Heterogeneous gan laser and active component

Abstract

A device comprising first, second, third and fourth elements fabricated on a common substrate. The first element comprises an active waveguide structure supporting a first optical mode, the second element comprises a passive waveguide structure supporting a second optical mode, the third element at least partially butt-coupled to the first element comprises an intermediate waveguide structure supporting an intermediate optical mode, and the fourth element comprising a TCO material is attached to the first element. If the first optical mode differs from the second optical mode by more than a predetermined amount, a tapered waveguide structure in at least one of the second and third elements facilitates an efficient adiabatic transformation. No adiabatic transformation occurs between any of the intermediate optical modes and the first optical mode. The mutual alignment of the first, second, third and fourth elements is defined using lithographic alignment marks.

Description

Technical Field

[0001] This invention relates to semiconductor lasers, amplifiers, modulators, and photodetectors. More specifically, certain embodiments of the invention relate to improved performance of heterogeneous integrated lasers, amplifiers, modulators, and photodetectors using optically coupled dissimilar materials. The development of this invention was partly supported by the U.S. government grant DARPA contract #HR001120C0135. Background Technology

[0002] 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 the functionality for applying information signals 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 emerged in the past decade using silicon instead of InP to implement PICs, due to the superior properties and processing capabilities of the former material, which balances the investments already made for electronic integrated circuits.

[0003] The biggest drawback of using silicon for PICs is that it is an indirect bandgap material, which makes it difficult to provide electrically pumped light sources. This problem is typically addressed by assembling a PIC comprising two or more chips made of dissimilar materials in a separate process. This approach is challenging due to the need for very fine alignment, which increases packaging costs and introduces scalability limitations. Another approach to address the bandgap problem is to combine two dissimilar materials together and process them together, thus eliminating the need for precise alignment during the bonding of larger wafers or complete wafers of dissimilar materials and allowing for large-scale manufacturing. In this disclosure, the term "hybrid" is used to describe the first approach, which involves precise assembly of separately processed portions, and the term "heterogeneous" is used to describe the latter approach, which combines two materials and then processes the bonded structure to define waveguides and other components of interest.

[0004] To transmit optical signals between dissimilar materials, heterojunction methods typically utilize tapered portions with gradually decreasing sizes until the effective mode refractive indices of the dissimilar materials match and efficient power transfer is achieved. This approach generally works well when the materials have refractive indices similar to those of silicon and InP. However, when there are significant differences in effective refractive indices, such as between SiN and GaN, the requirements for the tapered tip size become more challenging and potentially limit efficient power transfer. Specifically, a small tapered tip width in GaN may be necessary to provide good coupling. Achieving this size is complex and may not be cost-effective. Furthermore, electrical pumping of such narrow tapered portions is challenging and can lead to increased coupling losses if insufficient pumping is not performed.

[0005] While InP and silicon-based PICs meet many current needs, they have some limitations; one is the limitation on the operating wavelength range due to increased material absorption and losses, as well as the limitation on the maximum light intensity and therefore optical power that the PIC can handle. To address these limitations, alternative waveguide materials such as SiN, TiO2, Ta2O5, AlN, or others have been considered. Many current and emerging applications can utilize PICs operating at or near visible wavelengths (300 nm to 600 nm), a wavelength range typically addressed by GaN material systems, to provide efficient light generation.

[0006] Typically, the aforementioned dielectric waveguides possess high bandgap energies, which provide better high-power handling and transparency at shorter wavelengths; however, these materials also typically have low refractive indices. For example, SiN with a bandgap of ~5 eV has a refractive index of ~2, AlN has a bandgap of ~6 eV and a refractive index of approximately ~2, and SiO2 with a bandgap of ~8.9 eV has a refractive index of ~1.44. For comparison, GaN has a refractive index >2.4. This makes the tapered approach challenging.

[0007] This alternative hybrid approach has the drawbacks mentioned above, namely the need for precise alignment, as well as the corresponding complex encapsulation and scaling limitations.

