阅读说明：本技术 电吸收调制器及半导体器件 (Electro-absorption modulator and semiconductor device ) 是由 蔡艳 方青 余明斌 于 2018-07-04 设计创作，主要内容包括：本发明涉及半导体技术领域,尤其涉及一种电吸收调制器及半导体器件。所述电吸收调制器,包括：SOI衬底,具有由SOI衬底的顶层硅形成的第一波导层；器件结构,包括沿所述SOI衬底的轴向方向层叠设置的多个Ⅲ-Ⅴ族材料层,且多个Ⅲ-Ⅴ族材料层是在所述顶层硅上外延生长形成的；所述第二波导层,与多个所述Ⅲ-Ⅴ族材料层中的多重量子阱层对齐设置；所述第一波导层,位于所述SOI衬底的埋氧化层与所述第二波导层之间,且与所述第二波导层之间通过倏逝波耦合的方式实现光信号的传播。本发明减小了光波耦合损耗,提高了电吸收调制器的光调制效率,改善了电吸收调制器的光调制性能。(The invention relates to the technical field of semiconductors, in particular to an electro-absorption modulator and a semiconductor device. The electro-absorption modulator comprising: an SOI substrate having a first waveguide layer formed of a top silicon of the SOI substrate; a device structure comprising a plurality of III-V material layers stacked along an axial direction of the SOI substrate, wherein the plurality of III-V material layers are formed by epitaxial growth on the top layer silicon; the second waveguide layer is arranged in alignment with the multiple quantum well layers in the III-V material layers; the first waveguide layer is positioned between the buried oxide layer of the SOI substrate and the second waveguide layer, and the first waveguide layer and the second waveguide layer realize the propagation of optical signals in an evanescent wave coupling mode. The invention reduces the optical wave coupling loss, improves the optical modulation efficiency of the electro-absorption modulator and improves the optical modulation performance of the electro-absorption modulator.)

1. An electro-absorption modulator, comprising:

an SOI substrate having a first waveguide layer formed of top silicon of the SOI substrate;

a device structure comprising a plurality of III-V material layers stacked along an axial direction of the SOI substrate, wherein the plurality of III-V material layers are formed by epitaxial growth on the top layer silicon;

a second waveguide layer disposed in alignment with the multiple quantum well layers in the plurality of group III-V material layers;

the first waveguide layer is positioned between the buried oxide layer of the SOI substrate and the second waveguide layer, and the first waveguide layer and the second waveguide layer realize the propagation of optical signals in an evanescent wave coupling mode.

2. The electroabsorption modulator of claim 1, wherein the plurality of group iii-v material layers comprises an n-type group iii-v material layer, a multiple quantum well layer, and a p-type group iii-v material layer stacked in this order along an axial direction of the SOI substrate; the multiple quantum well layer is disposed with a center aligned with a center of the second waveguide layer.

3. The electroabsorption modulator of claim 2, wherein the n-type group iii-v material layer comprises an n-type contact layer and a first optical confinement layer stacked in this order along an axial direction of the SOI substrate; the p-type III-V group material layer comprises a second optical limiting layer, a covering layer and a p-type contact layer which are sequentially stacked along the axial direction of the SOI substrate.

4. The electroabsorption modulator of claim 2 wherein the multiple quantum well layer is separated from the first waveguide layer by a distance greater than 0 μ ι η and less than or equal to 2 μ ι η along the axial direction of the SOI substrate.

5. The electroabsorption modulator of claim 3 wherein the material of the second waveguide layer is silicon nitride, silicon oxynitride, or amorphous silicon.

6. The electroabsorption modulator of claim 2, wherein the device structure further comprises a first buffer layer disposed between the plurality of group iii-v material layers and the buried oxide layer of the SOI substrate, a first electrode at a surface of the first buffer layer, and a second electrode disposed on the plurality of group iii-v material layers in a stacked manner along an axial direction of the SOI substrate.

7. The electroabsorption modulator of claim 6, wherein a second buffer layer is further disposed between the plurality of group iii-v material layers and the second electrode; the first buffer layer is an n-type silicon layer or a p-type silicon layer, and the second buffer layer is a p-type silicon layer or an n-type silicon layer correspondingly.

