JPH05307200A - Waveguide type optical switch and its manufacture - Google Patents

Abstract

PURPOSE:To make a first clad layer thin, to facilitate the inter-element separation, to achieve a monolithic integration on the same substrate and to speed up the action of the elements. CONSTITUTION:This waveguide-type optical switch 31 is provided with a semi- insulating substrate 32 formed with plural first core layers 34 separated either by a semi-insulating layer or a highly resistant layer on the surface, plural first core layers 36, second core layers 38, a second layer 39 opposite conductive to the clad layers 34, a first electrode 41 and a second electrode 42. Further, the manufacturing method is constituted by injecting an element to be semi- insulated or highly resistant to the part excluding the clad layer of a conductive crystal layer on the surface of the semi-insulating substrate or forming the semi-insulating layer or the highly resistant layer after the same part is selectively removed and subsequently forming the plural first core layers, the second core layers and second clad layers successively.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical communication system for transmitting information by light, an optical switch suitable for use as a key device of an arithmetic unit and an information processing system using light, and a manufacturing method thereof. ..

[0002]

2. Description of the Related Art Conventionally, there are the following two typical structures of this type of semiconductor waveguide type optical switch. First, as a first example, as shown in FIG. 21, there is a directional coupler type optical switch (hereinafter abbreviated as an optical switch) 1 that utilizes a change in refractive index due to current injection. This optical switch 1 is formed on a high-concentration n-type indium phosphide (n-InP) semiconductor substrate 2 by an epitaxial crystal growth method.
Low concentration n-InP lower cladding layer 3, low concentration n-I
An nGaAsP first core layer 4 and a non-doped InP etch stop layer 5 are sequentially grown, and non-doped InGaAsP is formed at a predetermined position on the non-doped InP etch stop layer 5.
The second core layers 6, 6 are grown and these second core layers 6, 6 are
A non-doped or high-resistance InP upper clad layer 7 is grown so as to fill the upper portion 6 and zinc (Zn) is diffused at a predetermined position of the upper clad layer 7 to form high-concentration p-type semiconductor zinc diffusion layers 8 and 8. An insulating film 9 made of silicon dioxide (SiO ₂ ) is formed around these zinc diffusion layers 8 and, and an upper portion for independently applying voltage or current injection to each upper portion of the zinc diffusion layers 8 and 8. The electrodes 10 and 10 are formed, and the lower electrode 11 is formed on the bottom surface of the n-InP substrate 2, and the optical waveguide 1 is formed by the first core layer 4 and the second core layer 6.
2 (13) is constructed (reference document: E.L.
allier et al., ECOC'91 PD Papers, p44
-P47, 1991).

In order to operate the optical switch 1, a forward voltage, that is, a positive voltage is applied to the upper electrode 10 across both ends of the pin structure described above, and a current is injected into the second core layer 6. The refractive index of the second core layer 6 changes depending on the injected carriers. As a result, the propagation state of the light of the second core layer 6 to which the current is injected changes, and the perfect coupling condition of the directional coupler is broken, whereby the optical path of the light is switched and switching is performed. In addition, a reverse voltage, that is, a negative voltage is applied to the upper electrode 10,
Even if an electric field is applied to the core layer 6, the second
The refractive index of the core layer 6 changes, and similar switching is performed.

As a second example, as shown in FIG. 22, a directional coupler type optical switch (hereinafter abbreviated as an optical switch) 2 which utilizes the change of the refractive index with the application of voltage.
There is one. The optical switch 21 comprises a high-concentration n-InP lower clad layer 22 and a non-doped InGa layer formed on a high-concentration n-InP substrate 2 by an epitaxial crystal growth method.
A first core layer 23 having a multiple quantum well structure in which a number of well layers made of As and barrier layers made of non-doped InAlAs are stacked, and a non-doped InGaAsP etch stop layer 2
4. The etch stop layer 5 is sequentially grown, and InGaAsP second core layers 25, 25 made of non-doped or p-type semiconductor are grown at predetermined positions on the etch stop layer 5.
The high-concentration p-InP upper cladding layers 26, 26 and the high-concentration p-type so as to fill the second core layers 25, 25.
The InGaAs contact layers 27, 27 are grown, and the upper cladding layers 26, 26 and the contact layers 27, 27 are surrounded by high resistance or undoped or low concentration n-type In.
The contact layers 27 and 2 are buried by the P buried layer 28.
Upper electrodes 10 and 10 are formed on the upper part of the n-InP
The lower electrode 11 is formed on the bottom surface of the substrate 2, and the first core layer 23 and the second core layer 25 form an optical waveguide 29 (30).

In order to operate the optical switch 21, a reverse voltage, that is, a negative voltage is applied to the upper electrode 10 across the pin structure as described above, and the first core layer 2 is operated.
When an electric field is applied to the quantum well of the first core layer 23, the quantum well of the first core layer 23 becomes a quantum confined Stark effect.
The absorption coefficient and the refractive index are changed by the fined Stark Effect. As a result, the light propagation state of the first core layer 23 to which the voltage is applied also changes, and the perfect coupling condition of the directional coupler is broken, whereby the optical path of the light is switched and switching is performed.

[0006]

By the way, in the conventional optical switch 1, it is necessary to apply a voltage or inject a current to each of the optical waveguides 12 and 13 independently. Since the n-InP substrate 2 is commonly used as a common conductor, the electrical isolation of the optical waveguides 12 and 13 must be achieved by forming a p-type conductive layer. Therefore, in this optical switch 1, the upper clad layer 7
P-type zinc diffusion layers 8 and 8 are formed inside the non-doped or high-resistance upper cladding layer 7 by diffusing zinc into the upper cladding layer 7. However, this diffusion step has a drawback that the production yield is significantly reduced because of the risk of device damage due to the high temperature treatment necessary for diffusion and the need for a high level of control of the diffusion distance. Furthermore, the use of a conductive substrate causes an increase in stray capacitance associated with the wiring on the substrate, which makes it difficult to separate elements in monolithic integration with other electric elements. It also has the drawback of adversely affecting. Also, the lower electrode 1
Since 1 must be arranged on the bottom surface of the n-InP substrate 2, there is also a drawback that the process becomes complicated and the cost of the product increases.

Further, in the optical switch 21, since the conductive n-InP substrate 2 is shared as a common conductor, the electric separation of the optical waveguides 29 and 30 is achieved by the second core layers 25 and 25. It is inevitable that the p-type conductive layer of the upper clad layer 26 is processed into a ridge shape and then buried and grown again. However, in this buried growth, since the space between two ridges having a narrow interval of 2 μm is buried, there is a problem that the region selectivity between the buried part and the other part is difficult, and the light confinement and It is extremely difficult to flatly embed the upper clad layer 26, 26 having a thickness of about 1.5 to 2 μm, which is necessary for avoiding the light loss due to the electrode, up to the high resistance layer thereunder and having a large step difference. However, there is also a drawback that it requires a high degree of controllability. Further, when the buried layer 28 is made to have a high resistance, it is affected by the impurity diffusion from the p-type semiconductor in the ridge portion which is the buried layer 28, so that it becomes more difficult to control the growth condition and the manufacturing yield is increased. It had the drawback of significantly reducing it.

Further, the use of a conductive substrate has a problem that it causes an increase in stray capacitance due to wiring on the substrate and makes it difficult to isolate elements from each other in monolithic integration with other electrical elements. However, there is also a drawback that the device performance is adversely affected. In addition, the lower electrode 11 is formed of the n-InP.
Since it has to be arranged on the bottom surface of the substrate 2, there is a drawback that the process becomes complicated and the cost of the product increases.

Further, in the conventional optical switch 1 (21), since the electrical control of each optical waveguide 12, 13 (29, 30) is performed independently, each waveguide 12, 13 (29, 3) is controlled.
0) is required to be electrically separated. However, in the conventional method using a conductive substrate, in order to realize this separation, the conductive layer is electrically connected to the upper clad layer in the multilayer structure made of the epitaxial crystal that constitutes the switch. A high-resistance or non-doped crystal layer to form a switch after forming a conductive diffusion layer or processing the upper clad layer into a ridge shape. Manufacturing technology is required, and it has been difficult to secure the yield of device manufacturing.

The present invention has been made in view of the above circumstances, and solves various problems and drawbacks of the related art, and in addition to the steps of element processing or crystal growth associated with electrical isolation between optical waveguides. SUMMARY OF THE INVENTION It is an object of the present invention to provide a waveguide type optical switch and a method for manufacturing the same that can solve the above problems and improve the manufacturing yield.