[0008] A recent approach to addressing the aforementioned problems is proposed in U.S. Patent No. 10,859,764 B2. This approach employs a combination of butt-coupling and mode converters to allow for heterogeneous processes without requiring extremely small taper widths, even with significant differences in refractive index. The method proposed in U.S. Patent No. 10,859,764 B2 is applicable to InP and GaAs integration and generally offers greater flexibility in the growth of high-quality p-side contacts. The growth of GaN materials emitting in and near the visible wavelength range is more challenging, especially since p-side contacts and growth often result in increased growth defects requiring improved heterogeneous integration. Summary of the Invention

[0009] This invention relates to PICs employing GaN active materials integrated with high-performance waveguides, comprising lasers, amplifiers, modulators, and photodetectors with improved performance. In particular, the embodiments described below relate to the detailed design of heterogeneous integration, optical coupling structures, and mode control necessary for creating high-performance lasers, amplifiers, modulators, and photodetectors. Attached Figure Description

[0010] Figure 1 A device according to an embodiment of the present invention is shown in cross-sectional view.

[0011] Figures 2a-2c Three cross-sectional top views of a device according to some embodiments of the present invention are shown.

[0012] Figures 3a-3b A cross-sectional end view of a device according to some embodiments of the present invention is shown.

[0013] Figure 4 A cross-sectional view of a device according to some embodiments of the present invention is shown. Detailed Implementation

[0014] The embodiments described herein include those 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, and performance is optimized for robust, fabrication-tolerant coupling and mode control in the active region.

[0015] In the following detailed description, reference is made to the accompanying drawings, which form a part thereof, wherein like reference numerals always indicate like parts, and embodiments in which the subject matter of this disclosure can be practiced are illustrated by way of illustration in the drawings. It should be understood that other embodiments may be utilized, and structural or logical changes may be made without departing from the scope of this disclosure. Therefore, the following detailed description should not be construed in a limiting sense, and the scope of the embodiments is defined by the appended claims and their equivalents.

[0016] This description may use perspective-based descriptions such as top / bottom, in / out, up / down, etc. Such descriptions are for ease of discussion only and are not intended to limit the application of the embodiments described herein to any particular orientation. The description may use the phrases "in one embodiment" or "in an embodiment," which may each refer to one or more of the same or different embodiments. Furthermore, the terms "comprising," "including," "having," etc., as used with respect to embodiments of this disclosure are synonymous.

[0017] 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).

[0018] The term “coupled with” and its derivatives are 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 cooperating or interacting with each other, and can mean one or more other elements 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 coupling” is used herein in its usual sense, meaning “ends facing each other” or axial coupling, where there is a minimum or zero axial offset between the elements in question. In the case where some thin interlayer is formed between the elements, such as a thin coating typically used to provide high reflectivity or antireflectivity, 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 so that they can be precisely described as butt coupling. In other words, the interface between the elements does not need to be perpendicular to either axis. The following discussion Figures 2a-2c The embodiments are examples of this possibility.

[0019] The term "active device" may be used herein. A device, or part of a device, referred to as active, is capable of generating, amplifying, modulating, and / or detecting light. This is in contrast to the term "passive device," whose primary function is to confine and guide light, and / or provide separation, combination, filtering, and / or other functions typically associated with passive devices. Some passive devices can provide functionality that overlaps with active devices, such as phase tuning, for example, using thermal effects or analogues that can provide modulation. An absolute distinction between "active" and "passive" should not be assumed solely based 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.

[0020] Figure 1 This is a schematic cross-sectional view of an integrated photonic device 100 that utilizes docking coupling and mode switching to achieve effective coupling between dissimilar materials. Dashed lines A, B, C, and D correspond to cross-sectional end views of the device according to some embodiments of the invention, which are achieved by means of... Figure 3a and Figure 3b A more detailed description, and more specifically corresponding to end views 300A, 300B, 300C and 300D.

[0021] An exemplary cross-section includes a substrate 105, which can be any suitable substrate for semiconductor and dielectric processing, such as Si, quartz, sapphire, glass, 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. The primary purpose of layer 104 is to provide an optical cladding for material 102 (described below) if necessary to form an optical waveguide. 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 SiO2. In some embodiments, layer 104 is omitted, and the substrate 105 itself serves as the cladding.

[0022] Using techniques known in the art, 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. If layer 104 is present, the refractive index of layer 102 is higher than that of layer 104, or if layer 104 is absent, the refractive index of layer 102 is higher than that of substrate 105. In one embodiment, the material of layer 102 may be one or more of SiN, TiO2, Ta2O5, SiO2, LiNbO3, and AlN. In some embodiments, such as when layer 102 is SiO2, it may be doped with other materials to control the refractive index. As is known in the art, either or both of layers 104 and 102 may be patterned, etched, or redeposited.

