US 9525084

US Patent 9,525,084, titled "Microstructure enhanced absorption photosensitive devices," was issued to W&wsens Devices Inc. on December 20, 2016. The application was filed on November 18, 2015, with inventors Shih-Yuan Wang and Shih-Ping Wang.

Abstract:
The patent describes microstructure-enhanced absorption photosensitive devices, such as photodiodes (PDs) and avalanche photodiodes (APDs). These devices incorporate microstructures, like holes, to significantly increase photon absorption. For silicon PDs and APDs, this design allows for bandwidths exceeding 10 Gb/s at 850 nm wavelengths, with quantum efficiencies of 90% or more. The thinness of these devices makes them suitable for integration with CMOS, BiCMOS, and other electronics on a single silicon chip, offering benefits in packaging, reduced capacitance, and higher operating speeds.

Plain-Language Overview of Independent Claims:

• Independent Claim 1: This claim describes an integrated detector/processor circuit for data communication on a single semiconductor chip. It includes a photodetector with a photon absorbing region containing multiple holes that concurrently receive the same optical source signal, converting it into an electrical signal. An electronic processor, also on the same chip, processes this electrical signal. Crucially, the photodetector's photon absorbing region and the electronic processor have thicknesses of the same order of magnitude. The device also includes cathode and anode regions.
• Independent Claim 13: This claim describes a photodetector itself, featuring microstructure-enhanced photoabsorption. It has a photon absorbing region (preferably 0.5 to 5 micrometers thick) that absorbs photons from a modulated source signal for data communication, producing an electrical output. This region contains a plurality of holes extending through at least part of its thickness, configured to concurrently receive the same source signal at multiple holes. The region is designed to absorb over 40% (or 50% or 60%) of the incident signal at wavelengths in the 800-900 nm range or 1400-1700 nm range.
• Independent Claim 25: This claim specifies a photodetector with microstructure-enhanced photoabsorption that is made of silicon. It includes a cathode region, an anode region, and reverse biasing circuitry. The silicon photon absorbing region contains multiple holes, each with a cross-section parallel to the upper substrate surface, having a maximum dimension between 400 nm and 2500 nm. The center of each hole is spaced less than 3500 nm from the center of its nearest adjacent hole.
• Independent Claim 35: This claim describes a photodetector with microstructure-enhanced photoabsorption, similar to Claim 25, but the photon absorbing region is made of a germanium-based material. The holes in this germanium-based region have a maximum dimension between 750 nm and 3000 nm, and their centers are spaced apart by less than 5000 nm from the center of a nearest adjacent hole.
• Independent Claim 39: This claim describes an optical/electronic system. It comprises a photodetector and an active electronic circuit built on the same semiconductor substrate, forming a single integrated circuit chip. The system also includes a laser modulated at Gb/s rates to generate an optical source signal and an optical fiber to transport this signal. The photodetector receives the signal from the fiber and converts it to an electrical output, which the active electronic circuit then processes and outputs.

Litigation Status:
The patent family for US9525084 has litigation associated with it. Specifically, a PTAB case IPR2025-00997 was filed (with a procedural termination), and a US case was filed in the Texas Eastern District Court (case 2:24-cv-00854). The first worldwide family litigation was also filed. There is no information in the CAFC 2026 dockets directly listing US9525084 as a scheduled case for oral argument or decision. The USPTO PatentCenter and Assignment Search provide general search functionality but do not list specific litigation for this patent in the immediate search results. The patent was reassigned to IP LITFIN US 2024 LLC on October 23, 2024, via a patent security agreement.

Known litigation involving US patent 9525084 includes:

1. Case: IPR2025-00997 [cite: "PTAB case IPR2025-00997 filed (Procedural Termination)"]

   • Plaintiff(s): Unified Patents PTAB Data (Petitioner) [cite: "Petitioner: "Unified Patents PTAB Data" by Unified Patents is licensed under a Creative Commons Attribution 4.0 International License."]
   • Defendant(s): W&wsens Devices Inc (Patent Owner)
   • Jurisdiction: Patent Trial and Appeal Board (PTAB) [cite: "PTAB case IPR2025-00997 filed (Procedural Termination)"]
   • Filing Date: Not explicitly stated, but the case number suggests 2025.
   • Outcome/Current Status: Procedural Termination [cite: "PTAB case IPR2025-00997 filed (Procedural Termination)"]

