Integrated gaas active devices with improved optical coupling to dielectric waveguide

Abstract

The device includes three elements fabricated on a common substrate. The first element includes an active waveguide structure having at least three sub-layers supporting a first optical mode. The second element has a passive waveguide structure supporting a second optical mode, and the third element, which is butt-coupled to the first element, has an intermediate waveguide structure supporting an intermediate optical mode. One of the sub-layers in the active waveguide structure includes an n-type contact layer, another sub-layer includes a p-type contact layer, and a third sub-layer includes an active region. Tapered waveguide structures in at least one of the second and third elements facilitate efficient adiabatic conversion between the second optical mode and the intermediate optical mode. No adiabatic conversion occurs between the intermediate optical mode and the first optical mode. Mutual alignment of the three elements is defined by using photolithographic alignment marks that facilitate precise alignment between layers formed when fabricating the elements.

Description

[0001] Cross-reference to related applications

[0002] This application relates to U.S. Application No. 16878563, filed May 19, 2020, which is authorized as U.S. Patent No. 10,859,764. Technical Field

[0003] This invention relates to semiconductor fabrication. More specifically, certain embodiments of the invention relate to methods and systems for realizing photonic integrated circuits using optically coupled heterogeneous materials. Background Technology

[0004] Photonic integrated circuits (PICs), or integrated optical circuits, are devices that integrate multiple photonic functions and are therefore similar to electronic integrated circuits. The main difference lies in that photonic integrated circuits provide functionality for information signals applied to an optical carrier. The most commercially available material platform for photonic integrated circuits is indium phosphide (InP), which allows for the integration of various active and passive optical functions on the same chip. While many current PICs are implemented on the InP platform, significant research has been conducted over the past decade on implementing PICs using silicon instead of InP, leveraging the investments already made in electronic integrated circuits, due to silicon's superior properties and processing capabilities.

[0005] The biggest drawback of using silicon to implement a PIC is that it is an indirect bandgap material, making it difficult to provide an electrical pump source. This problem is typically addressed by assembling a PIC consisting of two or more chips made from dissimilar materials in separate processes. Such an approach is challenging because it requires very precise alignment, which increases packaging costs and imposes limitations on mass production. Another approach to address the bandgap problem is to combine two dissimilar materials and process them together, thus eliminating the need for precise alignment during the assembly of a larger component or complete wafer made from the dissimilar materials and allowing for mass production. In this disclosure, the term "hybrid" is used to describe the first approach, which involves the precise assembly of separately processed parts, and the term "heterogeneous" is used to describe the latter approach, which combines two materials and then processes the combined product to define waveguides and other components of interest.

[0006] To transmit optical signals between dissimilar materials, the heterojunction approach utilizes a tapered section whose size gradually decreases until the effective modulus refractive indices of the dissimilar materials match, resulting in effective power transfer. This approach typically works well when the materials have similar refractive indices, such as in the case of silicon and InP. However, when there is a significant difference in effective refractive indices (such as between SiN and GaAs), the required tapered tip size becomes prohibitively large, limiting effective power transfer. Specifically, very small tapered tip widths (on the nanometer scale) are needed to provide good coupling. Achieving such dimensions is complex and can be costly.

[0007] While InP and silicon-based PICs address many current needs, they still have some limitations; one is that the operating wavelength range is limited by material absorption, increasing losses, and the maximum light intensity and therefore optical power that the PIC can handle are also limited. To address these limitations, alternative waveguide materials such as SiN, TiO2, Ta2O5, AlN, or others have been considered. Generally, such dielectric waveguides have larger bandgap energies, which provide better high-power handling and transparency at shorter wavelengths, but generally, these materials also have lower refractive indices. For example, SiN with a ~5 eV bandgap has a refractive index of ~2, AlN has a ~6 eV bandgap and a refractive index of approximately ~2, and SiO2 with a ~8.9 eV bandgap has a refractive index of ~1.44. In comparison, GaAs has a refractive index >3. This makes tapered approaches challenging.

[0008] Alternative hybrid approaches suffer from the aforementioned drawbacks, namely the need for precise alignment and consequently, complex packaging that limits mass production.

[0009] A recent approach to addressing the problems discussed above is described in the aforementioned U.S. Patent No. 10,859,764 B2, which employs docking coupling in conjunction with a mode-converter to allow the use of heterogeneous processes without requiring extremely small taper widths. This invention relates to PICs that utilize docking coupling in this manner and include active devices such as lasers. Specifically, the embodiments described below relate to the detailed design of active material substructures required for creating high-performance lasers, amplifiers, modulators, and photodetectors. Attached Figure Description

[0010] Figure 1 The device according to an embodiment of the present invention is shown in axial cross section.

[0011] Figure 2a It shows the corresponding Figure 1 Cross-sectional end views of the device at three different axial positions in the embodiment.

[0012] Figure 2b It shows the corresponding Figure 1 A cross-sectional end view of the device at the fourth axial position in an embodiment.

[0013] Figure 3 A cross-sectional top view of a device according to some embodiments of the present invention is shown.

[0014] Figure 4 A cross-sectional top view of a device according to some embodiments of the present invention is shown.

[0015] Figure 5 A cross-sectional top view of a device according to some embodiments of the present invention is shown.

[0016] Figure 6a It shows the corresponding Figure 5 Cross-sectional end views of the device at three different axial positions in the embodiment.