[0023] Layer 108, whose refractive index is lower than that of layer 102, covers layer 102 and lies below layers 106 and 103 (described in more detail below), and serves 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, planarity is provided, for example, if the material of layer 108 is spin-on glass, a polymer, a photoresist, or other suitable material, due to the inherent properties of the method of depositing layer 108. Planarization can be controlled to leave a layer of desired thickness (typically very low) on top of layer 102 (e.g., ...). Figure 1 (as shown), or remove all material (not shown) above the height of the top surface of layer 102. With layer 108 remaining on top of layer 102, the target thickness ranges from a few nm to several hundred nm, where the actual thickness includes the typical wafer-wide inhomogeneities of a planarization process. In some embodiments, spin-coated material is used for planarization and then etched back, resulting in improved wafer-wide uniformity compared to a typical CMP process. In some embodiments, layer 108 is not deposited and the top surface is not planarized, as shown in [the diagram]. Figure 4 Described with the help of [the author / organization].

[0024] Layer 101 is bonded to the top of all or part of the corresponding (108, 102) top surfaces using layer 106 as an intermediate layer, thereby providing at least one of electrical contact, current spreading, optical mode limiting, and / or improvements in surface quality for bonding to the corresponding (108, 102) top surfaces, such as by means of Figures 3a-3bExplanation. In one embodiment, layer 106 comprises a transparent conductive oxide (TCO). A TCO is a metal oxide material that exhibits high light transmittance and near-metallic conductivity at visible wavelengths. Some examples of commonly used TCOs include indium tin oxide (ITO), zinc oxide (ZnO), and aluminum-doped zinc oxide (AZO). In some embodiments, the bottom surface of layer 101 is planarized before depositing layer 106 and bonding it to the corresponding (108, 102) top surfaces. In other embodiments, the deposition of layer 106 is used to improve surface quality before bonding. In some embodiments, the bottom surface of layer 101 is planarized before bonding, and layer 106 further improves surface quality.

[0025] The bonding can be direct molecular bonding, or additional materials can be used to promote bonding, such as polymer films known in the art, for example. Layer 101 constitutes what is commonly referred to as the active region and can be composed of materials including, but not limited to, GaN and GaN-based ternary and quaternary materials, as will be described in the following text. Figures 3a-3b The following description is provided with the assistance of [unclear text - likely a typo]. In one embodiment, layer 101 is multi-layered, including layers providing optical confinement, electrical confinement, and / or electrical contacts, as known in the field of active devices. In yet another embodiment, layer 101 uses underlying layers 106, 108, 102, 104, and / or 105 to provide optical confinement and / or one or more electrical contacts.

[0026] In some embodiments, layer 101 can be effectively electrically pumped to generate light emission and gain. The present invention, by using layer 106 as an intermediate layer between 101 and the corresponding (108 / 102) top surfaces, enables effective optical coupling between the waveguides formed in layers 101 and 102, and contributes to improved manufacturability and performance. The material of layer 102 can provide additional functionalities such as broadband transparency, high-strength processing, phase shifting, combining, separating, filtering, and / or other functions known in the art through temperature, strain, or other tuning mechanisms.

[0027] Effective coupling is facilitated by layer 103, which serves as an intermediate waveguide. In some embodiments, this intermediate waveguide receives a distribution of optical modes supported by the waveguide (shown by dashed line 150), for which layer 101 provides a core. This core effectively captures the distribution of optical modes as mode profile 151 and gradually transitions it to mode profile 152, and finally to 153. Mode profile 153 is effectively supported by the waveguide, for which layer 102 provides a core. In other embodiments, the direction of travel can be reversed, wherein layer 103 effectively captures the optical modes supported by the waveguide, layer 102 provides a core for the waveguide, and gradually transforms its mode profile to a mode profile supported by the waveguide for which layer 101 provides a core.

[0028] The refractive index of layer 103 can be designed to facilitate efficient coupling of mode distribution 150, and the mode can be efficiently transformed into a mode having mode distribution 153 by utilizing the tapered structure formed in at least one of layers 102 and 103. Prior to this invention, i.e., without the intermediate layer 103, the requirement for the width of the tapered tip would be problematic, as described above. However, the use of the intermediate layer 103 significantly reduces the stringent requirement for the width of the tapered tip, allowing efficient transfer between higher refractive index materials (such as, for example, GaN and its ternary and quaternary materials in layer 101) and lower refractive index materials (such as, for example, SiN, SiNOx, doped SiO2, etc. in layer 102).

