JP2004029171A - Optical switch and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical switch which operates at a shorter switching rate, and to provide its manufacturing method. <P>SOLUTION: In the optical switch to switch transmission routes of optical signals by changing the refractive index by injecting a carrier, the recombination level in the optical waveguide layer where optical waveguides to propagate light signals are formed is increased. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
The present invention relates to an optical switch that switches a transmission path of an optical signal by a change in refractive index due to carrier injection, and more particularly to an optical switch that can operate at a shorter switching speed and a method of manufacturing the same.
[0002]
[Prior art]
Current communication networks such as a LAN (Local Area Network) and a WAN (Wide Area Network) generally use a communication method in which information is transmitted using electric signals.
[0003]
Communication methods for transmitting information using optical signals are only used in backbone networks for transmitting large amounts of data and some other networks. In addition, these networks are “point to point” communications, and at present the communication networks that can be called “photonic networks” have not been developed.
[0004]
In order to realize such a “photonic network”, an “optical router” or “optical switching hub” having the same function as a device such as a router or a switching hub for switching a transmission destination of an electric signal is required. .
[0005]
Further, such a device requires an optical switch for switching a transmission path at high speed, and a device using a ferroelectric material such as lithium niobate or PLZT (Lead Lanthanum Zirconate Titanate) or an optical path waveguide formed in a semiconductor. There is a type in which a carrier is injected into a semiconductor to change a refractive index to switch a transmission path of an optical signal.
[0006]
"K. Ishida, H. Nakamura, H. matsumura, T. Kadoi, H. Inoue: InGaAsP / InP optical switches using carrier induced reciprocal reciprocating index, p. Describes an example of the latter optical switch.
[0007]
5 and 6 are a plan view and a sectional view, respectively, showing an example of a conventional optical switch described in the above-mentioned document. In FIG. 5, reference numeral 1 denotes a semiconductor substrate, 2 denotes an “X-shaped” optical waveguide, Is an electrode. An “X-shaped” optical waveguide 2 is formed on a substrate 1, and an electrode 3 is formed at an intersection of the “X-shaped” optical waveguide 2.
[0008]
On the other hand, FIG. 6 is a cross-sectional view taken along the line “AA ′” in FIG. 5, where 4 and 10 are electrodes, 5 is an InP substrate, 6 is an optical waveguide layer, 7 is an InP layer serving as a cladding layer, and 8 is a cap layer. Is an InGaAsP layer, and 9 is an oxide film such as SiO ₂ .
[0009]
On the InP substrate 5, Zn as a p-type impurity is diffused in portions indicated by “DR 11” and “DR 12” in FIG. 6, and thereafter, the optical waveguide layer 6, the InP layer 7, and the InGaAsP Layers 8 are formed sequentially.
[0010]
Further, Zn which is a p-type impurity is diffused in a portion indicated by “DR13” in FIG. 6, and an oxide film 9 is formed in a portion other than the diffusion region indicated by “DR13” in FIG. 6, the electrode 10 is formed on the diffusion region indicated by “DR13”, and the electrode 4 is formed on the back surface of the InP substrate 5. Further, “IR11” in FIG. 6 is a region where the refractive index changes.
[0011]
Here, the operation of the conventional example shown in FIG. 5 will be described with reference to FIG. When the optical switch is "OFF", no current is supplied to the electrode 3 and the electrode (not shown) on the back surface of the substrate 1 (corresponding to the electrode 4 in FIG. 6).
[0012]
Therefore, since the refractive index does not change at the intersection of the “X-shaped” optical waveguides 2, for example, the optical signal incident from “PI01” in FIG. 5 goes straight through the intersection and “PO01” in FIG. Are emitted from the portion indicated by "".
[0013]
On the other hand, when the optical switch is “ON”, a current is supplied to the electrode 3 and an electrode (corresponding to the electrode 4 in FIG. 6) on the back surface of the substrate 1 (not shown), and carriers (electrons and holes) are generated at the intersection. Injected.
[0014]
For this reason, the refractive index immediately below the electrode 3 at the intersection of the “X-shaped” optical waveguides 2 changes so as to be lower due to the plasma effect. For example, the optical signal incident from “PI01” in FIG. The light is totally reflected by the low-refractive-index portion generated at the point (a) and is emitted from the portion indicated by "PO02" in FIG.
[0015]
As a result, a current is supplied to the electrode to inject carriers (electrons and holes) into the intersection of the “X-shaped” optical waveguide 2 to control the refractive index of the intersection, thereby emitting an optical signal. Position, in other words, it is possible to switch the propagation path of the optical signal.
