Semiconductor structure for suppressing electrical crosstalk - Patents.com

Abstract

A semiconductor structure for an optical integrated circuit. The semiconductor structure comprises a waveguide and an active component of an optical integrated circuit. Between the waveguide and the active component, along the axis of light propagation between the waveguide and the active component, is an electrically resistive material. The electrically resistive material has a higher electrical resistivity than the waveguide.

Description

[Background technology]

[0001] Semiconductor structures can be used in photonic integrated circuits (PICs) to perform a variety of functions. The semiconductor structures of a PIC may include passive and active components to control the propagation of light. It may be desirable to also control the flow of electricity in the PIC. [Brief description of the drawings]

[0002] [Figure 1] 1 shows a schematic cross-sectional side view of a first semiconductor structure according to an embodiment; [Figure 2a] 1 is a first graph illustrating reflectivity as a function of wavelength of an electrically resistive material in a first semiconductor structure, according to an embodiment. [Figure 2b] 11 is a second graph illustrating the reflectivity as a function of wavelength of an electrically resistive material in a first semiconductor structure, according to an embodiment. [Diagram 3] 2 shows a schematic cross-sectional view of a first semiconductor structure according to an embodiment; [Figure 4] 1 illustrates a portion of a method for manufacturing a semiconductor structure, according to an embodiment. [Figure 5a] 1A-1D are schematic illustrations of example cross-sectional side views of a semiconductor structure at various stages during fabrication, according to an embodiment; [Figure 5b] 1A-1D are schematic illustrations of example cross-sectional side views of a semiconductor structure at various stages during fabrication, according to an embodiment; [Figure 5c] 1A-1D are schematic illustrations of example cross-sectional side views of a semiconductor structure at various stages during fabrication, according to an embodiment; [Figure 5d] 1A-1D are schematic illustrations of example cross-sectional side views of a semiconductor structure at various stages during fabrication, according to an embodiment; [Figure 5e] 1A-1D are schematic illustrations of example cross-sectional side views of a semiconductor structure at various stages during fabrication, according to an embodiment; [Figure 5f] 1A-1D are schematic illustrations of example cross-sectional side views of a semiconductor structure at various stages during fabrication, according to an embodiment; [Figure 5g] 1A-1D are schematic illustrations of example cross-sectional side views of a semiconductor structure at various stages during fabrication, according to an embodiment; [Figure 5h]1A-1D are schematic illustrations of example cross-sectional side views of a semiconductor structure at various stages during fabrication, according to an embodiment; [Figure 6] 4 illustrates a schematic cross-sectional side view of a second semiconductor structure according to an embodiment. [Figure 7] 13A and 13B show schematic cross-sectional views of a third semiconductor structure according to an embodiment; [Figure 8] 5a-c show schematic plan views of fourth, fifth and sixth semiconductor structures, respectively, according to embodiments. [Figure 9] 13A-13C show schematic plan views of seventh, eighth and ninth semiconductor structures, respectively, according to embodiments. [Figure 10] 13A-13C are schematic plan views of a tenth, an eleventh and a twelfth semiconductor structure, respectively, according to embodiments. [Figure 11] 13A and 13B are schematic diagrams illustrating plan views of a thirteenth semiconductor structure according to an embodiment; DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0003] The embodiments described herein relate to semiconductor structures of PICs, and more particularly, to semiconductor structures that include electrically resistive materials that suppress electrical crosstalk between waveguides and active components.

[0004] If there is a path for electricity to flow between the waveguide and the active component, the operation of the active component may be affected. For example, the waveguide may transmit electrical signals to the active component that interfere with the operation of the active component. For example, such unwanted electrical signals may originate from other components of the PIC to which the waveguide is connected (e.g., other active components).

[0005] If there is a path for electricity to flow between the waveguide and the active component, the operation of other components in the PIC may be affected. For example, electrical signals from the active component may be transmitted by the waveguide to other components in the PIC. The operation of these other components may be affected by the electrical signals from the active component.

[0006] Such problems can be mitigated or avoided by inhibiting the flow of electricity between the waveguide and the active component. As referred to herein, inhibiting the flow of electricity can be considered as significantly reducing the flow of electricity. For example, inhibiting the flow of electricity is reducing the flow of electricity between the waveguide and the active component by at least an order of magnitude (thus reducing the current by a factor of 10). In some embodiments, inhibiting the flow of electricity is completely blocking or preventing the flow of current between the waveguide and the active component. For example, inhibiting the flow of electricity includes electrically isolating the waveguide and the active component from each other. Electricity can flow between the active component and layers of the semiconductor structure other than the waveguide. For example, electricity can flow between the active component and an n-doped semiconductor layer and / or a p-doped semiconductor layer in contact with the waveguide.

[0007] In some embodiments, there are arrangements in which the active components are aligned with the waveguides such that light propagates between them without changing the general direction of light propagation. For example, the active components are at similar distances from the substrate layer of the semiconductor structure. For example, the surfaces of the waveguide and the active components are coplanar. Such an arrangement provides direct propagation of light between the waveguide and the active components, as compared to an arrangement in which light is coupled from the waveguide to an active component that is not aligned with the waveguide. However, the physical alignment of the waveguide (and adjacent conductive layers) with the active components can result in electrical crosstalk. Such an arrangement particularly benefits from the suppression of electrical flow between the waveguide and the active components.

[0008] The following description relates to a semiconductor structure in which electrical flow between a waveguide (and in an embodiment, a conductive layer in contact with the waveguide) and an active component is constrained.

[0009] FIG. 1 shows a schematic side cross-section of a first semiconductor structure 100 of a PIC according to an embodiment. In these examples, the first semiconductor structure 100 comprises a waveguide 102. The first semiconductor structure 100 also comprises an active component 104 of the PIC. The active component 104 is a component of the PIC to which, for example, a voltage can be applied and / or a current flow can be provided, continuously or otherwise, for the active component 104 to perform its function, as opposed to a so-called passive component. For example, the active component 104 comprises an electrical connection for applying a voltage to perform its function. In other embodiments, the active component has an electrode for the active component to output an electrical signal converted from an optical signal. In some embodiments, the active component 104 is a photodetector. In other embodiments, the active component 104 is an amplifier or another active component. In the following description, the active component 104 is considered to be a photodiode 104 having an electrode or contact, for example on the p-doped layer (126), to output a signal. For example, the photodiode 104 may be reverse biased to perform the function of converting the optical signal received from the waveguide 102 into an electrical signal.

[0010] The first semiconductor structure 100 includes an electrically resistive material 106 between the waveguide 102 and the photodiode 104. The electrically resistive material 106 is along an optical propagation axis 108 between the waveguide 102 and the photodiode 104. In the example of FIG. 1, the electrically resistive material 106 is in contact with the photodiode 104. In other embodiments, another waveguide exists between the electrically resistive material 106 and the photodiode 104. For example, a section (e.g., a relatively short section) of a layer corresponding to a layer to the left of the electrically resistive material 106 (in the orientation of FIG. 1) exists between the electrically resistive material 106 and the photodiode 104. The electrically resistive material has a higher electrical resistivity than the waveguide 102.

