JP6347486B2 - Optical active device - Google Patents

Description

  The present invention relates to an optical active device comprising an active layer made of germanium.

  An optical active device has been developed in which an n-type silicon layer and a p-type silicon layer sandwich an active layer made of germanium (Ge). This optical active element can be directly formed on a silicon substrate, and can be used with light having a wavelength in the vicinity of 1.55 μm in the communication wave band. For this reason, the above-mentioned optical active element has attracted much attention as a light emitting element and a modulation element for silicon photonics that can be formed on a silicon substrate (see Non-Patent Document 1).

  The above-described optical active element will be described with reference to FIG. FIG. 7 is a perspective view showing a configuration of a currently used photoactive element using Ge. This photoactive element includes an active layer 402 made of Ge formed on a silicon substrate 401, a first conductivity type first silicon layer 403 formed with the active layer 402 interposed therebetween, and a second conductivity type second layer. And a silicon layer 404. On the silicon substrate 401, a first silicon layer 403, an active layer 402, and a second silicon layer 404 are laminated in this order.

  In addition, the optical active element includes an insulating layer 405 formed on the first silicon layer 403 around the active layer 402, a first electrode 411 connected to the first silicon layer 403, and a second silicon layer 404. And a second electrode 412 to be connected. The insulating layer 405 functions as a clad. The first electrode 411 passes through the insulating layer 405 and is connected to the first silicon layer 403.

  Here, in order to emit light, the active layer 402 needs to be composed of a direct transition type semiconductor, but Ge is an indirect transition type semiconductor, and as it is, it can be used as the active layer 402 of the photoactive element. Can not. For this reason, it can be set as the state close | similar to a direct transition type by adding distortion to the active layer 402 comprised from Ge (refer nonpatent literature 2). For example, in the case of being configured as a light emitting diode, tensile strain may be applied to the active layer 402.

  In the case where the optical modulator is configured, it is used as an electroabsorption type, and compressive strain may be applied to the active layer 402. Since the light absorption spectrum edge of Ge is usually up to about 1600 nm, it is necessary to lower the spectrum edge to near 1550 nm in order to use it in the communication wave band C band as an electroabsorption type. Therefore, when an optical modulator is used, compressive strain is applied to the active layer 402 made of Ge.

R. E. Camacho-Aguilera et al., "An electrically pumped germanium laser", Optics Express, vol.20, no.10, pp.11316-11320,2012. J. Liu et al., "Tensile-strained, n-type Ge as a gain medium for monolithic laser integration on Si", Optics Express, vol.15, no.18, pp.11272-11277,2007.

  However, at present, strain is applied due to differences in thermal expansion coefficients from the bending of the substrate and other layers (cladding, etc.), so it is not easy to control the amount of strain, and the amount of strain is insufficient. is there. At present, the amount of strain applied to the active layer 402 is 0.2 to 0.3% (see Non-Patent Document 2).

  For example, in the case of a light emitting diode, the amount of strain is insufficient, and n-type impurities are introduced into the active layer 402 at a high concentration (see Non-Patent Document 2). However, introduction of a high concentration of n-type impurities into Ge is not technically easy and places a burden on the manufacturing process. Further, in the case of an optical modulator, it is necessary to control the absorption spectrum edge according to the wavelength band, and it is difficult to control the required amount of distortion with the conventional technique of applying strain.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to make it possible to configure a photoactive element by an active layer made of Ge to which a desired amount of strain is applied. To do.

An optical active device according to the present invention includes an active layer made of germanium formed on a substrate extending in a direction in which input light propagates, and a first conductivity type first formed by sandwiching the active layer. A strain in the strain application direction is formed by sandwiching the active layer in a strain application direction that is parallel to the plane of the substrate and perpendicular to the extending direction of the active layer on the substrate and the second silicon layer of the second conductivity type. A first strained layer and a second strained layer made of a piezoelectric material for imparting to the active layer, and a first insulating layer and a second insulating layer disposed between the active layer, the first strained layer and the second strained layer, respectively. A first electrode connected to the first silicon layer, a second electrode connected to the second silicon layer, a third electrode and a fourth electrode connected to one of the first strained layer and the second strained layer, A fifth electrode and a sixth electrode connected to the other of the first strain layer and the second strain layer.

