Prior art

The following prior art references are considered most relevant to US patent 12087871, based on their explicit mention and discussion within the patent text, or their early publication dates and relevance from the patent's own citations.

Non-Patent Literature References (Explicitly discussed in US12087871)

1. Garnett et al., "Light trapping in silicon nanowire solar cells," Nano Letters, 2010, 10, 1082-1087.

   • Full Citation: Garnett, E. C., & Yang, P. (2010). Light trapping in silicon nanowire solar cells. Nano Letters, 10(3), 1082-1087.
   • Publication/Filing Date: Published in 2010.
   • Brief Description: This paper presents experimental demonstrations of silicon nanowire arrays significantly increasing the optical path length of incident radiation, thereby enhancing light trapping in photovoltaic (solar cell) applications. The patent US12087871 notes this work demonstrated a 73-fold increase in optical path length compared to bulk silicon.
   • Potential Anticipation (35 U.S.C. § 102): This reference directly anticipates key aspects related to microstructure-enhanced absorption, especially in solar cells.
     • Claim 1: Potentially anticipates the concept of a "microstructure-enhanced photon absorbing semiconductor region configured to absorb photons from a source signal, wherein the absorbing region comprises a plurality of microstructures that are dimensioned and positioned to increase absorption." Nanowires are a type of microstructure used for this purpose.
     • Claim 2: Anticipates "microstructures are pillars" (nanowires can be considered pillars).
     • Claim 8: Anticipates the use of "silicon" for the absorbing region and microstructures.
     • Claim 25: Strongly anticipates this claim, which describes a "photovoltaic device comprising a semiconductor material having a plurality of voids buried therein... wherein the voids are microstructured voids and are configured to enhance absorption... thereby increasing conversion efficiency." Nanowires achieve similar light-trapping effects for enhanced absorption in PVs.

2. Kelzenberg et al., "Enhanced absorption and carrier collection in Si wire arrays for photovoltaic applications," Nature Materials, vol. 9, March 2010, 239-244.

   • Full Citation: Kelzenberg, M. D., Boettcher, S. W., Petykiewicz, J. A., Spurgeon, D. B., Trinh, K., Soriaga, B. S., ... & Atwater, H. A. (2010). Enhanced absorption and carrier collection in Si wire arrays for photovoltaic applications. Nature Materials, 9(3), 239-244.
   • Publication/Filing Date: Published in March 2010.
   • Brief Description: This publication details the use of silicon wire arrays to achieve enhanced absorption and efficient carrier collection, specifically for photovoltaic applications. It focuses on improving solar cell performance through these microstructures.
   • Potential Anticipation (35 U.S.C. § 102): Similar to Garnett et al., this reference describes the use of silicon microstructures for absorption enhancement in solar energy conversion.
     • Claim 1: Potentially anticipates the general concept of a "microstructure-enhanced photon absorbing semiconductor region" for increased absorption, specifically using "Si wire arrays."
     • Claim 25: Strongly anticipates this claim by demonstrating photovoltaic devices with silicon wire arrays configured for enhanced absorption and improved conversion efficiency.
     • Claim 8: Anticipates the use of "silicon" as the material for the absorbing region and microstructures.

3. Li et al., "Optical absorption enhancement in silicon nanowire and nanohole arrays for photovoltaic applications," Proceeding of SPIE, Vol. 7772, 77721G-1, 2010.