2. Case: 2:24-cv-00854 [cite: "US case filed in Texas Eastern District Court", "case/2:24-cv-00854"]

   • Plaintiff(s): Not explicitly stated in the provided text, but W&wsens Devices Inc is the current assignee of the patent.
   • Defendant(s): Not explicitly stated in the provided text.
   • Jurisdiction: Texas Eastern District Court [cite: "US case filed in Texas Eastern District Court", "Source: District Court Jurisdiction: Texas Eastern District Court"]
   • Filing Date: Not explicitly stated, but the case number (2:24-cv-00854) suggests 2024.
   • Outcome/Current Status: Litigation is active [cite: "US case filed in Texas Eastern District Court"].

Proceedings overview

One AIA trial proceeding has been filed against US Patent 9,525,084, which is currently terminated. This gives a defendant some defensive information, as the proceeding indicates a challenge to the patent's validity, though the "Procedural Termination" suggests the merits of the challenge were not fully adjudicated in a Final Written Decision.

IPR2025-00997 — [[[Samsung Electronics Co.](/litigations/by-defendant/Samsung%20Electronics%20Co.), Ltd.](/litigations/by-plaintiff/Samsung%20Electronics%20Co.%2C%20Ltd.) et al.](/litigations/by-plaintiff/Samsung%20Electronics%20Co.%2C%20Ltd.%20et%20al.) v. W&wsens Devices Inc.

• Type: Inter Partes Review
• Filed: 2025-07-14
• Status: Terminated
• Judge panel: Not publicly available without accessing the full PTAB record.
• Petition grounds: Not publicly available without accessing the full PTAB record.
• Institution decision: Not publicly available, as the case was terminated.
• Final Written Decision (if issued): Not issued due to procedural termination.
• Settlement / termination: The proceeding was terminated on 2026-03-09. The reasons for procedural termination are not specified in the provided data. [cite: "IPR2025-00997 — IPR — filed 2025-07-14 — last modified 2026-03-09 — status: Terminated — petitioner: Samsung Electronics Co., Ltd. et al. — inventor: Shih-Yuan WANG et al"]
• Appeal: No Federal Circuit appeal on record due to procedural termination.
• Defensive value: While the petition itself indicates that Samsung Electronics Co., Ltd. et al. found grounds to challenge the patent, the procedural termination means there is no final determination on the validity of any claims. This leaves the claims untested by a full IPR proceeding.

Strategic summary

The patent US9525084 has one IPR proceeding, IPR2025-00997, which was filed by Samsung Electronics Co., Ltd. et al. and subsequently terminated. As a result, all claims of US9525084 remain UNTESTED by a final written decision from the PTAB. There are no claims that have been formally canceled or sustained through an IPR.

Regarding the estoppel landscape, § 315(e)(2) estoppel bars the petitioner (Samsung Electronics Co., Ltd. et al.) and their privies from raising any ground that was raised or reasonably could have been raised in IPR2025-00997. However, because the proceeding was procedurally terminated without an institution decision or final written decision, the scope of estoppel may be limited. For a new defendant being asserted against, this means that most prior-art grounds are likely still available for a new IPR petition, as the merits were not decided.

The IPR was filed by Samsung Electronics Co., Ltd. et al., and Unified Patents is also listed in connection with a related PTAB case (IPR2025-00997) in the litigation status, indicating that there may be a defensive aggregator involved in the broader patent family's litigation. [cite: "PTAB case IPR2025-00997 filed (Procedural Termination) Petitioner: "Unified Patents PTAB Data" by Unified Patents is licensed under a Creative Commons Attribution 4.0 International License."]

Recommended next steps

Since IPR2025-00997 was terminated, there is no Final Written Decision to link to that would invalidate any claims. If you are a defendant facing assertion of this patent, you should perform your own prior art search and consider filing a new IPR petition, as the claims have not been substantively reviewed by the PTAB.

Inventors

• Shih-Yuan Wang (W&wsens Devices Inc.)
• Shih-Ping Wang (W&wsens Devices Inc.)