  In the optical active element, a third insulating layer formed from above the first insulating layer to the first strained layer, and a fourth insulating layer formed from above the second insulating layer to the second strained layer. May be provided.

  The optical active device may include a space formed in the substrate in a region where the active layer is formed.

In the optical active element, the first silicon layer and the second silicon layer are formed with the active layer sandwiched in the normal direction of the substrate , and the third electrode and the fourth electrode are disposed on the first silicon layer, on the third and fourth electrodes, oriented in a direction perpendicular to the plane of the substrate, the first strained layer and the second strained layer distorted distortion application direction by applying a voltage is being arranged relative to the alignment direction so that to. The first silicon layer and the second silicon layer is such that is formed by sandwiching an active layer strained application direction.

  As described above, according to the present invention, the first piezoelectric substrate is formed on the substrate with the active layer sandwiched in the strain application direction parallel to the plane of the substrate, and applies the strain in the strain application direction to the active layer. Since the strained layer and the second strained layer are provided, it is possible to obtain an excellent effect that an optical active element can be constituted by an active layer made of Ge to which a desired amount of strain is applied.

FIG. 1 is a perspective view showing a configuration of an optical active element according to Embodiment 1 of the present invention. FIG. 2 is a cross-sectional view showing the configuration of the optical active element according to Embodiment 2 of the present invention. FIG. 3 is a cross-sectional view showing the configuration of the optical active element according to Embodiment 3 of the present invention. FIG. 4 is a cross-sectional view showing the configuration of the optical active element according to Embodiment 4 of the present invention. FIG. 5 is a cross-sectional view showing the configuration of the optical active element according to Embodiment 5 of the present invention. FIG. 6 is a cross-sectional view showing a configuration of an optical active element according to Embodiment 6 of the present invention. FIG. 7 is a perspective view showing a configuration of a conventional photoactive element.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

[Embodiment 1]
First, Embodiment 1 of the present invention will be described with reference to FIG. FIG. 1 is a perspective view showing a configuration of an optical active element according to Embodiment 1 of the present invention. This optical active element includes an active layer 102 made of germanium (Ge) formed on a substrate 101, a first silicon layer 103 and a second silicon layer 104 formed with the active layer 102 sandwiched therebetween, A first strained layer 105 and a second strained layer 106 are formed with the active layer 102 sandwiched in the strain application direction (x-axis direction) parallel to the plane of the substrate 101. A first insulating layer 107 is provided between the active layer 102 and the first strained layer 105, and a second insulating layer 108 is provided between the active layer 102 and the second strained layer 106.

  The first electrode 111 is connected to the first silicon layer 103, and the second electrode 112 is connected to the second silicon layer 104. The third electrode 113 is connected to one of the first strained layers 105, and the fourth electrode 114 is connected to one of the second strained layers 106. The fifth electrode 115 is connected to the other side of the first strained layer 105, and the sixth electrode 116 is connected to the other side of the second strained layer 106. Note that the x-axis direction is a direction in which the first strained layer 105, the active layer 102, and the second strained layer 106 are arranged on a plane parallel to the plane of the substrate 101. Further, the y-axis direction is a direction in which the input light is propagated by the active layer 102 extending on a plane parallel to the plane of the substrate 101. The z-axis direction is the normal direction of the plane of the substrate 101.

  The substrate 101 is, for example, a silicon substrate. The first silicon layer 103 is a first conductivity type (for example, n-type), and the second silicon layer 104 is a second conductivity type (for example, p-type). In the first embodiment, the first silicon layer 103 and the second silicon layer 104 are formed with the active layer 102 sandwiched in the normal direction (z-axis direction) of the substrate 101, and the first silicon layer 103, the active layer 102, The second silicon layers 104 are stacked in contact with each other. Note that a part of the n-type impurities contained in the first silicon layer 103 is diffused, so that a part of the active layer 102 on the first silicon layer 103 side is n-type. Further, since a part of the p-type impurities contained in the second silicon layer 104 is diffused, a part of the active layer 102 on the second silicon layer 104 side is p-type.