[0011]

In order to solve the above problems, the present invention adopts the following waveguide type optical switch and its manufacturing method. That is, the waveguide type optical switch according to claim 1 is provided with a semi-insulating substrate and a plurality of conductive layers provided on the semi-insulating substrate and separated from each other by either the semi-insulating layer or the high resistance layer. A first cladding layer of
A plurality of first core layers provided on each of the plurality of first clad layers and parallel to each other; a second core layer provided on the first core layers; and a second core A second clad layer provided on the layer and having a conductivity type opposite to that of the first clad layer, a first electrode provided on the second core layer, and provided on the semi-insulating substrate. A plurality of second electrodes, and the plurality of first core layers and the plurality of second core layers respectively form optical waveguides, and the magnitude of the voltage or the current to be applied to these optical waveguides is large. The optical path of the light propagating in the optical waveguide is switched by controlling the height.

A waveguide type optical switch according to a second aspect is provided with a semi-insulating substrate and the semi-insulating substrate.
A plurality of conductive first clad layers separated from each other by either a semi-insulating layer or a high resistance layer; a first core layer provided on the plurality of first clad layers; A plurality of second core layers provided in parallel with each other on one core layer and above each of the plurality of first clad layers; and the first clad provided on these second core layers. A second clad layer having a conductivity type opposite to that of the layer, a first electrode provided on the plurality of second core layers, and a plurality of second electrodes provided on the semi-insulating substrate. Equipped with,
Optical waveguides are respectively constituted by the first core layer and the plurality of second core layers, and propagate in the optical waveguides by controlling the voltage applied to these optical waveguides or the magnitude of the injected current. It is characterized by switching the optical path of light.

A waveguide type optical switch according to a third aspect is provided with a semi-insulating substrate and the semi-insulating substrate.
A plurality of conductive first clad layers separated from each other by either a semi-insulating layer or a high resistance layer, and a plurality of first cores provided on each of the plurality of first clad layers and parallel to each other. A layer, a second core layer provided on the first core layer, and a second clad layer provided on the second core layer and having the same conductivity type as the first clad layer. A first electrode provided on the second core layer,
A plurality of second electrodes provided on the semi-insulating substrate, and the plurality of first core layers and the plurality of second core layers respectively form optical waveguides, and are applied to these optical waveguides. It is characterized in that the optical path of the light propagating in the optical waveguide is switched by controlling the applied voltage or the magnitude of the injected current.

A waveguide type optical switch according to a fourth aspect is provided with a semi-insulating substrate and the semi-insulating substrate.
A plurality of conductive first clad layers separated from each other by either a semi-insulating layer or a high resistance layer; a first core layer provided on the plurality of first clad layers; A plurality of second core layers provided in parallel to each other on one core layer and above each of the plurality of first clad layers, and the first clad provided on top of these second core layers. A second clad layer having the same conductivity type as the layer, a first electrode provided on the plurality of second core layers, and a plurality of second electrodes provided on the semi-insulating substrate. Optical waveguides are respectively constituted by the first core layer and a plurality of second core layers, and the optical waveguides are controlled by controlling the voltage applied to these optical waveguides or the magnitude of the injected current. The feature is that the optical path of light propagating inside is switched.

Further, a waveguide type optical switch according to a fifth aspect is the waveguide type optical switch according to the first, second, third or fourth aspect, wherein at least the width of the first and second core layers is wide. One of the core layers is characterized by being formed of a quantum well structure, a quantum wire structure, or a quantum box structure.

The waveguide type optical switch according to claim 6 is the waveguide type optical switch according to claim 3 or 4, wherein at least the wider core layer of the first and second core layers is used. Has an undoped quantum well layer, an n-type conductive layer having n-type conductivity, and conductivity intermediate between these layers, at least a part of which has a p-type conductivity type, and It is characterized by having a three-layer structure including an intermediate layer made of a semiconductor having a bandgap wider than that of the semiconductor forming the quantum well layer and the n-type conductive layer.

A waveguide type optical switch according to a seventh aspect is the waveguide type optical switch according to the sixth aspect, wherein the wider core layer has a multilayer structure in which the three-layer structure is repeated. It is characterized by being done.

A waveguide type optical switch according to claim 8 is provided with a semi-insulating substrate and the semi-insulating substrate.
A plurality of conductive first clad layers separated from each other by either a semi-insulating layer or a high resistance layer; and a plurality of core layers provided on each of the plurality of first clad layers and parallel to each other, A second clad layer provided on the core layers and having a conductivity type opposite to that of the first clad layer; a first electrode provided on the plurality of core layers; and a semi-insulating substrate. A plurality of second electrodes provided, and switching the optical path of light propagating in the optical waveguide by controlling the magnitude of the voltage applied or the current injected to the plurality of core layers. I am trying.

The waveguide type optical switch according to a ninth aspect is provided with a semi-insulating substrate and the semi-insulating substrate.
A plurality of conductive first clad layers separated from each other by either a semi-insulating layer or a high resistance layer; and a plurality of core layers provided on each of the plurality of first clad layers and parallel to each other, A second clad layer provided on these core layers and having the same conductivity type as the first clad layer, a first electrode provided on the plurality of core layers, and a semi-insulating substrate. A plurality of second electrodes provided, and switching the optical path of light propagating in the optical waveguide by controlling the magnitude of the voltage applied or the current injected to the plurality of core layers. I am trying.

The waveguide type optical switch according to claim 10 is the waveguide type optical switch according to claim 8 or 9, wherein the core layer has a quantum well structure, a quantum wire structure or a quantum box structure. It is characterized by being constituted by.

Further, the waveguide type optical switch according to claim 11 is the waveguide type optical switch according to claim 9, wherein the core layer is an undoped quantum well layer and an n-type having n-type conductivity. A conductive layer and an intermediate conductivity between these layers, at least a part of which has a p-type conductivity, and a wider bandgap than the semiconductor forming the quantum well layer and the n-type conductive layer. 3 consisting of a semiconductor intermediate layer
It is characterized by being configured by a layered structure.

A waveguide type optical switch according to a twelfth aspect is the waveguide type optical switch according to the eleventh aspect.
It is characterized in that the core layer has a multi-layer structure in which the three-layer structure is repeated.

In the method of manufacturing a waveguide type optical switch according to a thirteenth aspect, a conductive crystal layer is formed on the surface of a semi-insulating substrate, and a portion of the crystal layer other than a portion where a clad layer is to be formed. A plurality of first clad layers separated from each other by injecting an element for semi-insulating the crystal layer or increasing the resistance thereof, and then being parallel to each other on each of the plurality of first clad layers. A plurality of first core layers, a second core layer on the first core layers, and a second clad layer having a conductivity type opposite to that of the first clad layer on the second core layers in order; And then forming a first electrode on the second core layer and a plurality of second electrodes on the semi-insulating substrate.

According to a fourteenth aspect of the present invention, in the method of manufacturing a waveguide type optical switch, a conductive crystal layer is formed on the surface of a semi-insulating substrate, and a portion of the crystal layer other than a portion where a clad layer is to be formed. A plurality of first clad layers separated from each other by injecting an element for semi-insulating or increasing the resistance of the crystalline layer into a first core layer, and then forming a first core on the plurality of first clad layers. A layer, a plurality of second cores parallel to each other on the first core layer and above each of the plurality of first clad layers.
Core layers, a second clad layer having a conductivity type opposite to that of the first clad layer is sequentially formed on the second core layers, and then a first electrode is formed on the second core layers. Moreover, a plurality of second electrodes are respectively formed on the semi-insulating substrate.

In the method of manufacturing a waveguide type optical switch according to a fifteenth aspect, a conductive crystal layer is formed on a surface of a semi-insulating substrate, and a portion of the crystal layer other than a portion where a clad layer is to be formed. A plurality of first clad layers separated from each other by injecting an element for semi-insulating the crystal layer or increasing the resistance thereof, and then being parallel to each other on each of the plurality of first clad layers. A plurality of first core layers, a second core layer on the first core layers, and a second clad layer of the same conductivity type as the first clad layer on the second core layer in this order. And then forming a first electrode on the second core layer and a plurality of second electrodes on the semi-insulating substrate.

According to a sixteenth aspect of the present invention, in the method of manufacturing a waveguide type optical switch, a conductive crystal layer is formed on the surface of a semi-insulating substrate, and a portion of the crystal layer other than a portion where a clad layer is to be formed. A plurality of first clad layers separated from each other by injecting an element for semi-insulating or increasing the resistance of the crystalline layer into a first core layer, and then forming a first core on the plurality of first clad layers. A layer, a plurality of second cores parallel to each other on the first core layer and above each of the plurality of first clad layers.
Core layers, a second clad layer of the same conductivity type as the first clad layer is sequentially formed on the second core layer, and then a first electrode is formed on the second core layer. Moreover, a plurality of second electrodes are respectively formed on the semi-insulating substrate.

