 7 have a refractive index smaller than nl. A common electrode 10 and a first upper cladding layer 4 are disposed on the substrate 1.
A p-side electrode 11 of the light emitting element is formed on the p-side electrode 11 of the light emitting element, and a pill electrode 12 of the light modulating element is formed on the second upper cladding layer 8 .

In FIG. 1(B), a first lower cladding layer 2 of a light emitting device 20 is formed with a waveguide element 30a serving as a waveguide adjacent to the light emitting device 20 similar to that in FIG. 1(A). The extending portion has a recess 6 in a portion adjacent to the light emitting element, and forms a second lower cladding 2a of the waveguide element 30a. The second active layer 7a of the waveguide element 30a is formed on this to form a substantially flat plane. That is, the second active layer 7a has a partially increased thickness in a portion adjacent to the light emitting device 20. A second upper cladding layer 8a is provided on the second active layer 7a.
is formed, forming almost the same upper plane as the first upper cladding layer 4. The concave portion 6 of the second active layer 7a is limited to having a depth of -, but may have a depth that gradually changes as shown by the broken line in the figure.
At the other end, another optical element 3 including a third lower cladding layer 2b, a third active layer 7b, and a third upper cladding layer 8b is provided.
0b (for example a branching element) can be provided.

As described above, according to the present invention, the active layer of another optical element is partially thickened at the connection portion with the light emitting element.

[Function] Because the width of the active layer of another optical element is increased at the joint with the light emitting element, light scattering occurs at the interface between the active layer of the light emitting element and the active layer of the other optical element. However, the probability that it will be incorporated into the active layer of other optical elements increases. Therefore, the coupling efficiency between the light emitting element and other optical elements is improved, the light utilization rate is improved, and the optical noise component is reduced.

Therefore, for example, when coupled with an optical modulator, modulation efficiency can be improved.

[Example] An optical integrated device according to an example of the present invention is shown in FIGS.
), shown in (C), (A) is a perspective view, (B) is a cross-sectional view,
(C) is a plan view.

In FIGS. 2(A), (B), and (C), a laser emitting element 2 with an emission wavelength of 1.55 μm is placed on an n-type InP substrate 1.
0 and an electroabsorption optical modulation element 30 are formed. The laser emitting element 20 includes a first lower clubbed layer 2 formed of n-type 1nP on an lnP substrate 1, and an emission wavelength of 1.55 μm.
The electro-absorption optical modulator 30, which includes a first active layer 3 made of non-doped 11nGaASP and a first upper cladding layer 4 made of p-type 1nP, basically has a reverse bias diode structure. , n-type 1nP of 1 InP substrate
The second lower cladding layer 2a formed of
Nondogue I with a bandgap that becomes absorbent at m
Second active layer 7 formed of nGaAsP, P type 1nP
a second upper cladding layer 8 formed of .

The second lower cladding layer 2a is an n-type 1nP region continuous with the first lower cladding layer 2, but has a recessed portion 6 dug downward at a portion in contact with the laser emitting element 20.

For this reason, the active layer 7 has an increased thickness above the recess 6.

For example, the length of the laser emitting device 20 is 300 μm, the length of the electroabsorption optical modulation device 30 is 250 μm, the thickness tl of the lower cladding layer 2.2a is 2°0 μm, and the active layer 3.7
The thickness tl of the upper cladding layer 4.8 is 0.2 μm, the thickness t3 of the upper cladding layer 4.8 is 2.0 μm, and the length Q of the recess 6 is approximately 50 μm.
, the depth d is approximately 0.5 μm. For this reason, the second store sex pigeon 7
has a thickness of about 0.7 μm on the recess 6. It is preferable that the second active layer 7 has at least twice the thickness of the portion adjacent to the laser emitting element 20 (tl + d≧2t2).

The laser emitting device 20 and the electro-absorption optical modulating device 30 are shaped into a mesa stripe as shown in FIGS. Filled by region 9. The width of the stripe is, for example, approximately 2 μm.

A forward bias +v1 is applied to the laser emitting element 20, and a forward current is applied to cause laser oscillation.A reverse bias voltage -v2 and a modulation signal are superimposed and applied to the electroabsorption optical modulation element 30, and the laser oscillates. The laser light incident from the light emitting element 20 is modulated.

Next, a method for manufacturing an optical integrated device as shown in FIGS. 2(A), (B), and (C) will be described with reference to FIGS. 3(A>, (B), and (C)).