[0017] Figure 6b It shows the corresponding Figure 5 A cross-sectional end view of the device at the fourth axial position in an embodiment. Detailed Implementation

[0018] This document describes embodiments of methods and systems for realizing photonic integrated circuits using wafer bonding and heterogeneous material deposition, wherein optical coupling is improved by using mode switching and docking coupling schemes.

[0019] In the detailed description below, reference is made to the accompanying drawings, which form a part of the detailed description, wherein similar reference numerals refer to similar parts throughout, and embodiments in which the subject matter of this disclosure can be practiced are illustrated by the figures. It should be understood that other embodiments may be adopted, and structural or logical changes may be made without departing from the scope of this disclosure. Therefore, the following detailed description should not be interpreted in a limiting sense, and the scope of the embodiments is defined by the appended claims and their equivalents.

[0020] Descriptions may use perspective-based descriptions, such as top / bottom, inside / outside, above / below, etc. Such descriptions are used only to aid discussion and are not intended to limit the application of the embodiments described herein to any particular orientation. Descriptions may use the phrases "in one embodiment" or "in multiple embodiments," both of which can refer to one or more of the same or different embodiments. Furthermore, as used with respect to embodiments of this disclosure, the terms "comprising," "including," "having," etc., are synonymous.

[0021] For the purposes of this disclosure, the phrase "A and / or B" means (A), (B), or (A and B). For the purposes of this disclosure, the phrase "A, B, and / or C" means (A), (B), (C), (A and B), (A and C), (B and C), or (A, B, and C).

[0022] The term “coupled with” and its derivatives may be used herein. “Coupled” can mean one or more of the following: “Coupled” can mean two or more elements in direct physical, electrical, or optical contact. However, “coupled” can also mean two or more elements in indirect contact with each other, but still mating or interacting with each other, and can mean one or more other elements are coupled or connected between the elements referred to as being coupled to each other. The term “direct coupling” means two or more elements in direct contact in at least a portion of their surfaces. The term “butt-coupled” is used herein in its conventional sense, meaning “terminated” or axially coupled, where there is a minimum or zero axial offset between the elements involved. In the case where some thin interlayer is formed between the elements (as described below with respect to elements 106, 206, and 306), the axial offset may, for example, be slightly greater than zero. It should be noted that the axes of the two waveguide structures or elements need not be collinear to be accurately described as butt-coupled. In other words, the interface between the elements need not be perpendicular to either axis. The following discussion Figure 4 The embodiments are examples of this possibility.

[0023] This document may use the terms "active device" and / or "active region." A device or region of a device referred to as active is capable of generating, amplifying, modulating, and / or detecting light. The terms "active device" and "active region" are used interchangeably to mean either and / or both. This contrasts with the terms "passive device" and / or "passive region," whose primary function is to confine and guide light, and / or provide the splitting, combining, filtering, and / or other functions typically associated with passive devices. Some passive devices are capable of providing functions superimposed on those of active devices, such as phase tuning, for example, through the use of thermal effects or similar effects that can provide modulation. The difference in this case lies in performance, where active devices typically offer higher efficiency, lower power consumption, greater bandwidth, and / or other benefits. An absolute distinction between "active" and "passive" should not be considered based purely on material composition or device structure. For example, a silicon device may be considered active under certain conditions for modulating or detecting low-wavelength radiation, but passive in most other cases.

[0024] Figure 1This is a schematic cross-sectional view of an integrated photonic device 100 that uses docking coupling and mode switching for efficient coupling between dissimilar materials. An exemplary cross-section includes a substrate 105, which can be any suitable substrate for semiconductor and dielectric processing, such as Si, InP, GaAs, quartz, sapphire, glass, GaN, silicon on insulator, or other materials known in the art. In the illustrated embodiment, a second material layer 104 is deposited, grown, transferred, bonded, or otherwise attached to the top surface of the substrate 105 using techniques known in the art. If an optical waveguide is required, the primary purpose of layer 104 is to provide an optical cladding for material 102 (described below). Optical waveguides are typically implemented by placing a core with a higher refractive index between two layers with lower refractive indices to confine light waves. In some embodiments, layer 104 is omitted and the substrate 105 itself serves as the cladding.

[0025] Layer 102 is deposited, grown, transferred, bonded, or otherwise attached to the top of layer 104 (if present) and / or the top of substrate 105 using techniques known in the art. The refractive index of layer 102 is greater than that of layer 104 (if present), or, if layer 104 is absent, the refractive index of layer 102 is greater than that of substrate 105. In one embodiment, the material of layer 102 may include, but is not limited to, one or more of SiN, TiO2, Ta2O5, SiO2, LiNbO3, and AlN. In some embodiments, other common dielectric materials may be used for layer 102. In other embodiments, semiconductor materials may be used for layer 102. In some embodiments, the refractive index of layer 102 is between 1.8 and 2.5. Either or both of layers 104 and 102 can be patterned, etched, or re-deposited as is common in the art.