8. A semiconductor device, comprising:

an SOI substrate having a first waveguide layer formed of top silicon of the SOI substrate;

a first device structure comprising a plurality of first III-V family material layers which are stacked along the axial direction of the SOI substrate and formed by epitaxial growth on the top layer silicon; the first device structure is used for transmitting an optical signal to the second device structure;

a second device structure comprising a plurality of second III-V family material layers which are stacked along the axial direction of the SOI substrate and formed by epitaxial growth on the top layer silicon; the second device structure is used for modulating the optical signal;

a second waveguide layer between the first device structure and the second device structure disposed in alignment with a first multiple quantum well layer of the first plurality of group III-V material layers and a second multiple quantum well layer of the second plurality of group III-V material layers;

the first waveguide layer is positioned between the buried oxide layer of the SOI substrate and the second waveguide layer, and the first waveguide layer and the second waveguide layer realize the propagation of optical signals in an evanescent wave coupling mode.

9. The semiconductor device according to claim 8, wherein a material of the second waveguide layer is silicon nitride, silicon oxynitride, or amorphous silicon.

10. The semiconductor device according to claim 8, wherein a distance between the second waveguide layer and the first waveguide layer in an axial direction of the SOI substrate is greater than 0 μm and less than or equal to 2 μm.

Technical Field

The invention relates to the technical field of semiconductors, in particular to an electro-absorption modulator and a semiconductor device.

Background

High speed optical modulators are a very important component of silicon optical chips, and high speed, high performance, low cost, and compatibility with silicon optical platforms are major requirements for optical modulators. An Electro Absorption Modulator (EAM) is an optical signal modulation device fabricated by utilizing an exciton absorption effect in a semiconductor. Since the electro-absorption modulator is not limited by the carrier mobility rate, high rate modulation is easier to achieve.

Electro-absorption modulators made of three-five family materials are mature high-performance and high-rate optical modulation devices in the semiconductor field, but most of the existing three-five family electro-absorption modulators grow on the surfaces of three-five family based wafers, so that the cost is high, and the three-five family electro-absorption modulators are difficult to integrate with a CMOS (complementary metal oxide semiconductor) process. In order to solve this problem, one existing method is to bond a group iii-v optical device (e.g., a laser, an electro-absorption modulator, or a detector) to a silicon substrate, and light propagates between the group iii-v optical device and the silicon substrate by evanescent coupling; another existing method is to epitaxially grow a silicon germanium material directly onto a silicon substrate. However, neither of the above two methods can directly grow iii-v materials on silicon substrate, which limits the performance of semiconductor devices and results in higher manufacturing cost of the electro-absorption modulator.

Therefore, how to reduce the cost of the electro-absorption modulator while improving the optical modulation performance of the electro-absorption modulator is a technical problem to be solved.

Disclosure of Invention

The invention provides an electro-absorption modulator and a semiconductor device, which are used for solving the problem that the existing electro-absorption modulator can not improve the light modulation performance and simultaneously reduce the manufacturing cost.

In order to solve the above problems, the present invention provides an electro-absorption modulator comprising:

an SOI substrate having a first waveguide layer formed of top silicon of the SOI substrate;

a device structure comprising a plurality of III-V material layers stacked along an axial direction of the SOI substrate, wherein the plurality of III-V material layers are formed by epitaxial growth on the top layer silicon;

a second waveguide layer disposed in alignment with the multiple quantum well layers in the plurality of group III-V material layers;

the first waveguide layer is positioned between the buried oxide layer of the SOI substrate and the second waveguide layer, and the first waveguide layer and the second waveguide layer realize the propagation of optical signals in an evanescent wave coupling mode.

Preferably, the plurality of group iii-v material layers include an n-type group iii-v material layer, a multiple quantum well layer, and a p-type group iii-v material layer, which are sequentially stacked in an axial direction of the SOI substrate; the multiple quantum well layer is disposed with a center aligned with a center of the second waveguide layer.

Preferably, the n-type group iii-v material layer includes an n-type contact layer and a first optical confinement layer which are sequentially stacked along an axial direction of the SOI substrate; the p-type III-V group material layer comprises a second optical limiting layer, a covering layer and a p-type contact layer which are sequentially stacked along the axial direction of the SOI substrate.

Preferably, the multiple quantum well layer and the first waveguide layer are spaced apart from each other by a distance of greater than 0 μm and less than or equal to 2 μm in the axial direction of the SOI substrate.

Preferably, the second waveguide layer is made of silicon nitride, silicon oxynitride or amorphous silicon.