[0011] 1, the electrically resistive material 106 is in contact with the waveguide 102. In some other embodiments, there may be other materials (to provide a desired optical function) or other structures between the waveguide 102 and the electrically resistive material. In such examples, light is coupled into the electrically resistive material 106 through the other material.

[0012] The waveguide 102 is for guiding light. In use, light propagates within the waveguide 102 and is confined within the waveguide 102 by reflection at the boundaries of the waveguide 102. The waveguide 102 has a refractive index higher than the refractive index of the material in contact with the waveguide 102 at the boundaries where it is desired to confine the light. For example, this difference in refractive index at the boundaries where it is desired to confine the light causes total internal reflection when the angle of incidence at these boundaries of the waveguide 102 is greater than the critical angle. In this manner, the waveguide 102 guides the propagation of light. For a particular optical mode to propagate through the waveguide 102, it is desired that the light reflected at the boundaries of the waveguide 102 satisfy the conditions for constructive interference, as will be appreciated by those skilled in the art.

[0013] For example, depending on the desired application of the region of the PIC, it may be desired that a particular optical mode of light propagates through the waveguide 102. The direction in which the optical mode propagates within the waveguide 102 is referred to herein as the optical propagation direction. The optical propagation axis 108 shown in FIG. 1 is defined by the optical propagation direction.

[0014] The light propagation direction is the general direction in which the energy of an optical mode travels through the waveguide 102, and not necessarily the direction defined by, for example, the angle of incidence at the boundaries of the waveguide 102. In some applications, the light propagates from left to right in the orientation of Figure 1, while in other applications the light propagates from right to left in the orientation of Figure 1.

[0015] In the example of FIG. 1, the waveguide 102 comprises a material having a higher index of refraction than materials in contact with the waveguide 102 above and below the waveguide 102 in the orientation shown in FIG. 1. For example, the waveguide 102 comprises indium gallium arsenide phosphide (InGaAsP). More generally, in some embodiments, the waveguide 102 comprises (Al)InGaAs(P). The elements shown in brackets are interchangeable, and the composition of the various elements is selected depending on the desired function. For example, the composition of Ga and As in InGaAs can be selected depending on the desired bandgap. In some embodiments, the waveguide 108 is a layer of (Al)InGaAs(P). In other embodiments, the waveguide 108 comprises multiple sublayers. In some such examples, the waveguide 108 comprises a (Al)InGaAs(P) / (Al)InGaAs(P) multiple quantum well structure. In some embodiments, the sublayers are between 5 and 30 nanometers thick. The sublayer stack of the waveguide 108 has a bandgap selected according to the desired application of the polarization converter 100 .

[0016] The bandgap, and therefore the refractive index of the InGaAsP, can be tuned, for example, as one of ordinary skill in the art will appreciate. In some embodiments, the bandgap of the InGaAsP of the waveguide 108 is tuned to a wavelength of 1250 nanometers (e.g., for propagation of light with a wavelength of 1550 nanometers) or 1100 nanometers (e.g., for propagation of light with a wavelength of 1310 nanometers). In other embodiments, the wavelength at which the bandgap is tuned is different.

[0017] In the example of Figure 1, the waveguide 102 and the photodiode 104 are aligned with each other (perpendicular to the orientation shown in Figure 1). In some embodiments, the waveguide 102 includes a first surface 110 and the photodiode 104 includes a second surface 112, with the first surface 110 and the second surface 112 being coplanar. Thus, no offset in the direction that light propagates in the waveguide 102 is required for light to propagate into the photodiode 104. In other embodiments, the waveguide 102 and the photodiode 104 are vertically offset from each other but still overlap vertically (in the orientation shown in Figure 1), such that no offset in the direction that light propagates in the waveguide 102 is required for light to propagate into the photodiode 104.

[0018] In some embodiments, the electrical resistivity of the electrically resistive material 106 is at least four orders of magnitude, e.g., eight orders of magnitude, higher than the electrical resistivity of the waveguide 102. For example, if the resistivity value of the waveguide is, on average, 1 Ohm*micrometer, in such an example, the electrical resistivity of the electrically resistive material is 20 Ohm*meter or higher. For example, the electrically resistive material 106 has a sufficiently high resistivity such that it does not conduct electricity at the voltage levels expected between the waveguide 102 and the photodiode 104. Thus, the electrically resistive material 106 present between the waveguide 102 and the photodiode 104 inhibits the flow of electricity between the waveguide 102 and the photodiode 104. In some embodiments, the electrically resistive material is a dielectric material, e.g., silicon nitride (SiN) or silicon dioxide (SiO 2 ).

[0019] In use, light propagates between the waveguide 102 and the photodiode 104 through the electrically resistive material. In some embodiments, the electrically resistive material 106 has a refractive index lower than that of the photodiode 104. A lower refractive index than the photodiode 104 can avoid unwanted reflections of light at the interface between the electrically resistive material 106 and the photodiode 104, for example, to provide efficient injection of light into the photodiode 104.

[0020] As mentioned above, if other conductive layers are present, electrical flow between the photodiode 104 and such other conductive layers may also be inhibited.

[0021] In the example of Figure 1, the first semiconductor structure 100 includes a first layer 114 in contact with the waveguide 102 between the waveguide 102 and a substrate 118. In the example of Figure 1, the first semiconductor structure 100 also includes a second layer 116 in contact with the photodiode 104 between the photodiode 104 and the substrate 118. In the example of Figure 1, an electrically resistive material is between the first layer 114 and the second layer 116.

[0022] The first layer 114 and the second layer 116 are, for example, doped semiconductor layers. In some embodiments, the first layer 114 and the second layer 116 are n-doped semiconductor layers. Thus, the first layer 114 and the second layer 116 can conduct electricity. The electrically resistive material 106 between the first layer 114 and the second layer 116 inhibits the flow of electricity between the photodiode 104 and the first layer 114, thereby inhibiting electrical crosstalk. For example, the resistivity of the electrically resistive material 106 is for inhibiting the flow of electricity between the photodiode 104 and the waveguide 102 and between the photodiode 104 and the first layer 114.

[0023] The substrate layer 118 includes a material that does not conduct electricity at the potential difference associated with the first semiconductor structure 100. For example, the substrate layer 118 includes a semi-insulating material. A semi-insulating material has a band gap high enough to act as an insulator at the conditions within the first semiconductor structure 100. The components of the PIC are, for example, constructed on the substrate layer 118. For example, the substrate layer 118 is common to the entire PIC. In the example of FIG. 1, the substrate layer 118 supports the waveguide 102 and the photodiode 104 but is not in contact with the waveguide 102 and the photodiode 104.

