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InGaAs-based quantum dots for infrared imaging applications: growth and characterisation
Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
2007 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

In this thesis, results are presented from the development of quantum dot (QD) based infrared photodetectors (IPs). This includes epitaxial growth of QDs, investigations of the structural, optical and electronic properties of the QD based material as well as characterisation of the resulting components.

Metal organic vapour phase epitaxy is used for growth of selfassembled indium arsenide (lnAs) QDs on gallium arsenide (GaAs) substrates. Through characterisation by atomic force microscopy, the correlation between size distribution and density of quantum dots and different growth parameters, such as temperature, InAs deposition time and V/III-ratio (ratio between group Vand group III species) is achieved. The V/111ratio is identified as the most important parameter, in finding the right growth conditions for QDs. A route towards optimisation of the dot size distribution through successive variations of the growth parameters is presented.

The QD layers are inserted in Ino.15Gao.85As/GaAs quantum wells (QWs), forming so-called dots-in-a-well (DWELL) structures. These structures are used to fabricate IPs, primarily for detection in the long wavelength infrared region (LWIR, 8-12 µm).

The electron energy level schemes of the DWELL structures are deduced by means of Fourier transform photoluminescence (FTPL) and FTPL excitation (FTPLE) measurements. Further characterisation of the IPs, through interband and intersubband photocurrent (pe) measurements as weIl as dark current measurements, is performed. By comparisons of the deduced energy level scheme of the DWELL structure and the results of the intersubband PC measurements, the origin of the PC is determined. The main intersubband transition contributing to the PC is identified as the QD ground state to the QW excited state transition. Significant variations of PC and dark current are observed, when voltage and temperature are used as variable parameters. A possible explanation to this could be the strong variation of the escape probability from different energy states in the DWELL structure, as revealed by interband PC measurements. These results are important for the further optimisation of the DWELL lP.

Place, publisher, year, edition, pages
Kista Snabbtryck , 2007. , 49 p.
Series
Linköping Studies in Science and Technology. Thesis, ISSN 0280-7971 ; 1297
National Category
Engineering and Technology
Identifiers
URN: urn:nbn:se:liu:diva-52952Local ID: LIU-TEK-LIC-2007:6ISBN: 978-91-85715-85-5 (print)OAI: oai:DiVA.org:liu-52952DiVA: diva2:286399
Presentation
(English)
Supervisors
Available from: 2010-01-25 Created: 2010-01-14 Last updated: 2010-01-25Bibliographically approved
List of papers
1. Optimising uniformity of InAs/(InGaAs)/GaAs quantum dots grown by metal organic vapor phase epitaxy
Open this publication in new window or tab >>Optimising uniformity of InAs/(InGaAs)/GaAs quantum dots grown by metal organic vapor phase epitaxy
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2006 (English)In: Applied Surface Science, ISSN 0169-4332, E-ISSN 1873-5584, Vol. 252, no 15, 5525-5529 p.Article in journal (Refereed) Published
Abstract [en]

A route towards optimisation of uniformity and density of InAs/(InGaAs)/GaAs quantum dots grown by metal organic vapor phase epitaxy (MOVPE) through successive variations of the growth parameters is reported. It is demonstrated that a key parameter in obtaining a high density of quantum dots is the V/III ratio, a fact which was shown to be valid when either AsH3 (arsine) or tertiary-butyl-arsine (TBA) were used as group V precursors. Once the optimum V/III ratio was found, the size distribution was further improved by adjusting the nominal thickness of deposited InAs material, resulting in an optimum thickness of 1.8 monolayers of InAs in our case. The number of coalesced dots was minimised by adjusting the growth interruption time to approximately 30 s. Further, the uniformity was improved by increasing the growth temperature from 485 °C to 520 °C. By combining these optimised parameters, i.e. a growth temperature of 520 °C, 1.8 monolayers InAs thickness, 30 s growth stop time and TBA as group V precursor, a full-width-half-maximum (FWHM) of the low temperature luminescence band of 40 meV was achieved, indicating a narrow dot size distribution.

Place, publisher, year, edition, pages
Elsevier, 2006
Keyword
Quantum dot, Epitaxy, MOVPE, InAs/GaAs, TBA, Growth
National Category
Other Engineering and Technologies not elsewhere specified
Identifiers
urn:nbn:se:liu:diva-15764 (URN)10.1016/j.apsusc.2005.12.128 (DOI)
Note
Original Publication: Linda Höglund, E. Petrini, C. Asplund, H. Malm, J. Y. Andersson and Per-Olof Holtz, Optimising uniformity of InAs/(InGaAs)/GaAs quantum dots grown by metal organic vapor phase epitaxy, 2006, Applied Surface Science, (252), 15, 5525-5529 . http://dx.doi.org/10.1016/j.apsusc.2005.12.128 Copyright: Elsevier Science B.V., Amsterdam. http://www.elsevier.com/ Available from: 2009-07-09 Created: 2008-12-03 Last updated: 2017-12-14Bibliographically approved
2. Origin of photocurrent in lateral quantum dots-in-a-well infrared photodetectors
Open this publication in new window or tab >>Origin of photocurrent in lateral quantum dots-in-a-well infrared photodetectors
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2006 (English)In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 88, no 21Article in journal (Refereed) Published
Abstract [en]