Original assignee

The original assignee, W&wsens Devices Inc., is listed as "Current Assignee" and "Original Assignee" on Google Patents. There is no information provided within the patent text to determine if W&wsens Devices Inc. shipped a product embodying the claims. The patent does not explicitly state their primary line of business, though the nature of the patent (photosensitive devices) suggests it is in the field of semiconductor devices or optoelectronics. As of the latest information, W&wsens Devices Inc. appears to be an active entity as it was involved in a patent security agreement in 2024.

Assignment timeline

• 2016-09-19 (executed) / recorded 2016-09-19 — Reel 038676/0122
  • Conveyance: Assignment of Assignors Interest
  • Assignor: WANG, SHI-PING, WANG, SHI-YUAN
  • Assignee: W&WSENS DEVICES, INC.
  • Correspondent: BLAKELY, SOKOLOFF, TAYLOR & ZAFMAN LLP, 1279 OAKMEAD PARKWAY, SUNNYVALE, CALIFORNIA, 94085
  • Context: Transfer from individual inventors to their company.
• 2024-10-23 (executed) / recorded 2024-10-23 — Reel 066708/0748
  • Conveyance: Patent Security Agreement
  • Assignor: W&WSENS DEVICES, INC.
  • Assignee: IP LITFIN US 2024 LLC
  • Correspondent: Andrew D. Skale, Mintz, Levin, Cohn, Ferris, Glovsky and Popeo, P.C., 3580 Carmel Mountain Road, Suite 300, San Diego, CA 92130.
  • Context: Securitization of the patent.

Timeline diagram

timeline
    title Ownership of US 9525084
    2015 : Filed by W&wsens Devices Inc
    2016 : Inventors assign to W&wsens Devices Inc
         : Issued
    2024 : Security agreement to IP LITFIN US 2024 LLC

NPE / troll-pattern signals

1. Shell-entity transfer — present. The assignment from W&wsens Devices Inc. to IP LITFIN US 2024 LLC via a "Patent Security Agreement" on 2024-10-23 (Reel 066708/0748) is a strong indicator. "IP LITFIN" suggests a focus on intellectual property monetization rather than product development. Without further information on IP LITFIN US 2024 LLC, its name and the nature of the transaction (security agreement) align with characteristics of a shell entity likely involved in patent licensing or assertion.
2. Known asserter in the chain — unclear. IP LITFIN US 2024 LLC is not immediately recognizable from the provided list of common NPEs. However, the litigation status showing an IPR proceeding initiated by "Unified Patents PTAB Data" and a district court case in the Eastern District of Texas (a venue frequently used by NPEs) suggests the patent is currently being asserted or is subject to assertion.
3. Repeat correspondent across the chain — not present. The correspondent for the 2016 assignment was BLAKELY, SOKOLOFF, TAYLOR & ZAFMAN LLP, while for the 2024 security agreement it was Andrew D. Skale of Mintz, Levin, Cohn, Ferris, Glovsky and Popeo, P.C. These are different firms and individuals.
4. Cascading transfers — not present. There are only two recorded assignments, separated by eight years.
5. Pre-litigation transfer — unclear. A US case was filed in the Texas Eastern District Court (case 2:24-cv-00854), and the security agreement was recorded on 2024-10-23. The filing date of the Texas case is not precisely stated but its numbering "2:24-cv-00854" implies it was filed in 2024. If the case was filed within 6 months after October 23, 2024, it would indicate a pre-litigation transfer. More precise filing date for the litigation would be needed.
6. Bankruptcy fire-sale — not present. There is no indication in the patent record or Google Patents legal events that W&wsens Devices Inc. has filed for bankruptcy.
7. Privateering — unclear. There's no information available from SEC filings or other sources to suggest an operating company transferred the patent to an NPE for assertion against competitors.
8. Defensive aggregator (anti-NPE) — not present. The chain does not terminate at a known defensive aggregator.

Verdict

NPE — moderate confidence. The primary signal is the transfer to "IP LITFIN US 2024 LLC" via a patent security agreement on 2024-10-23 (Reel 066708/0748), which strongly suggests a shell entity focused on intellectual property monetization. This is further supported by the existence of a lawsuit in the Eastern District of Texas (case 2:24-cv-00854), a common venue for patent assertion entities. [cite: "US case filed in Texas Eastern District Court", "https://assignmentcenter.uspto.gov/"]

To identify the most relevant prior art for US Patent 9,525,084, I will review the "Prior art documents" section listed on its Google Patents page. A notable observation is that a substantial number of these cited prior art documents share the exact same title as US9525084: "Microstructure enhanced absorption photosensitive devices." This strongly suggests they are part of a patent family or represent closely related inventions by the same inventors/assignee. These will naturally be the most relevant.