  In addition, the first strain layer 105 and the second strain layer 106 are made of a piezoelectric material, and give a strain in a direction parallel to the plane of the substrate 101 (strain application direction) to the active layer 102 sandwiched therebetween. The piezoelectric body constituting the first strain layer 105 and the second strain layer 106 may be, for example, lead zirconate titanate (PZT). In the first embodiment, the third electrode 113 and the fourth electrode 114 on which a piezoelectric body is formed (deposited) may be made of an alloy of platinum (Pt) and titanium (Ti).

For example, in the case where the third electrode 113 and the fourth electrode 114 are formed by depositing an alloy of Pt and Ti by a sputtering method, a (111) orientation is formed on the third electrode 113 and the fourth electrode 114, and the (100) plane is z A polycrystalline body of PZT in the axial direction grows. If the fifth electrode 115 and the sixth electrode 116 are formed on the first strained layer 105 and the second strained layer 106 made of PZT in this way, a piezoelectric of about 100 to 150 pm / V without polarization treatment. A constant d ₃₁ is obtained.

For example, the active layer 102 is formed with a layer thickness of 300 μm and a width (dimension in the x-axis direction) of 1 μm, the first strained layer 105 and the second strained layer 106 are formed with a layer thickness of 300 μm and a width of 1 μm, and a piezoelectric constant d _{In the example, 31 is set} to 150 pm / V, and the first insulating layer 107 and the second insulating layer 108 are formed to have a width of 0.5 μm.

  In this case, if a negative voltage (for example, −20 V) with respect to the alignment direction is applied to each strained layer, the active layer 102 is given a 0.5% tensile strain in the x-axis direction. Thereby, the photoactive element of Embodiment 1 can be functioned as a light emitting diode. Current injection into the active layer 102 is performed through the first electrode 111, the third electrode 113, and the second electrode 112. While the light is emitted, the potential is continuously applied to the fifth electrode 115 and the sixth electrode 116.

  On the other hand, when a positive voltage (for example, +20 V) with respect to the alignment direction is applied to each strained layer, 0.5% compressive strain is applied to the active layer 102 in the x-axis direction. Thereby, the optical active element of Embodiment 1 can be functioned as an optical modulator. The modulation signal is input to the active layer 102 through the first electrode 111, the third electrode 113, and the second electrode 112. During the modulation, the potential is continuously applied to the fifth electrode 115 and the sixth electrode 116.

The amount of distortion is given by the following equation. Δw is the amount of displacement of the piezoelectric body (active layer 102), d ₃₁ is the piezoelectric constant (pm / V), w is the width of the piezoelectric body (active layer 102) (dimension in the x-axis direction), and d is the piezoelectric body ( It is the thickness (dimension in the z-axis direction) of the active layer 102).

In the case of the above-described example, when 20 V is applied, the displacement of the active layer 102 in the x-axis direction is 1 × 10 ⁻⁸ (m). In the first embodiment, since the first insulating layer 107 and the second insulating layer 108 are formed in the active layer 102, the first strained layer 105, and the second strained layer 106, they are combined to form the piezoelectric portion. If the width is 2 μm, the amount of distortion is 0.5%.

[Embodiment 2]
Next, Embodiment 2 of the present invention will be described with reference to FIG. FIG. 2 is a cross-sectional view showing the configuration of the optical active element according to Embodiment 2 of the present invention. This optical active element includes an active layer 102 made of Ge formed on a substrate 101, a first silicon layer 103 and a second silicon layer 104 formed with the active layer 102 sandwiched therebetween, and a substrate on the substrate 101. The first strained layer 105 and the second strained layer 106 are formed with the active layer 102 sandwiched in the strain application direction (x-axis direction) parallel to the plane 101. A first insulating layer 107 is provided between the active layer 102 and the first strained layer 105, and a second insulating layer 108 is provided between the active layer 102 and the second strained layer 106.

  The first electrode 111 is connected to the first silicon layer 103, and the second electrode 112 is connected to the second silicon layer 104. The third electrode 113 is connected to one of the first strained layers 105, and the fourth electrode 114 is connected to one of the second strained layers 106. The fifth electrode 115 is connected to the other side of the first strained layer 105, and the sixth electrode 116 is connected to the other side of the second strained layer 106.