[0026] Layer 108 (with a refractive index less than that of layer 102) overlaps with layer 102 and lies beneath layers 101 and 103 (described in more detail below) to planarize the patterned surface of layer 102. In some embodiments, the planarity of the top surface of layer 108 is provided by chemical mechanical polishing (CMP) or other etching, chemical, and / or mechanical polishing methods. In other embodiments, the planarity is provided due to the inherent nature of the method of depositing layer 108, for example, if the material of layer 108 is spin-on glass, a polymer, a photoresist, or other suitable material. Planarization can be controlled to leave a layer of desired (typically very small) thickness on top of layer 102 (e.g., ...). Figure 1As shown in the diagram, or all material above the top surface height of layer 102 (not shown) is removed. With layer 108 left on top of layer 102, the target thickness ranges from 10 nm to several hundred nm, where the actual thickness includes typical cross-wafer inhomogeneities during planarization. In some embodiments, spin-coated material is used for planarization followed by etch-back, resulting in improved cross-wafer uniformity compared to a typical CMP process. In all the above cases, the resulting top surface of 102 (without spin-coated material) or the resulting top surface of 108 (if spin-coated material is present) is a planar surface.

[0027] Layer 101 is bonded to the top of at least a portion of the corresponding (108, 102) top surfaces. This bonding can be a direct molecular bond or can be facilitated using additional materials, such as, for example, metal layers or polymer films known in the art. Layer 101 constitutes what is commonly referred to as an active region and can be composed of materials including, but not limited to, GaAs and GaAs-based ternary and quaternary materials, such as those utilizing… Figure 4 Described in more detail. In one embodiment, layer 101 is multilayered, including layers providing optical and electrical confinement as well as electrical contacts, as known in the art for active devices. In yet another embodiment, layer 101 uses underlying layers 102, 108, 104 and / or 105 to provide electrical and / or optical confinement and one or more electrical contacts.

[0028] In some embodiments, layer 101 can be effectively electrically pumped to generate light emission and gain. The present invention achieves effective optical coupling between waveguides formed in layers 101 and 102. Material 102 can provide additional functionalities such as broadband transparency, high-intensity processing, phase shifting, combining, splitting, filtering, and / or other functionalities known in the art through temperature, strain, or other tuning mechanisms.

[0029] Layer 103 facilitates effective coupling, and layer 106, in the presence of layer 106, facilitates effective coupling. Optionally, layer 106 primarily serves as an anti-reflective or high-reflective coating at the interface between layers 101 and 103. Layer 103 serves as an intermediate waveguide, which in some embodiments receives the profile (depicted by dashed line 150) of an optical mode supported by a waveguide cored by layer 101, effectively captures it as mode profile 151, gradually transfers it to mode profile 152, and finally to 153. Mode profile 153 is then effectively coupled to the waveguide cored by layer 102. In other embodiments, the direction of travel can be reversed, wherein layer 103 effectively captures the optical mode supported by the waveguide cored by layer 102 and gradually transfers its mode profile to the mode profile supported by the waveguide cored by layer 101.

[0030] The refractive index of layer 103 can be designed to facilitate efficient coupling of the mode profile 150 and to efficiently convert the mode into a mode having the mode profile 153 by utilizing the tapered structure fabricated in layers 102 and / or 103. In some embodiments, the refractive index of layer 103 is between 1.55 and 1.8. In some embodiments, layer 103 is such as SiNO x The dielectric layer. In some other embodiments, layer 103 can be a polymer. In still other embodiments, layer 103 can be any other material having a suitable refractive index.

[0031] The thickness of layer 103 is an optimized parameter, and in some embodiments it is between 400 nm and 2000 nm. Prior to this invention, without the intermediate layer 103, the requirement for the width of the tapered tip would be problematic, as discussed above. However, using the intermediate layer 103 significantly reduces the stringent requirement for the width of the tapered tip, thereby allowing efficient transfer between materials with very high reflectivity (such as GaAs in layer 101, for example) and materials with low reflectivity (such as SiN in layer 102, for example).

[0032] By observing the mode profiles, the differences between the optical modes supported by the waveguides in layers 101 and 102 may or may not be obvious; however, mode overlap of less than 100% (in the absence of intermediate layer 103) can lead to significant optical loss. In some cases, losses up to 1 dB may be considered acceptable, but losses greater than 1 dB will be considered unacceptable. In other cases, a 3 dB loss level may be the criterion for selection. The function of layer 103 is to keep the optical loss due to imperfect mode overlap below a level determined to be acceptable in a given application.

[0033] The upper cladding 107 of the waveguide implemented in 103 and / or 102 can be ambient air (meaning no actual cladding material is deposited) or can be any other suitable material that is intentionally deposited, such as... Figure 1 The materials shown include, but are not limited to, polymers, SiO2, and SiN. x SiNO x And so on. In some embodiments, the same material is used for layers 107 and 108. In some embodiments (not shown), multiple depositions can be used to provide the cladding function of layer 107, for example, one material provides cladding for a core-guided mold 153 formed in layer 102, and another material provides cladding for a core-guided mold 151 formed in layer 103. In all cases, the refractive index of the cladding material is less than the refractive index of the material providing the core for mold guidance. In yet other embodiments (such as...) Figure 5As shown in the diagram, layer 103, due to its designed low refractive index, is able to provide cladding functionality to layers 102 and 153. Reference will be made below. Figure 5 These embodiments will be discussed further.

[0034] Layer 109 is a contact metal deposited on top of a portion of layer 101. Layer 101 consists of at least three sublayers, which will be described below. Figure 2a This is discussed in detail in the description. There are one or more lithography alignment marks (not shown in this cross-sectional view, but see, for example, the description below). Figure 3 320 and Figure 4 (420 in the middle) to facilitate precise alignment between layers formed during various processing steps.