[0024] Those skilled in the art will understand that the flow of electricity can be inhibited by breaking the physical contact between the conductive parts of the structure. In the example of FIG. 1, the substrate layer 118 includes a first substrate surface 120 in contact with the first layer 114 and a second substrate surface 122 in contact with the second layer 116. The electrically resistive material 106 is between the first substrate surface 120 and the second substrate surface 122. This means that the electrically resistive material 106 extends beyond the first layer 114 and the second layer 116 in the direction of the substrate layer 118. This ensures that the first layer 114 does not come into contact with the second layer 116.

[0025] In the example of FIG. 1 , the first semiconductor structure 100 includes a first cladding layer 124 in contact with the waveguide 102. The first semiconductor structure 100 also includes a second cladding layer 126 in contact with the photodiode 104. An electrically resistive material is between the first cladding layer 124 and the second cladding layer 126. The first cladding layer 124 and the second cladding layer 126 are, for example, doped semiconductor layers. In some embodiments, the first cladding layer 124 and the second cladding layer 126 are p-doped semiconductor layers. Thus, the first cladding layer 124 and the second cladding layer 126 can conduct electricity. The electrically resistive material 106 between the first cladding layer 124 and the second cladding layer 126 inhibits the flow of electricity between the photodiode 104 and the first cladding layer 124, thereby inhibiting electrical crosstalk. For example, the resistivity of the electrically resistive material 106 is also such that it inhibits the flow of electricity between the photodiode 104 and the first cladding layer 124.

[0026] The waveguide 102 is for propagating therein a given wavelength of light (e.g., 1550 nanometers) along the optical propagation axis 108. The length 128 of the electrically resistive material 106 along the optical propagation axis 108 is equal to an odd integer multiplied by one-quarter of the given optical wavelength. Those skilled in the art will appreciate that this condition on the length 128 of the electrically resistive material 106 suppresses reflections. For example, the light entering the electrically resistive material 106 from the waveguide 102 and the light leaving the electrically resistive material 106 and entering the waveguide 102 (after being reflected at the interface of the electrically resistive material 106 and the photodiode 104) have a phase difference of π at the described length condition. This means that the reflected light destructively interferes with the light entering the electrically resistive material 106 from the waveguide 102, suppressing reflections.

[0027] FIG. 2a is a graph showing the reflectivity of the electrically resistive material 106 in the first semiconductor structure 100 in an example where the described length 128 of the electrically resistive material is 4296 nanometers. In FIG. 2a, the vertical axis represents the reflectivity of the electrically resistive material 106 as part of the first semiconductor structure 100, and the horizontal axis represents the wavelength of light in nanometers. In this example, the given wavelength of light is 1550 nanometers. Of course, 4296 nanometers is approximately 11.1 times one-quarter of the given wavelength 1550 nanometers. In this case, the length 128 of the electrically resistive material substantially (within acceptable tolerances) meets the described condition for suppressing reflection. From FIG. 2a, it can be seen that the reflectivity of the electrically resistive material 106 in the first semiconductor structure 100 is very low at a wavelength of 1550 nanometers.

[0028] FIG. 2b is a graph showing the reflectivity of the electrically resistive material 106 in the first semiconductor structure 100 in an example where the described length 128 of the electrically resistive material is 4570 nanometers. In FIG. 2b, the vertical axis represents the reflectivity of the electrically resistive material 106 as part of the first semiconductor structure 100, and the horizontal axis represents the wavelength of light in nanometers. In this example, the given wavelength of light is 1550 nanometers. Of course, 4570 nanometers is approximately 11.8 times one-quarter of the given wavelength 1550 nanometers. In this case, the length 128 of the electrically resistive material does not meet the described condition of suppressing reflection because 11.8 is close to an even number (i.e., 12). From FIG. 2b, it can be seen that the reflectivity of the electrically resistive material 106 in the first semiconductor structure 100 is high at a wavelength of 1550 nanometers. Thus, a length 128 that is 4296 nanometers provides less unwanted reflections compared to a length 128 that is 4570 nanometers.

[0029] By appropriately selecting the length 128 of the electrically resistive material along the light propagation axis 108, the electrically resistive material can also function as an anti-reflection layer, for example, to provide efficient injection of light into the photodiode 104.

[0030] While the described length 128 of the electrically resistive material 106 may be any odd integer multiple of a quarter of a given wavelength, in some embodiments, a shorter length is desired. For example, the longer the electrically resistive material 106 is along the light propagation axis 108, the more difficult it may be to control the length 128 to an odd multiple of a quarter of a given wavelength. For example, a shorter length allows for better control of the length of the electrically resistive material 106 along the light propagation axis 108.

[0031] 1, the electrically resistive material 106 is between the photodiode 104 and the waveguide 102, between the first layer 114 and the second layer 116, and between the first cladding layer 124 and the second cladding layer 126. Thus, the thickness of the electrically resistive material 106 in a first direction 130 perpendicular to the first substrate surface 120 is greater than the thickness of the waveguide 102 in the first direction.

[0032] In some such embodiments, light diffracted at the interface of the waveguide 102 and the electrically resistive material 106 may have a propagating component in the first direction 130. By increasing the thickness (perpendicular to the orientation of FIG. 1 and perpendicular to the light propagation axis 108) of the electrically resistive material 106, less light is confined in the first direction 130. Due to such a propagating component, the greater the length 128 of the electrically resistive material along the light propagation axis 108, the less light reaches the photodiode 104. Thus, the shorter the stated length 128 of the electrically resistive material 106, the greater the amount of light that can be coupled between the waveguide 102 and the photodiode 104.

[0033] On the other hand, the greater the length 128 (and possibly other physical dimensions of the electrically resistive material 106), the greater the electrical resistance of the electrically resistive material 106. In embodiments, the dimensions of the electrically resistive material are selected with these factors in mind. In one example, the length 128 is 4570 nanometers, as in FIG. 2a.

[0034] The width (e.g., in a second direction 304 perpendicular to the length 128 (in the first direction 130) and thickness) of the electrically resistive material is equal to or greater than the width of the portion of the waveguide that contacts the electrically resistive material. In some embodiments, the electrically resistive material is in the shape of a cubic block, while in other embodiments, the electrically resistive material is in the shape of a cubic block that surrounds an active component, such as a photodiode, when viewed in plan. Thus, in the latter example, the active component is not only more electrically isolated on the waveguide side, but also more electrically isolated from all sides in plan. This can be fabricated by etching a space around the active component as a trench (with a thickness and length similar to those described herein for feature 106) and then providing / depositing one or more electrically resistive materials in that space (e.g., there is a gas, such as air, between the waveguide and the active component, and an electrically resistive material is deposited in the remaining space surrounding the active component).

[0035] In some embodiments, the width of the portion of the waveguide that is in contact with the electrically resistive material is greater than the width of the portion of the waveguide that is not in contact with the electrically resistive material. This wider portion of the waveguide at the interface with the electrically resistive material helps to mitigate edge rounding from lithography and / or etching processes that may otherwise impair light transmission from the waveguide to the electrically resistive material. In the wider portion of the waveguide, such rounding during fabrication is comprised of the waveguide material at the edge of the wider portion away from the portion of the waveguide where light is transmitted to the electrically resistive portion.