[0029] By observing the mode distribution, the differences between the optical modes supported by the waveguides in layers 101 and 102 may be obvious or insignificant, but the mode overlap is less than 100%, and the vertical offset between modes 150 and 153 may (in the absence of intermediate layer 103) result in significant optical loss. In some cases, losses up to 1 dB can be considered acceptable, but losses greater than that are unacceptable. In other cases, a 3 dB loss level can be the chosen criterion. The function of layer 103 is to keep the optical loss due to imperfect mode overlap below any value determined to be acceptable in a given application.

[0030] The upper cladding layer 107 used for waveguides implemented in 103 and / or 102 can be ambient air (meaning no actual cladding material is deposited) or can be as follows: Figure 1 Any other suitable material intentionally deposited as shown, including but not limited to polymers, SiO2, SiNx, SiNOx, etc. In some embodiments, the same material is used for layers 107 and 108. Figure 1 (Not shown in the image), the cladding function of cladding 107 can be provided by multiple deposits, for example, one material provides cladding for the mold 153 guided by a core formed in layer 102, and another material provides cladding for the mold 151 guided by a core formed in layer 103. In other embodiments, as known in the art, additional material in layer 107 is used to passivate, for example, the surface of layer 101. In all cases, the refractive index of the cladding material is lower than that of the material providing the core for mold guidance. In yet another embodiment, layer 103 may provide cladding functionality to both layer 102 and mold 153 because its refractive index is designed to be lower, such as by means of... Figure 2b And the integrated photonic device 230 described.

[0031] Layer 109 is a contact metal deposited on top of layer 101, such as by means of Figures 3a-3bA more detailed description is provided. There are one or more lithography alignment marks (not shown in this cross-sectional view, but see, for example, the description below). Figures 2a-2c (220, 250 and / or 280) to facilitate precise alignment between layers formed during various processing steps.

[0032] In some embodiments, layer 108 is absent, and both layers 101 / 106 are bonded together, with layer 103 deposited on top of patterned layer 102. In such embodiments, no method is used... Figure 4 The flattening steps are described.

[0033] Figures 2a-2c Three top views are provided for some embodiments of integrated photonic devices 200, 230, and 260, which utilize docking coupling and mode switching to achieve effective coupling between dissimilar materials.

[0034] The integrated photonic device 200 transfers the mode supported by the active device 201, guiding it through layer 203 for mode conversion to efficiently couple it to layer 202. Optional coatings (not shown), such as, for example, high reflectivity and / or anti-reflection coatings, can be used at any interface between the layers. Dashed lines A, B, C, and D correspond to devices according to some embodiments of the invention, using… Figures 3a-3b The cross-sectional end views are described in more detail, and correspond more specifically to end views 300A, 300B, 300C and 300D.

[0035] To facilitate coupling between the modules supported by layers 201 and 202, the size of layer 202 gradually decreases toward layer 201, as shown by the relatively small width of the tip 211 relative to the width of layer 202 shown at the leftmost part of the figure.

[0036] It has been calculated that the requirements for the tapered portion size are significantly relaxed due to the presence of layer 203. Conversely, without layer 203, layer 201 would have to be tapered so that its mode could be directly coupled into layer 202, and for similar coupling efficiency, the size of the tapered tip (not shown) of layer 201 would have to be much smaller. Furthermore, electric pumping of such a narrow tapered portion is challenging and could lead to increased coupling losses if not pumped sufficiently.

[0037] In another embodiment, a tapered portion (not shown) is formed in layer 203 instead of layer 202. In yet another embodiment, tapered portions may be formed in both layers 202 and 203 for efficient coupling (not shown). In some embodiments, the tapered portions in layers 202 and 203 may be multi-stage tapered portions, meaning they utilize more than one etch depth to facilitate more efficient coupling. When the tapered portion is in layer 203, the width of layer 203 typically decreases towards the left side of the figure to facilitate more efficient mode transfer.

[0038] Layer 209 is the contact metal deposited on top of layer 201, as will be Figures 3a-3b With the help of [the relevant authorities], this can be described in more detail. One or more lithographic alignment marks 220 (only one is shown for simplicity) are used for precise alignment between various processing steps.