[0016]
[Problems to be solved by the invention]
However, in the conventional examples shown in FIGS. 5 and 6, as one factor for determining the switching speed, the carriers injected into the intersection of the optical waveguide 2 when the switch is turned from “ON” to “OFF” disappear. Speed, in other words, carrier lifetime.
[0017]
Such a carrier life depends on many parameters such as a semiconductor material to be used and its carrier concentration, but the carrier life of GaAs or InP is generally said to be "10 ^-9 to 10 ^-10 seconds".
[0018]
That is, for example, when a material having a carrier lifetime of “10 ⁻⁹ seconds” is used, it is theoretically difficult to make the switching speed of the optical switch shorter than “1 ns (10 ⁻⁹ seconds)”. There was a problem.
Accordingly, an object of the present invention is to realize an optical switch that can operate at a shorter switching speed and a method of manufacturing the same.
[0019]
[Means for Solving the Problems]
In order to achieve such an object, the invention according to claim 1 of the present invention is:
In an optical switch that switches a transmission path of an optical signal by a change in refractive index due to carrier injection,
By increasing the recombination level of the optical waveguide layer in which the optical waveguide through which the optical signal propagates is formed, the lifetime of carriers is shortened, and thus operation can be performed at a shorter switching speed.
[0020]
The invention according to claim 2 is
The optical switch according to claim 1,
A semiconductor substrate, an optical waveguide layer having an increased recombination level on which the optical waveguide on which the optical signal propagates is formed on the semiconductor substrate, a contact layer formed on the optical waveguide layer, An electrode formed on the back surface of the semiconductor substrate and on the contact layer to inject carriers and control the refractive index of the optical waveguide to switch the propagation path of the optical signal, thereby shortening the life of the carriers. Therefore, operation can be performed at a shorter switching speed.
[0021]
The invention according to claim 3 is
The optical switch according to claim 2,
By providing a second contact layer on the back surface of the semiconductor substrate and forming the electrode on the second contact layer, the life of carriers is shortened, so that operation can be performed at a shorter switching speed.
[0022]
The invention according to claim 4 is
The optical switch according to claim 1,
A semiconductor substrate;
An optical waveguide layer having an increased recombination level on the semiconductor substrate where an optical waveguide through which the optical signal propagates is formed; a pair of contact layers formed on the optical waveguide layer; An electrode that is formed on each of the layers and controls a refractive index of the optical waveguide by injecting a carrier to switch a propagation path of the optical signal; and an electrode formed on the optical waveguide layer other than on the contact layer. With the provision of the insulating film, the life of the carrier is shortened, so that the operation can be performed at a shorter switching speed.
[0023]
The invention according to claim 5 is
An optical switch according to any one of claims 1 to 4, wherein
The optical waveguide layer,
Since the lifetime of carriers is shortened by being formed of an InGaAsP-based semiconductor material, operation can be performed at a shorter switching speed.
[0024]
The invention according to claim 6 is
An optical switch according to any one of claims 1 to 4, wherein
The optical waveguide layer,
Since the carrier is shortened by being formed of the SiGe-based semiconductor material, the operation can be performed at a shorter switching speed.
[0025]
The invention according to claim 7 is
An optical switch according to any one of claims 1 to 4, wherein
The optical waveguide layer,
Since the carrier is shortened by being formed of a GaAs-based semiconductor material, operation can be performed at a shorter switching speed.
[0026]
The invention according to claim 8 is
An optical switch according to any one of claims 1 to 4, wherein
The optical waveguide layer,
Since the lifetime of carriers is shortened by being formed of an InP-based semiconductor material, operation can be performed at a shorter switching speed.
[0027]
The invention according to claim 9 is
A method for manufacturing an optical switch that switches a transmission path of an optical signal by a change in refractive index due to carrier injection,
Forming an optical waveguide layer by lowering the epitaxial growth temperature on the semiconductor substrate, forming a contact layer on the optical waveguide layer, and forming electrodes on the back surface of the semiconductor substrate and the contact layer, respectively. , The life of the carrier is shortened, so that operation at a shorter switching speed becomes possible.
[0028]
The invention according to claim 10 is
A method for manufacturing an optical switch that switches a transmission path of an optical signal by a change in refractive index due to carrier injection,
Forming an optical waveguide layer on the semiconductor substrate by lowering the epitaxial growth temperature, forming a contact layer on the optical waveguide layer, forming a second contact layer on the back surface of the semiconductor substrate, Forming the electrodes on the back surface of the second contact layer and on the contact layer, respectively, thereby shortening the life of the carriers, thereby enabling operation at a shorter switching speed.