The above configuration is the same as that of the first embodiment. In the second embodiment, the first strain layer 105 and the second strain layer made of PZT are disposed on the fourth electrode 114 and the fifth electrode 115 made of an alloy of Pt and Ti via the buffer layer 109 made of LaNiO _3. 106 is formed.

  As described above, by forming the first strained layer 105 and the second strained layer 106 through the buffer layer 109, compared to the case where the first strained layer 105 and the second strained layer 106 are directly formed on the fourth electrode 114 and the fifth electrode 115, The degree of orientation can be improved. By improving the degree of orientation, it is possible to improve the piezoelectric constants in the first strained layer 105 and the second strained layer 106. Therefore, according to the second embodiment, a larger strain can be applied to the active layer 102. . Note that the material constituting the buffer layer 109 is appropriately selected depending on the piezoelectric body constituting the first strained layer 105 and the second strained layer 106.

[Embodiment 3]
Next, Embodiment 3 of the present invention will be described with reference to FIG. FIG. 3 is a cross-sectional view showing the configuration of the optical active element according to Embodiment 3 of the present invention. This optical active element includes an active layer 102 made of Ge formed on a substrate 101, a first silicon layer 103 and a second silicon layer 104 formed with the active layer 102 sandwiched therebetween, and a substrate on the substrate 101. The first strained layer 105 and the second strained layer 106 are formed with the active layer 102 sandwiched in the strain application direction (x-axis direction) parallel to the plane 101. A first insulating layer 107 is provided between the active layer 102 and the first strained layer 105, and a second insulating layer 108 is provided between the active layer 102 and the second strained layer 106.

  The first electrode 111 is connected to the first silicon layer 103, and the second electrode 112 is connected to the second silicon layer 104. The third electrode 113 is connected to one of the first strained layers 105, and the fourth electrode 114 is connected to one of the second strained layers 106. The fifth electrode 115 is connected to the other side of the first strained layer 105, and the sixth electrode 116 is connected to the other side of the second strained layer 106.

  The above configuration is the same as that of the first embodiment. In the third embodiment, first, an upper insulating layer (third insulating layer) 121 formed from the upper surface of the first strained layer 105 to the upper surface of the first insulating layer 107 is provided. Therefore, the first strained layer 105 and the first insulating layer 107 are in a state where their upper surfaces are connected by the upper insulating layer 121 in addition to the close contact by the side surfaces in contact with each other. As a result, when tensile strain is generated by the first strained layer 105, the first insulating layer 107 is prevented from being peeled off from the first strained layer 105, and the active layer 102 has a uniform action. Will be able to give.

  Similarly, an upper insulating layer (fourth insulating layer) 122 formed from the upper surface of the second strained layer 106 to the upper surface of the second insulating layer 108 is provided. Therefore, the second strained layer 106 and the second insulating layer 108 are brought into a state in which the upper surfaces of the second strained layer 106 and the second insulating layer 108 are connected by the upper insulating layer 122 in addition to the close contact by the side surfaces in contact with each other. As a result, when tensile strain is generated by the second strained layer 106, the second insulating layer 108 is prevented from being peeled off from the second strained layer 106, and the active layer 102 has a more uniform action. Will be able to give.

  Note that when an upper insulating layer is formed on each strained layer, strain in each strained layer is suppressed. When a voltage is applied to each strained layer, the strain is distorted in the x-axis direction and the z-axis direction. The presence of the upper insulating layer suppresses this distortion. For this reason, the same strain as in the above-described embodiment cannot be applied to the active layer 102.

  In the case of the third embodiment, if a negative voltage is applied to each strained layer with respect to the orientation direction, compressive stress is applied to the upper surface (surface facing the z-axis direction) of each strained layer, and the side surface ( A tensile stress is applied to the surface facing the x-axis direction. As a result, tensile stress is applied to the active layer 102. On the other hand, if a positive voltage with respect to the orientation direction is applied to each strained layer, tensile stress is applied to the upper surface (the surface facing the z-axis direction) of each strained layer, and the side surface (each facing the x-axis direction) of each strained layer. Surface) is subjected to compressive stress. As a result, compressive stress is applied to the active layer 102.

  Even if the lattice constant changes due to such stress, it is possible to change the Ge band structure, so that the same effect as when the active layer 102 is strained can be expected.