Preferably, the device structure further includes a first buffer layer disposed between the plurality of group iii-v material layers and the buried oxide layer of the SOI substrate, a first electrode located on a surface of the first buffer layer, and a second electrode stacked on the plurality of group iii-v material layers along an axial direction of the SOI substrate.

Preferably, a second buffer layer is further disposed between the plurality of iii-v material layers and the second electrode; the first buffer layer is an n-type silicon layer or a p-type silicon layer, and the second buffer layer is a p-type silicon layer or an n-type silicon layer correspondingly.

Preferably, the device further comprises a buried oxide layer located on the surface of the SOI substrate, and the first waveguide layer and the device structure are located on the surface of the buried oxide layer.

The present invention also provides a semiconductor device comprising:

an SOI substrate having a first waveguide layer formed of top silicon of the SOI substrate;

a first device structure comprising a plurality of first III-V family material layers which are stacked along the axial direction of the SOI substrate and formed by epitaxial growth on the top layer silicon; the first device structure is used for emitting optical signals to the second device structure;

a second device structure comprising a plurality of second III-V family material layers which are stacked along the axial direction of the SOI substrate and formed by epitaxial growth on the top layer silicon; the second device structure is used for modulating the optical signal;

a second waveguide layer between the first device structure and the second device structure disposed in alignment with a first multiple quantum well layer of the first plurality of group III-V material layers and a second multiple quantum well layer of the second plurality of group III-V material layers;

the first waveguide layer is positioned between the buried oxide layer of the SOI substrate and the second waveguide layer, and the first waveguide layer and the second waveguide layer realize the propagation of optical signals in an evanescent wave coupling mode.

Preferably, the second waveguide layer is made of silicon nitride, silicon oxynitride or amorphous silicon.

The distance between the second waveguide layer and the first waveguide layer along the axial direction of the SOI substrate is more than 0 μm and less than or equal to 2 μm.

According to the electro-absorption modulator and the semiconductor device, the plurality of III-V family material layers are directly grown on the top silicon surface of the SOI substrate in an epitaxial growth mode, so that the manufacturing process of the electro-absorption modulator is simplified, and the overall manufacturing cost of the electro-absorption modulator is reduced; and an upper waveguide layer and a lower waveguide layer are arranged along the axial direction of the SOI substrate, wherein the waveguide layer positioned on the upper layer is aligned with the multiple quantum well layers in the III-V group material layers, so that the optical wave coupling loss is reduced, the optical modulation efficiency of the electro-absorption modulator is improved, and the optical modulation performance of the electro-absorption modulator is improved.

Drawings

FIG. 1 is a schematic diagram of the overall structure of an electro-absorption modulator in a first embodiment of the present invention;

FIG. 2 is a schematic cross-sectional view of the device structure of an electro-absorption modulator in a first embodiment of the present invention;

fig. 3 is a schematic structural view of a semiconductor device in a second embodiment of the present invention.

Detailed Description

The following describes in detail embodiments of the electro-absorption modulator and the semiconductor device according to the present invention with reference to the drawings.

First embodiment

The present embodiment provides an electro-absorption modulator, fig. 1 is a schematic diagram of an overall structure of the electro-absorption modulator according to the present embodiment, and fig. 2 is a schematic cross-sectional diagram of a device structure of the electro-absorption modulator according to the present embodiment.

As shown in fig. 1 and fig. 2, the present embodiment provides an electro-absorption modulator, which includes an SOI (Silicon-On-Insulator) substrate, a device structure, a first waveguide layer 12, and a second waveguide layer 17. The first waveguide layer 12 is formed from the top silicon of the SOI substrate. Specifically, as shown in fig. 1, the SOI substrate includes a bottom layer silicon 10, a buried oxide layer 11, and a top layer silicon, which are stacked in this order from bottom to top along an axial direction of the SOI substrate. The first waveguide layer 12 is formed by etching the top silicon, for example, dry etching or wet etching.

The underlying silicon 10 of the SOI substrate is used to support the device structures, first waveguide layer 12 and second waveguide layer 17 thereon. The device structure comprises a plurality of III-V family material layers which are stacked along the axial direction of the SOI substrate, and the III-V family material layers are formed by sequentially carrying out epitaxial growth on the top layer silicon; the second waveguide layer 17 disposed in alignment with a Multiple Quantum Well (MQW) layer 14 in the plurality of iii-v material layers; the first waveguide layer 12 is located between the buried oxide layer 10 of the SOI substrate and the second waveguide layer 17, and the first waveguide layer 12 and the second waveguide layer 17 realize propagation of optical signals in an evanescent coupling manner. Wherein the group iii-v material layer refers to a material layer formed of a compound composed of elements of group iii and group v of the periodic table.