[0036] Figure 3 shows a schematic plan cross-sectional view of a first semiconductor structure 100 according to an embodiment. Figure 3 shows a cross-section along line AA shown in Figure 1. In the example of Figure 3, the waveguide 102 includes a tapered portion 302 in contact with the electrically resistive material 106. The tapered portion 302 is tapered to reduce the refractive index mismatch of light propagating from the waveguide 102 to the electrically resistive material 106.

[0037] 3, the width of the tapered portion 302 in the second direction 304 gradually increases the further away from the electrically resistive material 106. The second direction 304 is perpendicular to the light propagation axis 108 and parallel to the first substrate surface 120.

[0038] For example, the tapered section 302 reduces the refractive index mismatch of light propagating from the waveguide 102 to the electrically resistive material 106. This is because the taper affects the effective refractive index of the light in the tapered section 302. As used herein, the effective refractive index is the refractive index experienced by light propagating in a material. The effective refractive index is not necessarily, for example, the refractive index of the material through which the light propagates alone. For example, as light propagates in the waveguide 102, other materials surrounding the waveguide 102 may also affect the refractive index experienced by the light propagating in the waveguide 102. This is because some of the optical modes overlap other materials near the waveguide 102. For example, the effective refractive index depends on the waveguide structure 100 as a whole. One skilled in the art will appreciate that the effective refractive index depends on parameters including the wavelength of the light, and on the particular optical mode of interest.

[0039] The width of tapered section 302 in second direction 304 becomes progressively smaller as the position approaches electrically resistive material 106. Thus, as light propagates within tapered section 302 toward electrically resistive material 106, the optical mode of the light experiences increasingly greater overlap with other materials proximate tapered section 302. This causes the effective refractive index experienced by the optical mode of the light to change as the light propagates toward electrically resistive material 106.

[0040] In some embodiments, the refractive index of the waveguide 102 is higher than the refractive index of the electrically resistive material 106. The refractive index of the waveguide 102 is also higher than the materials that otherwise surround the waveguide 102. Thus, the effective refractive index experienced by light propagating towards the electrically resistive material 106 in the tapered section 302 is gradually reduced, reducing the refractive index mismatch for light propagating from the waveguide 102 into the electrically resistive material 106.

[0041] The first semiconductor structure 100 may include additional layers (not shown), for example, on top of the portion of the structure shown in FIG.

[0042] By providing the electrically resistive material 106 in the described arrangement, the photodiode 104 is electrically isolated from all conductive layers on the waveguide 102 side of the electrically resistive material 106. For example, the arrangement is such that no layers on the waveguide 102 side of the electrically resistive material 106 contact the photodiode 104, even in the direction into or out of the page of FIG.

[0043] 4 is a flow diagram illustrating a method 400 for fabricating a semiconductor structure of a PIC, for example, the first semiconductor structure 100 described above, or any other example described herein.

[0044] In block 402 of method 400, the waveguide and active components are at least partially formed on a substrate. For example, the illustrated waveguide 102 and the illustrated photodiode 104 are at least partially formed on a substrate layer 118 as part of block 402. As referred to herein, formed on a substrate means supported by the substrate and does not preclude the presence of other layers between the substrate and the waveguide and / or active components. In some embodiments, the waveguide 102 and the photodiode 104 are in contact with the substrate layer 118. In other embodiments, there are one or more other layers between the waveguide 102 and the substrate layer 118 and there are one or more other layers between the active components and the substrate layer 118.

[0045] 5a-5h show schematic side cross-sectional views of the first semiconductor structure 100 at various levels of detail and at various stages of fabrication during the method 400 being performed. For example, not all layers that may be present are shown in each of FIGS. 5a-5h. FIG. 5a shows the first semiconductor structure 100 after block 402 has been performed. There are one or more underlying layers 502. For example, the underlying layers 502 may represent the substrate layer 118, as well as the first layer 114 and the second layer 116 described above. The contact side 504 of the waveguide 102 is in contact with the photodiode 104.

[0046] In block 404 of the method 400, a portion 506 of the waveguide 102 including the contact side 504 is removed. The result of performing block 504 is shown in Figure 5b. The removal of the portion 506 of the waveguide 102 forms a space 508. In block 406, an electrically resistive material 106 as described is deposited in the space 508 formed by the removal of the portion 506 of the waveguide 102. The electrically resistive material 106 has a higher resistivity than the waveguide 102. The result of performing block 406 is shown in Figure 5c.

[0047] In some embodiments, method 400 includes further acts. For example, method 400 further includes at least partially forming an intermediate layer 508 on the substrate layer 118. In such examples, method 400 also includes at least partially forming the waveguide 102 and the photodiode 104 on the intermediate layer 508. For example, material for the intermediate layer 508 is deposited on the substrate layer 118. Material for the waveguide 102 and the photodiode 104 is then deposited on top of the intermediate layer 508, resulting in the arrangement shown in FIG. 5d.

[0048] For example, a first portion 510 of the intermediate layer 508 in contact with the described portion of the waveguide 102 including the contact side 504 is removed. The first portion 510 is removed along with the described portion 506 of the waveguide 102 including the contact side 504. An electrically resistive material 106 is deposited in the space formed by the removal of the first portion 510 of the intermediate layer 508 and the portion 506 of the waveguide 102 including the contact side 504. By performing these actions, the first layer 114 and second layer 116 described above are formed. By performing these actions, the arrangement shown in FIG. 5e is obtained.

[0049] In some embodiments, method 400 also includes removing portions of substrate layer 118 covered by portion 506 of waveguide 102 including contact side 504, and depositing electrically resistive material 106 in a space formed by removing the portions of substrate layer 118. By performing such acts, first substrate surface 120 and second substrate surface 122 are formed, with electrically resistive material 106 between the first substrate surface and second substrate surface, as shown in FIG.

[0050] In some embodiments, the method 400 includes at least partially forming a cladding layer 512 over the waveguide and active components. The cladding layer 512 is at least partially formed prior to the above removal of material and deposition of an electrically resistive material in the space formed by the removal of material. In some embodiments, other layers are at least partially formed over the cladding layer 512 prior to the removal of material. FIG. 5f illustrates an exemplary result of at least partially forming the cladding layer 512. For example, a portion 514 of the cladding layer 512 in contact with the portion 506 of the waveguide 102 including the contact side 504 is removed, and an electrically resistive material is deposited in the space formed by the removal of the portion 514 of the cladding layer 512. An example result of these actions being performed is illustrated in FIG. 5g. In the example of FIG. 5g, a portion of the substrate layer 118 that will be filled with the electrically resistive material 106 has also been removed, as described above. Upon performing the actions leading to the arrangement of FIG. 5g, the first cladding layer 124 and the second cladding layer 126 are also formed.