[0039] Integrated photonic device 230 transfers the mode supported by active device 231, guiding it through layer 233 for mode conversion to efficiently couple it to layer 232. Optional coatings (not shown), such as, for example, high reflectivity and / or anti-reflection coatings, can be used at any interface between the layers. In contrast to integrated photonic device 200, in this embodiment shown in integrated photonic device 230, layer 233 also acts as a cladding material for the waveguide, with layer 232 providing the core on the left side of the image.

[0040] To facilitate coupling between the modules supported by layers 231 and 232, the size of layer 232 gradually decreases toward layer 231, as shown by the relatively small width of tip 241 relative to the width of layer 232 shown at the far left of the figure.

[0041] It has been calculated that the requirements for the tapered portion size are significantly relaxed due to the presence of layer 233. Conversely, without layer 233, layer 231 would have to be tapered so that its mode can be directly coupled into layer 232, and the size of the tapered tip (not shown) of layer 231 would have to be much smaller for similar coupling efficiency. Furthermore, electric pumping of such a narrow tapered portion is challenging and could lead to increased coupling losses if not pumped sufficiently.

[0042] Layer 239 is a contact metal deposited on top of layer 231, such as by means of Figures 3a-3b A more detailed description. One or more lithographic alignment marks 250 (only one is shown for simplicity) are used for precise alignment between various processing steps.

[0043] Integrated photonic device 260 illustrates an embodiment of the invention, wherein the boundary between dissimilar materials is angled to control transmission and back reflection. An optical mode supported by active device 261 is guided through layer 263, which is used to convert the mode for efficient coupling to layer 262. Optional coatings (not shown), such as, for example, high reflectivity and / or anti-reflection coatings, can be used at any interface between layers. As described by means of integrated photonic devices 200 and 230, both types of structures can utilize angled boundaries as described by means of integrated photonic device 260, although integrated photonic device 260 shows an angled transition for devices of the type described by means of integrated photonic device 200.

[0044] To facilitate coupling between the modules supported by layers 261 and 262, the dimensions of layer 262 gradually decrease towards layer 261, as shown by the relatively small width of tip 271 relative to the width of layer 262 shown at the far left of the figure. It has been calculated that, due to the presence of layer 263, the requirement for the tapered portion size is significantly relaxed to up to several hundred nanometers. In another embodiment, the tapered portion (not shown) is formed in layer 263 instead of layer 262. In yet another embodiment, the tapered portion can be formed in both layers 262 and 263 for efficient coupling. In some embodiments, the tapered portions in layers 262 and 263 can be multi-stage tapered portions, meaning they utilize more than one etch depth to facilitate more efficient coupling.

[0045] Additionally, in this embodiment, one or more of the interfaces between layers 261 and / or 263 are angled to reduce the corresponding back reflections(s). If a coating (not shown) is used, multiple interfaces may exist.

[0046] Angle 285 defines the angle between the tangent to the wave's propagation direction within structure 261 and the facet (the interface facing 263). Angle 285 is primarily used to control the back reflection of modes supported by layer 261 as they reach the interface facing 263. In one embodiment, this angle is substantially equal to 0º. In another embodiment, it is between 1º and 45º. In yet another embodiment, it is substantially equal to 8º. In yet another embodiment, it is greater than 8º and less than 20º. In yet another embodiment, it is greater than 20º.

[0047] Angle 290 defines the angle between the wave propagation direction within structure 261 and the wave propagation direction within structure 263. This angle is an optimized parameter for the coupling efficiency between the modes supported by layers 261 and 263, and is related to the selection of angle 285 and the refractive index of the materials used in layers 261 and 263 and their respective claddings. In one embodiment, it is substantially equal to 0°. In another embodiment, it is between 1° and 45°. In yet another embodiment, it is substantially equal to 8°. In yet another embodiment, it is greater than 8° and less than 25°. In yet another embodiment, it is greater than 25°.

[0048] As the optical mode propagates within structure 261, the precise vertical alignment (up / down in view 260) between the axis defined by the center of the optical mode and the center of waveguide 263 at the interface between 261 and 263 is an optimization parameter, where such offset can be positive (up in view 260), negative (down in view 260), and / or substantially equal to 0 (no offset). This optimization is performed directly by digital software to maximize transition performance while optimizing angle 290.