Interband and intersubband transitions of lateral InAs/In0.15Ga0.85As dots-in-a-well quantum dot infrared photodetectors were studied in order to determine the origin of the photocurrent. The main intersubband transition contributing to the photocurrent (PC) was associated with the quantum dot ground state to the quantum well excited state transition. By a comparison between intersubband PC measurements and the energy level scheme of the structure, as deduced from Fourier transform photoluminescence (FTPL) and FTPL excitation spectroscopies, the main transition contributing to the PC was identified.

Place, publisher, year, edition, pages
American Institute of Physics, 2006
Keyword
indium compounds, gallium arsenide, III-V semiconductors, semiconductor quantum wells, semiconductor quantum dots, photodetectors, infrared detectors, photoluminescence, ground states, excited states, Fourier transform spectra, photoconductivity
National Category
Other Engineering and Technologies not elsewhere specified
Identifiers
urn:nbn:se:liu:diva-15766 (URN)10.1063/1.2207493 (DOI)
Note
Original Publication: Linda Höglund, Per-Olof Holtz, C. Asplund, Q. Wang, S. Almqvist, H. Malm, E. Petrini, H. Pettersson and J. Y. Andersson, Origin of photocurrent in lateral quantum dots-in-a-well infrared photodetectors, 2006, Applied Physics Letters, (88), 213510. http://dx.doi.org/10.1063/1.2207493 Copyright: American Institute of Physics http://www.aip.org/ Available from: 2009-01-15 Created: 2008-12-03 Last updated: 2017-12-14Bibliographically approved
3. Quantum dots-in-a-well infrared photodetectors for long wavelength infrared detection
Open this publication in new window or tab >>Quantum dots-in-a-well infrared photodetectors for long wavelength infrared detection
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2006 (English)In: Optical Materials in Defence Systems Technology III,2006, Proceedings of SPIE 6401: SPIE Digital Library , 2006, 640109- p.Conference paper, Published paper (Refereed)
Abstract [en]

We report on a quantum dots-in-a-well infrared photodetector (DWELL QDIP) grown by metal organic vapor phase epitaxy. The DWELL QDIP consisted of ten stacked InAs/In0.15Ga0.85As/GaAs QD layers embedded between n-doped contact layers. The density of the QDs was about 9 x 1010 cm-2 per QD layer. The energy level structure of the DWELL was revealed by optical measurements of interband transitions, and from a comparison with this energy level scheme the origin of the photocurrent peaks could be identified. The main intersubband transition contributing to the photocurrent was associated with the quantum dot ground state to the quantum well excited state transition. The performance of the DWELL QDIPs was evaluated regarding responsivity and dark current for temperatures between 15 K and 77 K. The photocurrent spectrum was dominated by a LWIR peak, with a peak wavelength at 8.4 μm and a full width at half maximum (FWHM) of 1.1 μm. At an operating temperature of 65 K, the peak responsivity was 30 mA/W at an applied bias of 4 V and the dark current was 1.2×10-5 A/cm2. Wavelength tuning from 8.4 μm to 9.5 μm was demonstrated, by reversing the bias of the detector.

Place, publisher, year, edition, pages
Proceedings of SPIE 6401: SPIE Digital Library, 2006
National Category
Natural Sciences
Identifiers
urn:nbn:se:liu:diva-36653 (URN)10.1117/12.690010 (DOI)32031 (Local ID)32031 (Archive number)32031 (OAI)
Available from: 2009-10-10 Created: 2009-10-10 Last updated: 2010-01-25Bibliographically approved
4. Studies of photocurrent and dark current in quantum dots-in-a-well infrared photodetectors
Open this publication in new window or tab >>Studies of photocurrent and dark current in quantum dots-in-a-well infrared photodetectors
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(English)Manuscript (preprint) (Other academic)
Abstract [en]

The performance of quantum dots-in-a-well infrared photodetectors (DWELL IPs) has been studied by means of interband and intersubband photocurrent measurements as well as dark current measurements. Using interband photocurrent measurements, substantial escape of electrons from lower lying states in the DWELL structure at large biases was revealed. Furthermore, a significant variation of the escape probability from energy states in the DVELL sturcture with voltage was observed. These facts could be possible explanations to the strong temperature and voltage dependence of hoth photocurrent and dark current in DWELL IPs. In a comparison between DWELL IPs and quantum well infrared photocdetectors (QWIPs), the dark current was shown to be considerably lower in DWELL IPs than in QWIPs, but alos the responsivity was low in comparison to QWIPs.

National Category
Natural Sciences
Identifiers
urn:nbn:se:liu:diva-53588 (URN)
Available from: 2010-01-25 Created: 2010-01-25 Last updated: 2010-01-25

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