According to a seventeenth aspect of the present invention, in the method of manufacturing a waveguide type optical switch, a conductive crystal layer is formed on the surface of a semi-insulating substrate, and the crystal layer is selectively removed to separate predetermined layers. A plurality of first clad layers each having a shape, a semi-insulating layer or a high resistance layer is formed in a selectively removed portion of the crystal layer, and a plurality of parallel first parallel clad layers are formed on each of the plurality of first clad layers. A first core layer, a second core layer on the first core layer, and the first core layer on the second core layer.
Second cladding layer of opposite conductivity type to that of the first cladding layer are sequentially formed, and then a first electrode is formed on the second core layer.
A plurality of second electrodes are respectively formed on the semi-insulating substrate.

In the method of manufacturing a waveguide type optical switch according to claim 18, a conductive crystal layer is formed on the surface of a semi-insulating substrate, and the crystal layer is selectively removed so as to be separated from each other in a predetermined manner. A plurality of first clad layers having a shape, a semi-insulating layer or a high resistance layer is formed on the selectively removed portion of the crystal layer, and then a first insulating layer is formed on the plurality of first clad layers.
Core layers, a plurality of second core layers that are parallel to each other on the first core layer and above each of the plurality of first clad layers, and the first clad on the second core layers. A second cladding layer having a conductivity type opposite to that of the layer, and then forming a first electrode on the second core layer and a plurality of second electrodes on the semi-insulating substrate. It is characterized by doing.

In the method of manufacturing a waveguide type optical switch according to a nineteenth aspect of the invention, a conductive crystal layer is formed on the surface of a semi-insulating substrate, and the crystal layer is selectively removed so as to be separated from each other by a predetermined distance. A plurality of first clad layers each having a shape, a semi-insulating layer or a high resistance layer is formed in a selectively removed portion of the crystal layer, and a plurality of parallel first parallel clad layers are formed on each of the plurality of first clad layers. A first core layer, a second core layer on the first core layer, and the first core layer on the second core layer.
A second clad layer having the same conductivity type as that of the first clad layer is sequentially formed, and then a first electrode is formed on the second core layer.
A plurality of second electrodes are respectively formed on the semi-insulating substrate.

According to a twentieth aspect of the present invention, in a method of manufacturing a waveguide type optical switch, a conductive crystal layer is formed on a surface of a semi-insulating substrate, and the crystal layer is selectively removed to separate predetermined layers. A plurality of first clad layers having a shape, a semi-insulating layer or a high resistance layer is formed on the selectively removed portion of the crystal layer, and then a first insulating layer is formed on the plurality of first clad layers.
Core layers, a plurality of second core layers that are parallel to each other on the first core layer and above each of the plurality of first clad layers, and the first clad on the second core layers. A second clad layer having the same conductivity type as that of the first layer, and then forming a first electrode on the second core layer and a plurality of second electrodes on the semi-insulating substrate. It is characterized by doing.

The above-mentioned semi-insulating substrate is one that becomes an insulator in the vicinity of room temperature among semiconductor substrates, and is, for example, a III-V group compound semiconductor such as indium phosphide (InP) or gallium arsenide (GaAs). Can be mentioned. Further, as the element for semi-insulating or increasing the resistance of the crystal layer, for example, in the case of a crystal layer of a III-V group compound semiconductor such as InP or GaAs, oxygen (O), hydrogen (H), iron (Fe) is used. ,
Chromium (Cr) and the like are effective.

[0032]

In the waveguide type optical switch according to claim 1, 2, 3 or 4, the use of the semi-insulating substrate eliminates absorption of light by the substrate, and the semi-insulating substrate serves as a lower clad. It can be used as a part.
Therefore, the first clad layer can be thinned and downsized. In addition, it becomes easy to separate the elements from other elements that perform electrical operation, and monolithic integration with other elements on the same substrate becomes possible, and stray capacitance such as wiring can be reduced, and high-speed element operation can be achieved. Can be realized.

Further, by forming a plurality of conductive first clad layers separated from each other by either the semi-insulating layer or the high resistance layer on the semi-insulating substrate, the first clad layer in these first clad layers is formed. Good electrical isolation. Further, by forming a plurality of optical waveguides with the first core layer and the second core layer, it is possible to reduce the thickness of the core layer and to reduce the step difference at the time of buried growth to about 0.5 μm or less. Therefore, the difficulty of burying growth can be alleviated. Therefore, it becomes possible to provide a waveguide type optical switch which is easy to manufacture and has a high yield.

Further, in the optical waveguide switch according to the present invention, at least the wider core layer of the first and second core layers has a quantum well structure, a quantum wire structure, or a quantum box structure. With either configuration, the operating voltage required for switching is reduced.

In the waveguide type optical switch according to a sixth aspect of the present invention, of the first and second core layers, at least the wider core layer is an undoped quantum well layer and n-type conductivity. An n-type conductive layer having, and conductivity intermediate between these layers, at least a part of which has a p-type conductivity type,
Further, by adopting a three-layer structure including an intermediate layer made of a semiconductor having a bandgap wider than that of the semiconductor forming the quantum well layer and the n-type conductive layer, the operating voltage required for switching is further reduced.

In the waveguide type optical switch according to the present invention, the operating voltage required for switching is further reduced by forming the wider core layer with a multi-layer structure in which the three-layer structure is repeated. To do.

In the waveguide type optical switch according to the present invention, the use of the semi-insulating substrate eliminates absorption of light by the substrate, and the semi-insulating substrate is used as a part of the lower clad. It will be possible. Therefore, the first clad layer can be thinned and downsized. In addition, it becomes easy to separate the elements from other elements that perform electrical operation, and monolithic integration with other elements on the same substrate becomes possible, and stray capacitance such as wiring can be reduced, and high-speed element operation can be achieved. Can be realized.

Further, by forming a plurality of conductive first clad layers separated from each other by either the semi-insulating layer or the high resistance layer on the semi-insulating substrate, the first clad layer in these first clad layers can be formed. Good electrical isolation. In addition, by forming a plurality of optical waveguides with a core layer having a single-layer structure, it is possible to reduce the difficulty of buried growth. Therefore, it becomes possible to provide a waveguide type optical switch which is easy to manufacture and has a high yield.

In the waveguide type optical switch according to a tenth aspect, the core layer is made up of a quantum well structure, a quantum wire structure,
By using any of the quantum box structures, the operating voltage required for switching is reduced.

Further, in the optical waveguide switch according to the eleventh aspect, the core layer is an undoped quantum well layer, and n.
-Type conductive layer having p-type conductivity, and an intermediate conductivity between these layers, at least a part of which has p-type conductivity, and constitutes the quantum well layer and the n-type conductive layer By adopting a three-layer structure including an intermediate layer made of a semiconductor having a wider bandgap than that of the semiconductor, the operating voltage required for switching is further reduced.

Further, in the waveguide type optical switch according to the twelfth aspect, the operating voltage required for switching is further reduced by forming the core layer with a multi-layer structure in which the three-layer structure is repeated.

Further, claim 13, 14, 15 or 16
In the method for manufacturing a waveguide type optical switch described in the above, in a conductive crystal layer formed on a surface of a semi-insulating substrate, the crystal layer is semi-insulated or has high resistance in a portion other than a portion where a clad layer is to be formed. By injecting the element for forming a conductive first clad layer, a plurality of conductive first clad layers which are separated from each other and have good electric isolation are formed. Since the first cladding layer satisfactorily separates the electric action exerted on the waveguide, it is possible to avoid the step of regrowth filling the upper cladding layer having a thickness of 1.5 to 2 μm and the zinc diffusion step. Will be easier.

Further, by sequentially forming the first core layer, the second core layer, and the second clad layer on the plurality of first clad layers, an electric action is independently applied to each waveguide. It becomes possible to exert. Furthermore, by embedding only the core layer, the film thickness of this layer can be 0.5 μm or less, and the embedding growth becomes extremely easy. Therefore, it is not necessary to perform the burying growth on a portion having a large step difference, which is conventionally performed. Further, by using the semi-insulating substrate, it becomes easy to separate the devices from other devices that perform an electrical action, and it becomes easy to integrate the devices on the same substrate.

Further, claim 17, 18, 19 or 20
In the method for manufacturing a waveguide type optical switch described in the above, a conductive crystal layer formed on a surface of a semi-insulating substrate is selectively removed, and a semi-insulating layer or a high resistance layer is formed on the selectively removed portion. Thus, a plurality of conductive first clad layers which are separated from each other and have good electric isolation are formed. Since the first cladding layer satisfactorily separates the electric action exerted on the waveguide, it is possible to avoid the step of regrowth filling the upper cladding layer having a thickness of 1.5 to 2 μm and the zinc diffusion step. Will be easier.