[0035] In some embodiments, layer 108 is absent, and layer 101 is bonded and layer 103 is deposited on top of patterned layer 102. In such embodiments, there is no planarization step.

[0036] The dashed lines A, B, C, and D corresponding to the cross-sectional end view of the device according to some embodiments of the present invention are shown by way of end view 200D. Figure 2a And showing end views 200A, 200B and 200C Figure 2b It was described in more detail.

[0037] Figure 2a It shows the relationship with Figure 1 (and Figures 3-4 Cross-sectional view 200D corresponding to the feature position marked D in ) , where Figure 2b It shows the relationship with Figure 1 (and Figures 3-4 The three feature locations marked A, B, and C in the diagram correspond to three cross-sectional views 200A, 200B, and 200C. Functional layers 201 to 209 (unless explicitly defined differently) correspond to... Figure 1 The functional layers 101 to 109 are described and correspond to the information about Figure 3 The functional layers 301 to 309 are described and correspond to the information about Figure 4 The functional layers described are 401 to 409.

[0038] Section 200D is a through section including the active layer 201 (corresponding to Figure 1 , Figure 3 , Figure 4An exemplary cross-section of regions 101, 301, and 401 in the diagram. Layer 201 includes multiple sublayers to provide the necessary functionality to implement active devices. In the illustrated embodiment, layer 201 is on top of layer 208, thereby providing a planarized surface for bonding. In another embodiment (not shown), layer 201 is on top of layer 202 because the previously present planarization layer 208 has been completely removed from the top of layer 202. In yet another embodiment (not shown), layer 201 is on top of layer 202 without any planarization layer ever being present. In yet another embodiment (not shown), layer 201 is on top of layer 204 (if layer 202 is completely removed) and / or on top of layer 205 (if layers 202 and 204 are completely removed).

[0039] Layer 201 is used to define optical and electrical confinement to contribute to high-performance active devices. Optical confinement in the vertical direction (as observed in Figure 2) is provided by causing the material composition to correspond to different refractive indices, and optical confinement in the horizontal direction is provided by providing a cladding (207) with a smaller refractive index than that of layer 201 through at least one etching. Cladding 207 can comprise a variety of materials, some of which can provide passive functionality to the etched surface, resulting in improved laser performance. Electrical confinement is provided by appropriate material composition and by creating etched or implanted current channels.

[0040] In one embodiment, the active layer 201 includes five different functional layers: 201-1, 201-2, 201-3, 201-4, and 201-5.

[0041] 201-1 provides an n-type contact layer comprising a highly N+ doped GaAs layer. In some embodiments, the doping is >1e18. In some embodiments, 201-1 includes a superlattice layer to promote bonding and / or prevent dislocations. Examples of superlattices would be a combination of GaAs and AlGaAs layers, a combination of InGaP and InAlP layers, or other suitable combinations. The thickness of this layer is typically between 50 nm and 200 nm, although it can be larger in some embodiments. The N-type metal and the vias for connecting to the pads (210a and 210b) are laterally offset from the optical modulus 250 (whose lateral confinement is defined by at least one etch), resulting in very low or negligible optical loss due to the n-type contact metal.

[0042] Sublayer 201-2 provides an n-side cladding and is typically implemented as an AlGaAs layer. The Al content can be fixed, stepped, or gradually varied, depending on the operating wavelength. Because the n-type contact metals (210a and 210b) are laterally offset, the thickness is not driven by metal loss and is an optimized parameter to contribute to the mode shape, active region confinement, and coupling with layer 203. In some embodiments, the thickness of 201-2 is between 100 nm and 1000 nm. 201-2 can also include one or more etch stop layers, such as, for example, InGaP or other material layers. In some embodiments, the etch stop layer thickness is between 5 nm and 80 nm. Sublayer 201-2 is doped at a fixed concentration or at a varying concentration, i.e., increasing from a minimum concentration at its boundary with 201-3 to a high doping level between 5e17 and 4e18 at its boundary with layer 201-1.

[0043] 201-3 is an active region, which in one embodiment includes a quantum well, a quantum barrier, and a separate confined heterostructure (SCH) layer on at least one side of a quantum well / barrier structure. In some embodiments, quantum dots are used instead of quantum wells. In other embodiments, quantum dots embedded in quantum wells are used. In yet another embodiment, a large number of p(i)n junctions are defined in the active region to provide, for example, photodetector functionality or bulk phase / intensity modulator functionality. The SCH layer can be hierarchical or non-hierarchical. In some embodiments, it is implemented as an AlGaAs material with constant or varying doping concentrations. In the case of hierarchical doping, the doping typically increases with increasing distance from the quantum well / quantum dot / pn junction.

[0044] 201-4 is a p-type side cladding layer, typically implemented as an AlGaAs layer. The Al content can be fixed, stepped, or gradually varied, depending on the operating wavelength. The thickness and Al content of 201-4 are parameters optimized to reduce the impact of absorption losses in this layer and the absorption losses in the overlying contact layer. In some embodiments, the thickness of 201-4 is between 100 nm and 2000 nm. 201-4 can also include one or more etch stop layers, such as, for example, InGaP or others. In some embodiments, the etch stop layer thickness is between 5 nm and 80 nm. The layers are doped at a fixed level or at varying concentrations, decreasing from a maximum concentration at the boundary with layer 201-5 to a lower doping level at the boundary with layer 201-3.