[Embodiment 4]
Next, Embodiment 4 of the present invention will be described with reference to FIG. FIG. 4 is a cross-sectional view showing the configuration of the optical active element according to Embodiment 4 of the present invention. This optical active element includes an active layer 102 made of Ge formed on a substrate 101, a first silicon layer 103 and a second silicon layer 104 formed with the active layer 102 sandwiched therebetween, and a substrate on the substrate 101. The first strained layer 105 and the second strained layer 106 are formed with the active layer 102 sandwiched in the strain application direction (x-axis direction) parallel to the plane 101. A first insulating layer 107 is provided between the active layer 102 and the first strained layer 105, and a second insulating layer 108 is provided between the active layer 102 and the second strained layer 106.

  The first electrode 111 is connected to the first silicon layer 103, and the second electrode 112 is connected to the second silicon layer 104. The third electrode 113 is connected to one of the first strained layers 105, and the fourth electrode 114 is connected to one of the second strained layers 106. The fifth electrode 115 is connected to the other side of the first strained layer 105, and the sixth electrode 116 is connected to the other side of the second strained layer 106.

  The above configuration is the same as that of the first embodiment. The fourth embodiment includes a space 141 formed in the substrate 101 in a region where the active layer 102 is formed. For example, the space 141 can be formed by etching using a mask pattern formed by a known lithography technique. By providing the space 141, the lower layer of the active layer 102 is only the first silicon layer 103, and the substrate 101 is not restrained. As a result, the active layer 102 becomes more easily distorted.

[Embodiment 5]
Next, Embodiment 5 of the present invention will be described with reference to FIG. FIG. 5 is a cross-sectional view showing the configuration of the optical active element according to Embodiment 5 of the present invention. This optical active element includes an active layer 102 made of Ge formed on a substrate 101, a first silicon layer 103 and a second silicon layer 104 formed with the active layer 102 sandwiched therebetween, and a substrate on the substrate 101. A first strain layer 205 and a second strain layer 206 formed with the active layer 102 sandwiched in a strain application direction (x-axis direction) parallel to the plane of 101. A first insulating layer 107 is provided between the active layer 102 and the first strained layer 205, and a second insulating layer 108 is provided between the active layer 102 and the second strained layer 206.

  The first electrode 111 is connected to the first silicon layer 103, and the second electrode 112 is connected to the second silicon layer 104. In addition, the third electrode 113 is connected to one of the first strain layers 205, and the fourth electrode 114 is connected to one of the second strain layers 206. Further, the fifth electrode 115 is connected to the other side of the first strained layer 205, and the sixth electrode 116 is connected to the other side of the second strained layer 206.

  In the fifth embodiment, the upper surface heights of the first strain layer 205 and the second strain layer 206 are made lower than the upper surface height of the active layer 102, and the layer thicknesses of the first strain layer 205 and the second strain layer 206 are made thinner. doing. The configuration other than the first strain layer 205 and the second strain layer 206 is the same as that of the first embodiment described above, and detailed description thereof is omitted.

  Since the tensile strain due to the piezoelectric body becomes larger as the piezoelectric body becomes thinner, as described above, if the layer thickness of the first strain layer 205 and the second strain layer 206 is made thinner, a larger strain amount can be expected. In this case, however, the active layer 102 is subjected to non-uniform strain. For example, the upper surface height of each strained layer may be higher than the upper surface height of the active layer 102, and each strained layer may be formed thicker. If each strained layer is made thicker, the amount of strain is reduced, but the leakage current can be suppressed by reducing the threading dislocations of the piezoelectric body constituting each strained layer.

[Embodiment 6]
Next, a sixth embodiment of the present invention will be described with reference to FIG. FIG. 6 is a cross-sectional view showing a configuration of an optical active element according to Embodiment 6 of the present invention. This optical active element includes an active layer 302 made of Ge formed on a substrate 301, a first silicon layer 303 and a second silicon layer 304 formed with the active layer 302 in between, and a substrate on the substrate 301. The first strain layer 305 and the second strain layer 306 are formed with the active layer 302 sandwiched in the strain application direction (x-axis direction) parallel to the plane 301. A first insulating layer 307 is provided between the active layer 302 and the first strained layer 305, and a second insulating layer 308 is provided between the active layer 302 and the second strained layer 306.