Due to the extensive list of cited documents with identical titles, I will focus on a few key examples from this group, particularly those with earlier filing or publication dates than US9525084's priority date of November 18, 2014. Additionally, I will examine a relevant prior art document with a different title that appears to address core aspects of the invention.

The selected prior art documents for detailed analysis are:

1. US8502693B2: This patent shares the exact title and has an earlier publication date.
2. US20130099279A1: This is an earlier published application with the same title.
3. US7442978B2: This patent has a different title but addresses high-speed photodiodes on silicon, which is a core technical area of US9525084.

Most Relevant Prior Art for US9525084:

1. US8502693B2 - Microstructure enhanced absorption photosensitive devices

• Full Citation: US8502693B2, "Microstructure enhanced absorption photosensitive devices," issued to W&wsens Devices Inc., on August 6, 2013. Inventors: Shih-Yuan Wang, Shih-Ping Wang.
• Publication/Filing Date: Published: August 6, 2013. Filed: March 29, 2012.
• Brief Description: This patent describes photosensitive devices, such as photodiodes (PDs) and avalanche photodiodes (APDs), that incorporate microstructures to enhance photon absorption. It discloses that for silicon PDs and APDs, this design can achieve bandwidths exceeding 10 Gb/s at 850 nm wavelengths with quantum efficiencies of 50% or more. The devices' thinness makes them compatible with CMOS, BiCMOS, and other electronics on a single silicon chip, aiming to reduce packaging costs, capacitance, and improve operating speed. The microstructures can be holes, pillars, or a combination, with dimensions in the micrometer or sub-micrometer scale to enhance effective absorption coefficient and/or length. The devices can be silicon or germanium-based.
• Potential Anticipation (35 U.S.C. § 102): Given the identical title, inventors, and assignee, along with a substantially similar abstract, this patent appears to anticipate many aspects of US9525084, particularly the fundamental concept of using microstructures (holes) to enhance absorption in photosensitive devices like PDs and APDs, achieving high bandwidth and quantum efficiency, and enabling integration with CMOS electronics on a single chip. Specific features such as the range of absorption percentages (e.g., in excess of 40% at specified wavelengths) and the general idea of arrays of holes described in independent claims 1, 13, 25, 35, and 39 of US9525084 could be broadly anticipated by US8502693B2. This would likely be considered a foundational patent within the same patent family, potentially serving as prior art for common subject matter.

2. US20130099279A1 - Microstructure enhanced absorption photosensitive devices

• Full Citation: US20130099279A1, "Microstructure enhanced absorption photosensitive devices," published by W&wsens Devices Inc., on April 25, 2013. Inventors: Shih-Yuan Wang, Shih-Ping Wang.
• Publication/Filing Date: Published: April 25, 2013. Filed: October 22, 2012.
• Brief Description: This publication describes photosensitive devices with microstructure-enhanced absorption characteristics, including photodiodes (PDs) and avalanche photodiodes (APDs). The abstract highlights the use of microstructures, such as holes, to increase photon absorption, enabling high bandwidths (e.g., >10 Gb/s) and quantum efficiencies (e.g., >50%) for silicon devices at wavelengths like 850 nm. It emphasizes the thinness of these devices, facilitating integration with CMOS, BiCMOS, or bipolar devices on a single silicon chip, leading to reduced packaging costs, decreased capacitance, and improved operating speeds. The absorption region can be silicon or germanium-based.
• Potential Anticipation (35 U.S.C. § 102): As an earlier published application with the same title, inventors, and assignee, and an abstract nearly identical to US8502693B2 and US9525084, this document likely anticipates a wide range of claims in US9525084. Specifically, the core inventive concept of using microstructures to enhance absorption in high-speed, high-efficiency photodetectors and their integration with electronics on a single chip (as described in independent claims 1, 13, 25, 35, and 39) would be strongly anticipated. This appears to be a direct earlier publication of the same subject matter.