Further, by sequentially forming the first core layer, the second core layer, and the second clad layer on the plurality of first clad layers, an electric action is independently applied to each waveguide. It becomes possible to exert. Furthermore, by embedding only the core layer, the film thickness of this layer can be 0.5 μm or less, and the embedding growth becomes extremely easy. Therefore, it is not necessary to perform the burying growth on a portion having a large step difference, which is conventionally performed. Further, by using the semi-insulating substrate, it becomes easy to separate the devices from other devices that perform an electrical action, and it becomes easy to integrate the devices on the same substrate.

[0046]

EXAMPLES Examples of a waveguide type optical switch and a method of manufacturing the same according to the present invention will be described below. (First Embodiment) FIG. 1 is a sectional view showing a waveguide type optical switch (hereinafter abbreviated as an optical switch) 31 according to a first embodiment of the present invention. Directionality of operation by current injection or voltage application. It is a coupler type optical switch. The optical switch 31 as it has conductivity vertical structure of pin, semi-insulating on the surface of the InP substrate 32 is a semiconductor substrate, a high-resistance InP layer 33, the impurity concentration separated from each other by ... 5 × 10 ¹⁷
Two conductive n-InP lower cladding layers (first cladding layers) 34, 34 having a cm ⁻³ are formed.

A non-doped InP buffer layer 35 is formed on the lower cladding layers 34, 34, and electrically isolated and parallel to each other on the buffer layer 35 and above the lower cladding layers 34, 34. Non-doped I
The nGaAsP first core layers 36, 36 are formed, and a high resistance or non-doped InP buried layer 37, a non-doped InGaAsP second core layer 38, and an impurity concentration of 5 are formed thereon.
P-InP upper clad layer (second clad layer) 39 doped with impurities to have a concentration of × 10 ¹⁷ cm ^-3 ,
The p-InGaAs contact layers 40 doped with impurities so that the impurity concentration becomes 5 × 10 ¹⁸ cm ⁻³ are sequentially epitaxially grown, and these buffer layers 35 or contact layers 40 are processed into a waveguide type optical switch structure. There is.

AuZnN is formed on the contact layer 40.
An upper electrode (first electrode) 41 made of a metal vapor deposition film in which an i alloy and Au are laminated is formed, and the lower clad layer 34,
34 lower electrodes (second electrodes) 42, 4 made of a metal deposition film in which AuGeNi alloy and Au are laminated on each
2 is formed. And two first core layers 36,
The optical waveguides 43 and 44 are configured by the 36 and the second core layer 38.

Next, a method of manufacturing the optical switch 31 will be described with reference to FIGS. First, as shown in FIG. 2, an n-InP crystal layer 46 having an impurity concentration of 5 × 10 ¹⁷ cm ⁻³ is formed on the InP substrate 32 by epitaxial growth. Then, as shown in FIG.
A silicon oxide (SiO ₂ ) film 47 serving as a mask is formed on a region 46a of the P crystal layer 46 where a cladding layer is to be formed, and oxygen (O) ion implantation 48 is performed on a region 46b of the n-InP crystal layer 46. The high resistance InP layer 3 is formed in the region 46b.
3 and lower clad layers 34, 34 are formed. Next, as shown in FIG. 4, the SiO ₂ film 47 is removed, and the buffer layer 3 is epitaxially grown on the crystal layer 46.
5, a non-doped InGaAsP layer 49 is formed, and this I
The nGaAsP layer 49 is processed into a predetermined shape to form the first core layers 36, 36.

Next, as shown in FIG. 5, the buffer layer 3
5 and the first core layer 36, 36, the buried layer 37, the second
The core layer 38, the upper cladding layer 39, and the contact layer 40 are sequentially epitaxially grown. Next, as shown in FIG. 6, the epitaxially grown buffer layer 35 or contact layer 40 is processed into a structure of a waveguide type optical switch, and an upper electrode 41 is formed on the contact layer 40 by vapor deposition, and lower clad layers 34, 34. Lower electrode 42 on each
To form. By the above, the optical switch 31 can be manufactured.

In this optical switch 31, a positive voltage is applied to the upper electrode 41 and a negative voltage is applied to the lower electrode 42, and the pin
When a forward bias is applied to the structure, a current flows through the electrodes to each layer. The carriers injected into the second core layer 38 by this current change the refractive index of the second core layer 38, so that the propagation constant of light passing through the first core layer 36 of each of the optical waveguides 43 and 44 is directionally coupled. A change in the fully coupled state of the device causes switching of light. In addition, the upper electrode 41
To the lower electrode 42 and a positive voltage to the lower electrode 42,
When the n-structure is reverse-biased, an electric field is applied to each layer via the electrodes. A change in refractive index occurs in the first core layer 36 due to the electro-optic effect based on this electric field, and light switching similar to that in the case of current injection occurs.

As described above, this optical switch 31
According to the above, since the InP substrate 32, which is a semi-insulating substrate, is used, light absorption by the substrate is eliminated and the InP substrate 32 is removed.
Can be utilized as part of the lower cladding. Therefore, the lower clad layer 34 can be thinned and downsized. In addition, it becomes easy to separate the elements from other elements that perform electrical operation, and monolithic integration with other elements on the same substrate becomes possible, and stray capacitance such as wiring can be reduced, and high-speed element operation can be achieved. Can be realized.

On the InP substrate 32, a lower clad layer 34, which is separated from each other by a high resistance InP layer 33 ,.
34 is formed, these lower clad layers 3
The electrical isolation at 4, 34 can be improved. Further, since the plurality of optical waveguides 43 and 44 are configured by the first core layers 36 and 36 and the second core layer 38, the thickness of these core layers can be reduced, and the step difference during the buried growth can be reduced to 0. Can be reduced to about 5 μm or less,
The difficulty of buried growth can be alleviated. Therefore, it is possible to provide a waveguide type optical switch which is easy to manufacture and has a high yield.

According to the method of manufacturing the optical switch 31, the n-InP crystal layer 46 is formed on the InP substrate 32, and oxygen (O) is added to the region 46b of the n-InP crystal layer 46.
Since the region 46b is made into the high resistance InP layer 33 by performing the ion implantation 48 and the lower cladding layers 34, 34 are formed, it is possible to form the lower cladding layers 34, 34 which are separated from each other and have good electrical isolation. Therefore, the step of burying a clad layer having a thickness of 1.5 to 2 μm by regrowth and the step of diffusing zinc can be avoided, and the manufacturing becomes easy.

Further, the buffer layer 35, the first core layers 36, 36, and the buffer layer 35 are epitaxially grown on the InP substrate 32.
Since the buried layer 37, the second core layer 38, the upper clad layer 39, and the contact layer 40 are formed, it is possible to exert an electrical action on each waveguide independently, and further, only the core layer is buried. Thereby, the film thickness of the layer can be set to 0.5 μm or less, and the buried growth becomes extremely easy. Therefore, it is not necessary to perform the burying growth on a portion having a large step difference, which is conventionally performed.

In this optical switch 31, the InP substrate 32 was used as the semi-insulating substrate.
It is possible to apply semi-insulating substrates of various materials without being limited to the substrate 32. For example, when a GaAs substrate is used, GaAs and AlG are added to the GaAs substrate.
Even if aAs is epitaxially grown, the same effect can be obtained.

(Second Embodiment) FIG. 7 is a sectional view showing a waveguide type optical switch 51 according to a second embodiment of the present invention. Is. In the figure, the optical switch 31 described above is used.
The same components as those of the above are denoted by the same reference numerals and the description thereof will be omitted. The optical switch 51 has a pin conductive vertical structure, and on the surface of an InP substrate 32, two lower clad layers 34, 34 separated from each other by a high resistance InP layer 52, ... Are formed.

A buffer layer 35, a first core layer 53 having a multiple quantum well structure composed of a non-doped InGaAlAs quantum well layer and an InAlAs barrier layer, and a non-doped InP etch stop layer 5 are formed on the lower cladding layers 34, 34.
4. The p-InGaAsP second core layers 55, 55, which are doped with impurities so as to have an impurity concentration of 5 × 10 ¹⁷ cm ⁻³ , are electrically separated and are parallel to each other, are sequentially epitaxially grown, and the etch stop layer 54 is formed. And the second
An upper clad layer 39 and a contact layer 40 are sequentially epitaxially grown on the core layers 55, 55, and the buffer layer 35 and the contact layer 40 are processed into a waveguide type optical switch structure.