[0049] Layer 269 is a contact metal deposited on top of layer 261, as will be Figures 3a-3b With the help of [the relevant authorities], this can be described in more detail. One or more lithographic alignment marks 280 (only one is shown for simplicity) are used for precise alignment between various processing steps.

[0050] Figures 3a-3b It shows the corresponding Figure 1 and Figure 2a and Figure 2c Four cross-sectional views 300A, 300B, 300C, and 300D of four feature locations (A, B, C, and D) in devices 200 and 260. For Figure 2b Device 230 can be plotted in a similar cross-sectional view, with the key difference being the feature locations marked A (not shown). Functional layers 301 to 308 (unless explicitly defined differently) correspond to, as per [reference to...] Figure 1 The functional layers described are 101 to 108.

[0051] Section 300A shows the completion of optical coupling with layer 302 (assuming in Figure 1 After the optical signal stream occurs from right to left in the middle, such as Figure 1The leftmost embodiment of the device shown. Section 300B illustrates an embodiment where a mode transition is facilitated from a mode predominantly located in layer 303 to a mode predominantly located in layer 302. This transition is facilitated by a tapered portion implemented in at least one of layers 302 and 303. Section 300C illustrates an embodiment where the mode is predominantly located in layer 303 after the mode is coupled from a guided structural mating in section 300D. Typical heights and widths of waveguides formed in layers 301, 302, and 303 can range from submicron (as small as 20 nm) to several micrometers, although they depend heavily on the specific material system, operating wavelength, and implementation. Optimal dimensions (width, height, sidewall angles, etc.) for efficient coupling can be readily calculated using, for example, commercial simulation tools or the like. In some embodiments, the thickness of layer 302 ( Figures 3a-3b The vertical dimension (in the figure) is between 20 nm and 400 nm, and in another embodiment, it is between 400 nm and 2000 nm.

[0052] Section 300D shows an exemplary cross-section through the region including the active device. Layer 301 includes multiple sublayers to provide the necessary functionality to realize the active device. In one embodiment (as shown in 300D), layer 306 provides at least one of electrical contact, current spreading, optical mode limiting, and / or an improvement in surface quality compared to the surface quality of layer 301, while layer 308 provides a planarized top surface for bonding. In another embodiment (not shown), layer 306 is on top of layer 302 when the planarization layer 308 is completely removed on top of layer 302. In another embodiment (not shown, but by means of...) Figure 4 In the description, layer 306 is on top of layer 302, but layer 308 is not planarized, thus creating air gaps (not shown) in the patterned areas of layer 302. In yet another embodiment (not shown), layer 306 is on top of layer 304 (if layer 302 is completely removed) and / or on top of layer 305 (if layers 302 and 304 are completely removed). In one embodiment, layer 106 includes TCO.

[0053] Layer 301 (or layer 306 in some embodiments) is used to define optical and electrical confinement to facilitate high-performance active devices. Optical confinement in the vertical direction (in view 300D) is provided by a material composition corresponding to different refractive indices, and optical confinement in the horizontal direction is provided by at least one etching process to provide a cladding (312) with a reduced refractive index. Cladding 312 may include a variety of materials, some of which may provide passivation to the etched surfaces, resulting in improved laser performance. Electrical confinement is provided by the material composition and by the etched or implanted current channels.

[0054] In one embodiment, the active layer 301 includes five distinct functional sublayers: 301-1, 301-2, 301-3, 301-4, and 301-5. In some other embodiments, not all sublayers need to exist; only 301-1, 301-3, and 301-5 are required.

[0055] Sublayer 301-1 is a p-type contact layer. Growing such a layer in GaN material systems is typically challenging; therefore, in some embodiments, layer 306 is used to provide electrical contact to metals 310a and 310b and current spreading functionality, while keeping layer 301-1 relatively thin. In addition to the aforementioned p-type contact layer, sublayer 301-1 may include multiple sublayers, such as etch stop layers, bandgap smoothing layers, and / or other layers typically used to improve device performance or semiconductor processing uniformity.

[0056] Sublayer 301-2 is a p-cladding layer, which may include multiple sublayers. Its main purpose is to control the optical mode 350 and provide optimized confinement in the active region. Layer 301-2 may also include an etch stop layer, a bandgap smoothing layer, and / or other layers. In some embodiments, the confinement function may be implemented at least in part using layer 306.

