Real-Time Monitoring and Control of HgCdTe MBE Using an Integrated Multi-Sensor System PDF Download
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Languages : en
Pages : 13
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We present recent progress on the use of an integrated real-time sensing and control system for monitoring and controlling substrate temperature, layer composition, and effusion cell flux during MBE growth of HgCdTe epilayers for advanced IR detectors. Substrate temperature is measured and controlled in real-time using absorption-edge spectroscopy (ABES). This allows the substrate temperature to be maintained at +/-1.5 deg C from the desired setpoint, even during actuation of effusion cell shutters which under conventional thermocouple-based control would produce a substantial (10-15 deg C) temperature change. In situ spectroscopic ellipsometry (SE) is used for monitoring HgCdTe layer composition in real-time. We describe the development of a comprehensive temperature- and composition-dependent SE dielectric function database which can be used for accurate and precise monitoring of Hg(1-x)Cd(x)Te layer composition over a wide range of x-values, from 0.2 to 0.42. The composition changes inferred from the real-time SE measurements obtained during growth of a two-layer structure are in excellent agreement with actual composition vs. depth profiles obtained using post-growth SIMS analysis. Likewise, the accuracy and precision of SE measurements conducted over multiple growth runs are shown to be suitable for robust SE-based composition control. Changes in gas-phase concentration of Cd atoms produced by a CdTe effusion cell are detected using an atomic absorption method (optical-absorption flux monitoring OFM). The OFM method allows changes in HgCdTe layer composition to be correlated directly with variations in Cd flux. The in situ optical sensors are linked using a custom software framework to provide the foundation for integrated, real-time monitoring and control of HgCdTe MBE growth of high performance IR detector structures over a wide range of compositions, layer thickness and substrate temperature.
Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 13
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Book Description
We present recent progress on the use of an integrated real-time sensing and control system for monitoring and controlling substrate temperature, layer composition, and effusion cell flux during MBE growth of HgCdTe epilayers for advanced IR detectors. Substrate temperature is measured and controlled in real-time using absorption-edge spectroscopy (ABES). This allows the substrate temperature to be maintained at +/-1.5 deg C from the desired setpoint, even during actuation of effusion cell shutters which under conventional thermocouple-based control would produce a substantial (10-15 deg C) temperature change. In situ spectroscopic ellipsometry (SE) is used for monitoring HgCdTe layer composition in real-time. We describe the development of a comprehensive temperature- and composition-dependent SE dielectric function database which can be used for accurate and precise monitoring of Hg(1-x)Cd(x)Te layer composition over a wide range of x-values, from 0.2 to 0.42. The composition changes inferred from the real-time SE measurements obtained during growth of a two-layer structure are in excellent agreement with actual composition vs. depth profiles obtained using post-growth SIMS analysis. Likewise, the accuracy and precision of SE measurements conducted over multiple growth runs are shown to be suitable for robust SE-based composition control. Changes in gas-phase concentration of Cd atoms produced by a CdTe effusion cell are detected using an atomic absorption method (optical-absorption flux monitoring OFM). The OFM method allows changes in HgCdTe layer composition to be correlated directly with variations in Cd flux. The in situ optical sensors are linked using a custom software framework to provide the foundation for integrated, real-time monitoring and control of HgCdTe MBE growth of high performance IR detector structures over a wide range of compositions, layer thickness and substrate temperature.
Author: Gertjan Koster
Publisher: Elsevier
ISBN: 0857094955
Category : Technology & Engineering
Languages : en
Pages : 295
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Book Description
Advanced techniques for characterizing thin film growth in situ help to develop improved understanding and faster diagnosis of issues with the process. In situ characterization of thin film growth reviews current and developing techniques for characterizing the growth of thin films, covering an important gap in research. Part one covers electron diffraction techniques for in situ study of thin film growth, including chapters on topics such as reflection high-energy electron diffraction (RHEED) and inelastic scattering techniques. Part two focuses on photoemission techniques, with chapters covering ultraviolet photoemission spectroscopy (UPS), X-ray photoelectron spectroscopy (XPS) and in situ spectroscopic ellipsometry for characterization of thin film growth. Finally, part three discusses alternative in situ characterization techniques. Chapters focus on topics such as ion beam surface characterization, real time in situ surface monitoring of thin film growth, deposition vapour monitoring and the use of surface x-ray diffraction for studying epitaxial film growth. With its distinguished editors and international team of contributors, In situ characterization of thin film growth is a standard reference for materials scientists and engineers in the electronics and photonics industries, as well as all those with an academic research interest in this area. Chapters review electron diffraction techniques, including the methodology for observations and measurements Discusses the principles and applications of photoemission techniques Examines alternative in situ characterisation techniques
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Category : Infrared detectors
Languages : en
Pages : 284
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Category : Chemistry
Languages : en
Pages : 2668
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Category : Ceramics
Languages : en
Pages : 950
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Category : Aeronautics
Languages : en
Pages : 440
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Author: National Research Council
Publisher: National Academies Press
ISBN: 0309162300
Category : Technology & Engineering
Languages : en
Pages : 194
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Book Description
The Department of Defense recently highlighted intelligence, surveillance, and reconnaissance (ISR) capabilities as a top priority for U.S. warfighters. Contributions provided by ISR assets in the operational theaters in Iraq and Afghanistan have been widely documented in press reporting. While the United States continues to increase investments in ISR capabilities, other nations not friendly to the United States will continue to seek countermeasures to U.S. capabilities. The Technology Warning Division of the Defense Intelligence Agency's (DIA) Defense Warning Office (DWO) has the critical responsibility, in collaborations with other components of the intelligence community (IC), for providing U.S. policymakers insight into technological developments that may impact future U.S. warfighting capabilities. To this end, the IC requested that the National Research Council (NRC) investigate and report on key visible and infrared detector technologies, with potential military utility, that are likely to be developed in the next 10-15 years. This study is the eighth in a series sponsored by the DWO and executed under the auspices of the NRC TIGER (Technology Insight-Gauge, Evaluate, and Review) Standing Committee.
Author: National Institute of Standards and Technology (U.S.)
Publisher:
ISBN:
Category :
Languages : en
Pages : 400
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Author:
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ISBN:
Category : Aeronautics
Languages : en
Pages : 1016
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Author:
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ISBN:
Category : Electrical engineering
Languages : en
Pages : 1360
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