The upper electrode 4 is formed on the contact layer 40.
1 is formed, and lower electrodes 42, 42 are formed on the lower clad layers 34, 34, respectively. The first core layer 53 and the two second core layers 55, 55 form optical waveguides 56, 57.

Next, a method of manufacturing the optical switch 51 will be described with reference to FIGS. First, as shown in FIG. 8, an n-InP crystal layer 46 is formed on the InP substrate 32 by epitaxial growth. Then, FIG.
, The SiO ₂ film 47 serving as a mask is formed on the region 46a of the n-InP crystal layer 46 where the cladding layer is to be formed.
Region 46b other than the region 46a of the n-InP crystal layer 46 is removed by dry etching process or wet etching process.
46a is the lower cladding layers 34, 34. Then, as shown in FIG. 10, the SiO ₂ film 47 is used as a mask to selectively grow the high-resistance InP layer 52 in the region 46b to flatten the surface, and thereafter the SiO ₂ film 47 is removed.

Then, as shown in FIG. 11, the buffer layer 35 and the first core layer 5 are epitaxially grown on the lower cladding layers 34, 34 and the high resistance InP layers 52 ,.
3, etch stop layer 54, p-InGaAsP layer 58
To form. Then, as shown in FIG. 12, p-InG
The aAsP layer 58 is processed into a predetermined shape, and the second core layer 5
5,55. Then, on the etch stop layer 54 and the second core layers 55, 55, the upper clad layer 39,
The contact layer 40 is sequentially epitaxially grown.

Then, as shown in FIG. 13, the epitaxially grown buffer layer 35 or contact layer 40 is processed into a structure of a waveguide type optical switch, and an upper electrode 41 and a lower clad layer are formed on the contact layer 40 by vapor deposition. A lower electrode 42 is formed on each of 34 and 34. By the above, the optical switch 51 can be manufactured.

In this optical switch 51, a positive voltage is applied to the upper electrode 41 and a negative voltage is applied to the lower electrode 42, and the pin
When a forward bias is applied to the structure, a current flows through the electrodes to each layer. The carriers injected into the second core layer 55 by this current change the refractive index of the second core layer 55, so that the propagation constant of light passing through the second core layer 55 of each of the optical waveguides 56 and 57 is directionally coupled. A change in the fully coupled state of the device causes switching of light. In addition, the upper electrode 41
To the lower electrode 42 and a positive voltage to the lower electrode 42,
When the n-structure is reverse-biased, an electric field is applied to each layer via the electrodes. Due to the quantum confined Stark effect based on this electric field, a change in refractive index occurs in the first core layer 53 having a multiple quantum well structure, and light switching similar to that in the case of current injection occurs.

As described above, this optical switch 51
According to the above, since the InP substrate 32, which is a semi-insulating substrate, is used, light absorption by the substrate is eliminated and the InP substrate 32 is removed.
Can be utilized as part of the lower cladding. Therefore, the lower clad layer 34 can be thinned and downsized. In addition, it becomes easy to separate the elements from other elements that perform electrical operation, and monolithic integration with other elements on the same substrate becomes possible, and stray capacitance such as wiring can be reduced, and high-speed element operation can be achieved. Can be realized.

On the surface of the InP substrate 32, a high resistance I
Since the two lower clad layers 34, 34 separated from each other by the nP layers 52, ... Are formed, electrical isolation in these lower clad layers 34, 34 can be improved. In addition, the first core layer 53 and the second core layer 55,
Since a plurality of optical waveguides 56 and 57 are configured by 55, the thickness of these core layers can be reduced, and the step difference in the buried growth can be reduced to about 0.5 μm or less, which makes the buried growth difficult. The sex can be eased. Therefore, it is possible to provide a waveguide type optical switch which is easy to manufacture and has a high yield.

The first core layer 53 is made of non-doped InG.
Since the multiple quantum well structure including the aAlAs quantum well layer and the InAlAs barrier layer is used, the operating voltage required for switching can be further reduced.

Further, according to the method of manufacturing the optical switch 51, the region 46b of the n-InP crystal layer 46 formed on the InP substrate 32 is removed by the dry etching process or the wet etching process, and the region 46b is exposed to a high level. The resistance InP layer 52 is selectively grown to form the lower clad layer 34,
Since 34 is formed, the lower clad layer 34 which is isolated from each other and has good electric isolation can be formed. Therefore, the step of burying the clad layer having a thickness of 1.5 to 2 μm by regrowth and the diffusion of zinc can be performed. The process can be avoided and the manufacturing becomes easy.

Further, the buffer layer 35, the first core layer 53, and the etch stop layer 5 are epitaxially grown on the lower clad layers 34, 34 and the high resistance InP layers 52, ....
4, the second core layers 55, 55, the upper clad layer 39, and the contact layer 40 are formed, so that each waveguide can be electrically acted independently, and by embedding only the core layer. The film thickness of the layer can be set to 0.5 μm or less, and the embedded growth becomes extremely easy.
Therefore, it is not necessary to perform the burying growth on a portion having a large step difference, which is conventionally performed.

Also in this optical switch 51, as in the above-described optical switch 31, a semi-insulating substrate is I.
It is possible to apply semi-insulating substrates of various materials without being limited to the nP substrate 32.

(Third Embodiment) FIGS. 14 to 16 are views showing a waveguide type optical switch 61 according to a third embodiment of the present invention. A directional coupler which operates by injecting a current or applying a voltage. Type optical switch. This optical switch 61
The structure of the epitaxial layer is the same as that of the optical switch 31 of the first embodiment. The difference is that after the buffer layer 35 or the contact layer 40 is processed into the structure of the waveguide type optical switch, the switch body portion 62 is A high resistance or non-doped InP burying layer 64 is buried in a surrounding peripheral portion (a portion around the optical waveguide) 63, and through holes 65, 65 extending from the surface to the lower cladding layer 34 are buried in the burying layer 64.
And an insulating film 66 is formed on the inner surfaces of these through holes 65, 65 in order to avoid unnecessary electric contact with each layer, and a lower electrode 67 made of a wiring metal film is formed in these through holes 65, 65. That is the point.

In this optical switch 61, a positive voltage is applied to the upper electrode 41 and a negative voltage is applied to the lower electrode 67, and the pin
When the structure is forward biased, a current flows through the electrodes to each layer. The carriers injected into the second core layer 38 by this current change the refractive index of the second core layer 38, so that the propagation constant of light passing through the first core layer 36 is higher than that in the fully coupled state of the directional coupler. It changes and causes switching of light. Also, the upper electrode 41 is minus, the lower electrode 6
When a positive voltage is applied to 7 and the pin structure is reversely biased, an electric field is applied to each layer through the electrodes. Due to the electro-optic effect based on this electric field
Light switching occurs in the core layer 36, similar to the case of current injection.

As described above, this optical switch 61
Also in the above, the same operation and effect as the optical switch 31 can be achieved. Moreover, the switch body portion 6
Since the peripheral portion 63 that surrounds 2 is formed by the buried layer 64, the absorption of light by the conductive crystal can be avoided, and the optical waveguide loss can be reduced.

The upper cladding layer 39 may have a ridge structure 68 as shown in FIG. 17 in order to enhance the confinement of light and reduce the radiation loss in the curved waveguide. Although the second core layer 38 is made of InGaAsP crystal, it may have a structure other than the above-mentioned crystal, for example, a multiple quantum well structure such as InGaAs / InAlAs. In this case, the light absorption of the second core layer 38 cannot be ignored, and if it is unsuitable as the core layer of the routing waveguide, this core layer is also removed, and the non-doped InGa is newly formed.
The AsP core layer and the high-resistance or non-doped InP upper cladding layer may be grown by burying.

Further, also in the optical switch 61, the InP substrate 32 is used in the same manner as the optical switches 31 and 51 described above.
It is possible to apply semi-insulating substrates made of various materials without being limited to.

(Fourth Embodiment) FIG. 18 is a sectional view showing a waveguide type optical switch 71 according to a fourth embodiment of the present invention, which is a directional coupler type optical switch operated by applying a voltage. 19 and 20 show the second part of the optical switch 71.
It is a band diagram of a core layer. In the figure, the same components as those of the optical switches 31, 51 and 61 described above are designated by the same reference numerals and the description thereof will be omitted.

The optical switch 71 has a conductive vertical structure of the same conductivity type. The lower clad layer, the upper clad layer and the contact layer have the same conductivity type (n type) structure, and the second core. It is characterized in that the layer has a quantum well structure in which the refractive index changes significantly by applying a voltage.