[0057] Sublayer 301-3 is the active region. In one embodiment, the active region includes at least one of a quantum well, a quantum barrier, and a separation-confined heterostructure (SCH) layer, as known to those skilled in the art of designing GaN-based active optics. In some embodiments, quantum dots are used instead of quantum wells. In other embodiments, quantum dots embedded within quantum wells are used. In yet another embodiment, a large number of p(i)n junctions are confined within the active region to provide, for example, photodetector functionality or bulk phase / intensity modulator functionality. If one or more SCH layers are present, they can be hierarchical or non-hierarchical. Additional etch stop layers can be incorporated for better semiconductor processing control.

[0058] Sublayer 301-4 is an n-type cladding layer, which may include multiple sublayers. The thickness and refractive index of 301-4 are optimized parameters to control confinement in the active region and reduce absorption losses in the overlying contact layer. 301-4 may also include one or more etch stop and bandgap smoothing layers.

[0059] Sublayer 301-5 is an n-type contact layer that provides effective electrical contact with metal 309.

[0060] At least two metal contacts are used to provide carrier injection, electric field application and / or both to the active region, and three of these metal contacts (309, 310a and 310b) are shown in view 300D.

[0061] In the embodiment shown in section 300D, two etchings are utilized: one typically stops above the active region, defining the photomask 350 and providing current limiting functionality, and a second opening leads to layer 306 to provide at least one set of electrical contacts 310a / 310b. In other embodiments, a single etching through the entire layer 301 can provide all the aforementioned functions. In other embodiments, more than two etchings may be used for better control of process quality. It should be understood that a particular etching (intended to stop at a precise location in layer 301) may include both dry and wet etching to improve quality, as well as multiple photolithography steps as known in the art.

[0062] Figure 4 This is a schematic cross-sectional view of an embodiment of an integrated photonic device 400 that utilizes docking coupling and mode switching to achieve effective coupling between dissimilar materials, where there is no such... Figure 1 The planarization layer 108 is described. Functional layers 401 to 409 (unless explicitly defined differently) correspond to, as per [the relevant information] Figure 1 The functional layers 101 to 109 are described, and the modulo 450 to 453 corresponds to, as per the description of, functional layers 101 to 109. Figure 1 The described modulus is similar to 150 to 153. Due to the absence of a planarization layer ( Figure 1 In section 108), the bottom surface of layer 403 is not flat, thus causing... Figure 1 The planarization described herein represents a generally reduced coupling efficiency compared to the 450 to 453. The advantage of this method lies in its simplified processing, as it eliminates the need for material deposition to provide planarization with or without chemical mechanical polishing (CMP). A major challenge of CMP is the ability to provide good uniformity on the wafer; without this ability, device performance varies considerably. Although, with the help of… Figure 4 As explained, this nominally reduces coupling efficiency, but some applications can benefit from simplified processing.

[0063] This invention relates to PICs employing GaN active materials integrated with high-performance waveguides, comprising lasers, amplifiers, modulators, and photodetectors with improved performance. In particular, the embodiments described below relate to the detailed design of heterogeneous integration, optical coupling structures, and mode control necessary for creating high-performance lasers, amplifiers, modulators, and photodetectors.

[0064] Embodiments of the present invention offer numerous benefits. The integrated platform enables the scalable fabrication of GaN-based PICs to large wafers (currently up to 12 inches) using die-to-wafer or wafer-to-wafer bonding, and also provides high-performance waveguides and passive components.

[0065] Other methods have relied on die attachment of prefabricated optical active devices to passive waveguides. This requires extremely tight alignment precision, often exceeding that offered by typical die-bonded connectors. This limits the throughput of the process and the performance of the optical coupling.

[0066] Efficient optical transfer between dissimilar materials is facilitated by using a docking coupling method incorporating a mode converter (intermediate waveguide). This mode converter eliminates the need for narrow tapered tips in the active material, which are challenging to address and fabricate with current-level tools, while also providing challenging optical pumping. The transition between the intermediate waveguide and the passive waveguide utilizes tapered portions in both to facilitate efficient coupling, but typically provides high performance even for tapered portions with widths exceeding 100 nm.

[0067] It should be understood that the optical coupling between modes in the active and passive layers is reciprocal; therefore, with Figure 1 As an example, the structure can be configured to facilitate light transmission from region 101 to region 102, and also to facilitate transmission from region 102 to region 101 in the opposite direction. It should be understood that multiple such transitions can be implemented on a suitably configured PIC without limitation on their number or orientation.

