| 1. |
- Gustafsson, Oscar, et al.
(författare)
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A performance assessment of type-II interband In0.5Ga 0.5Sb QD photodetectors
- 2013
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Ingår i: Infrared physics & technology. - : Elsevier BV. - 1350-4495 .- 1879-0275. ; 61, s. 319-324
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Tidskriftsartikel (refereegranskat)abstract
- 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 In0.5Ga 0.5Sb 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.
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| 2. |
- Gustafsson, Oscar, et al.
(författare)
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Long-wavelength infrared photoluminescence from InGaSb/InAs quantum dots
- 2013
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Ingår i: Infrared physics & technology. - : Elsevier BV. - 1350-4495 .- 1879-0275. ; 59, s. 89-92
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 3. |
- Gustafsson, Oscar, et al.
(författare)
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Photoluminescence photoresponse from InSb/InAs-based quantum dot structures
- 2012
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Ingår i: Optics Express. - : Optical Society of America. - 1094-4087. ; 20:19, s. 21264-71
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Tidskriftsartikel (refereegranskat)abstract
- 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 μm and photoresponse, interpreted to originate from type-II interband transitions in a p-i-n photodiode, was measured up to 6 μm, both at 80 K. The possibilities and benefits of operation in the LWIR range (8-12 μm) are discussed and the results suggest that InSb-based quantum dot structures can be suitable candidates for photon detection in the LWIR regime.
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| 4. |
- Karim, Amir, et al.
(författare)
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Characterization of InAs/GaSb type€II superlattice photodiodes for mid€wave IR with different mesa sidewall passivation schemes
- 2012
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Ingår i: Physica Status Solidi. C, Current topics in solid state physics. - : Wiley. - 1610-1634 .- 1610-1642. ; c9:7, s. 1690-2
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Tidskriftsartikel (refereegranskat)abstract
- We report on the electrical material characterization of InAs/GaSb type-II superlattice (T2SL) mid-wave infrared (MWIR) photodiodes with different passivation schemes on the mesa-sidewalls with significant differences in the resulting low temperature dark currents. Devices fabricated by dry etching passivated with polymerized photoresist, show orders of magnitude lower dark currents as compared to unpassivated devices. The mesa side walls were examined using high resolution transmission electron microscopy (HRTEM) with a special focus on the interface between the superlattice material the dielectric passivation. Material analysis on nanometer scale at the mesa sidewall interface was performed using energy dispersive X-ray (EDX) spectrometry. EDX line scans were obtained from interfaces for different passivated unpassivated devices, using the highly focused electron beam in TEM, to investigate the chemical compositions. The unpassivated photoresist-passivated mesas, with different electrical properties, revealed different sidewall morphologies compositions. An oxygen containing layer was observed in photoresist-passivated devices covering the whole mesa sidewall. We think this plays a role in reducing surface leakage dark current. In HR-TEM the mesa sidewall topography reveals preferential etching of one superlattice component as previously observed. Nevertheless, the dielectric material covers the sidewall uniformly.
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| 5. |
- Karim, Amir, et al.
(författare)
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In(Ga)Sb/InAs quantum dot based IR photodetectors with thermally activated photoresponse
- 2013
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Ingår i: Proceedings of SPIE. - : SPIE. - 9780819494955
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Konferensbidrag (refereegranskat)abstract
- We report on the device characterization of In(Ga)Sb/InAs quantum dots (QDs) based photodetectors for long wave IR detectors. The detection principle of these quantum-dot infrared photodetectors (QDIPs) is based on the spatially indirect transition between the In(Ga)Sb QDs and the InAs matrix, as a result of the type-II band alignment. Such photodetectors are expected to have lower dark currents and higher operating temperatures compared to the current state of the art InSb and mercury cadmium telluride (MCT) technology. The In(Ga)Sb QD structures were grown using metal-organic vapour-phase epitaxy and explored using structural, electrical and optical characterization techniques. Material development resulted in obtaining photoluminescence up to 10 μm, which is the longest wavelength reported in this material system. We have fabricated different photovoltaic IR detectors from the developed material that show absorption up to 8 μm. Photoresponse spectra, showing In(Ga)Sb QD related absorption edge, were obtained up to 200 K. Detectors with different In(Ga)Sb QDs showing different cut-off wavelengths were investigated for photoresponse. Photoresponse in these detectors is thermally activated with different activation energies for devices with different cut-off wavelengths. Devices with longer cut-off wavelength exhibit higher activation energies. We can interpret this using the energy band diagram of the dots/matrix system for different QD sizes.