  The first electrode 311 is connected to the first silicon layer 303, and the second electrode 312 is connected to the second silicon layer 304. The third electrode 313 is connected to one of the first strained layers 305, and the fourth electrode 314 is connected to one of the second strained layers 306. The fifth electrode 315 is connected to the other side of the first strained layer 305, and the sixth electrode 316 is connected to the other side of the second strained layer 306.

  The substrate 301 is, for example, a silicon substrate. The first silicon layer 303 is a first conductivity type (for example, n-type), and the second silicon layer 304 is a second conductivity type (for example, p-type). In the sixth embodiment, the first silicon layer 303 and the second silicon layer 304 are formed with the active layer 302 sandwiched in the strain application direction (x-axis direction) parallel to the plane of the substrate 301.

  The first silicon layer 303 extends from between the first strained layer 305 (first insulating layer 307) and the active layer 302 to between the surface of the substrate 301 and the first strained layer 305 (third electrode 313). It is formed in an L shape in a sectional view. Similarly, the second silicon layer 304 is between the second strained layer 306 (second insulating layer 308) and the active layer 302 and between the surface of the substrate 301 and the second strained layer 306 (fourth electrode 314). And is formed in an L shape in cross-sectional view.

  Note that a part of the n-type impurities contained in the first silicon layer 303 is diffused, so that a part of the active layer 302 on the first silicon layer 303 side is n-type. In addition, since a part of the p-type impurity contained in the second silicon layer 304 is diffused, a part of the active layer 302 on the second silicon layer 304 side is p-type.

  The first strain layer 305 and the second strain layer 306 are made of a piezoelectric material, and give the strain in the strain application direction parallel to the plane of the substrate 301 to the active layer 302 sandwiched between them. The piezoelectric body constituting the first strain layer 305 and the second strain layer 306 may be PZT, for example. In the sixth embodiment, the third electrode 313 and the fourth electrode 314 on which the piezoelectric body is formed (deposited) may be made of an alloy of Pt and Ti.

For example, when the third electrode 313 and the fourth electrode 314 are formed by depositing an alloy of Pt and Ti by sputtering, 111 orientation is provided on the third electrode 313 and the fourth electrode 314, and the (100) plane is oriented in the z-axis direction. A polycrystalline body of PZT was grown. If the fifth electrode 315 and the sixth electrode 316 are formed on the first strained layer 305 and the second strained layer 306 made of PZT in this way, a piezoelectric of about 100 to 150 pm / V without polarization treatment is performed. A constant d ₃₁ is obtained.

For example, the active layer 302 is formed with a layer thickness of 300 μm and a width (dimension in the x-axis direction) of 1 μm, the first strained layer 305 and the second strained layer 306 are formed with a layer thickness of 300 μm and a width of 1 μm, and a piezoelectric constant d _{In the example, 31 is set} to 150 pm / V, and the first insulating layer 307 and the second insulating layer 308 are formed to have a width of 0.5 μm.

  In this case, if a negative voltage (for example, −20 V) with respect to the alignment direction is applied to each strained layer, the active layer 302 is given a 0.5% tensile strain in the x-axis direction. Thereby, the optical active element of Embodiment 6 can be functioned as a light emitting diode. Current injection into the active layer 302 is performed through the first electrode 311, the third electrode 313, and the second electrode 312. While the light is emitted, the potential is continuously applied to the fifth electrode 315 and the sixth electrode 316.

  On the other hand, when a positive voltage (for example, +20 V) with respect to the alignment direction is applied to each strained layer, 0.5% compressive strain is applied to the active layer 302 in the x-axis direction. Thereby, the optical active element of Embodiment 6 can be functioned as an optical modulator. The modulation signal is input to the active layer 302 through the first electrode 311, the third electrode 313, and the second electrode 312. During the modulation, the potential is continuously applied to the fifth electrode 315 and the sixth electrode 316.

In the example described above, the displacement of the active layer 302 in the x-axis direction is 1 × 10 ⁻⁸ (m) by applying 20 V. In Embodiment 6, since the first insulating layer 307 and the second insulating layer 308 are formed in the active layer 302, the first strained layer 305, and the second strained layer 306, these are combined to form the piezoelectric portion. If the width is 2 μm, the amount of distortion is 0.5%.