[0051] As discussed above, material is removed to create a space in which the electrically resistive material 106 will be deposited. As previously discussed, in some embodiments, the length 128 of the electrically resistive material 106 along the light propagation axis 108 is equal to an odd integer multiplied by one-quarter of a given wavelength of light to suppress reflections. In these examples, a removal technique is used that is precise enough to control the length of the space created by removing precisely enough to provide a length equal to an odd integer multiplied by one-quarter of a given wavelength of light. For example, lithography techniques and / or equipment (known to those skilled in the art) that provide such precision are used.

[0052] In some embodiments, as part of method 400, material is removed from the waveguide 102 to form the described tapered portion to reduce the refractive index mismatch of light propagating from the waveguide 102 into the electrically resistive material 106. For example, material is removed from the waveguide 102 to form the described tapered portion before the cladding layer material is deposited on the waveguide 102.

[0053] As described above, material is removed from various layers to create spaces that will be filled by the electrically resistive material 106. While this has been described above with respect to removing portions of the waveguide, in other embodiments, portions of the active components and / or portions of the waveguide are removed. In some embodiments, depositing the electrically resistive material 106 deposits the material over the currently top layer of the semiconductor structure. For example, the electrically resistive material 106 is deposited over the first cladding layer 124 and the second cladding layer 126, filling the spaces created by the described removal of material. The result of such deposition is shown in FIG. 5g. For example, the unwanted electrically resistive material 106 is then removed. For example, the electrically resistive material 106 is removed to expose the top surfaces of the first cladding layer 124 and the second cladding layer 126, but is not removed from the spaces created by the above removal of material from the cladding layers, the waveguide, and the intermediate layers. FIG. 5h shows an example result of such removal.

[0054] For example, after arriving at the structure shown in FIG. 5h, another layer (eg, third cladding layer 132) is deposited over the structure of FIG. 5h.

[0055] In some embodiments, the method 400 includes removing material overlying the second portion of the interlayer to expose the interlayer material and forming an electrical connection to the exposed interlayer material, including electrical contact to the cladding that contacts the waveguide 102 and the photodiode 104.

[0056] In the above description, reference is made to the removal of material. Those skilled in the art will understand techniques for removing material. For example, wet or dry etching techniques may be used depending on the desired results. For example, a mask may be used and etching techniques may be employed to remove material not covered by the mask.

[0057] In the above description, reference is made to at least partially forming a layer, etc. In some embodiments, the layer so referred to is simply formed by depositing the relevant material without the need for further steps. In other embodiments, further steps are performed to complete the formation of the layer (e.g., a curing step to define the extent of the layer, an etching step, etc.). In some embodiments, the further steps to complete the formation of a layer are performed before further material is deposited on the layer. In other embodiments, the further steps to complete the formation of a layer are performed after further material is deposited on the layer.

[0058] As one skilled in the art will appreciate, various techniques can be used to deposit material according to the described embodiments. Such techniques include, for example, chemical vapor deposition techniques such as vapor phase epitaxy (VPE), metalorganic vapor phase epitaxy (MOVPE), or molecular beam epitaxy (MBE). One skilled in the art will appreciate that etching techniques (e.g., using a patterned mask) are used to remove material according to the described embodiments. The above embodiments should be understood as exemplary examples.

[0059] FIG. 6 shows a schematic side cross-section of a second semiconductor structure 600 for a PIC, according to an embodiment. The second semiconductor structure 200 is similar to the first semiconductor structure 100 described above, except that the second semiconductor structure includes a light leakage reducing material 602. In these examples, a portion of the space between the first layer 114 and the second layer 116 is occupied by the light leakage reducing material 602, and a portion of the space between the first layer 114 and the second layer 116 is occupied by the electrically resistive material 106. In the embodiment, the light leakage reducing material 602 is also electrically resistive to inhibit the flow of electricity. However, the light leakage reducing material 602 is included to reduce light leakage into the substrate layer 118. For example, the light leakage reducing material 602 may be SiO 2For example, in method 400, the space created by the removal of a portion of the substrate layer, a first portion of the intermediate layer, a portion of the waveguide, and a portion of the cladding layer is first partially filled with light leakage reduction material 602 prior to deposition of the electrically resistive material 106, as described above with reference to Figures 5a-5h.

[0060] FIG. 7 shows a schematic cross-sectional plan view of a third semiconductor structure 700 according to an embodiment. The third semiconductor structure 700 may include any of the features described above. The third semiconductor structure 700 differs in that a first side 702 of the electrically resistive material 106 in contact with the active component 104 is at a non-zero angle with respect to a second side 704 of the electrically resistive material 106 in contact with the waveguide 102. Light entering the active component 104 can be reflected at the first side 702. However, the described angle of the first side 702 means that the reflected light does not follow the optical propagation axis 108 of the light propagating from the waveguide 102. Thus, due to the angle, less light reflected at the first side 702 enters the waveguide 102. The arrangement of the third semiconductor structure 700 thus suppresses unwanted reflections from coupling into the waveguide 102.

[0061] Further examples of semiconductor structures are shown and described in Figures 8a-8c, 9a-9c, 10a-10c, and 11 below. The exemplary semiconductor structures described below may include any of the features described above. That is, the following examples include a waveguide 102, an active component 104 of an optical integrated circuit, and an electrically resistive material 106 disposed along an optical propagation axis 108. Differences between the examples presented below and the previously presented examples are explicitly described.

[0062] 8a-8c are schematic diagrams illustrating plan views of a fourth semiconductor structure 800A, a fifth semiconductor structure 800B, and a sixth semiconductor structure 800C, respectively, according to an embodiment.

[0063] A fourth semiconductor structure 800A is shown in FIG. 8a. The fourth semiconductor structure 800A differs from the previously presented embodiments in that it includes a tapered portion 302A. The tapered portion 302A has a width that gradually increases with distance from the electrically resistive material 106 in a direction perpendicular to the optical propagation axis 108, similar to the tapered portion 302 of the semiconductor structure 100 shown in FIG. 3. In the semiconductor structure 800A, the tapered portion 302A tapers to a width of less than 400 nanometers. In general, the tapered portion 302A can be considered to taper to a point that is closest to the electrically resistive material or active component. The tapered portion 302A can be considered to taper to a point, as long as that point is achievable within manufacturing tolerances.

[0064] The tapered section 302A of the waveguide 102 approaches a cutoff condition for light guiding at that wavelength and in a particular mode when it tapers to a width that is small compared to the wavelength of light. The cutoff condition refers, for example, to a geometry of the waveguide where light is no longer considered to be guided. That is, light having a first wavelength that is guided in a mode of the waveguide 102 propagates in the tapered section 302A. The tapered section 302A tapers to a width, such as the above example width of 400 nanometers, whereby the mode at the first wavelength is cut off. This means that light at the first wavelength is no longer guided by the tapered section 302A of the waveguide 102 in this mode. Instead of being guided, the light exits the tapered section 302A and couples into the electrically resistive material 106 in this example. The reflection of light back along the waveguide 102 can be reduced when tapering the tapered section 302A to meet the cutoff condition. In general, the width of the tapered section 302A that satisfies the blocking condition depends on the wavelength of the light guided in the waveguide 102 and the tapered section 302A. In this example, the taper profile, i.e., how the width of the tapered section 302A perpendicular to the light propagation axis 108 varies with the length parallel to the light propagation axis, is an adiabatic taper. As one skilled in the art will appreciate, an adiabatic taper means that the width varies slowly so that the evolution of the mode within the taper can be considered lossless. This improves the coupling of light into the electrically resistive material 106, thereby allowing more light from the waveguide 102 to be received by the active component 106 and reducing the reflection of light back along the waveguide 102.