This optical switch 71 has a high resistance In on the surface.
Lower clad layer 3 separated from each other by P layers 33, ...
The buffer layer 35 and the first core layers 34 and 34 are sequentially formed on the InP substrate 32 having the layers 4 and 34 formed thereon, and the buried layer 37, the second core layer 72, and the impurity concentration of 5 × 1.
N− doped with impurities so as to have a concentration of 0 ¹⁷ cm ⁻³
The InP upper clad layer (second clad layer) 73 and the n-InGaAs contact layer 74 doped with impurities so that the impurity concentration becomes 5 × 10 ¹⁸ cm ⁻³ are sequentially epitaxially grown to form the buffer layer 35 or the contact layer. 74 is processed into a structure of a waveguide type optical switch.

On the contact layer 74, an upper electrode (first electrode) made of a metal vapor deposition film in which AuGeNi alloy and Au are laminated is formed.
Electrode 75), and lower electrodes 42, 42 are formed on the lower cladding layers 34, 34, respectively.
Then, the two first core layers 36, 36 and the second core layer 72
Optical waveguides 76 and 77 are constituted by and.

The second core layer 72 is made of n-InGaAlAs.
Layer 72a, p-InAlAs layer 72b, undoped I
The nGaAs layer 72c and the n-InGaAlAs layer 72d are four layers, and the InGaAs layer 72c serves as a quantum well.

In order to manufacture this optical switch 71, In
Lower clad layers 34, 34 separated from each other by a high resistance InP layer 33, are formed on the surface of the P substrate 32, and InP is grown on the InP substrate 32 by epitaxial growth.
The buffer layer 35 and the first core layers 36, 36 are formed, and then the buried layer 37, the second core layer 72, the upper clad layer 73, and the contact layer 74 are formed thereon, and the buffer layer 3
5 to the contact layer 74 are processed into a structure of a waveguide type optical switch, and the upper electrode 75 is formed on the contact layer 74 and the lower electrode 42 is formed on each of the lower clad layers 34, 34 by vapor deposition.

Here, the band diagnosis of the second core layer 72 is performed.
Explain Ram. An electric field is imprinted on the second core layer 72.
If not added, as shown in FIG.
First quantum level E of the electron in the quantum well of the s layer 72c_e1Is
Fermi level E _fThe electrons in the quantum well because they are above
The concentration is low.

Here, when an electric field is applied to the second core layer 72, a positive potential is applied to the right side in the figure, for example, as shown in FIG. 20, that is, between the n-InGaAlAs layer 72a and the p-InAlAs layer 72b. When a reverse bias is applied to the pn-junction of, the first quantum level E _e1 of the electron in the quantum well is lower than the Fermi level E _f , so the electron is n-InGaA
It moves from the 1As layer 72d into the quantum well of the InGaAs layer 72c. As a result, the effect of excitons in the quantum well is suppressed by the band-filling effect of the moved electrons, so that the refractive index of the second core layer 72 changes. Therefore, according to this operating principle, the propagation constant of light passing through the two optical waveguides 76 and 77 changes from the fully coupled state of the directional coupler, and light switching occurs.

As described above, this optical switch 71
According to the above, since the InP substrate 32, which is a semi-insulating substrate, is used, light absorption by the substrate is eliminated and the InP substrate 32 is removed.
Can be utilized as part of the lower cladding. Therefore, the lower clad layer 34 can be thinned and downsized. In addition, it becomes easy to separate the elements from other elements that perform electrical operation, and monolithic integration with other elements on the same substrate becomes possible, and stray capacitance such as wiring can be reduced, and high-speed element operation can be achieved. Can be realized.

On the InP substrate 32, the lower clad layer 34, which is separated from each other by the high-resistance InP layer 33 ,.
34 are formed, these lower clad layers 3
The electrical isolation at 4, 34 can be improved. Further, since the plurality of optical waveguides 76, 77 are constituted by the first core layers 36, 36 and the second core layer 72, the thickness of these core layers can be reduced, and the step difference during the buried growth can be reduced to 0. Can be reduced to about 5 μm or less,
The difficulty of buried growth can be alleviated. Therefore, it is possible to provide a waveguide type optical switch which is easy to manufacture and has a high yield.

Further, the second core layer 72 is formed of n-InGa.
The InGaAs layer 72c has a quantum well structure, which is composed of four layers of the AlAs layer 72a, the p-InAlAs layer 72b, the undoped InGaAs layer 72c, and the n-InGaAlAs layer 72d. Therefore, the operating voltage required for switching can be further reduced. ..

In the optical switch 71, the second
Although the core layer 72 has a single quantum well structure, a multiple quantum well structure in which the single quantum well structure is repeated, for example, the n-InGaAlAs layer 72a and the p-InAlAs layer 7 described above.
2b, non-doped InGaAs layer 72c, n-InG
A multi-quantum well structure in which four layers of the aAlAs layer 72d are periodically repeated may be used. In this case, the operating voltage required for switching can be further reduced.

Also in this optical switch 71, similarly to the above-mentioned optical switches 31, 51, 61, it is possible to apply semi-insulating substrates of various materials without being limited to the InP substrate 32. ..

[0088]

As described above, according to the waveguide type optical switch of the present invention, since the semi-insulating substrate is used, light absorption by the substrate is eliminated. The semi-insulating substrate can be used as part of the lower cladding. Therefore, the first clad layer can be thinned and the size can be reduced. In addition, it becomes easy to separate the elements from other elements that perform electrical operation, and monolithic integration with other elements on the same substrate becomes possible, and stray capacitance such as wiring can be reduced, and high-speed element operation can be achieved. Can be realized.

Further, since a plurality of conductive first clad layers separated from each other by either the semi-insulating layer or the high resistance layer is formed on the semi-insulating substrate, these first clad layers are formed. Good electrical isolation in the layers. Moreover, since the plurality of optical waveguides are configured by the first core layer and the second core layer, the thickness of these core layers can be reduced, and the step difference during the buried growth is about 0.5 μm. It can be reduced to the following and the difficulty of burying growth can be alleviated. Therefore, it is possible to provide a waveguide type optical switch which is easy to manufacture and has a high yield.

According to the waveguide type optical switch of the fifth aspect, in the waveguide type optical switch of the first, second, third or fourth aspect, among the first and second core layers,
Since at least the wider core layer is configured to have the quantum well structure, the quantum wire structure, or the quantum box structure, the operating voltage required for switching can be reduced.

According to a sixth aspect of the waveguide type optical switch, in the third aspect of the waveguide type optical switch, at least the wider one of the first and second core layers is used. The core layer is an undoped quantum well layer and n
-Type conductive layer having p-type conductivity, and an intermediate conductivity between these layers, at least a part of which has p-type conductivity, and constitutes the quantum well layer and the n-type conductive layer Since the semiconductor device has a three-layer structure including an intermediate layer made of a semiconductor having a wider bandgap than that of the semiconductor, the operating voltage required for switching can be further reduced.

According to the waveguide type optical switch of the seventh aspect, in the waveguide type optical switch of the sixth aspect, the wide core layer is a multi-layer structure in which the three-layer structure is repeated. Since the above configuration is adopted, the operating voltage required for switching can be further reduced.

According to the waveguide type optical switch of the eighth or ninth aspect, since the semi-insulating substrate is used, light absorption by the substrate is eliminated and the semi-insulating substrate is part of the lower clad. Can be used as Therefore, the first clad layer can be thinned and the size can be reduced. In addition, it becomes easy to separate the elements from other elements that perform electrical operation, and monolithic integration with other elements on the same substrate becomes possible, and stray capacitance such as wiring can be reduced, and high-speed element operation can be achieved. Can be realized.

Since a plurality of conductive first clad layers separated from each other by either the semi-insulating layer or the high resistance layer is formed on the semi-insulating substrate, these first clad layers are formed. Good electrical isolation in the layers. Moreover, since the plurality of optical waveguides are configured by the core layer having the single structure, the difficulty of the buried growth can be alleviated. Therefore, it becomes possible to provide a waveguide type optical switch which is easy to manufacture and has a high yield.

According to a tenth aspect of the waveguide type optical switch of the tenth aspect, in the waveguide type optical switch of the eighth or ninth aspect, the core layer is formed of a quantum well structure, a quantum wire structure or a quantum box structure. Since it is configured by either of them, the operating voltage required for switching can be reduced.

According to the waveguide type optical switch of the eleventh aspect, in the waveguide type optical switch of the ninth aspect, the core layer has an undoped quantum well layer and n-type conductivity. an n-type conductive layer and an intermediate conductivity between these layers, at least a part of which has a p-type conductivity type,
Moreover, since the three-layer structure including the intermediate layer made of a semiconductor having a wider band gap than the semiconductor forming the quantum well layer and the n-type conductive layer is adopted, the operating voltage required for switching can be further reduced. ..