FIG. 3(A) shows the epitaxial growth process. On an n-type 1nP substrate 1, an n-type 1nP lower cladding layer 2 and a first active layer 3 of InGaASP for a laser emitting device 20 are formed by, for example, liquid crystal epitaxial growth. And continue to grow.

FIG. 3(B) shows the selective etching process.

For example, a mask 14 is formed and a portion of the first active layer 3 is selectively removed by wet chemical etching. Here, a mask 16 is also provided on a portion of the exposed second lower cladding layer 2a, which allows a gentle slope to be obtained by chemical etching, to expose the portion adjacent to the laser light emitting element. Furthermore, selective etching is performed on the exposed portion to remove only a portion of the thickness of the second lower cladding layer 2a, thereby forming the recess 6.

FIG. 3(C) shows the subsequent epitaxial growth process. First, the second active layer 7 of 1nGaAsP of the light modulation element 30 is selectively grown epitaxially on the exposed second lower cladding layer 2a. . After growing the second active layer 7 until it is substantially flush with the first active layer 3, a p-type 1nP upper cladding layer 4.8 is grown. Thereafter, electrodes are formed to create an optical integrated device including the laser emitting element 20 and the light modulating element 30.

Note that after first epitaxially growing up to the first active layer,
Although the case where selective etching is performed has been described, selective etching may be performed after first epitaxially growing up to the first upper cladding layer 4.

Although an embodiment of an optical integrated device including a laser emitting element and a light modulating element has been described, it is possible to similarly configure an optical integrated device including a laser emitting element and a waveguide element or other optical elements. It will be obvious to those skilled in the art.

Furthermore, it is obvious that the above-mentioned embodiments are not meant to be equally restrictive, and that various modifications, modifications, combinations, etc. are possible.4 [Effects of the Invention] The optical coupling between the element and other optical elements is improved, making it possible to increase the light utilization rate and lower the optical noise component0. For example, if the other optical element is a light modulation element, the modulation characteristics can be improved. You can improve.

Further, the optical integrated device as described above can be easily manufactured.

[Brief explanation of the drawing]

1(A) and (B) are diagrams explaining the principle of the optical integrated device of the present invention, and FIG. 2 (A), (B), and (C) are schematic diagrams of the optical integrated device according to the embodiment of the present invention. 3 (A>, (B), and (C) are sectional views showing the steps of manufacturing the optical integrated device shown in FIG. 2 according to an embodiment of the present invention; FIG. 4 7.7a 8.8a 10, 11, 12 First lower cladding layer Second lower cladding layer First active layer First upper cladding layer Recessed part. In the electrode diagram of the second active layer and second upper cladding layer, the substrate (A) light emitting element and light modulating element (A) it schematic perspective view (B) schematic top view CB) light emitting element and waveguide element Fig. 1<c>tpus plane area FIG. 2 shows an optical integrated channel device according to an embodiment of the present invention. (A) Epitaxial growth (B) Selective etching, (C) Epitaxial growth. Figure 2: Manufacturing process of the light concentrator M-channel device Figure 3: Figure 4

Claims (2)

[Claims] (1) An optical integrated device in which a light emitting element (20) and other optical elements (30, 30a) are integrated on the same substrate (1), wherein the light emitting element (20) is integrated on the substrate (1). a first lower cladding layer (2) above, a first active layer (3) made of a first semiconductor above it, and a first upper cladding layer (
4), and the other optical element (30, 30a) is
a second lower cladding layer (2a) which is an extension of the first lower cladding layer (2), and which is disposed adjacent to the first active layer (3) and further from the first semiconductor layer; A second active layer (7, 7) formed of a second semiconductor with a wide bandgap.
a) and a second upper cladding layer (8, 8a) thereon, the second active layer (7, 7a) comprising a first active layer (
3) An optical integrated device characterized by having an increased thickness on the second lower cladding layer (2a) side at a portion in contact with the second lower cladding layer (2a). (2) A method for manufacturing an optical integrated device including a light emitting element and other optical elements, the method comprising: depositing a layered structure including a first lower cladding layer (2) and a first active layer (3) on a substrate; (1) a step of epitaxially growing on the layered structure; a step of forming a mask on the layered structure and removing the exposed portion of the first active layer (3) to leave the active layer of the light emitting device; A part of the thickness of the first lower cladding layer (2) is removed to form a recess, and a second lower cladding layer (2) whose thickness is partially reduced is removed.
2a) and forming a second active layer (7, 7a) having a wider bandgap than the first active layer (3) on the second lower cladding layer (2a) including the recess. 1. A method of manufacturing an optical integrated device, comprising a step of selectively epitaxially growing.