[0065] Furthermore, the tapered section 302A can reduce the wavelength sensitivity of the reflection of the electrically resistive material 106 shown in FIG. 2a. That is, a low reflectance of the electrically resistive material 106 can be achieved over a wider wavelength range. As one skilled in the art will appreciate, the resonance condition that gives rise to the reflection can result from periodically spaced interfaces of the electrically resistive material 106 with materials having different refractive indices. In this example, the resonance condition results from the distance between the interface of the electrically resistive material 106 with the waveguide 102 and the interface of the electrically resistive material 106 with the active component 104. The shape of the tapered section 302A can be considered to disrupt this resonance condition, thereby reducing the reflection of light back up the waveguide 102 from the electrically resistive material 106 over a wider wavelength range. This allows the semiconductor structure 800A to be used over a wider wavelength range, which in turn makes the semiconductor structure 800A more robust to fabrication errors.

[0066] A fifth semiconductor structure 800B is shown in FIG. 8b. In the fifth semiconductor structure 800B, the waveguide 102 includes a facet 150a that is at least partially in contact with the electrically resistive material 106, and in FIG. 8b is substantially completely in contact with the electrically resistive material such that all portions of the facet 150a are in contact with the electrically resistive material 106. The facet can be considered to be, for example, an end or entrance face of a waveguide, or more generally, of an integrated optical circuit structure through which light can propagate. Light propagating in the waveguide 102 along the light propagation axis 108 propagates through the facet 150a into the electrically resistive material 106. The facet 150a intersects the light propagation axis 108 at a non-perpendicular angle. Thus, the facet 150a can be considered to be angled with respect to the light propagation axis 108. In this example, facet 150a is 7 degrees away from perpendicular to the optical propagation axis 108 and therefore can be considered to have an angle of 7 degrees. The angled facet 150a can suppress unwanted reflections from propagating back up the waveguide 102.

[0067] A sixth semiconductor structure 800C is shown in FIG. 8C. The sixth semiconductor structure 800C includes a tapered portion 302B and a facet 150b, angled at 7 degrees in this example. The facet 150b is located at the end of the tapered portion 302 closest to the electrically resistive material 106, and light from the waveguide 102 propagates at least partially through the facet 150b into the electrically resistive material 106. The tapered portion 302B can reduce the mode mismatch between the waveguide 102 and the electrically resistive material 106, but does not necessarily tapere to a width associated with mode blocking, such as the tapered portion 302A of FIG. 8a, and the facet 150b can suppress unwanted reflections from propagating back into the waveguide 102.

[0068] 9a-9c are schematic diagrams illustrating plan views of a seventh semiconductor structure 900A, an eighth semiconductor structure 900B, and a ninth semiconductor structure 900C, respectively, according to an embodiment.

[0069] A seventh semiconductor structure 900A is shown in FIG. 9a. The active component 104 includes a facet 155a that is in at least partial contact with the electrically resistive material 106, and in FIG. 9a is in full contact with the electrically resistive material 106. Light propagating through the electrically resistive material 106 along the light propagation axis 108 enters the active component 104 through the facet 155a. The facet 155a is convex. That is, the facet 155a is curved and curves outward relative to the active component 155a. The facet 155a being curved, in this example convex, can mean that the light is reflected away from the light propagation axis 108, which can prevent the light from being reflected back into the waveguide 102. The facet 155a being convex can act as a lens, and can collimate or focus the light into the active component 104 when receiving light that has spread out after leaving the waveguide 102. Facet 155 a is convex, which can increase the amount of light received by active component 104 .

[0070] An eighth semiconductor structure 900B is shown in FIG. 9b. The active component is in at least partial contact with the electrically resistive material 106, and in FIG. 9b includes a facet 155b that is in contact with the electrically resistive material 106 over a majority of the facet 155b. The facet 155b is convex, similar to the facet 155a in FIG. 9a. The facet 155b is also angled in that it does not intersect the optical propagation axis 108 perpendicularly. This can further reduce reflections of light back into the waveguide 102.

[0071] A ninth semiconductor structure 900C is shown in FIG. 9c. The ninth semiconductor structure 900C includes a second waveguide 180. The second waveguide 180 is disposed between the electrically resistive material 106 and the active component 104. Light propagating along a light propagation axis through the electrically resistive material 106 couples into the second waveguide 180, where the light propagates through the second waveguide 180 into the active component 104. The second waveguide 180 may include a similar or identical material composition as the first waveguide 102 described above, or may include a different material composition.

[0072] The second waveguide 180 is in at least partial contact with the electrically resistive material 106, and in FIG. 9c includes a facet 155c that is in contact with the electrically resistive material 106 over a majority of the facet 155c. As with facets 155a, 155b discussed above, light propagating along the light propagation axis 108 through the electrically resistive material 106 propagates through facet 155c.

[0073] The second waveguide 180 has a width in a direction perpendicular to the light propagation axis 108 that is greater than a width of the first waveguide 102 in a direction perpendicular to the light propagation axis 108. The second waveguide 180 can collect the light exiting the first waveguide 102, even though the light spreads after exiting the first waveguide 102.

[0074] The second waveguide 180 includes a second tapered section 182. The width of the second tapered section 182 in a direction perpendicular to the light propagation axis 182 gradually increases with distance from the active component 104. The size of the active component 104, such as its width in a direction perpendicular to the light propagation axis 182, can play a role in determining the behavior of the active component 104, such as determining its operating speed or rate. High speed operation or function may require the active component to be less than a certain spatial size, for example, to have a sufficiently small width in a direction perpendicular to the light propagation axis 108. Thus, the second waveguide 180 including the second tapered section 182 can collect light into an electrically resistive material at the wider end and can be tapered to a smaller size to interface with the active component 104. In this way, the active component 104 may remain small, for example to maintain high speed functionality, while the second waveguide 180 collects light from the first waveguide 102 .

[0075] The second waveguide 180 includes a facet 155c in at least partial contact with the electrically resistive material 106. In this example, the facet 155c of the second waveguide 180 is curved, in this example convex, similar to the facets 155a, 155b described above with reference to Figures 9a and 9b. The facet 155c of the second waveguide 180 is curved, in this example convex, and may reduce reflection of light back into the waveguide 102. The convex facet 155c of the second waveguide 180 may act as a lens, thereby more effectively coupling light into the second waveguide 180 by effectively collimating and / or focusing the light.