According to a twelfth aspect of the waveguide type optical switch of the eleventh aspect, in the waveguide type optical switch of the eleventh aspect, the core layer has a multi-layer structure in which the three-layer structure is repeated. Therefore, the operating voltage required for switching can be further reduced.

Further, claim 13, 14, 15 or 16
According to the method for manufacturing a waveguide type optical switch as described above, the crystal layer is semi-insulated or high-insulated in a portion other than the portion where the cladding layer of the conductive crystal layer formed on the surface of the semi-insulating substrate is to be formed. Since a plurality of first cladding layers are formed by injecting a resistance-imparting element, it is possible to form the first cladding layers which are isolated from each other and have good electrical isolation, and therefore 1.5 to 2 μm. It is possible to avoid the process of filling the thick upper clad layer with regrowth and the diffusion process of zinc,
Manufacturing is easy.

Further, since the first core layer, the second core layer, and the second clad layer are sequentially formed on the plurality of first clad layers, it is possible to electrically connect each waveguide independently. Can have an effect. Furthermore, by embedding only the core layer, the film thickness of this layer can be set to 0.5 μm or less, and embedding growth can be performed extremely easily. Therefore, it is not necessary to perform the burying growth on a portion having a large step difference, which is conventionally performed. Further, since the semi-insulating substrate is used, it is easy to separate the devices from other devices that perform an electrical action, and the devices can be integrated on the same substrate.

In addition, claim 17, 18, 19 or 20
According to the method for manufacturing a waveguide type optical switch described in the above, a conductive crystal layer formed on the surface of a semi-insulating substrate is selectively removed, and a semi-insulating layer or a high resistance layer is formed on the selectively removed portion. Therefore, it is possible to form the first clad layer which is isolated from each other and has good electrical isolation, and therefore, a step of burying an upper clad layer having a thickness of 1.5 to 2 μm by regrowth and a zinc diffusion step. Can avoid
Manufacturing is easy.

Further, since the first core layer, the second core layer, and the second clad layer are sequentially formed on the plurality of first clad layers, it is possible to electrically connect each waveguide independently. Can have an effect. Furthermore, by embedding only the core layer, the film thickness of this layer can be set to 0.5 μm or less, and embedding growth can be performed extremely easily. Therefore, it is not necessary to perform the burying growth on a portion having a large step difference, which is conventionally performed. Further, since the semi-insulating substrate is used, it is easy to separate the devices from other devices that perform an electrical action, and the devices can be integrated on the same substrate.

As described above, it is possible to omit a complicated manufacturing process conventionally required to achieve electrical isolation between waveguides, and to provide a waveguide type optical switch which can be expected to have a high yield and a manufacturing method thereof. You can

[Brief description of drawings]

FIG. 1 is a sectional view showing a waveguide type optical switch according to a first embodiment of the present invention.

FIG. 2 is a process drawing showing the method of manufacturing the waveguide type optical switch according to the first embodiment of the present invention.

FIG. 3 is a process drawing showing the method of manufacturing the waveguide type optical switch according to the first embodiment of the present invention.

FIG. 4 is a process chart showing the method of manufacturing the waveguide type optical switch according to the first embodiment of the present invention.

FIG. 5 is a process drawing showing the method of manufacturing the waveguide type optical switch according to the first embodiment of the present invention.

FIG. 6 is a process chart showing the method of manufacturing the waveguide type optical switch according to the first embodiment of the present invention.

FIG. 7 is a sectional view showing a waveguide type optical switch according to a second embodiment of the present invention.

FIG. 8 is a process drawing showing the method of manufacturing the waveguide type optical switch according to the second embodiment of the present invention.

FIG. 9 is a process drawing showing the method of manufacturing the waveguide type optical switch according to the second embodiment of the present invention.

FIG. 10 is a process drawing showing the method of manufacturing the waveguide type optical switch according to the second embodiment of the present invention.

FIG. 11 is a process drawing showing the method of manufacturing the waveguide type optical switch according to the second embodiment of the present invention.

FIG. 12 is a process drawing showing the method of manufacturing the waveguide type optical switch according to the second embodiment of the present invention.

FIG. 13 is a process drawing showing the method of manufacturing the waveguide type optical switch according to the second embodiment of the present invention.

FIG. 14 is a perspective view showing a waveguide type optical switch according to a third embodiment of the present invention.

15 is a sectional view taken along the line AA of FIG.

16 is a cross-sectional view taken along the line BB of FIG.

FIG. 17 is a sectional view showing a modification of the upper clad layer of the waveguide type optical switch according to the third embodiment of the present invention.

FIG. 18 is a sectional view showing a waveguide type optical switch according to a fourth embodiment of the present invention.

FIG. 19 is a diagram showing a band diagram of a second core layer of a waveguide type optical switch according to a fourth example of the present invention.

FIG. 20 is a diagram showing a band diagram of a second core layer of a waveguide type optical switch according to a fourth embodiment of the present invention.

FIG. 21 is a cross-sectional view showing a conventional waveguide type optical switch.

FIG. 22 is a cross-sectional view showing a conventional waveguide type optical switch.

[Explanation of symbols]

31 Optical Switch 32 InP Substrate (Semi-Insulating Substrate) 33 High Resistance InP Layer 34 n-InP Lower Cladding Layer (First Cladding Layer) 35 Nondoped InP Buffer Layer 36 Nondoped InGaAsP First Core Layer 37 High Resistance or Nondoped InP buried layer 38 Non-doped InGaAsP second core layer 39 p-InP upper clad layer (second clad layer) 40 p-InGaAs contact layer 41 upper electrode (first electrode) 42 lower electrode (second electrode) 43 , 44 Optical waveguide 46 n-InP crystal layer 46a Region where clad layer is to be formed 46b Region other than region 46a 47 Silicon oxide (SiO ₂ ) film 48 Oxygen (O) ion implantation 49 Non-doped InGaAsP layer 51 Optical switch 52 High resistance InP Layer 53 First core layer having a multiple quantum well structure 54 Undoped InP etch stop layer 55 p-InGaAsP second core layer 56, 57 Optical waveguide 58 p-InGaAsP layer 61 Optical switch 62 Switch body portion 63 Surrounding portion 64 High resistance or non-doped InP buried layer 65 Through hole 66 Insulating film 67 Lower electrode 68 Ridge structure 71 Optical switch 72 Second core layer 72a n-InGaAlAs layer 72b p-InAlAs layer 72c Non-doped InGaAs layer (quantum well) 72d n-InGaAlAs layer 73 n-InP upper clad layer (second cladding layer) 74 n-InGaAs contact layer 75 Upper electrode (first electrode) 76, 77 Optical waveguide E _e1 First quantum level of electron in quantum well E _f Fermi level

Claims (20)