[0029]
The invention according to claim 11 is
A method for manufacturing an optical switch that switches a transmission path of an optical signal by a change in refractive index due to carrier injection,
Doping an impurity that forms a recombination level on a semiconductor substrate to form an optical waveguide layer; forming a contact layer on the optical waveguide layer; and forming a contact layer on the back surface of the semiconductor substrate and the contact layer. Since the steps of forming the respective electrodes are performed, the life of the carriers is shortened, so that the operation can be performed at a shorter switching speed.
[0030]
The invention according to claim 12 is
A method for manufacturing an optical switch that switches a transmission path of an optical signal by a change in refractive index due to carrier injection,
Forming an optical waveguide layer by lowering the epitaxial growth temperature on the semiconductor substrate; forming a pair of contact layers by impurity diffusion or ion implantation on the optical waveguide layer; Since the method includes a step of forming an insulating film in a portion other than on the contact layer and a step of forming a pair of electrodes on the contact layer, the life of carriers is shortened. Becomes possible.
[0031]
The invention according to claim 13 is
A method for manufacturing an optical switch that switches a transmission path of an optical signal by a change in refractive index due to carrier injection,
Doping an impurity for forming a recombination level on a semiconductor substrate to form an optical waveguide layer; forming a pair of contact layers on the optical waveguide layer by impurity diffusion or ion implantation; Since the process of forming an insulating film on a portion of the waveguide layer other than on the contact layer and the process of forming a pair of electrodes on the contact layer, respectively, shortens the life of carriers. , Operation at a shorter switching speed.
[0032]
The invention according to claim 14 is
In the method for manufacturing an optical switch according to claim 11 or 13,
The impurity is
When the semiconductor material forming the optical waveguide layer is Au when the semiconductor material is SiGe-based, the lifetime of the carrier is shortened, so that the operation can be performed at a shorter switching speed.
[0033]
The invention according to claim 15 is
In the method for manufacturing an optical switch according to claim 11 or 13,
The impurity is
When the semiconductor material forming the optical waveguide layer is Cr when the semiconductor material is GaAs, the life of the carrier is shortened, so that the operation can be performed at a shorter switching speed.
[0034]
The invention according to claim 16 is
In the method for manufacturing an optical switch according to claim 11 or 13,
The impurity is
When the semiconductor material forming the optical waveguide layer is InGaAsP-based or InP-based Fe and the semiconductor material is Fe, the life of the carrier is shortened, so that the operation can be performed at a shorter switching speed.
[0035]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, the present invention will be described in detail with reference to the drawings. 1 and 2 are a plan view and a sectional view showing an embodiment of the optical switch according to the present invention.
[0036]
1, reference numerals 1 and 3 denote the same reference numerals as in FIG. 5, and reference numeral 11 denotes an "X-shaped" optical waveguide having an increased recombination level. An “X-shaped” optical waveguide 11 is formed on the substrate 1, and an electrode 3 is formed at an intersection of the “X-shaped” optical waveguide 11.
[0037]
On the other hand, FIG. 2 is a cross-sectional view taken along the line "BB '" in FIG. 1, and 4, 5, 7, 8, 9, and 10 are denoted by the same reference numerals as in FIG. It is an optical waveguide layer that has been increased.
[0038]
The Zn, which is a p-type impurity, is diffused in portions indicated by “DR21” and “DR22” in FIG. 2 on the InP substrate 5, and thereafter, an optical waveguide having an increased recombination level is formed on the InP substrate 5. The layer 12, the InP layer 7, and the InGaAsP layer 8 are sequentially formed.
[0039]
Further, Zn which is a p-type impurity is diffused in a portion indicated by "DR23" in FIG. 2, and an oxide film 9 is formed in a portion other than the diffusion region indicated by "DR23" in FIG. 2, the electrode 10 is formed on the diffusion region indicated by “DR23”, and the electrode 4 is formed on the back surface of the InP substrate 5.
[0040]
Here, the operation of the embodiment shown in FIG. 1 will be described. In particular, a method of forming the optical waveguide layer 12 having an increased recombination level will be mainly described.
[0041]
As a method of increasing the first recombination level, in the step of epitaxial growth for forming the optical waveguide layer 12, the epitaxial growth temperature is lowered to increase the recombination level in the optical waveguide layer 12.
[0042]
As a method of increasing the second recombination level, in the step of epitaxial growth for forming the optical waveguide layer 12, the impurity that forms the recombination level during the growth of the optical waveguide layer 12 is doped to perform the recombination level. Increase.