3. US7442978B2 - High speed and high quantum efficiency photodiode on silicon substrate

• Full Citation: US7442978B2, "High speed and high quantum efficiency photodiode on silicon substrate," issued to W&wsens Devices Inc., on October 28, 2008. Inventor: Shih-Yuan Wang.
• Publication/Filing Date: Published: October 28, 2008. Filed: May 23, 2007.
• Brief Description: This patent describes a high-speed and high quantum efficiency photodiode (PD) suitable for integration on a silicon substrate. The device achieves high efficiency and speed for wavelengths ranging from 700 nm to 1000 nm, and particularly for longer wavelengths (800 nm to 900 nm or 850 nm) that are difficult for conventional silicon detectors. It discloses a vertical p-i-n structure with a relatively thin intrinsic absorption region (e.g., 2-5 microns) to reduce transit time and an undoped or lightly doped silicon buffer layer. The patent highlights the use of reflective coatings to increase the optical path length within the absorption region, thereby enhancing quantum efficiency without significantly increasing the absorption layer thickness. While not explicitly mentioning "microstructures" in the same way as US9525084, it focuses on optimizing absorption in a thin silicon intrinsic region for high performance.
• Potential Anticipation (35 U.S.C. § 102): This patent, by the same inventor and assignee, precedes the filing of US9525084 by several years and addresses the challenge of achieving high speed and high quantum efficiency in silicon photodiodes, especially at wavelengths where silicon's absorption is weak. While it does not explicitly claim "holes" or "pillars" as "microstructures" for absorption enhancement, its discussion of using a thin absorption region combined with techniques like reflective coatings to increase optical path length (analogous to enhancing effective absorption length) could potentially anticipate the problem solved by US9525084 and some of the broader aspects of high-speed silicon photodetectors with enhanced absorption. Specifically, elements of independent claim 13 (a photon absorbing region configured to absorb over 40% of incident signal at 800-900nm) and claim 39 (an optical/electronic system with a high-speed photodetector on a silicon substrate) could find some foundational anticipation here, particularly regarding the performance targets and the use of silicon for the photodetector and integration. However, the specific microstructure feature of a plurality of holes as the primary means for absorption enhancement, as claimed in US9525084, might distinguish US9525084 from US7442978B2. [cite: "US7442978B2"]

To analyze the obviousness of US patent 9,525,084 under 35 U.S.C. § 103, we will identify combinations of prior art references that would render the claims obvious and explain the motivation for a person having ordinary skill in the art (POSITA) to combine them. Given that the provided patent text does not include a "References Cited" section with specific prior art patent or publication numbers, we will rely on the descriptions of "known" and "conventional" technologies presented within the patent itself as representative of the prior art.

Identified Prior Art References:

1. Prior Art A1 (Conventional Silicon Photodetector): A conventional silicon photodiode (PD) for 850 nm wavelength operation, with a data rate of 1.25 Gb/s, an epitaxial layer greater than 10 micrometers (µm) thickness, and a 53% quantum efficiency. This type of device is characterized by an absorption region whose thickness is too large for high bandwidth and is not easily compatible with CMOS processing. [cite: "a conventional silicon photodiode at 850 nm with a data rate of 1.25 Gb/s has an epitaxial layer greater than 10 ⁇ m thickness and a 53% quantum efficiency.", "However, in order to obtain adequate quantum efficiency, the thickness of the silicon “I” region becomes so large that the device's maximum bandwidth is too low for many current and future telecom and data center applications.", "the relatively thick layers of conventional silicon photodiodes are not easily compatible with CMOS processing."]
2. Prior Art A2 (Conventional Germanium Photodetector): A conventional germanium (Ge) photodetector, known to detect infrared out to a wavelength of 1700 nm, but with relatively high multiplication noise. [cite: "Germanium (Ge) detects infrared out to a wavelength of 1700 nm, but has relatively high multiplication noise."]
3. Prior Art B (General Knowledge of Microstructures for Absorption Enhancement): It is generally known that microstructures (e.g., pillars, voids, holes) are used to improve the bulk absorption constant or absorption of a material at wavelengths near the semiconductor material's band gap. This enhancement can be attributed to various optical effects such as resonance, coupled resonances, field enhancement, scattering, and sub-wavelength effects. [cite: "microstructures are used to improve bulk absorption constant or absorption of the material at wavelengths in the proximity of the semiconductor material's band gap. This allows for extending the operating optical wavelengths and/or operating spectrum of the photosensor.", "the microstructures can have effects such as resonance, coupled resonances, field enhancement, near field and sub wavelength effects, scattering, plasmonics, linear and non linear optical field, photonic crystal, absorption mode or lossy mode in high contrast grating at the near field regime, which are both linear and non linear effects that can effectively increase the effective absorption length resulting in a greater absorption of the photons for a given physical length and or the absorption coefficient can be enhanced to an effective coefficient."]
4. Prior Art C (Desire for Monolithic Integration): The art recognizes the desirability of monolithically integrating photodetectors with electronic circuits (e.g., CMOS ASICs) on a single silicon chip to reduce packaging costs, increase data transmission bandwidth, and reduce electrical power usage. However, this was challenging for conventional photodetectors due to their thick absorption layers being incompatible with standard CMOS processes. [cite: "photodiodes on Si based material as described in this patent specification, can be monolithically integrated with integrated electronic circuits on a single Si chip, thereby significantly reducing the cost of packaging.", "a top or bottom illuminated Si and Ge on Si PD/APD that can be integrated with Si is not known to be commercially available at data rates of 5 Gb/s or more at wavelengths of 850 nm and 1550 nm.", "the relatively thick layers of conventional silicon photodiodes are not easily compatible with CMOS processing."]

Obviousness Analysis of Independent Claims:

1. Independent Claim 25: Silicon Photodetector with Microstructure-Enhanced Absorption

• Claim Summary: A photodetector with a silicon photon absorbing region including a plurality of holes, each having a cross-section parallel to the upper substrate surface with a maximum dimension between 400 nm and 2500 nm, and each hole's center spaced apart by less than 3500 nm from a nearest adjacent hole's center.
• Combination of Prior Art References: Prior Art A1 (Conventional Silicon Photodetector) + Prior Art B (General Knowledge of Microstructures for Absorption Enhancement).
• Motivation to Combine: A POSITA would recognize that the conventional silicon photodiode (Prior Art A1) at 850 nm, while functional, suffers from limited bandwidth due to its thick (>10 µm) absorption layer. To achieve higher data rates (e.g., >5 Gb/s for current and future applications), a thinner absorption region is necessary to reduce carrier transit time. However, simply reducing the thickness of a conventional silicon absorption layer would drastically decrease its quantum efficiency. A POSITA, aware of the general knowledge that microstructures can enhance light absorption (Prior Art B), would be motivated to introduce such microstructures (e.g., holes) into the silicon absorption region of the conventional photodetector. This would enable a reduction in the physical thickness of the silicon layer while maintaining or improving the quantum efficiency, thereby overcoming the trade-off between bandwidth and absorption. [cite: "However, in order to obtain adequate quantum efficiency, the thickness of the silicon “I” region becomes so large that the device's maximum bandwidth is too low for many current and future telecom and data center applications.", "microstructures are used to improve bulk absorption constant or absorption of the material at wavelengths in the proximity of the semiconductor material's band gap. This allows for extending the operating optical wavelengths and/or operating spectrum of the photosensor."]
• Reasonable Expectation of Success: The application of known optical effects (resonance, scattering, slow-wave, etc.) associated with microstructures (as explained in Prior Art B) to a semiconductor material like silicon is a recognized approach in photonics. Optimizing the specific dimensions (hole diameter and spacing) as claimed (400-2500 nm maximum dimension, <3500 nm spacing) would be considered a matter of routine design and optimization for a POSITA, utilizing established simulation techniques (like FDTD, which the patent frequently references) to achieve desired absorption characteristics at specific wavelengths (e.g., 850 nm). The patent itself demonstrates through numerous simulations and examples that such microstructure designs achieve significant absorption enhancement.