[Claims] 1. A semi-insulating substrate, a plurality of conductive first clad layers provided on the semi-insulating substrate and separated from each other by either a semi-insulating layer or a high resistance layer, A plurality of first core layers provided on each of the plurality of first clad layers and parallel to each other; a second core layer provided on the first core layers; and a second core layer A second clad layer having a conductivity type opposite to that of the first clad layer, the first electrode provided on the second core layer, and the second clad layer provided on the semi-insulating substrate. And a plurality of second electrodes, and the plurality of first core layers and the plurality of second core layers respectively form optical waveguides, and the magnitude of voltage or current to be applied to these optical waveguides. The optical path of light propagating in the optical waveguide is switched by controlling Waveguide type optical switch. 2. A semi-insulating substrate, a plurality of conductive first cladding layers provided on the semi-insulating substrate and separated from each other by either a semi-insulating layer or a high resistance layer, A first core layer provided on the plurality of first cladding layers, and a plurality of first core layers provided on the first core layer and above the plurality of first cladding layers in parallel with each other. Second core layer, a second clad layer provided on the second core layers and having a conductivity type opposite to that of the first clad layer, and a second clad layer provided on the plurality of second core layers. One electrode and a plurality of second electrodes provided on the semi-insulating substrate, wherein the first core layer and the plurality of second core layers respectively form an optical waveguide, By controlling the voltage applied to the optical waveguide of the Waveguide type optical switch and switches the optical path of light propagating within the road. 3. A semi-insulating substrate, a plurality of conductive first cladding layers provided on the semi-insulating substrate and separated from each other by either a semi-insulating layer or a high resistance layer, A plurality of first core layers provided on each of the plurality of first clad layers and parallel to each other; a second core layer provided on top of the first core layers; and a second core layer A second clad layer having the same conductivity type as that of the first clad layer, a first electrode provided on the second core layer, and a second insulating layer provided on the semi-insulating substrate. And a plurality of second electrodes, and the plurality of first core layers and the plurality of second core layers respectively form optical waveguides, and the magnitude of voltage or current to be applied to these optical waveguides. The optical path of the light propagating in the optical waveguide is switched by controlling Waveguide-type optical switch to. 4. A semi-insulating substrate, a plurality of conductive first clad layers provided on the semi-insulating substrate and separated from each other by either a semi-insulating layer or a high resistance layer, A first core layer provided on the plurality of first cladding layers, and a plurality of first core layers provided on the first core layer and above the plurality of first cladding layers in parallel with each other. Second core layer, a second clad layer provided on the second core layer and having the same conductivity type as the first clad layer, and a second clad layer provided on the plurality of second core layers. One electrode and a plurality of second electrodes provided on the semi-insulating substrate, wherein the first core layer and the plurality of second core layers respectively form an optical waveguide, By controlling the voltage applied to the optical waveguide of the Waveguide type optical switch and switches the optical path of light propagating within waveguide. 5. The waveguide type optical switch according to claim 1, 2, 3 or 4, wherein at least the wider core layer of the first and second core layers is a quantum well structure or a quantum wire. A waveguide type optical switch characterized by comprising either a structure or a quantum box structure. 6. The waveguide type optical switch according to claim 3, wherein at least the wider core layer of the first and second core layers is an undoped quantum well layer and an n-type core layer. An n-type conductive layer having conductivity, and a semiconductor having conductivity between these layers, at least a part of which has p-type conductivity, and which constitutes the quantum well layer and the n-type conductive layer. A waveguide type optical switch characterized by comprising a three-layer structure including an intermediate layer made of a semiconductor having a bandgap wider than that of the semiconductor layer. 7. The waveguide type optical switch according to claim 6, wherein the wider core layer has a multi-layer structure in which the three-layer structure is repeated. switch. 8. A semi-insulating substrate, a plurality of conductive first clad layers provided on the semi-insulating substrate and separated from each other by either a semi-insulating layer or a high resistance layer, A plurality of core layers provided on each of the plurality of first clad layers and parallel to each other; a second clad layer provided on the core layers and having a conductivity type opposite to that of the first clad layer; A first electrode provided on the core layer and a plurality of second electrodes provided on the semi-insulating substrate, the voltage applied to the plurality of core layers or the current injected A waveguide type optical switch characterized by switching the optical path of light propagating in the optical waveguide by controlling the size. 9. A semi-insulating substrate, and a plurality of conductive first cladding layers provided on the semi-insulating substrate and separated from each other by either a semi-insulating layer or a high resistance layer, A plurality of core layers provided on each of the plurality of first clad layers and parallel to each other; a second clad layer provided on the core layers and having the same conductivity type as the first clad layer; A first electrode provided on the core layer and a plurality of second electrodes provided on the semi-insulating substrate, the voltage applied to the plurality of core layers or the current injected A waveguide type optical switch characterized by switching the optical path of light propagating in the optical waveguide by controlling the size. 10. The waveguide type optical switch according to claim 8 or 9, wherein the core layer is formed of any one of a quantum well structure, a quantum wire structure, and a quantum box structure. Type optical switch. 11. The waveguide type optical switch according to claim 9, wherein the core layer is an undoped quantum well layer, an n-type conductive layer having n-type conductivity, and an intermediate conductivity between these layers. A three-layer structure comprising an intermediate layer made of a semiconductor having a p-type conductivity type and having a bandgap wider than that of the semiconductor forming the quantum well layer and the n-type conductivity layer. A waveguide type optical switch characterized by being configured. 12. The waveguide type optical switch according to claim 11, wherein the core layer has a multi-layer structure in which the three-layer structure is repeated. 13. A conductive crystal layer is formed on the surface of a semi-insulating substrate, and an element for semi-insulating or increasing the resistance of the crystal layer is provided in a portion of the crystal layer other than a portion where a clad layer is to be formed. Forming a plurality of first clad layers separated from each other by implanting, and then forming a plurality of first core layers parallel to each other on each of the plurality of first clad layers; A second core layer, a second clad layer having a conductivity type opposite to that of the first clad layer are sequentially formed on the second core layer, and a second clad layer is formed on the second core layer. 1. A method of manufacturing a waveguide type optical switch, comprising forming one electrode and a plurality of second electrodes on the semi-insulating substrate. 14. A conductive crystal layer is formed on the surface of a semi-insulating substrate, and an element for semi-insulating or increasing the resistance of the crystal layer is added to a portion of the crystal layer other than a portion where a clad layer is to be formed. Forming a plurality of first clad layers that are separated from each other by implanting, and then forming a first core layer on the plurality of first clad layers; and on the first core layer and the plurality of first clad layers. A plurality of second core layers that are parallel to each other above each of the first clad layers, and a second clad layer having a conductivity type opposite to that of the first clad layer is sequentially formed on the second core layers; A method of manufacturing a waveguide type optical switch, comprising forming a first electrode on the second core layer and forming a plurality of second electrodes on the semi-insulating substrate. 15. A conductive crystal layer is formed on the surface of a semi-insulating substrate, and an element for semi-insulating or increasing the resistance of the crystal layer is provided in a portion of the crystal layer other than a portion where a clad layer is to be formed. Forming a plurality of first clad layers separated from each other by implanting, and then forming a plurality of first core layers parallel to each other on each of the plurality of first clad layers; A second core layer, a second clad layer having the same conductivity type as that of the first clad layer on the second core layer, and a second clad layer on the second core layer. 1. A method of manufacturing a waveguide type optical switch, comprising forming one electrode and a plurality of second electrodes on the semi-insulating substrate. 16. A conductive crystal layer is formed on the surface of a semi-insulating substrate, and an element for semi-insulating or increasing the resistance of the crystal layer is provided in a portion of the crystal layer other than a portion where a clad layer is to be formed. Forming a plurality of first clad layers that are separated from each other by implanting, and then forming a first core layer on the plurality of first clad layers; and on the first core layer and the plurality of first clad layers. A plurality of second core layers that are parallel to each other above each of the first clad layers, and a second clad layer of the same conductivity type as the first clad layer is sequentially formed on these second core layers; A method of manufacturing a waveguide type optical switch, comprising forming a first electrode on the second core layer and forming a plurality of second electrodes on the semi-insulating substrate. 17. A conductive crystal layer is formed on the surface of a semi-insulating substrate, and the crystal layer is selectively removed to form a plurality of first clad layers having a predetermined shape separated from each other. A semi-insulating layer or a high resistance layer is formed on the selectively removed portion, and then a plurality of first core layers parallel to each other are formed on each of the plurality of first cladding layers, and a plurality of first core layers are formed on the first core layers. A second core layer, a second clad layer of opposite conductivity type to the first clad layer on the second core layer, and a first clad layer on the second core layer. And a plurality of second electrodes are formed on the semi-insulating substrate, respectively. 18. A conductive crystal layer is formed on the surface of a semi-insulating substrate, and the crystal layer is selectively removed to form a plurality of first clad layers having a predetermined shape separated from each other. A semi-insulating layer or a high resistance layer is formed on the selectively removed portion, and then a first core layer is formed on the plurality of first cladding layers, and the first core layer is formed on the plurality of first cladding layers. A plurality of second core layers parallel to each other above each of the clad layers, and a second clad layer having a conductivity type opposite to that of the first clad layer are sequentially formed on the second core layers, A method of manufacturing a waveguide type optical switch, comprising forming a first electrode on the second core layer and forming a plurality of second electrodes on the semi-insulating substrate. 19. A conductive crystal layer is formed on the surface of a semi-insulating substrate, and the crystal layer is selectively removed to form a plurality of first clad layers having a predetermined shape separated from each other. A semi-insulating layer or a high resistance layer is formed on the selectively removed portion, and then a plurality of first core layers parallel to each other are formed on each of the plurality of first cladding layers, and a plurality of first core layers are formed on the first core layers. A second core layer, a second clad layer of the same conductivity type as the first clad layer on the second core layer, and a first clad layer on the second core layer. And a plurality of second electrodes are formed on the semi-insulating substrate, respectively. 20. A conductive crystal layer is formed on a surface of a semi-insulating substrate, and the crystal layer is selectively removed to form a plurality of first clad layers having a predetermined shape separated from each other. A semi-insulating layer or a high resistance layer is formed on the selectively removed portion, and then a first core layer is formed on the plurality of first cladding layers, and the first core layer is formed on the plurality of first cladding layers. A plurality of second core layers that are parallel to each other above each of the clad layers, and a second clad layer of the same conductivity type as the first clad layer are sequentially formed on the second core layers, A method of manufacturing a waveguide type optical switch, comprising forming a first electrode on the second core layer and forming a plurality of second electrodes on the semi-insulating substrate.