[0043]
However, in the latter method of increasing the recombination level, the impurity to be doped differs depending on the material series used for the optical waveguide layer 12.
[0044]
For example, the impurity is “Au” in the “SiGe-based” material, “Cr” in the “GaAs-based” material, and “Fe” in the “InP-based” material.
[0045]
That is, in the optical waveguide layer 12 in which the method for increasing the recombination level of both of the above is performed, the extinction of carriers is promoted by the increased recombination level as compared with the untreated optical waveguide layer, in other words, Since the life of the carrier is shortened, the operation can be performed at a shorter switching speed.
[0046]
As a result, by increasing the recombination level of the optical waveguide layer 12, the lifetime of carriers is shortened, so that operation at a shorter switching speed becomes possible.
[0047]
In the embodiment shown in FIGS. 1 and 2, an "X-shaped" optical waveguide similar to the conventional example is formed in the optical waveguide layer 12, but the transmission path of the optical signal is changed due to a change in the refractive index due to carrier injection. There is no limitation on the shape of the optical waveguide as long as the optical switch can be switched.
[0048]
In the embodiment shown in FIGS. 1 and 2, the optical waveguide layer 12, the InP layer 7 as a cladding layer, and the InGaAsP layer 8 as a cap layer are formed on the InP substrate 5. The optical waveguide layer 12 and the contact layer may be formed thereon by diffusion or ion implantation.
[0049]
Alternatively, the substrate may be semi-insulating, and a lower contact layer may be formed on the back surface of the substrate by diffusion or ion implantation, and an electrode may be formed on the back surface of the lower contact layer. In this case, the parasitic capacitance can be reduced.
[0050]
In the embodiment shown in FIGS. 1 and 2, the optical waveguide layer 12 is formed of an "InGaAsP-based" material. However, the optical waveguide layer 12 is formed of an "SiGe-based", "GaAs-based", or "InP-based" material. 12 may be formed.
[0051]
In addition, in the embodiment shown in FIGS. 1 and 2, a region for diffusing Zn which is a p-type impurity as shown by “DR21”, “DR22” and “DR23” in FIG. Not an element.
[0052]
In the embodiment shown in FIGS. 1 and 2, the cladding layer and the cap layer are sequentially formed on the optical waveguide layer 12, but a pair of contact layers are formed on the optical waveguide layer by impurity diffusion or ion implantation. And a pair of electrodes may be formed on the contact layer.
[0053]
3 and 4 are a plan view and a sectional view showing another embodiment of the optical switch according to the present invention.
[0054]
In FIG. 3, 1 and 11 have the same reference numerals as in FIG. 1, and 13 and 14 are electrodes. An “X-shaped” optical waveguide 11 is formed on the substrate 1. An electrode 13 is formed at the intersection of the “X-shaped” optical waveguide 11, and an electrode 14 is formed near the electrode 13.
[0055]
On the other hand, FIG. 4 is a cross-sectional view taken along the line “CC ′” in FIG. 3. In FIG. 4, 13 and 14 are denoted by the same reference numerals as in FIG. 3, 15 is a semiconductor substrate, and 16 is a recombination level. The optical waveguide layers 17 and 18 are contact layers, and 19 is an insulating film such as SiO ₂ .
[0056]
An optical waveguide layer 16 having an increased recombination level is formed on a semiconductor substrate 15, and contact layers 17 and 18 are formed on the optical waveguide layer 16 by impurity diffusion or ion implantation. Then, an insulating film 19 is formed on portions other than on the contact layers 17 and 18, and electrodes 13 and 14 are formed on the contact layers 17 and 18.
[0057]
Here, the operation of the embodiment shown in FIGS. 3 and 4 and the method of forming the optical waveguide layer 16 are the same as those in the embodiment shown in FIGS.
[0058]
【The invention's effect】
As is apparent from the above description, the present invention has the following effects.
According to claims 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15 and the invention of claim 16, the recombination level of the optical waveguide layer is determined. By increasing, the life of the carrier is shortened, so that operation at a shorter switching speed becomes possible.
[Brief description of the drawings]
FIG. 1 is a plan view showing an embodiment of an optical switch according to the present invention.
FIG. 2 is a sectional view showing an embodiment of the optical switch according to the present invention.
FIG. 3 is a plan view showing another embodiment of the optical switch according to the present invention.
FIG. 4 is a sectional view showing another embodiment of the optical switch according to the present invention.
FIG. 5 is a plan view showing an example of a conventional optical switch.
