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A performance assessment of type-II interband In0.5Ga0.5Sb QD photodetectors
KTH, School of Information and Communication Technology (ICT), Integrated Devices and Circuits.
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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.

Place, publisher, year, edition, pages
2013. Vol. 61, 319-324 p.
Keyword [en]
Photodetector, LWIR, QD, MOVPE, Type-II
National Category
Other Physics Topics
Identifiers
URN: urn:nbn:se:kth:diva-122438DOI: 10.1016/j.infrared.2013.09.009ISI: 000328233600043Scopus ID: 2-s2.0-84887033680OAI: oai:DiVA.org:kth-122438DiVA: diva2:622364
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
In thesis
1. Type-II interband quantum dot photodetectors
Open this publication in new window or tab >>Type-II interband quantum dot photodetectors
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
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:nbn:se:kth:diva-122294 (URN)978-91-7501-779-2 (ISBN)
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

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Hammar, Mattias

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