[0045] 201-5 is a p-type contact layer. In some embodiments, a highly p+ doped GaAs layer is used for the p-type contact. In some embodiments, the doping level is >1e18.

[0046] In some embodiments, not all layers 201-1 to 201-5 are present, but at least the active region (201-3), the n-type contact region (201-1), and the p-type contact region (201-5) are present. In some embodiments, an additional etch stop layer is introduced to facilitate better process control.

[0047] exist Figure 2b In the diagram, section 200A shows the completion of optical coupling with layer 402 (assuming the optical signal flow occurs during...). Figure 1 , Figure 3 and Figure 4 (From right to left) then as Figure 1 In China (and as described below) Figure 3 and Figure 4 The leftmost embodiment of the device is shown in section 200B. Section 200B illustrates an embodiment facilitating mode conversion from one predominantly present in layer 203 to one predominantly present in layer 202. This conversion is facilitated by a tapered portion implemented in at least one of layers 202 and 203. Section 200C illustrates an embodiment in which the mode predominantly resides in layer 203 after docking with a structure provided with guidance in section 200D. Typical heights and widths of waveguides formed in layers 201, 202, and 203 can range from submicrometers (down to 20 nm) to several micrometers, although they depend heavily on the specific material system and implementation. Optimal dimensions (width, height, sidewall angles, etc.) that facilitate effective coupling can be readily calculated, for example, using commercial simulation tools or the like. In some embodiments, the thickness of layer 202 (the vertical dimension in FIG. 2) is between 20 nm and 400 nm, and in still other embodiments, it is between 400 nm and 2000 nm.

[0048] In some embodiments, at least two etchings (such as...) are used Figure 2a (As shown in the diagram). One etch defines the optical mode constraint, and another etch opens the n-type contact region for metal deposition. In some embodiments, a single etch is used to define the optical mode constraint and open the n-type contact region for metal deposition. In other embodiments, two or more etches are used to provide additional control over optical mode constraint, sidewall remodeling, active region pumping efficiency, and n-type contact region access. The etches can be timed and / or can utilize an etch stop layer to improve control.

[0049] In some embodiments, the patterns defined in layers 202, 204, 205, and / or 208 can provide frequency-selective feedback to the optical mode predominantly present in layer 201 via the evanescent tail of the mode. Such frequency-selective feedback can be used to define a single-frequency laser (e.g., a distributed feedback laser or other laser).

[0050] Figure 3 A top view of an integrated photonic device 300 is provided, which utilizes docking coupling and mode switching to achieve effective coupling between dissimilar materials. Dashed lines A, B, C, and D correspond to the methods described above using... Figure 2a and Figure 2b Cross-sectional end views of devices according to some embodiments of the present invention are described in more detail, and more specifically end views 200A, 200B, 200C and 200D.

[0051] The optical mode supported by active layer 301 is guided through optional coating 306 to layer 303, which is used for mode conversion to effectively couple to layer 302. Layer 306 can provide high reflectivity or, when designed as an anti-reflective coating, can promote reduced reflection. To facilitate coupling between the modes supported by layers 301 and 302, the dimensions of layer 302 taper towards layer 301, as shown by the relatively small width of the tip 311 relative to the width of layer 302, as indicated by the leftmost part of the figure. It has been calculated that the requirements for the tapered portion size are significantly relaxed, up to several hundred nanometers, due to the presence of layer 303. For example, even with a tip width greater than one hundred nanometers, coupling efficiency greater than 70% between 301 and 302 can be achieved, even when the refractive index difference between 301 and 302 is greater than one. In contrast, without layer 303, layer 301 would have to taper so that its mode could be directly coupled into layer 302. To achieve similar coupling efficiency, the size of the tapered tip of layer 301 (not shown) would have to be much smaller than one hundred nanometers. In another embodiment, a tapered portion (not shown) is formed in layer 303 instead of layer 302. In yet another embodiment, tapered portions can be formed in both layers 302 and 303 to achieve efficient coupling. In some embodiments, the tapered portions in layers 302 and 303 can be multi-stage tapered portions, meaning they utilize more than one etch depth to facilitate more efficient coupling.

[0052] In some embodiments (not shown), the tapered tip can physically contact layer 306, or contact layer 301 if layer 306 is absent. In yet another embodiment (not shown), layer 302 in the tapered tip does not have an abrupt break, but rather its width varies continuously to facilitate more efficient coupling.

[0053] Layer 309 is the contact metal deposited on top of layer 301, corresponding to the above regarding... Figure 1 The contact metal 109 on the top of layer 101 as described in the embodiment, such as Figure 2a As shown in the image.

[0054] One or more lithographic alignment marks 320 (only one is shown for simplicity) are used for precise alignment between various processing steps.