  According to the sixth embodiment, Ge is not deposited on the silicon layer of the first conductivity type, so that the burden on the manufacturing process can be reduced. Further, the leakage current of the active layer 302 due to the vertical penetration transition extending in the normal direction of the substrate 301 can be suppressed.

  As described above, according to the present invention, the active layer is sandwiched between the two strain layers via the insulating layer in the strain application direction parallel to the plane of the substrate on the substrate. An optical active element can be formed by an active layer made of Ge to which an amount of strain is applied. As a result, for example, a Ge light emitting diode having higher efficiency than that of a conventional Ge light emitting diode and having wavelength selectivity can be obtained. In addition, since it is not necessary to introduce high-concentration n-type impurities into the active layer made of Ge, the process burden is reduced. Further, the drive wavelength of the Ge modulator can be set accurately, and the drive wavelength can be varied.

The present invention is not limited to the embodiment described above, and many modifications and combinations can be implemented by those having ordinary knowledge in the art within the technical idea of the present invention. It is obvious. For example, the piezoelectric body may be BaTiO ₃ , LiNbO ₃ , KNbO ₃ , BiNaTiO ₃ , PbMgNbO ₃ —PrTiO ₃ .

  DESCRIPTION OF SYMBOLS 101 ... Substrate, 102 ... Active layer, 103 ... First silicon layer, 104 ... Second silicon layer, 105 ... First strain layer, 106 ... Second strain layer, 107 ... First insulation layer, 108 ... Second insulation layer 111... First electrode 112. Second electrode 113. Third electrode 114. Fourth electrode 115. Fifth electrode 116.

Claims (4)

An active layer made of germanium formed on the substrate extending in the direction in which the input light propagates ;
A first conductivity type first silicon layer and a second conductivity type second silicon layer formed by sandwiching the active layer;
A piezoelectric body formed on the substrate sandwiching the active layer in a strain application direction parallel to the plane of the substrate and perpendicular to the extending direction of the active layer, and applying strain in the strain application direction to the active layer A first strain layer and a second strain layer,
A first insulating layer and a second insulating layer disposed between the active layer and each of the first strained layer and the second strained layer;
A first electrode connected to the first silicon layer;
A second electrode connected to the second silicon layer;
A third electrode and a fourth electrode connected to one of the first strained layer and the second strained layer;
A fifth electrode and a sixth electrode connected to the other of the first strain layer and the second strain layer,
The first silicon layer and the second silicon layer are formed sandwiching the active layer in a normal direction of the substrate,
The third electrode and the fourth electrode are disposed on the first silicon layer;
The first strain layer and the second strain layer, which are aligned on the third electrode and the fourth electrode in a direction perpendicular to the plane of the substrate, and generate strain in the strain application direction by applying a voltage to the alignment direction. An optical active element characterized in that is arranged. An active layer made of germanium formed on the substrate extending in the direction in which the input light propagates ;
A first conductivity type first silicon layer and a second conductivity type second silicon layer formed by sandwiching the active layer;
A piezoelectric body formed on the substrate sandwiching the active layer in a strain application direction parallel to the plane of the substrate and perpendicular to the extending direction of the active layer, and applying strain in the strain application direction to the active layer A first strain layer and a second strain layer,
A first insulating layer and a second insulating layer disposed between the active layer and each of the first strained layer and the second strained layer;
A first electrode connected to the first silicon layer;
A second electrode connected to the second silicon layer;
A third electrode and a fourth electrode connected to one of the first strained layer and the second strained layer;
A fifth electrode and a sixth electrode connected to the other of the first strain layer and the second strain layer,
The optical active element, wherein the first silicon layer and the second silicon layer are formed with the active layer sandwiched in the strain application direction. The optical active device according to claim 1 or 2 ,
A third insulating layer formed from above the first insulating layer to the first strained layer;
And a fourth insulating layer formed from above the second insulating layer to the second strained layer. The optical active device according to any one of claims 1 to 3 ,
An optical active device comprising a space formed in the substrate in a region where the active layer is formed.

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