[0068] 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.

[0069] 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 is defined by the appended claims.

Claims

1. An integrated active device, comprising: The first element, the second element, the third element, and the fourth element are fabricated on a common substrate; The first element includes an active waveguide structure supporting a first optical mode, the second element includes a passive waveguide structure supporting a second optical mode, the third element, which is at least partially mated to the first element, includes an intermediate waveguide structure supporting an intermediate optical mode, and a fourth element comprising a TCO material is attached to the first element, the fourth element providing at least one of electrical contact, current spread and / or optical mode limitation, and an improved surface quality compared to the bonding surface of the first element, and the fourth element is located between the first element and the second element; Wherein, if the difference between the first optical mode and the second optical mode is greater than a predetermined amount, the tapered waveguide structure in at least one of the second element and the third element facilitates an effective thermal transformation between the second optical mode and one of the intermediate optical modes; Wherein, no adiabatic transformation occurs between any of the intermediate optical modes and the first optical mode; and Photolithographic alignment marks are used to define the mutual alignment of the first element, the second element, and the third element. These photolithographic alignment marks facilitate precise alignment between layers formed during the manufacturing processes of the first element, the second element, the third element, and the fourth element.

2. The integrated active device according to claim 1, The lower surface of the third element is flat.

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

4. The integrated active device according to claim 3, further comprising: An anti-reflective coating is deposited on at least one angled interface.

5. The integrated active device according to claim 1, in, The first element includes a GaN-based semiconductor layer.

6. The integrated active device according to claim 1, The refractive index of the second element is between 1.6 and 2.

45.

7. The integrated active device according to claim 1, in, The second element comprises a SiN-based material.

8. The integrated active device according to claim 6, in, The refractive index of the third element is between 1.55 and 2.15 and is lower than that of the second element.

9. The integrated active device according to claim 1, This includes the first element of the active waveguide structure having at least three sub-layers; The active waveguide structure includes at least one of its sublayers, which includes an n-type contact layer; at least one of its sublayers includes an active region; and at least one of its sublayers includes a p-type contact layer.

10. The integrated active device according to claim 9, At least one of the sublayers includes an etch stop layer.

11. The integrated active device according to claim 9, in, At least one etching is used to define the first element to provide a light-mode confinement and open contact area in the fourth element for metal deposition.

12. An integrated active device, comprising: The first element, the second element, the third element, and the fourth element are fabricated on a common substrate; The first element includes an active waveguide structure supporting a first optical mode, the second element includes a passive waveguide structure supporting a second optical mode, the third element, which is at least partially mated to the first element, includes an intermediate waveguide structure supporting an intermediate optical mode, and a fourth element comprising a TCO material is attached to the first element, the fourth element providing at least one of electrical contact, current spread and / or optical mode limitation, and an improved surface quality compared to the bonding surface of the first element, and the fourth element is located between the first element and the second element; The third element provides a cladding for the second element; Wherein, if the difference between the first optical mode and the second optical mode is greater than a predetermined amount, the tapered waveguide structure in the second element facilitates an effective thermal transformation between the second optical mode and one of the intermediate optical modes; Wherein, no adiabatic transformation occurs between any of the intermediate optical modes and the first optical mode; and Photolithographic alignment marks are used to define the mutual alignment of the first element, the second element, and the third element. These photolithographic alignment marks facilitate precise alignment between layers formed during the manufacturing processes of the first element, the second element, the third element, and the fourth element.

13. The integrated active device according to claim 12, The lower surface of the third element is flat.

14. The integrated active device according to claim 12, in, The interface between the first element and the third element is tilted at an angle optimized to minimize reflection.

15. The integrated active device according to claim 14, further comprising: An anti-reflective coating is deposited on at least one angled interface.

16. The integrated active device according to claim 12, The first element includes a GaN-based semiconductor layer.

17. The integrated active device according to claim 12, The refractive index of the second element is between 1.6 and 2.

45.

18. The integrated active device according to claim 12, in, The second element comprises a SiN-based material.

19. The integrated active device according to claim 17, The refractive index of the third element is between 1.55 and 2.15 and is lower than that of the second element.

20. The integrated active device according to claim 1, The second element comprises an AlN-based material.

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