[0055] Figure 4 A top view of an integrated photonic device 400 according to an embodiment of the present invention is shown, wherein the boundary between the dissimilar materials is angled to control both transmission and back reflection. An optical mode supported by an active layer 401 is guided through an optional coating 406 to a layer 403, which is used for mode conversion to efficiently couple to a layer 402. Layer 406 can provide high reflectivity or, when designed as an anti-reflective coating, can promote reduced reflection. To facilitate coupling between modes supported by layers 401 and 402, the dimensions of layer 402 taper towards layer 401, as shown by the relatively small width of the tip 411 relative to the width of layer 402, as indicated by the leftmost position of the figure. It has been calculated that the requirements for the tapered portion size are significantly relaxed, up to several hundred nanometers, due to the presence of layer 403. For example, even with a tip width greater than one hundred nanometers, coupling efficiency greater than 70% between 401 and 402 can be achieved, even when the refractive index difference between 401 and 402 is greater than one. In contrast, without layer 403, layer 401 would have to taper so that its mode could be directly coupled into layer 402. To achieve similar coupling efficiency, the size of the tapered tip of layer 401 (not shown) would have to be much smaller than one hundred nanometers. In another embodiment, a tapered portion (not shown) is formed in layer 403 instead of layer 402. In yet another embodiment, tapered portions can be formed in both layers 402 and 403 to achieve efficient coupling. In some embodiments, the tapered portions in layers 402 and 403 can be multi-stage tapered portions, meaning they utilize more than one etch depth to facilitate more efficient coupling.

[0056] Additionally, in this embodiment, one or more of the interfaces between layers 401, 406 and / or 403 are angled to reduce the corresponding back reflection.

[0057] Angle 420 is defined as the angle between the tangent to the direction of wave propagation within structure 401 and the facet (the interface facing 406 and / or 403 if layer 406 is absent). Angle 420 is primarily used to control the back reflection of the mode supported by layer 401 when the mode reaches the interface facing 406 and / or 403. In one embodiment, it is substantially equal to 0 degrees. In another embodiment, it is between 1 degree and 45 degrees. In yet another embodiment, it is substantially equal to 8 degrees. In yet another embodiment, it is substantially equal to 12 degrees.

[0058] Angle 430 is defined as the angle between the direction of wave propagation within structure 401 and the angle of the waveguide formed by 403. This angle is an optimization parameter for the coupling efficiency between modes supported by layers 401 and 403 and relates to the selection of angle 420 and / or the refractive index of the materials used in layers 401 and 403 and their respective claddings. In one embodiment, it is substantially equal to 0 degrees. In another embodiment, it is between 1 degree and 45 degrees. In yet another embodiment, it is substantially equal to 16 degrees. In yet another embodiment, it is substantially equal to 20 degrees. In all cases, the optimal angle 430 can be calculated using an electromagnetic solver for a given combination of angle 420 and the effective refractive index of the modes in layers 401 and 403.

[0059] Precise vertical alignment between the axis defined by the direction of wave propagation within structure 401 and the center of waveguide 403 at the interface facing 403, 406, and / or 401 (in Figure 4 (Middle / Top) are optimization parameters, where such offsets can be positive (in...) Figure 4 (middle is above), negative (in) Figure 4 (middle is below) and / or essentially equal to 0 (no offset). This optimization can be performed directly using numerical software to maximize conversion performance while optimizing for both angles 420 and 430.

[0060] Prior to this invention, the requirement for the tapered tip width for direct transfer between layers 101 / 301 / 401 and 102 / 302 / 402 was problematic, i.e., without the intermediate layer 103 / 303 / 403. However, using an intermediate layer 103 / 303 / 403 (though with an angled interface in some embodiments) dock-coupled to layers 101 / 301 / 401 significantly reduces the stringent requirement for tapered tip width, thereby allowing efficient transfer between very high reflectivity materials (such as, for example, GaAs-based layers in 101 / 301 / 401) and low reflectivity materials (such as, for example, SiN, LiNbO3, or similar materials in layers 102 / 302 / 402). Layer 403 may comprise a dielectric material, a polymer, and / or any other suitable material. At the dock-coupled interface, no adiabatic transition occurs between the optical modes supported by elements 101 / 301 / 401 and 103 / 303 / 403. Layers 103 / 303 / 403 and / or layers 102 / 302 / 402 may include bends (not shown) to control the path selection of the guided light waves. One or more lithographic alignment marks 320 / 420 are present to facilitate precise alignment between layers formed during various processing steps.

[0061] Figure 5A top view of one embodiment of an integrated photonic device 500 is provided, which utilizes docking coupling and mode switching to achieve efficient coupling between dissimilar materials. Dashed lines A, B, C, and D correspond to cross-sectional end views of devices according to some embodiments described in more detail by means of end views 500A, 500B, 500C, and 500D.

[0062] The optical mode supported by active layer 501 is guided through optional coating 506 to layer 503, which is used for mode conversion to effectively couple to layer 502. Layer 506 can provide high reflectivity or, when designed as an anti-reflective coating, can promote reflection reduction. To facilitate coupling between modes supported by layers 501 and 502, the dimensions of layer 502 taper towards layer 501, as shown by the relatively small width of tip 511 relative to the width of layer 502, as indicated by the leftmost part of the figure. It has been calculated that the requirements for the tapered portion size are significantly relaxed, up to several hundred nanometers, due to the presence of layer 503. For example, coupling efficiency greater than 70% between 501 and 502 can be achieved even when the tip width is greater than one hundred nanometers, and even when the refractive index difference between 501 and 502 is greater than one. In contrast, without layer 503, layer 501 would have to taper so that its mode could be directly coupled into layer 502. To achieve similar coupling efficiency, the size (not shown) of the tapered tip of layer 501 would have to be much smaller than one hundred nanometers. In some embodiments (not shown), the tapered tip can physically contact layer 506, or, if layer 506 is absent, layer 501. In yet another embodiment (not shown), layer 502 does not abruptly break in the tapered tip, but rather its width changes continuously to facilitate more efficient coupling.