2. Independent Claim 35: Germanium-Based Photodetector with Microstructure-Enhanced Absorption

• Claim Summary: A photodetector with a germanium-based photon absorbing region including a plurality of holes, each having a cross-section parallel to the upper substrate surface with a maximum dimension between 750 nm and 3000 nm, and each hole's center spaced apart by less than 5000 nm from a nearest adjacent hole's center.
• Combination of Prior Art References: Prior Art A2 (Conventional Germanium Photodetector) + Prior Art B (General Knowledge of Microstructures for Absorption Enhancement).
• Motivation to Combine: A POSITA would know that conventional germanium detectors (Prior Art A2) can detect infrared light out to 1700 nm but are associated with relatively high multiplication noise. Similar to silicon, enhancing absorption in a thinner germanium layer could lead to improved bandwidth and potentially better noise performance due to shorter transit times. Thus, a POSITA, motivated to improve the performance of germanium photodetectors, would apply the known principle of using microstructures to enhance absorption (Prior Art B) to the germanium-based absorbing region. This would allow for a thinner Ge layer, enabling higher speed operation and potentially mitigating some noise issues associated with thicker devices, particularly at wavelengths greater than 1200 nm or 1400 nm. [cite: "Germanium (Ge) detects infrared out to a wavelength of 1700 nm, but has relatively high multiplication noise.", "microstructures are used to improve bulk absorption constant or absorption of the material at wavelengths in the proximity of the semiconductor material's band gap. This allows for extending the operating optical wavelengths and/or operating spectrum of the photosensor."]
• Reasonable Expectation of Success: The principles of light-matter interaction and absorption enhancement through microstructures (Prior Art B) are universally applicable across different semiconductor materials. A POSITA would routinely apply these principles to germanium-based materials, adjusting the specific dimensions (hole diameter 750-3000 nm, spacing <5000 nm) to optimize performance for the target longer wavelengths, using standard simulation and fabrication techniques available in the art. The patent presents extensive examples and simulation results for Ge on Si microstructured photodetectors, confirming the feasibility of such structures. [cite: "FIGS. 82A-82C relate to a simulation using finite difference time domain (FDTD) on a Ge on Si microstructured photodiode similar to the structure depicted in FIG. 79", "FIGS. 83A-83C relate to a simulation using finite difference time domain (FDTD) on a Ge on Si microstructured photodiode similar to the structure in FIG. 80"]

3. Independent Claim 1 (Integrated Detector/Processor Circuit) and Independent Claim 39 (Optical/Electronic System)

• Claim Summary: These claims describe a single semiconductor chip integrating a microstructure-enhanced photodetector with an electronic processor/active electronic circuit. A key feature is that the photon absorbing region of the photodetector and the electronic processor have thicknesses of the same order of magnitude. Claim 39 further specifies a laser modulated at Gb/s rates and an optical fiber for signal transport.

• Combination of Prior Art References: Prior Art A1 (Conventional Silicon Photodetector) + Prior Art B (General Knowledge of Microstructures for Absorption Enhancement) + Prior Art C (Desire for Monolithic Integration).

• Motivation to Combine: A POSITA is strongly motivated to monolithically integrate photodetectors with electronic processing circuits (e.g., CMOS, BiCMOS, bipolar devices) on a single silicon chip (Prior Art C) to reduce packaging costs and improve overall system performance, particularly for high-speed data communication. However, a significant barrier to this integration is that conventional silicon photodetectors (Prior Art A1) require thick (>10 µm) absorption layers for adequate quantum efficiency, making them "not easily compatible with CMOS processing," which typically utilizes much thinner active layers. [cite: "photodiodes on Si based material as described in this patent specification, can be monolithically integrated with integrated electronic circuits on a single Si chip, thereby significantly reducing the cost of packaging.", "the relatively thick layers of conventional silicon photodiodes are not easily compatible with CMOS processing."]

  To overcome this incompatibility, a POSITA would turn to the known principle of using microstructures to enhance absorption (Prior Art B). By incorporating microstructures (e.g., holes) into the photodetector's absorbing region, its effective absorption coefficient can be significantly increased, allowing for a drastic reduction in the physical thickness of the absorbing layer (e.g., to 0.5-5 µm, as claimed in Claim 13). This reduction in thickness makes the photodetector's absorbing region compatible with the typical thicknesses of electronic circuits like CMOS, bringing their respective thicknesses to "the same order of magnitude" as required by the claims. This compatibility directly enables the desired monolithic integration on a single silicon substrate, thereby achieving the goals of reduced cost and enhanced data transmission capabilities. The patent explicitly states that "the MS-PD/APD epitaxial layer thickness is compatible with the epitaxial layer thickness and structure of CMOS (Complementary metal-oxide-semiconductor) processes and therefore can be integrated with a CMOS ASIC." [cite: "the MS-PD/APD epitaxial layer thickness is compatible with the epitaxial layer thickness and structure of CMOS (Complementary metal-oxide-semiconductor) processes and therefore can be integrated with a CMOS ASIC."]