   • Full Citation: Li, X., Cai, B., Lin, P. N., Huang, P. T., Lo, W. C., & Tsakalakos, L. (2010, August). Optical absorption enhancement in silicon nanowire and nanohole arrays for photovoltaic applications. In Next Generation (Nano) Photonic and Cell Technologies for Solar Energy Conversion (Vol. 7772, pp. 77721G-1). International Society for Optics and Photonics.
   • Publication/Filing Date: Published in 2010.
   • Brief Description: This work investigates optical absorption enhancement in both silicon nanowire and nanohole arrays for photovoltaic applications, explicitly mentioning nanoholes as effective light traps.
   • Potential Anticipation (35 U.S.C. § 102): This reference directly addresses various microstructures for absorption enhancement in PVs.
     • Claim 1: Potentially anticipates the concept of "microstructure-enhanced photon absorbing semiconductor region" using nanowires and nanoholes.
     • Claim 2: Strongly anticipates this claim by explicitly disclosing "nanowire and nanohole arrays," where nanowires can be considered pillars and nanoholes are a form of holes/voids.
     • Claim 8: Anticipates the use of "silicon" for the absorbing region and microstructures.
     • Claim 25: Strongly anticipates this claim by presenting photovoltaic devices utilizing silicon nanowire and nanohole arrays for enhanced absorption and improved conversion efficiency.

4. Kang et al., "Epitaxially-grown Ge/Si avalanche photodiodes for 1.3 μm light detection," 23 Jun. 2008/Vol. 16, No. 13/OPTICS EXPRESS 9365.

   • Full Citation: Kang, Y., Liu, H., Morse, M., Rubino, A. Z., Georgas, D., Kuo, B., ... & Agarwal, A. (2008). Epitaxially-grown Ge/Si avalanche photodiodes for 1.3 μm light detection. Optics Express, 16(13), 9365-9371.
   • Publication/Filing Date: Published on June 23, 2008.
   • Brief Description: This paper describes the fabrication and performance of epitaxially-grown Germanium-on-Silicon (Ge/Si) avalanche photodiodes (APDs) for detecting light at 1.3 μm wavelength. While it addresses Ge/Si APDs, the patent US12087871 contrasts its performance (e.g., 56% Quantum Efficiency at 1 μm Ge absorption length) with the improvements offered by microstructures.
   • Potential Anticipation (35 U.S.C. § 102): This reference provides foundational prior art for Ge/Si APDs, a core component of some embodiments of US12087871, but likely lacks the specific "microstructure-enhanced absorption" feature.
     • Claim 1 (Preamble): Anticipates a "photodetector comprising: a cathode region; an anode region; reverse biasing circuitry configured to apply a voltage between the cathode and anode regions."
     • Claim 15: Partially anticipates the material combination of "silicon and germanium" for the absorbing region in an APD context.
     • Claim 17: Partially anticipates the use of "germanium" as an absorbing semiconductor material.
     • Claim 22: Anticipates an "avalanche photodiode configured to detect source signals at a data bandwidth... at source signal wavelengths of 1750 nanometers or shorter, and having a gain of greater than 2." This reference provides a baseline for such devices.

Patent Literature References (Cited by US12087871)

The "Cited patents" section of US12087871 lists 197 patents. A significant number of these, especially the earliest ones, are invented by Shih-Yuan Wang, the same inventor as US12087871, indicating these are likely related patents within a family or broader portfolio. For relevance, we focus on a few of the earliest by the inventor as they represent foundational work in this domain leading up to US12087871.

1. US8618464B2 - Photosensitive devices having microstructure enhanced absorption and related methods

   • Full Citation: US8618464B2, "Photosensitive devices having microstructure enhanced absorption and related methods," invented by Wang, Shih-Yuan.
   • Publication/Filing Date: Filed on November 10, 2011; Granted on December 31, 2013.
   • Brief Description: This patent describes photosensitive devices, such as photodiodes or avalanche photodiodes, that incorporate a microstructure-enhanced photon absorbing semiconductor region. The microstructures (e.g., pillars, holes, voids) are dimensioned to increase photon absorption at specific wavelengths, often having at least one dimension equal to or shorter than the longest signal wavelength. The patent also covers methods of manufacturing these devices.
   • Potential Anticipation (35 U.S.C. § 102): This patent is highly relevant and appears to be a direct predecessor or part of the same inventive family as US12087871, sharing many core concepts.
     • Claim 1: Directly anticipates almost all elements of Claim 1, including the "photodetector comprising... a microstructure-enhanced photon absorbing semiconductor region configured to absorb photons... wherein the absorbing region comprises a plurality of microstructures that are dimensioned and positioned to increase absorption... and wherein the microstructures have at least one dimension that is equal to or shorter than a longest signal wavelength."
     • Claim 2: Anticipates "microstructures are pillars, holes, and/or voids."
     • Claim 3: Anticipates various arrangements of microstructures (periodically-spaced array, non-periodically-spaced array, randomly-spaced array or a multiperiodically-spaced array).
     • Claim 7: Anticipates the mechanism of increased absorption "at least in part by forming an absorbing mode high contrast grating that makes use of resonance effects, scattering effects, near field effects, sub-wavelength effects, and/or interference effects."
     • This patent broadly anticipates much of the foundational microstructure enhancement technology described in US12087871, particularly for photodetectors.