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| 6. |
- Karim, Amir, et al.
(författare)
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Infrared detectors : Advances, challenges and new technologies
- 2013
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Ingår i: IOP Conference Series.
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Konferensbidrag (refereegranskat)abstract
- Human knowledge of infrared (IR) radiation is about 200 years old. However it was in the late 20th century that we developed a wide range of smart technologies for detection and started to take advantage for our benefit. Today IR detector technology is in its 3rd generation and comes with challenging demands. Based on the propagation of IR radiation through free space it is divided into different transmission windows. The most interesting for thermal imaging are the mid-wave IR (MWIR) and the long-wave IR (LW IR). Infrared detectors for thermal imaging have a number of applications in industry, security, search & rescue, surveillance, medicine, research, meteorology, climatology and astronomy. Currently high-performance IR imaging technology is mainly based on epitaxially grown structures of the small-bandgap bulk alloy mercury-cadmium-telluride (MCT), indium antimonide (InSb) and GaAs based quantum-well infrared photodetectors (QWIPs), depending on the application and wavelength range. However, they operate at low temperatures requiring costly and bulky cryogenic systems. In addition there is always a need for better performance, which generates possibilities for developing new technologies. Some emerging technologies are quantum dot infrared photodetectors (QDIPs), type-II strained layer super-lattice, and QDIPs with type-II band alignment. In this report a brief review of the current and new technologies for high performance IR detectors, will be presented.
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| 7. |
- Wang, Qin, et al.
(författare)
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Analysis of surface oxides on narrow bandgap III-V semiconductors leading towards surface leakage free IR photodetectors
- 2012
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Ingår i: Proceedings of SPIE, the International Society for Optical Engineering. - : SPIE. - 0277-786X .- 1996-756X. ; 8353, s. 835311-
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Tidskriftsartikel (refereegranskat)abstract
- Narrow bandgap semiconductors GaSb, InAs, and InSb are important building blocks for infrared photodetectors based on type-II InSb quantum dots or an InAs/GaSb strained layer superlattice. Understanding the surface chemical composition of these materials can provide valuable information that enables optimization of device surface passivation techniques leading towards surface leakage free IR photodetectors. We report on an investigation into Ga-, In-, Sb-, and As-oxides and other chemical species on the surface of untreated, dry etched and thermally treated GaSb, InAs and InSb samples by x-ray photoelectron spectroscopy. The experimental results reveal the presence of Sb- and Ga-oxides on the surfaces of the untreated and treated GaSb samples. Both Sb- and In-oxides were observed on the surface of all InSb samples, and especially the dry etched sample had thicker oxide layers. In the case of the InAs samples, not only In-and As-oxides XPS signals were obtained, but also AsCl species were found on the ICP dry etched sample. These results helped to analyze the dark current of our fabricated IR detectors.
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| 8. |
- Wang, Qin, et al.
(författare)
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MWIR interband transitions in type-II (III) In(GaAl)Sb quantum dots
- 2015
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Konferensbidrag (refereegranskat)abstract
- In this work we present an alternative approach for realizing desired IR devices with appropriate operating wavelengths in the MWIR region utilizing In(GaAl)Sb quantum dots embedded in an InAs matrix grown by MBE. The QDs exhibit spatially indirect interband transitions in a type-II broken bandgap alignment, with a transition energy that can be tuned by bandgap and strain engineering utilizing either the quantum dot size or the incorporation of Ga or (GaAl) into the QDs. Furthermore, the growth of such QDs does not require sophisticated epitaxial designs needed for superlattices or quantum cascade structures regarding large numbers of alternating layers and very exact interfaces. The QD structures are expected to exhibit key advantages for IR devices e.g. higher operating temperature, lower power consumption, size, weight, and cost. The structural and composition properties of designed and grown In(GaAl)Sb QDs were characterized using AFM, SEM, TEM, and XRD. The corresponding optical properties, both in terms of absorption and emission, were analyzed and compared for selected QD samples before and after annealing at 650 °C.
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