[0063] One or more lithographic alignment marks 520 (only one is shown for simplicity) are used for precise alignment between various processing steps.

[0064] exist Figure 5 In the embodiment shown, once the optical mode is converted to a mode primarily existing in the waveguide for which layer 502 provides the core, layer 503 is not removed from the top of layer 502, which differs from the previous embodiment. Figure 1 The cases of layers 103 and 102 in the embodiments (or respectively corresponding to) Figure 3 and Figure 4 Layers 303 and 302 or 403 and 402 in the middle). This can be achieved by using... Figure 6aThis difference is readily apparent in end views 600A, 600B, and 600C. This variation is made possible in this embodiment because the material is chosen such that the refractive index of layer 503 is less than that of layer 502, allowing layer 503 to function as a cladding layer for layer 502. This embodiment simplifies the fabrication of integrated photonic devices because it relaxes the need for etch control required in cases where intermediate layers must be removed from the region above the passive layer, such as... Figure 1 The case of layer 103 above layer 102 (or in separate layers) Figure 3 and Figure 4 (The case of layers 303 and 403 above layers 302 and 402).

[0065] Functional layers 501, 502, 503, 506, and 509 (unless explicitly defined differently) correspond to the following regarding Figure 3 The functional layers 301, 301, 303, 306, and 309 described below, and those described below... Figure 6a and Figure 6b Layers 601, 602, 603, 606, and 609.

[0066] Figure 6a Three cross-sectional views, 600A, 600B, and 600C, are shown, corresponding to... Figure 5 The three feature locations labeled A, B, and C are shown in the image. Figure 6b Showing the corresponding Figure 5 Cross-sectional view 600D shows the feature location marked D. Functional layers 601 to 609 (unless explicitly defined differently) correspond to the information about Figure 1 The functional layers 101 to 109 are described and correspond to the information about Figure 3 The functional layers 301 to 309 are described and correspond to the information about Figure 4 The functional layers described are 401 to 409.

[0067] exist Figure 6a In the diagram, section 600A shows the optical coupling completed to layer 602 (assuming the optical signal flow occurs at...). Figure 5 (From right to left in view 500) then through Figure 5 View 500 shows a cross-sectional view of the leftmost plane of the device. Layer 602 provides the core of the waveguide, while layers 603, 604, and 608 serve as cladding. Section 600B shows an embodiment in which a mode transition is facilitated from one predominantly present in layer 603 to one predominantly present in layer 602. This transition is facilitated by a tapered portion implemented in layer 602. Section 600C shows an embodiment in which, in relation to... Figure 1 , Figure 3 and Figure 4After the guided structural docking coupling is provided in the active region, the module mainly resides in layer 603.

[0068] exist Figure 6b In the middle, section 600D shows the penetration including the active layer 601 (corresponding to Figure 2a An exemplary section of region 201 in [the document]. Functional layers 601 to 610b (unless explicitly defined differently) correspond to [the following] regarding [the following]. Figure 2a The functional layers 201 to 210b are described, with the key difference being that layer 603 is used as the main cladding layer, and... Figure 2a The difference lies in Figure 2a In this configuration, layer 207 serves as the primary cladding layer. Note that although layer 607 is present in some portions of the device, it is not used as a cladding layer for layer 602 in or near the tapered region. In some embodiments, an additional thin layer exists between layers 603 and 601 to provide surface passivation. The mold shape 650 is generally slightly different from mold shape 250 because the refractive index contrast at the boundary between 601 and the cladding layer is different in both cases.

[0069] Embodiments of the present invention offer numerous benefits. Compared to typical Si-based or InP-based PICs, this integrated platform allows for the scalable fabrication of PICs made from a variety of materials and is capable of handling high optical power.

[0070] Previous methods have generally used tapered structures to transfer optical modes from active to passive devices, where the width of the composite semiconductor region adiabatically tapers down to submicron sizes. However, as the difference in refractive index increases, the required width of the tapered tip rapidly decreases to tens of nanometers. This invention employs a docking coupling scheme to relax the requirement for the size of the tapered portion in any coupled waveguide, which simplifies the fabrication of such structures.

[0071] Other methods have relied on die bonding of prefabricated optical active devices to passive waveguides. This requires extremely tight alignment precision, often exceeding the accuracy achievable by typical die bondingrs. This limitation restricts the production capacity of the process and the performance of the optical coupling.

[0072] This invention employs a process flow comprising a typical wafer bonding of a composite semiconductor material overlay on a carrier wafer to a dielectric waveguide, and subsequent semiconductor manufacturing processes as known in the art. It allows for precise optical alignment between active and passive waveguides via a typical photolithography step, thereby eliminating the need for precise physical alignment. This photolithography-based alignment enables scalable manufacturing using wafer-level technologies.

[0073] By combining it with a mode converter (intermediate waveguide), the docking coupling method facilitates efficient optical transmission between dissimilar materials, eliminating the need for narrow tapered tips that are challenging to solve and manufacture with existing tools.