In the specific embodiment, a plurality of III-V group material layers are directly grown on the top silicon of the SOI substrate in an epitaxial growth mode, so that the high-speed modulation of the electro-absorption modulator is improved, and the cost of the epitaxial growth mode is lower, so that the overall manufacturing cost of the electro-absorption modulator is reduced; by arranging the upper waveguide layer and the lower waveguide layer which are coupled by evanescent waves, the coupling efficiency between the waveguide and the device structure is improved, the coupling loss is reduced, and the optical modulation efficiency is further improved.

In the present embodiment, the multiple Quantum well layer 14 is used as an active center of the device structure, and the QCSE (Quantum Confined Stark Effect) of the multiple Quantum well is used to change the voltage applied to the device structure (for example, whether or not the voltage is applied or the magnitude of the applied voltage is adjusted), so as to adjust the light absorption coefficient of the multiple Quantum well layer 14, and to better realize the modulation of light.

In order to have better optical coupling efficiency with the first waveguide layer 12, the material of the second waveguide layer 17 is preferably silicon nitride, silicon oxynitride or amorphous silicon.

In order to further reduce the coupling loss between the second waveguide layer 17 and the device structure, it is preferable that the device structure includes an n-type group iii-v material layer 15, a multiple quantum well layer 14, and a p-type group iii-v material layer 13, which are sequentially stacked in the axial direction of the SOI substrate; the multiple quantum well layers 14 are arranged with their centers aligned with the center of the second waveguide layer 17.

Specifically, as shown in fig. 1, an n-type group iii-v material layer, a multiple quantum well layer, and a p-type group iii-v material layer are sequentially arranged on the SOI substrate from bottom to top; or vice versa, namely the n-type III-V family material layer, the multiple quantum well layer and the p-type III-V family material layer are sequentially arranged on the SOI substrate from top to bottom. In the present embodiment, the direction from the underlying silicon 10 to the buried oxide layer 11 in the SOI substrate in the axial direction of the SOI substrate is taken as upward, and the direction from the buried oxide layer 11 to the underlying silicon 10 in the SOI substrate in the axial direction of the SOI substrate is taken as downward.

For example, an n-type iii-v group material layer, a multiple quantum well layer, and a p-type iii-v group material layer are sequentially arranged on the SOI substrate from bottom to top, as shown in fig. 2, the n-type iii-v group material layer 15 includes an n-type contact layer 151 and a first optical confinement layer 152 sequentially stacked along an axial direction of the SOI substrate; the p-type group iii-v material layer 13 includes a second optical confinement layer 131, a cladding layer 132, and a p-type contact layer 133, which are sequentially stacked in the axial direction of the SOI substrate. Wherein, the n-type contact layer 151 is directly formed by growing on the top silicon of the SOI substrate by using a selective epitaxial growth technique, and serves as a base for subsequently growing the multiple quantum well layer 14.

The materials of the n-type contact layer 151, the first optical confinement layer 152, the second optical confinement layer 131, the cladding layer 132 and the p-type contact layer 133 are all compounds composed of elements of main groups iii and v of the periodic table, i.e., iii-v materials. The specific material, doping type and thickness of each iii-v material layer in the device structure may be selected by those skilled in the art according to actual needs, for example, the selection may be performed according to the wavelength of light to be modulated by the electro-absorption modulator, and table 1 gives detailed information of a plurality of iii-v material layers in the device structure by way of example. In table 1, specific values of x, y, z, a, b, C, d, e and f may be set by those skilled in the art according to actual needs, for example, according to whether the light modulated by the electro-absorption modulator belongs to a C-band or an O-band, wherein the specific number of layers of the multiple quantum well layer 14 may be set by those skilled in the art according to actual needs, and the total thickness of the multiple quantum well layer 14 is preferably several tens nanometers to several hundreds nanometers.

