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Long-Wavelength Infrared (LWIR) Quantum Dot Infrared Photodetector (QDIP) Focal Plane ArrayWe have exploited the artificial atomlike properties of epitaxially self-assembled quantum dots for the development of high operating temperature long wavelength infrared (LWIR) focal plane arrays. Quantum dots are nanometer-scale islands that form spontaneously on a semiconductor substrate due to lattice mismatch. QDIPs are expected to outperform quantum well infrared detectors (QWIPs) and are expected to offer significant advantages over II-VI material based focal plane arrays. QDIPs are fabricated using robust wide bandgap III-V materials which are well suited to the production of highly uniform LWIR arrays. We have used molecular beam epitaxy (MBE) technology to grow multi-layer LWIR quantum dot structures based on the InAs/InGaAs/GaAs material system. JPL is building on its significant QWIP experience and is basically building a Dot-in-the-Well (DWELL) device design by embedding InAs quantum dots in a QWIP structure. This hybrid quantum dot/quantum well device offers additional control in wavelength tuning via control of dot-size and/or quantum well sizes. In addition the quantum wells can trap electrons and aide in ground state refilling. Recent measurements have shown a 10 times higher photoconductive gain than the typical QWIP device, which indirectly confirms the lower relaxation rate of excited electrons (photon bottleneck) in QDPs. Subsequent material and device improvements have demonstrated an absorption quantum efficiency (QE) of approx. 3%. Dot-in-the-well (DWELL) QDIPs were also experimentally shown to absorb both 45 deg. and normally incident light. Thus we have employed a reflection grating structure to further enhance the quantum efficiency. JPL has demonstrated wavelength control by progressively growing material and fabricating devices structures that have continuously increased in LWIR response. The most recent devices exhibit peak responsivity out to 8.1 microns. Peak detectivity of the 8.1 micrometer devices has reached approx. 1 x 10(exp 10) Jones at 77 K. Furthermore, we have fabricated the first long-wavelength 640x512 pixels QDP focal plane array. This QDIP focal plane may has produced excellent infrared imagery with noise equivalent temperature difference of 40 mK at 60K operating temperature. In addition, we have managed to increase the quantum efficiency of these devices from 0.1% (according to the data published in literature) to 20% in discrete devices. This is a factor of 200 increase in quantum efficiency. With these excellent results, for the first time QDIP performance has surpassed the QWIP performance. Our goal is to operate these long-wavelength detectors at much higher operating temperature than 77K which can be passively achieved in space. This will be a huge leap in high performance infrared detectors specifically applicable to space science instruments.
Document ID
20070023744
Acquisition Source
Jet Propulsion Laboratory
Document Type
Preprint (Draft being sent to journal)
External Source(s)
Authors
Gunapala, Sarath D.
(Jet Propulsion Lab., California Inst. of Tech. Pasadena, CA, United States)
Bandara, S. V.
(Jet Propulsion Lab., California Inst. of Tech. Pasadena, CA, United States)
Liu, J. K.
(Jet Propulsion Lab., California Inst. of Tech. Pasadena, CA, United States)
Hill, C. J.
(Jet Propulsion Lab., California Inst. of Tech. Pasadena, CA, United States)
Rafol, S. B.
(Infravision Systems Altadena, CA, United States)
Mumolo, J. M.
(Jet Propulsion Lab., California Inst. of Tech. Pasadena, CA, United States)
Shott, C. A.
(FLIR Systems, Inc. Goleta, CA, United States)
Date Acquired
August 23, 2013
Publication Date
April 17, 2006
Subject Category
Instrumentation And Photography
Meeting Information
Meeting: SPIE Infrared Technology and Applications XXXII
Location: Orlando, FL
Country: United States
Start Date: April 17, 2006
End Date: April 21, 2006
Sponsors: International Society for Optical Engineering
Distribution Limits
Public
Copyright
Other
Keywords
infrared imaging
quantum wells
Infrared detectors
quantum well infrared detectors (QWIPs)
quantum dots,
quantum dot infrared photodetector (QDIP)
focal plane arrays
hand-held camera

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