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Type-II interband quantum dot photodetectors
KTH, School of Information and Communication Technology (ICT), Integrated Devices and Circuits.
2013 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Photon detectors based on single-crystalline materials are of great interest for high performance imaging applications due to their low noise and fast response. The major detector materials for sensing in the long-wavelength infrared (LWIR) band (8-14 µm) are currently HgCdTe (MCT) and AlGaAs/GaAs quantum wells (QW) used in intraband-based quantum-well infrared photodetectors (QWIPs). These either suffer from compositional variations that are detrimental to the system performance as in the case of MCT, or, have an efficient dark current generation mechanism that limits the operating temperature as for QWIPs. The need for increased on-wafer uniformity and elevated operating temperatures has resulted in the development of various alternative approaches, such as type-II strained-layer superlattice detectors (SLSs) and intraband quantum-dot infrared photodetectors (QDIPs).

In this work, we mainly explore two self-assembled quantum-dot (QD) materials for use as the absorber material in photon detectors for the LWIR, with the aim to develop low-dark current devices that can allow for high operating temperatures and high manufacturability. The detection mechanism is here based on type-II interband transitions from bound hole states in the QDs to continuum states in the matrix material.

Metal-organic vapor-phase epitaxy (MOVPE) was used to fabricate (Al)GaAs(Sb)/InAs and In(Ga)Sb/InAs QD structures for the development of an LWIR active material. A successive analysis of (Al)GaAs(Sb) QDs using absorption spectroscopy shows strong absorption in the range 6-12 µm interpreted to originate in intra-valence band transitions. Moreover, record-long photoluminescence (PL) wavelength up to 12 µm is demonstrated in InSb- and InGaSb QDs.

Mesa-etched single-pixel photodiodes were fabricated in which photoresponse is demonstrated up to 8 µm at 230 K with 10 In0.5Ga0.5Sb QD layers as the active region. The photoresponse is observed to be strongly temperature-dependent which is explained by hole trapping in the QDs. In the current design, the photoresponse is thermally limited at typical LWIR sensor operating temperatures (60-120 K), which is detrimental to the imaging performance. This can potentially be resolved by selecting a matrix material with a smaller barrier for thermionic emission of photo-excited holes. If such an arrangement can be achieved, type-II interband InGaSb QD structures can turn out to be interesting as a high-operating-temperature sensor material for thermal imaging applications.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2013. , 81 p.
Series
Trita-ICT/MAP, 1653-7310Trita-ICT/MAP AVH, ISSN 1653-7610 ; 2013:03
Keyword [en]
photodetector, quantum dot, infrared, MOVPE, thermal imaging, type-II, photoluminescence, III/V, InSb, InGaSb, InAs
National Category
Nano Technology
Research subject
SRA - ICT
Identifiers
URN: urn:nbn:se:kth:diva-122294ISBN: 978-91-7501-779-2 (print)OAI: oai:DiVA.org:kth-122294DiVA: diva2:621903
Public defence
2013-06-14, Room D, Isafjordsgatan 39, Kista, 10:00 (English)
Opponent
Supervisors
Note

QC 20130521

Available from: 2013-05-21 Created: 2013-05-17 Last updated: 2013-05-21Bibliographically approved
List of papers
1. Long-wavelength infrared quantum-dot based interband photodetectors
Open this publication in new window or tab >>Long-wavelength infrared quantum-dot based interband photodetectors
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2011 (English)In: Infrared physics & technology, ISSN 1350-4495, E-ISSN 1879-0275, Vol. 54, no 3, 287-291 p.Article in journal (Refereed) Published
Abstract [en]

We report on the design and fabrication of (Al)GaAs(Sb)/InAs tensile strained quantum-dot (QD) based detector material for thermal infrared imaging applications in the long-wavelength infrared (LWIR) regime. The detection is based on transitions between confined dot states and continuum states in a type-II band lineup, and we therefore refer to it as a dot-to-bulk (D2B) infrared photodetector with expected benefits including long carrier lifetime due to the type-II band alignment, suppressed Shockley-Read-Hall generation-recombination due to the relatively large-bandgap matrix material, inhibited Auger recombination processes due to the tensile strain and epitaxial simplicity. Metal-organic vapor-phase epitaxy was used to grow multiple (Al)GaAs(Sb) QD layers on InAs substrates at different QD nominal thicknesses, compositions, doping conditions and multilayer periods, and the material was characterized using atomic force and transmission electron microscopy, and Fourier-transform infrared absorption spectroscopy. Dot densities up to 1 x 10(11) cm(-2), 1 x 10(12) cm(-2) and 3 x 10(10) cm(-2) were measured for GaAs, AlGaAs and GaAsSb QDs, respectively. Strong absorption in GaAs, AlGaAs and GaAsSb multilayer QD samples was observed in the wavelength range 6-12 mu m. From the wavelength shift in the spectral absorption for samples with varying QD thickness and composition it is believed that the absorption is due to an intra- valance band transition. From this it is possible to estimate the type-II inter-band transition wavelength, thereby suggesting that (Al)GaAs(Sb) QD/InAs heterostructures are suitable candidates for LWIR detection and imaging.