TABLE 1 detailed information of multiple III-V material layers in device structures

Preferably, the distance between the multiple quantum well layer 14 and the first waveguide layer 12 in the axial direction of the SOI substrate is greater than 0 μm and less than or equal to 2 μm. More preferably, the multiple quantum well layer 14 is spaced from the first waveguide layer 12 by a distance of 100nm to 900nm in the axial direction of the SOI substrate. This is because the device structure includes a plurality of iii-v material layers stacked in the axial direction of the SOI substrate, i.e., a plurality of iii-v material layers need to be epitaxially grown on the top silicon of the SOI substrate, and in order to ensure the thickness of each layer and the overall performance of the device structure, the present embodiment has the distance between the multiple quantum well layer 14 and the first waveguide layer 12 in the axial direction of the SOI substrate greater than 0 μm and less than or equal to 2 μm. Since the center of the second waveguide layer 17 is disposed in alignment with the center of the multiple quantum well layer 14, the distance between the second waveguide layer 17 and the first waveguide layer 12 in the axial direction of the SOI substrate is also greater than 0 μm and less than or equal to 2 μm. As shown in fig. 1, a dielectric layer 18 is filled between the first waveguide layer 12 and the second waveguide layer 17.

For example, the first waveguide layer 12 includes a first sub-waveguide 121 and a second sub-waveguide 122 located on opposite sides of the device structure, the second waveguide layer 17 also includes a third sub-waveguide 171 and a fourth sub-waveguide 172 located on opposite photo-books of the device structure, and the first sub-waveguide 121 and the third sub-waveguide 171 are located on the same side of the device structure, and the second sub-waveguide 122 and the fourth sub-waveguide 172 are located on the same side of the device structure. The external light is transmitted to the third sub-waveguide 171 through the first sub-waveguide 121 in an evanescent coupling manner; the third sub-waveguide 171 couples the external light into the device structure, and then couples the external light into the fourth sub-waveguide 172 after being modulated by the device structure; the fourth sub-waveguide 172 transmits the external light modulated by the device structure to the second sub-waveguide 122 in an evanescent coupling manner; and finally transmitted to the outside through the second sub-waveguide 122.

Preferably, the device structure further includes a first buffer layer disposed between the plurality of group iii-v material layers and the buried oxide layer of the SOI substrate, a first electrode located on a surface of the first buffer layer, and a second electrode stacked on the plurality of group iii-v material layers along an axial direction of the SOI substrate. In order to be compatible with the CMOS process, it is further preferable that a second buffer layer is further disposed between the plurality of group iii-v material layers and the second electrode; the first buffer layer is an n-type silicon layer or a p-type silicon layer, and the second buffer layer is a p-type silicon layer or an n-type silicon layer correspondingly.

For example, an n-type iii-v group material layer, a multiple quantum well layer and a p-type iii-v group material layer are sequentially arranged on the SOI substrate from bottom to top, as shown in fig. 2, the device structure further includes a first buffer layer 16 disposed between the n-type iii-v group material layer 15 and the buried oxide layer 11 of the SOI substrate, an n-electrode 22 disposed on a surface of the first buffer layer 16, and a p-electrode 21 disposed on a surface of the p-type iii-v group material layer 13. By adopting the structure, the p-i-n diode is formed in the whole device structure, and when negative voltage is applied to the electro-absorption modulator, the higher the electric field intensity is, the better the modulation performance is. The first buffer layer 16 is an n-type silicon layer; a second buffer layer 23 is further disposed between the p-type iii-v material layer 13 and the p-electrode 21, and the second buffer layer 23 is a p-type silicon layer. Wherein the first buffer layer 16 may be formed by n-type ion doping a partial region in the top silicon in the SOI substrate.

The electroabsorption modulator provided by the specific embodiment directly grows a plurality of III-V family material layers on the top silicon surface of the SOI substrate in an epitaxial growth mode, simplifies the manufacturing process of the electroabsorption modulator, and reduces the overall manufacturing cost of the electroabsorption modulator; and an upper waveguide layer and a lower waveguide layer are arranged along the axial direction of the SOI substrate, wherein the waveguide layer positioned on the upper layer is aligned with the quantum well layers in the III-V group material layers, so that the optical wave coupling loss is reduced, the optical modulation efficiency of the electro-absorption modulator is improved, and the optical modulation performance of the electro-absorption modulator is improved.

Second embodiment

Fig. 3 is a schematic structural diagram of a semiconductor device according to an embodiment of the present invention, and for the same points as those in the first embodiment, the detailed description of the present embodiment is not repeated, and the following mainly describes differences from the first embodiment.