• Reasonable Expectation of Success: Given the clear motivation for monolithic integration and the known mechanism of absorption enhancement via microstructures, a POSITA would have a reasonable expectation of success in combining these elements. The technical challenge would lie in optimizing the microstructure design and fabrication processes to achieve both high quantum efficiency at reduced thickness and compatibility with existing electronic circuit fabrication processes. However, such optimization is well within the capabilities of a POSITA in semiconductor device engineering, supported by simulation tools and extensive knowledge of material science and optical physics. The patent details how this integration can be achieved (e.g., FIGS. 44-52 illustrating integration with TIAs and ASICs).

In summary, the independent claims of US9525084 would likely be considered obvious to a person having ordinary skill in the art when combining conventional photodetector designs with the known principles of microstructure-enhanced absorption, driven by a clear motivation to improve bandwidth, reduce packaging costs, and enable monolithic integration with electronic circuits. The specific dimensions and performance metrics claimed would be considered parameters optimized through routine experimentation and simulation.

Patent Term Adjustments (PTA) and Patent Term Extensions (PTE)

Patent Term Adjustment (PTA)

US Patent 9,525,084 is subject to a terminal disclaimer and has an adjustment of 0 days. Patent Term Adjustment (PTA) can add time to a patent's term to compensate for certain administrative delays by the USPTO during patent prosecution. These delays generally fall into categories such as:

• "A delay": Failure of the USPTO to issue an office action within 14 months of filing, respond to an applicant's reply within 4 months, or issue a patent within 4 months of the issue fee payment.
• "B delay": The application pending for more than three years.
• "C delay": Delays due to interferences, secrecy orders, or successful appellate review.

Applicant delays can reduce the PTA.

Patent Term Extension (PTE)

Patent Term Extensions (PTEs) are available under 35 U.S.C. § 156 for patents claiming products that require regulatory approval, such as human drugs, medical devices, food additives, animal drugs, and veterinary biological products, to restore time lost during the premarket government approval process. There is no information to suggest that US 9,525,084 is related to a product requiring regulatory approval for a PTE.

Continuation and Divisional Applications

US Patent 9,525,084 (application Ser. No. 14/945,003) is referenced as a parent application for other patents in its family. For example, U.S. patent application Ser. No. 15/309,922 (now U.S. Pat. No. 9,818,893) is a continuation of U.S. patent application Ser. No. 14/945,003 (now U.S. Pat. No. 9,525,084).

The patent itself claims benefit from numerous provisional applications, starting with U.S. Prov. Ser. No. 62/081,538, filed on November 18, 2014, and including several others filed throughout 2015. It also relates to International Patent Appl. No. PCT/US14/39208, filed May 22, 2014, and several earlier U.S. Provisional applications dating back to May 22, 2013.

Related Family Members

The patent explicitly identifies other family members, including those with continuation-in-part or continuation relationships. Some of these include:

• U.S. Pat. No. 9,530,905 (from U.S. patent application Ser. No. 14/943,898)
• U.S. Pat. No. 9,818,893 (from U.S. patent application Ser. No. 15/309,922)
• U.S. Patent No. 10,468,543
• U.S. Patent No. 10,446,700
• U.S. Patent No. 11,621,360

These related patents share common subject matter, as indicated by references in PTAB proceedings.

Projected Expiration Date

The anticipated expiration date for US Patent 9,525,084 is November 18, 2035. This date is typically calculated as 20 years from the earliest filing date (priority date) of the non-provisional application, plus any Patent Term Adjustments (PTA) or extensions (PTE), and considering any terminal disclaimers. Given that the patent notes a 0-day adjustment and is subject to a terminal disclaimer, the expiration date is directly tied to the earliest effective filing date, which is November 18, 2015.