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Silicon Based Mid-Infrared SiGeSn Heterostructure Emitters and Detectors

(a) A cross-sectional schematic of the GeSn p-i-n photodiode. (b) Dark I-V characteristics of the three samples. (c) Spectral response of the samples measured at zero bias. (d) Calculated responsivity of the samples.

Enhancing the performance of GeSn p-i-n photodiodes using gold metal nanostructures.

The goal of this research project was to advance the science and technology of silicon-based photonic devices using SiGeSn heterostructures. Such devices work in mid-IR spectral range and form the foundation for mid-IR photonics that enable on-chip systems for applications ranging from vibrational spectroscopy, chem/bio sensing, medical/health uses, to environmental monitoring. This project was mostly directed toward improving GeSn detectors with the use of surface plasmons induced by carefully designed metal nanostructures. The goal was to replace the current mid-IR detectors that are usually photodiodes made from narrow bandgap III-V or II-VI semiconductor compounds such as InGaAs, InSb, HgCdTe (MCT) or type-II In-GaAs/InGaSb superlattice. These photodiodes are incompatible with the CMOS process and cannot be easily integrated with Si electronics. The GeSn mid-IR detectors developed in this project are fully compatible with the CMOS process.

Beginning with GeSn-based p-i-n photodiodes with an active GeSn layer that is almost fully strained, the strategy is to use the surface plasmon effect to enhance the optical field in the GeSn active region, which leads to increased absorption of incident photons and creates electron-hole pairs that contribute to the electric current that can be detected. Specifically, the use of a gold metal film perforated with a two-dimensional subwavelength hole array as the plasmonic structure to be deposited on top of the GeSn p-i-n photodetector was considered. Such structures are capable of producing enhanced optical fields under the illumination of some wavelengths residing in its surface plasmon resonance range. They have been used to improve the performance of quantum dot infrared photodetectors (QDIPs). Increased photocurrent and detection wavelength selection have been demonstrated.

The device structure of the GeSn p-i-n photodetector used for this research is shown in Figure (a). There are a set of three samples, all p-i-n photodiodes that were previously produced. Their measured dark I-V characteristics, and measured and simulated spectral response, are shown in Figures (b) through (d).

This work was done by Greg Sun of the University of Massachusetts for the Air Force Research Laboratory. AFRL-0249

Topics:
Electronics & Computers Environmental testing Metals Optics Research and development Semiconductors Semiconductors & ICs Sensors and actuators Spectroscopy Sun and solar
This Brief includes a Technical Support Package (TSP).
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Silicon Based Mid-Infrared SiGeSn Heterostructure Emitters and Detectors

(reference AFRL-0249) is currently available for download from the TSP library.

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    Aerospace & Defense Technology Magazine

    This article first appeared in the February, 2017 issue of Aerospace & Defense Technology Magazine (Vol. 2 No. 1).

    Read more articles from this issue here.

    Read more articles from the archives here.

    Overview

    The document is a final report on a research project titled "Silicon based mid infrared SiGeSn heterostructure emitters and detectors," authored by Greg Sun from the University of Massachusetts. The project, funded by the Air Force Office of Scientific Research (AFOSR), spanned from June 17, 2014, to December 15, 2015, and aimed to advance the science and technology of silicon-based photonic devices utilizing SiGeSn heterostructures.

    The primary focus of the research was on developing mid-infrared photonic devices that operate around the 2.0-micron wavelength range. These devices are crucial for applications in vibrational spectroscopy, chemical and biological sensing, medical diagnostics, and environmental monitoring. The report highlights the collaboration between the University of Massachusetts and National Taiwan University (NTU), which led to significant advancements, including the demonstration of GeSn light-emitting diodes (LEDs) with a direct bandgap and studies on the strain dependence of GeSn Raman shifts.

    A key aspect of the project was the exploration of plasmon-enhanced GeSn photodetectors. The research involved various methodologies, including invention, numerical modeling, simulation, device design, fabrication, and characterization. The findings indicated that integrating metal nanostructures, specifically gold nanoparticles, could significantly enhance the detectivity of GeSn photodetectors. This enhancement is achieved through surface plasmon resonance, which improves optical absorption and overall device performance.

    The report details the experimental implementation of the device design, demonstrating the feasibility of using metal nanostructures in focal plane arrays, where each detector pixel operates under back illumination. The metal nanostructures serve as contacts to the readout circuits, optimizing the detector's efficiency.

    In addition to the primary research objectives, the project fostered collaborations with other scientists in Taiwan and the U.S., leading to further advancements in related fields. The report concludes that the research contributes valuable insights into group IV photonics for mid-infrared applications, laying the groundwork for future developments in silicon-based photonic technologies.

    Overall, this report encapsulates significant progress in the field of mid-infrared photonics, emphasizing the potential of SiGeSn heterostructures and plasmonic enhancements in advancing photonic device capabilities.

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