As shown in fig. 3, the semiconductor device includes an SOI substrate, a first device structure, a second device structure, a first waveguide layer 335, and a second waveguide layer 336. The first waveguide layer 335 is formed from the top silicon of the SOI substrate. Specifically, as shown in fig. 1, the SOI substrate includes a bottom layer silicon 30, a buried oxide layer 31, and a top layer silicon, which are stacked in this order from the bottom to the top in the axial direction of the SOI substrate. The first waveguide layer 335 is formed by etching the top silicon, for example, dry etching or wet etching.

The underlying silicon 30 of the SOI substrate is used to support the first device structure, the second device structure, the first waveguide layer 335 and the second waveguide layer 336 thereon. The first device structure comprises a plurality of first III-V family material layers which are stacked along the axial direction of the SOI substrate and formed by epitaxial growth on the top layer silicon; the first device structure is used for emitting optical signals to the second device structure; the second device structure comprises a plurality of second III-V family material layers which are stacked along the axial direction of the SOI substrate and formed by epitaxial growth on the top layer silicon; the second device structure is used for modulating the optical signal; the second waveguide layer 336 between the first device structure and the second device structure, disposed in alignment with the first multiple quantum well layer 322 of the first plurality of group iii-v material layers, and the second multiple quantum well layer 332 of the second plurality of group iii-v material layers; the first waveguide layer 335 is located between the buried oxide layer 31 of the SOI substrate and the second waveguide layer 336, and the first waveguide layer and the second waveguide layer 336 realize propagation of an optical signal by evanescent coupling. The specific material and thickness of each of the first iii-v material layers and the second iii-v material layers may be selected by those skilled in the art according to actual needs, for example, according to the wavelength band of the optical signal.

For example, the first device structure may be a laser structure and the second device structure may be an electro-absorption modulator structure. Wherein the laser further comprises gratings 325 on opposite sides of the plurality of first group iii-v material layers. In order to further improve the optical coupling efficiency and reduce the coupling loss, it is preferable that the grating 325 is simultaneously aligned with the first multiple quantum well layer and the second multiple quantum well layer. More preferably, the grating 325 is a DBR (distributed bragg reflector) type grating.

This embodiment enables the on-chip integration of two different types of device structures, such as the on-chip integration of an electro-absorption modulator with a laser. Specifically, as shown in fig. 2, the plurality of first iii-v group material layers include a first buffer layer 324, a first n-type iii-v group material layer 321, a first multiple quantum well layer 322, and a first p-type iii-v group material layer 323, which are sequentially stacked in the axial direction of the SOI substrate, and the center of the first multiple quantum well layer 322 is aligned with the center of the second waveguide layer 336; the plurality of second iii-v group material layers include a second buffer layer 334, a second n-type iii-v group material layer 331, a second multiple quantum well layer 332, and a second p-type iii-v group material layer 333, which are sequentially stacked in the axial direction of the SOI substrate, and the second multiple quantum well layer 332 is disposed in alignment with the center of the second waveguide layer 336. The first buffer layer 324 and the second buffer layer 334 may be formed by n-type ion doping of the top silicon of the SOI substrate.

The second waveguide layer 336 may include a first sub-waveguide layer 3361 and a second sub-waveguide layer 3362 on opposite sides of the second device structure. An optical signal emitted by the first device structure is coupled into the second device structure via the first sub-waveguide layer 3361, and the second device structure modulates the light and then couples the modulated light into the second sub-waveguide layer 3362; then, depending on the performance of the passive device, the modulated optical signal may be directly processed in the second sub-waveguide layer 3362, or may be transmitted to the first waveguide layer 335 by evanescent coupling for processing.

Preferably, the second waveguide layer 336 is made of silicon nitride, silicon oxynitride or amorphous silicon. To simplify at least the process, the grating 325 is made of the same material as the second waveguide layer 336. The distance between the second waveguide layer 336 and the first waveguide layer 335 along the axial direction of the SOI substrate is also greater than 0 μm and less than or equal to 2 μm. As shown in fig. 3, the first waveguide layer 335 and the second waveguide layer 336 are filled with a dielectric layer 34 therebetween.

The foregoing is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, various modifications and decorations can be made without departing from the principle of the present invention, and these modifications and decorations should also be regarded as the protection scope of the present invention.