[0076] 10a-10c are schematic diagrams illustrating plan views of a tenth semiconductor structure 1000A, an eleventh semiconductor structure 1000B, and a twelfth semiconductor structure 1000C, respectively, according to an embodiment.

[0077] A tenth semiconductor structure 1000A is shown in FIG. 10a. In the tenth semiconductor structure 1000A, the active component 104 includes a facet 155c. The facet 155c is curved, in this example concave. That is, the facet 155c is curved inward relative to the active component 104. The fact that the facet 155c is curved, in this example concave, means that light can be reflected away from the light propagation axis 108, thereby reducing the reflection of light back into the waveguide 102. Furthermore, the concave nature of the facet 155c means that the reflected light can be reflected towards a common focal point f. The common focal point f is shown in FIG. 10a, but omitted in FIG. 10b and FIG. 10c. This can prevent reflection of light towards surrounding elements of the optical integrated circuit, which can hinder performance. This can improve the reliability and performance of the optical integrated circuit.

[0078] The tenth semiconductor structure 1000A includes an absorber element 160. The absorber element 160 is disposed between the active component 104 and the waveguide 102 with respect to the light propagation axis 108, but is spatially offset from the light propagation axis 108 and angled toward the active component 104. In other embodiments, the absorber element 160 may be disposed next to the waveguide 102. In general, the absorber element 160 is disposed between the facet 155c and the common focal point f of the facet 155c, such that light reflected by the facet 155c is absorbed by the absorber element 160. Thus, the location of the absorber element 160 in any given example may depend on the optical properties of the facet 155, such as the angle at which light is reflected from the facet 155 and where, if any, the focal point of the facet 155 is located.

[0079] More generally, in other embodiments, an absorber element 160, or multiple absorber elements, may be disposed around the waveguide 102, the electrically resistive material 106, and the active component 104 to absorb reflected light. In some embodiments, the absorber element 160 is formed from a stack of semiconductor layers suitable for use as a photodetector. In some such embodiments, the absorber element 160 may be used as a photodetector and may receive focused light reflected from the concave facets 155d, 155e, 155f, thereby improving the performance of the photodetector. In some embodiments, the active component 104 may not be used, or may be used intermittently, since a photodetector as the absorber element 160 is used instead. The absorber element 160 is separated from the waveguide 102 by the electrically resistive material 106, as is the active component 104. In some embodiments, both the absorber element 160 and the active component 104 may be photodetectors and may be used simultaneously as photodetectors, for example, to introduce redundancy into the photodetector measurements that may improve the reliability of the PIC performance.

[0080] An eleventh semiconductor structure 1000B is shown in FIG. 10b. The eleventh semiconductor structure 1000B comprises a second waveguide 180b, the purpose of which is similar to that of the second waveguide 180 of the ninth semiconductor structure 900C of FIG. 9c. The second waveguide 180 includes a facet 155e that is at least partially in contact with the electrically resistive material 106. The facet 155e is concave and is similar to the facet 155d of the active component 104 of the tenth semiconductor structure 1000A of FIG. 10a. Again, similar to the ninth semiconductor structure, the second waveguide 180b has a larger width in a direction perpendicular to the light propagation axis 108 than the active component 140. In this way, the active component 104 may be suitable for high speed operation, and the second waveguide 180b may collect light from the first waveguide 102.

[0081] A twelfth semiconductor structure 1000C is shown in Figure 10c. The twelfth semiconductor structure 1000C of Figure 10c is otherwise identical to the eleventh semiconductor structure 1000B of Figure 10b, except that the second waveguide 180b includes a facet 155f that is concave and intersects the light propagation axis at a non-perpendicular angle. This can further reduce reflections back into the waveguide 102 and can reflect light further away from the light propagation axis 108. In other embodiments, the second waveguide 180c may not be included and instead the active component 104 may include a concave facet such as facet 155f.

[0082] FIG. 11 illustrates a thirteenth semiconductor structure 1100 according to an embodiment. In the thirteenth semiconductor structure 1100, the waveguide 102 includes a first facet 150c in at least partial contact with the electrically resistive material 106, and the active component 104 includes a second facet 155g in at least partial contact with the electrically resistive material 106, and in FIG. 11, the first facet 150c and the second facet 155g are substantially in full contact with the electrically resistive material 106. Each facet 150c, 155g includes a respective periodic structure 152 configured as an anti-reflection grating. For example, a surface including a periodic structure 152 having a sub-wavelength distance between constituent structures of the periodic structure 152 can reduce reflection, for example, relative to a flat surface made of the same material as the periodic structure 152. In other words, in some embodiments, the periodic structure 152 has a pitch on a sub-wavelength scale. The constituent features of the periodic structure 152 are tooth-shaped features in this example, but in other embodiments the constituent features may have other shapes, such as grooves. In a thirteenth embodiment of the semiconductor structure 1100, the semiconductor structure 1100 is intended for use with light having a wavelength of 1550 nm, and the periodic structure 152 has a pitch of 500 nm. Those skilled in the art will understand that the pitch of the periodic structure 152 can be smaller, for example, if a shorter wavelength is used, or can be longer, for example, if a longer wavelength is used.

[0083] The waveguide 102 includes a first facet 150c configured as an anti-reflection grating, which can reduce light reflection from the interface between the waveguide 102 and the electrically resistive material 106. Similarly, the active component 104 includes a second facet 155f configured as an anti-reflection grating, which can reduce light reflection from the interface between the electrically resistive material 106 and the active component 104. This can reduce light reflection into the waveguide 102. In other embodiments, only one of the waveguide 102 or the active component 104 includes a periodic structure configured as an anti-reflection grating.

[0084] It will be understood that the features illustrated by the above examples can be combined and are not limited to those appearing in the above examples. In the examples, any of the aforementioned waveguides may be used with any of the aforementioned active components. For example, the semiconductor structure may comprise a waveguide including a first facet that is convex or concave, and an active component including a second facet that is convex or concave. Furthermore, the facet may be concave or convex and may also include a periodic structure configured as an anti-reflection grating. In the above examples, the facet associated with the active component 104 in some examples may instead be associated with a second waveguide between the active component 104 and the electrically insulating material 106. For example, the second waveguide may include a periodic structure configured as an anti-reflection grating.

[0085] In embodiments, the active component, or a second waveguide associated with the active component, may include a facet that is not curved but is angled relative to the optical propagation axis, similar to facet 150a. In some embodiments where the first waveguide includes a first facet, e.g., at 7 degrees, the active component may include a second facet that is angled 1-2 degrees differently than the first facet, which may have an angle of, e.g., 6 degrees or 9 degrees. In other embodiments, the first facet and the second facet are angled by the same amount, e.g., both 7 degrees. In general, the angle may be determined by optical mode characteristics, such as optical mode field size, and may be selected to select the lowest reflection in a particular mode.