FIG. 6 is a cross-sectional view illustrating an example of a conventional optical switch.
[Explanation of symbols]
1, 15 Substrate 2, 11 Optical waveguide 3, 4, 10, 13, 14 Electrode 5 InP substrate 6, 12, 16 Optical waveguide layer 7 InP layer 8 InGaAsP layer 9, 19 Oxide film 17, 18 Contact layer

Claims (16)

In an optical switch that switches a transmission path of an optical signal by a change in refractive index due to carrier injection,
An optical switch, wherein a recombination level of an optical waveguide layer in which an optical waveguide through which the optical signal propagates is formed is increased. A semiconductor substrate;
An optical waveguide layer having an increased recombination level on which the optical waveguide on which the optical signal propagates is formed on the semiconductor substrate,
A contact layer formed on the optical waveguide layer;
2. An electrode formed on the back surface of the semiconductor substrate and on the contact layer, the carrier being injected to control a refractive index of the optical waveguide to switch a propagation path of the optical signal. An optical switch as described. 3. The optical switch according to claim 2, wherein a second contact layer is provided on a back surface of the semiconductor substrate, and the electrode is formed on the second contact layer. A semiconductor substrate;
An optical waveguide layer having an increased recombination level on which the optical waveguide on which the optical signal propagates is formed on the semiconductor substrate,
A pair of contact layers formed on the optical waveguide layer,
An electrode formed on the contact layer to inject carriers and control the refractive index of the optical waveguide to switch the propagation path of the optical signal;
2. The optical switch according to claim 1, further comprising: an insulating film formed on the optical waveguide layer and in a portion other than on the contact layer. The optical waveguide layer,
The optical switch according to claim 1, wherein the optical switch is formed of an InGaAsP-based semiconductor material. The optical waveguide layer,
The optical switch according to any one of claims 1 to 4, wherein the optical switch is formed of a SiGe-based semiconductor material. The optical waveguide layer,
The optical switch according to any one of claims 1 to 4, wherein the optical switch is formed of a GaAs-based semiconductor material. The optical waveguide layer,
The optical switch according to claim 1, wherein the optical switch is formed of an InP-based semiconductor material. A method for manufacturing an optical switch that switches a transmission path of an optical signal by a change in refractive index due to carrier injection,
Forming an optical waveguide layer by lowering the epitaxial growth temperature on the semiconductor substrate;
Forming a contact layer on the optical waveguide layer;
Forming an electrode on each of the back surface of the semiconductor substrate and the contact layer. A method for manufacturing an optical switch that switches a transmission path of an optical signal by a change in refractive index due to carrier injection,
Forming an optical waveguide layer by lowering the epitaxial growth temperature on the semiconductor substrate;
Forming a contact layer on the optical waveguide layer;
Forming a second contact layer on the back surface of the semiconductor substrate;
Forming an electrode on the back surface of the second contact layer and on the contact layer, respectively. A method for manufacturing an optical switch that switches a transmission path of an optical signal by a change in refractive index due to carrier injection,
Forming an optical waveguide layer by doping an impurity that forms a recombination level on the semiconductor substrate;
Forming a contact layer on the optical waveguide layer;
Forming an electrode on each of the back surface of the semiconductor substrate and the contact layer. A method for manufacturing an optical switch that switches a transmission path of an optical signal by a change in refractive index due to carrier injection,
Forming an optical waveguide layer by lowering the epitaxial growth temperature on the semiconductor substrate;
Forming a pair of contact layers on the optical waveguide layer by impurity diffusion or ion implantation;
Forming an insulating film on the optical waveguide layer and on a portion other than on the contact layer;
Forming a pair of electrodes on the contact layer, respectively. A method for manufacturing an optical switch that switches a transmission path of an optical signal by a change in refractive index due to carrier injection,
Forming an optical waveguide layer by doping an impurity that forms a recombination level on the semiconductor substrate;
Forming a pair of contact layers on the optical waveguide layer by impurity diffusion or ion implantation;
Forming an insulating film on the optical waveguide layer and on a portion other than on the contact layer;
Forming a pair of electrodes on the contact layer, respectively. The impurity is
14. The method of manufacturing an optical switch according to claim 11, wherein the semiconductor material forming the optical waveguide layer is Au when the semiconductor material is SiGe-based. The impurity is
14. The method according to claim 11, wherein the semiconductor material forming the optical waveguide layer is Cr when the semiconductor material is GaAs. The impurity is
14. The method according to claim 11, wherein the semiconductor material forming the optical waveguide layer is Fe when the semiconductor material is InGaAsP or InP.

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