[0074] It should be understood that the optical coupling between modes in the active and passive layers is mutual, making it possible for... Figure 1 For example, the structure can be configured to facilitate the transmission of light from region 101 to region 102, and also to facilitate transmission in the opposite direction (from region 102 to region 101). It should be understood that multiple such conversions can be implemented on a properly configured PIC without limitation on their number or orientation.

[0075] In some embodiments, the active region can utilize the substrate for more efficient heat dissipation because it is in direct contact with the substrate without a dielectric between them. In such embodiments, the active region completely defines the optical waveguide within the active region and is transferred to the passive region via the aforementioned docking coupling.

[0076] In some embodiments, the active region generates a hybrid waveguide structure with a dielectric layer, which can be used, for example, to generate wavelength-selective components formed inside a laser cavity for, for example, a distributed feedback (DFB) laser or similar components.

[0077] The embodiments of the optical devices described herein can be incorporated into a variety of other devices and systems, including, but not limited to, various computing and / or consumer electronics devices / appliances, communication systems, sensors, and sensing systems.

[0078] It should be understood that this disclosure teaches only a few examples of illustrative embodiments, and many variations of the invention can be readily devised by those skilled in the art upon reading this disclosure, and the scope of the invention should be determined by the appended claims.

Claims

1. An integrated active device, comprising: The first, second, and third components are manufactured on a common substrate; The first element includes an active waveguide structure comprising at least three sub-layers supporting a first optical mode, the second element includes a passive waveguide structure supporting a second optical mode, and the third element, which is at least partially docked to the first element, includes an intermediate waveguide structure supporting two or more intermediate optical modes. The first sub-layer in the active waveguide structure includes an n-type contact layer, the second sub-layer in the active waveguide structure includes a p-type contact layer, and the third sub-layer in the active waveguide structure includes an active region. The tapered waveguide structure in at least one of the second and third elements facilitates an efficient thermally adiabatic transition between one of the intermediate optical modes and the second optical mode. Wherein, no adiabatic transition occurs between the first optical mode and any of the intermediate optical modes; and The first, second, and third elements are aligned with each other using photolithographic alignment marks, which facilitate precise alignment between layers formed during the fabrication steps of the first, second, and third elements. The n-type contact layer is connected to the n-type contact metal, and the n-type contact metal is laterally offset from the active region.

2. The integrated active device according to claim 1, The second element includes a planar top surface that is below and in direct contact with the lower surface of the third element.

3. The integrated active device according to claim 1, The interface between the first element and the third element is optimized to minimize the angle of reflection between the first element and the third element.

4. The integrated active device according to claim 1, The n-type contact layer and the p-type contact layer comprise highly doped GaAs layers.

5. The integrated active device according to claim 1, The active region mentioned therein includes a quantum well.

6. The integrated active device according to claim 1, The active region mentioned above includes quantum dots.

7. The integrated active device according to claim 1, The active region mentioned therein includes a pin junction.

8. The integrated active device according to claim 1, The second element has a refractive index between 1.8 and 2.5 and a thickness between 20 nm and 2000 nm.

9. The integrated active device according to claim 1, The third element has a refractive index between 1.55 and 2.2, and The refractive index of the third element is less than that of the second element.

10. The integrated active device according to claim 1, The active waveguide structure in the first element includes at least five sub-layers supporting the first optical mode; and The fourth sublayer in the active waveguide structure includes an n-type cladding, and the fifth sublayer in the active waveguide structure includes a p-type cladding.

11. The integrated active device according to claim 10, The n-type cladding and the p-type cladding comprise AlGaAs layers, wherein the Al concentration is between 5% and 60%.

12. The integrated active device according to claim 10, The sixth sub-layer in the active waveguide structure includes an etch stop layer.

13. The integrated active device according to claim 10, The first element is defined by using at least one etching process to provide optical mode confinement and open up an n-type contact region for metal deposition.

14. An integrated active device, comprising: The first, second, and third components are manufactured on a common substrate; The first element includes an active waveguide structure comprising at least three sub-layers supporting a first optical mode, the second element includes a passive waveguide structure supporting a second optical mode, and the third element, which is at least partially docked to the first element, includes an intermediate waveguide structure supporting two or more intermediate optical modes. The third element provides a cladding for the second element; The first sub-layer in the active waveguide structure includes an n-type contact layer, the second sub-layer in the active waveguide structure includes a p-type contact layer, and the third sub-layer in the active waveguide structure includes an active region. The tapered waveguide structure in the second element facilitates an efficient thermal transition between one of the intermediate optical modes and the second optical mode; Wherein, no adiabatic transition occurs between any of the intermediate optical modes and the first optical mode; and The first, second, and third elements are aligned with each other using photolithographic alignment marks, which facilitate precise alignment between layers formed during the fabrication steps of the first, second, and third elements. The n-type contact layer is connected to the n-type contact metal, and the n-type contact metal is laterally offset from the active region.

15. The integrated active device according to claim 14, The second element includes a planar top surface that is below and in direct contact with the lower surface of the third element.

16. The integrated active device according to claim 14, The interface between the first element and the third element is optimized to minimize the angle of reflection between the first element and the third element.

17. The integrated active device according to claim 16, further comprising: An anti-reflective coating deposited on an angled interface.

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