[0086] In the above examples, facets described as being at least partially in contact with an electrically resistive material may in some embodiments be in complete contact with the electrically resistive material, such that all portions of the facet surface are in contact with the electrically resistive material, while in other embodiments, a majority of the facet surface is in contact with the electrically resistive material.

[0087] In an embodiment, the electrically resistive material 106 is a vacuum, air, or another gas, and the waveguide 102 can be considered to be separated from the active component 104 by an air gap.

[0088] In the illustrated figures, dashed lines included at the edge of a particular part indicate the continuation of that part beyond what is shown diagrammatically in the figure. The figures include schematic illustrations of structures related to the illustrated embodiments of semiconductor structures. No figure should be construed as being to scale with respect to any other figure.

[0089] It is to be understood that any feature described in connection with any one embodiment may be used alone or in combination with the other features described, and may also be used in combination with one or more features of any other embodiment, or in any combination of any other embodiment. Moreover, equivalents and modifications not described above may be employed without departing from the scope of the appended claims.

Claims

1. A semiconductor structure for optical integrated circuits, Waveguides and The active component of the aforementioned optical integrated circuit, Between the waveguide and the active component, there is an electrical resistance material along the optical propagation axis between the waveguide and the active component, The electrical resistance material has a semiconductor structure having a higher electrical resistivity than the waveguide.

2. The semiconductor structure according to claim 1, wherein the electrical resistivity of the electrical resistive material is at least eight orders of magnitude higher than the electrical resistivity of the waveguide.

3. The semiconductor structure according to claim 2, wherein the electrical resistance material comprises silicon nitride.

4. The waveguide includes a first surface, The active component includes a second surface, The semiconductor structure according to claim 1 or 2, wherein the first surface and the second surface are on the same plane.

5. Between the waveguide and the substrate, there is a first layer in contact with the waveguide, Between the active component and the substrate, there is a second layer that contacts the active component, Includes, The semiconductor structure according to claim 1 or 2, wherein the electrical resistance material is located between the first layer and the second layer.

6. The substrate includes a first substrate surface that contacts the first layer and a second substrate surface that contacts the second layer. The semiconductor structure according to claim 5, wherein the semiconductor structure includes a light leakage reducing material between the first substrate surface and the second substrate surface.

7. The substrate includes a first substrate surface that contacts the first layer and a second substrate surface that contacts the second layer. The semiconductor structure according to claim 5, wherein the semiconductor structure includes the electrical resistance material between the first substrate surface and the second substrate surface.

8. A first cladding layer in contact with the waveguide, A second cladding layer in contact with the active component, Includes, The semiconductor structure according to claim 1 or 2, wherein the electrical resistance material is located between the first cladding layer and the second cladding layer.

9. The waveguide is configured such that a given optical wavelength propagates through it along the optical propagation axis. The semiconductor structure according to claim 1 or 2, wherein the length of the electrical resistance material along the optical propagation axis is equal to an odd integer multiplied by one-quarter of the given optical wavelength.

10. The semiconductor structure according to claim 1 or 2, wherein the active component is a photodetector.

11. The semiconductor structure according to claim 1 or 2, wherein the electrical resistance material is a dielectric material.

12. The waveguide includes a tapered portion that contacts the electrical resistance material, The semiconductor structure according to claim 1 or 2, wherein the width of the tapered portion in a direction perpendicular to the optical propagation axis gradually increases as it moves away from the electrical resistance material.

13. The semiconductor structure according to claim 12, wherein the width of the tapered portion at the position closest to the electrical resistance material is less than 400 nanometers.

14. The semiconductor structure according to claim 1 or 2, wherein at least one of the waveguide and the active component includes a facet that is at least partially in contact with the electrical resistance material.

15. The semiconductor structure according to claim 14, wherein the facets intersect the optical propagation axis at an angle not perpendicular to it.

16. The semiconductor structure according to claim 14, wherein the facets are convex.

17. The semiconductor structure according to claim 14, wherein the facets are concave.

18. The waveguide is a first waveguide, The semiconductor structure according to claim 14, wherein the active component is in contact with a second waveguide including the facets, which is disposed between the electrical resistance material and the active component.

19. The second waveguide includes a second tapered portion, The semiconductor structure according to claim 18, wherein the width of the second tapered portion in a direction perpendicular to the optical propagation axis gradually increases as it moves away from the active component.

20. The semiconductor structure according to claim 19, wherein the second waveguide has a width in the direction perpendicular to the optical propagation axis that is greater than the width of the first waveguide in the direction perpendicular to the optical propagation axis.

21. The semiconductor structure according to claim 14, wherein the facet includes a periodic structure configured as an anti-reflective grating.

22. The semiconductor structure according to claim 21, wherein the periodic structure has a pitch of less than 500 nm.

23. The semiconductor structure according to claim 14, further comprising an absorber element arranged to absorb light reflected from the facets.

24. The semiconductor structure according to claim 14, wherein the electrical resistance material is air.

25. A method for manufacturing semiconductor structures for optical integrated circuits, Forming waveguides and active components at least partially on a substrate, wherein the contact side of the waveguide is in contact with the active component, Removing a portion of the waveguide or at least one of the active components, Depositing an electrical resistance material in the space formed by removing at least one of the waveguide or active components, Includes, The method wherein the electrical resistance material has a higher resistivity than the waveguide.

26. Forming an intermediate layer at least partially on the substrate, The waveguide and the active component are formed at least partially on the intermediate layer, Removing the first portion of the intermediate layer that is in contact with at least one of the waveguides or active components, The electrical resistance material is deposited in the space formed by the removal of the first portion of the intermediate layer, The method according to claim 25, including the method described in claim 25.

27. The material superimposed on the second portion of the intermediate layer is removed to expose the intermediate layer material, To form an electrical connection with the exposed intermediate layer material, The method according to claim 26, including the method described in claim 26.

28. Removing the portion of the substrate covered by the waveguide or at least one of the active components, The electrical resistance material is deposited in the space formed by removing the aforementioned portion of the substrate, The method according to any one of claims 25 to 27, including the method described in any one of claims 25 to 27.

29. Forming a cladding layer at least partially on the waveguide and the active component, Removing the portion of the cladding layer that is in contact with the waveguide or at least one portion of the active component, The electrical resistance material is deposited in the space formed by removing the portion of the cladding layer. The method according to any one of claims 25 to 27, including the method described in any one of claims 25 to 27.

30. The material is removed from the waveguide to form a tapered portion that reduces the mismatch in refractive index of light propagating from the waveguide into the electrical resistance material. The method according to any one of claims 25 to 27, including the method described in any one of claims 25 to 27.

31. The semiconductor structure according to claim 1 or 2, wherein the first side of the electrical resistance material in contact with the active component forms a non-zero angle with respect to the second side of the electrical resistance material in contact with the waveguide.

32. The semiconductor structure according to claim 1 or 2, wherein the electrical resistance material is in contact with the active component.

33. An optical integrated circuit comprising the semiconductor structure described in claim 1 or 2.

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