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Proceedings Paper

Long-wavelength infrared (LWIR) quantum dot infrared photodetector (QDIP) focal plane array
Author(s): S. D. Gunapala; S. V. Bandara; C. J. Hill; D. Z. Ting; J. K. Liu; S. B. Rafol; E. R. Blazejewski; J. M. Mumolo; S. A. Keo; S. Krishna; Y. C. Chang; C. A. Shott
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Paper Abstract

We have exploited the artificial atomlike properties of epitaxially grown 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/InGaAs 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 QDIPs. Subsequent material and device improvements have demonstrated an absorption quantum efficiency (QE) of ~ 3%. Dot-in-the-well (DWELL) QDIPs were also experimentally shown to absorb both 45° 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 µm devices has reached ~ 1 × 1010 Jones at 77 K. Furthermore, we have fabricated the first long-wavelength 640×512 pixels QDIP focal plane array. This QDIP focal plane array 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% [1-2] 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.

Paper Details

Date Published: 17 May 2006
PDF: 10 pages
Proc. SPIE 6206, Infrared Technology and Applications XXXII, 62060J (17 May 2006); doi: 10.1117/12.662462
Show Author Affiliations
S. D. Gunapala, Jet Propulsion Lab. (United States)
S. V. Bandara, Jet Propulsion Lab. (United States)
C. J. Hill, Jet Propulsion Lab. (United States)
D. Z. Ting, Jet Propulsion Lab. (United States)
J. K. Liu, Jet Propulsion Lab. (United States)
S. B. Rafol, Infravision Systems (United States)
E. R. Blazejewski, Jet Propulsion Lab. (United States)
J. M. Mumolo, Jet Propulsion Lab. (United States)
S. A. Keo, Jet Propulsion Lab. (United States)
S. Krishna, Univ. of New Mexico (United States)
Y. C. Chang, Jet Propulsion Lab. (United States)
C. A. Shott, FLIR Systems Inc. (United States)

Published in SPIE Proceedings Vol. 6206:
Infrared Technology and Applications XXXII
Bjørn F. Andresen; Gabor F. Fulop; Paul R. Norton, Editor(s)

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