Keyword
Photodetector, LWIR, QD, MOVPE
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-34662 (URN)10.1016/j.infrared.2010.12.031 (DOI)000290973200028 ()2-s2.0-79955029475 (Scopus ID)
Note

QC 20110621 Ingår i konferens: International Conference on the Quantum Structure Infrared Photodector (QSIP), Istanbul, TURKEY, AUG 15-20, 2010

Available from: 2011-06-21 Created: 2011-06-13 Last updated: 2017-12-11Bibliographically approved
2. Photoluminescence and photoresponse from InSb/InAs-based quantum dot structures
Open this publication in new window or tab >>Photoluminescence and photoresponse from InSb/InAs-based quantum dot structures
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2012 (English)In: Optics Express, ISSN 1094-4087, E-ISSN 1094-4087, Vol. 20, no 19, 21264-21271 p.Article in journal (Refereed) Published
Abstract [en]

InSb-based quantum dots grown by metal-organic vapor-phase epitaxy (MOVPE) on InAs substrates are studied for use as the active material in interband photon detectors. Long-wavelength infrared (LWIR) photoluminescence is demonstrated with peak emission at 8.5 mu m and photoresponse, interpreted to originate from type-II interband transitions in a p-i-n photodiode, was measured up to 6 mu m, both at 80 K. The possibilities and benefits of operation in the LWIR range (8-12 mu m) are discussed and the results suggest that InSb-based quantum dot structures can be suitable candidates for photon detection in the LWIR regime.

Keyword
Molecular-Beam Epitaxy, Infrared Photodetectors, Inas, Detectors, Growth
National Category
Other Physics Topics
Identifiers
urn:nbn:se:kth:diva-103127 (URN)10.1364/OE.20.021264 (DOI)000308865600068 ()2-s2.0-84866264107 (Scopus ID)
Funder
Vinnova
Note

QC 20121008

Available from: 2012-10-08 Created: 2012-10-04 Last updated: 2017-12-07Bibliographically approved
3. Long-wavelength infrared photoluminescence from InGaSb/InAs quantum dots
Open this publication in new window or tab >>Long-wavelength infrared photoluminescence from InGaSb/InAs quantum dots
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2013 (English)In: Infrared physics & technology, ISSN 1350-4495, E-ISSN 1879-0275, Vol. 59, 89-92 p.Article in journal (Refereed) Published
Abstract [en]

We study the growth of self-assembled InGaSb/InAs quantum dots (QDs) and investigate how gallium can be used to reduce the optical transition energy in the InSb QD system. InGaSb QDs were grown on InAs (0 0 1) substrates by metal-organic vapor-phase epitaxy (MOVPE) and the material was characterized by photoluminescence (PL) measurements. A PL peak wavelength is demonstrated beyond 8 μm at 77 K, which is significantly longer than what has been reported for InSb QDs. The results suggest that InGaSb QDs can be grown at a larger size than InSb QDs leading to reduced confinement in the QDs.

Keyword
InGaSb, QD, MOVPE, LWIR
National Category
Other Physics Topics
Identifiers
urn:nbn:se:kth:diva-122437 (URN)10.1016/j.infrared.2012.12.020 (DOI)000320974800016 ()2-s2.0-84878345768 (Scopus ID)
Note

QC 20130816

Available from: 2013-05-21 Created: 2013-05-21 Last updated: 2017-12-06Bibliographically approved
4. A performance assessment of type-II interband In0.5Ga0.5Sb QD photodetectors
Open this publication in new window or tab >>A performance assessment of type-II interband In0.5Ga0.5Sb QD photodetectors
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2013 (English)In: Infrared physics & technology, ISSN 1350-4495, E-ISSN 1879-0275, Vol. 61, 319-324 p.Article in journal (Refereed) Published
Abstract [en]

Self-assembled quantum-dot (QD) structures with type-II band alignment to the surrounding matrix material have been proposed as a III/V material approach to realize small-bandgap device structures suitable for photon detection and imaging in the long-wavelength infrared (LWIR) band. Here, we analyze the photoresponse of In0.5Ga0.5Sb/InAs QD photodiodes and estimate the system performance of type-II QD - based photodetectors. A review of alternative design approaches is presented and the choice of matrix material is discussed in terms of band alignment and its effect on the photoresponse. Photodiodes were fabricated consisting of 10 layers of In0.5Ga0.5Sb QDs grown on InAs (0 0 1) substrates with metal-organic vapor-phase epitaxy (MOVPE). The photoresponse and dark current were measured in single pixel devices as a function of temperature in the range 20-230 K. The quantum efficiency shows an Arrhenius type behavior, which is attributed to hole trapping. This severely limits the detector performance at typical LWIR sensor operating temperatures (60-120 K). A device design with the matrix material InAs0 6Sb0 4 is proposed as a mean to improve the performance by reducing the barrier for hole transport. This can potentially allow type-II InGaSb QDs to be a competitive sensor material for LWIR detection.

Keyword
Photodetector, LWIR, QD, MOVPE, Type-II
National Category
Other Physics Topics
Identifiers
urn:nbn:se:kth:diva-122438 (URN)10.1016/j.infrared.2013.09.009 (DOI)000328233600043 ()2-s2.0-84887033680 (Scopus ID)
Funder
Knowledge FoundationVinnovaSwedish Foundation for Strategic Research
Note

QC 20140114. Updated from submitted to published.

Available from: 2013-05-21 Created: 2013-05-21 Last updated: 2017-12-06Bibliographically approved
5. GaSb/Ga0.51In0.49P self assembled quantum dots grown by MOVPE
Open this publication in new window or tab >>GaSb/Ga0.51In0.49P self assembled quantum dots grown by MOVPE
2009 (English)In: Proceedings from EW-MOVPE XIII, 2009, Vol. 7298, 273-276 p.Conference paper, Published paper (Refereed)
National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:kth:diva-122439 (URN)
Conference
EW-MOVPE XIII
Note

NQC 2013

Available from: 2013-05-21 Created: 2013-05-21 Last updated: 2013-05-21Bibliographically approved

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