2. US8288761B2 - Silicon avalanche photodiode based on silicon on insulator material for telecommunication applications

   • Full Citation: US8288761B2, "Silicon avalanche photodiode based on silicon on insulator material for telecommunication applications," invented by Wang, Shih-Yuan.
   • Publication/Filing Date: Filed on November 10, 2011; Granted on October 16, 2012.
   • Brief Description: This patent details a silicon avalanche photodiode (APD) built on silicon-on-insulator (SOI) material. It aims to achieve high-speed operation (e.g., >10 Gb/s) and high quantum efficiency for telecommunication wavelengths (e.g., 850 nm) by utilizing a thin silicon absorption layer and an integrated multiplication layer, possibly with resonant optical structures to enhance absorption.
   • Potential Anticipation (35 U.S.C. § 102): While not explicitly mentioning "microstructures" in the same breadth as US12087871, it focuses on high-speed silicon APDs on SOI for enhanced performance, a context highly relevant to US12087871's goals.
     • Claim 1 (Preamble): Anticipates a "photodetector" configured as an APD with cathode, anode, and reverse biasing.
     • Claim 8: Anticipates "absorbing region and the microstructures are formed of silicon" by teaching silicon APDs.
     • Claim 10 & 11: Potentially anticipates the performance characteristics, such as "silicon photodiode configured to detect source signals at a data bandwidth of greater than 10 gigabits per second, at signal wavelengths of 850 nanometers with a quantum efficiency of at least 60%" (Claim 10) and "silicon avalanche photodiode configured to detect source signals at a data bandwidth of greater than 5 gigabits per second, at wavelengths of 850 nanometers, while having a gain of greater than 2" (Claim 11), by aiming for these performances in silicon APDs. It mentions resonant structures, which could imply an early form of microstructure.

3. US8575619B2 - Optical waveguides with buried voids and related methods of fabrication

   • Full Citation: US8575619B2, "Optical waveguides with buried voids and related methods of fabrication," invented by Wang, Shih-Yuan.
   • Publication/Filing Date: Filed on July 10, 2012; Granted on November 5, 2013.
   • Brief Description: This patent describes optical waveguide structures that include buried voids. These voids are used to modify the effective refractive index of the waveguide's supporting material, enabling improved light confinement and guidance. The patent also covers methods for fabricating such structures.
   • Potential Anticipation (35 U.S.C. § 102): This patent directly anticipates the use of buried voids for optical manipulation, which is a specific microstructure concept in US12087871.
     • Claim 24: Anticipates "microstructures include voids buried within the absorbing semiconductor region," although this patent focuses on waveguides rather than general photodetector absorption enhancement.
     • Claim 33: Directly anticipates this claim, which describes an "optical waveguide structure comprising: an optical mode region; and a supporting semiconductor material adjacent to the optical mode region, wherein the supporting material includes a plurality of microstructured voids that are configured to alter an effective index of refraction of the supporting material based on the size, shape, density, etc. of the microstructured voids."

These selected prior art references highlight the evolutionary development of microstructure-enhanced devices, particularly from the same inventor, addressing both the general concept of enhanced absorption via microstructures and specific applications in photodiodes, APDs, PVs, and optical waveguides.