Prior art

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"]