| 1. |
- Höglund, Linda, 1974-, et al.
(författare)
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Energy level scheme of InAs/InxGa1-xAs/GaAs quantum-dots-in-a-well infrared photodetector structures
- 2010
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - Woodbury, NY : American Physical Society. - 1098-0121 .- 1550-235X. ; 82:3, s. 035314-
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Tidskriftsartikel (refereegranskat)abstract
- A thorough investigation of quantum-dots-in-a-well structures for infrared photodetector applications has been performed employing different experimental techniques. The electronic structure of self-assembled InAs quantum dots embedded in an In0.15Ga0.85As/GaAs quantum well (QW) was deduced from photoluminescence (PL) and PL excitation (PLE) spectroscopy. From polarization-dependent PL it was revealed that the quantum dots hold two electron energy levels and two heavy-hole levels. Tunnel capacitance spectroscopy confirmed an electron energy level separation of about 50 meV, and additionally, that the conduction-band ground state and excited state of the dots are twofold and fourfold degenerates, respectively. Intersubband photocurrent spectroscopy, combined with simultaneous interband pumping of the dots, revealed a dominant transition at 150 meV (8.5 mu m) between the ground state of the quantum dots and the excited state of the QW. Results from detailed full three-dimensional calculations of the electronic structure, including effects of composition intermixing and interdot interactions, confirm the experimentally unravelled energy level scheme of the dots and well.
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| 2. |
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| 3. |
- Höglund, Linda, 1974-, et al.
(författare)
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Quantum dots-in-a-well infrared photodetectors for long wavelength infrared detection
- 2006
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Ingår i: Proceedings of SPIE. - Bellingham, Wash. : SPIE - International Society for Optical Engineering. - 9780819464996 ; 6401, s. 1-640109
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Konferensbidrag (refereegranskat)abstract
- 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/In0.5Ga0.85As/GaAs QD layers embedded between n-doped contact layers. The density of the QDs was about 9 × 10 10 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.
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| 4. |
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| 5. |
- Junique, Stéphane, et al.
(författare)
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Multiple quantum well spatial light modulators design-fabrication-characterization
- 2001
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Ingår i: Proceedings of SPIE - The International Society for Optical Engineering. - San Diego, CA : SPIE. ; , s. 62-71
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Konferensbidrag (refereegranskat)abstract
- Multiple quantum well spatial light modulators (MQW SLMs) are promising devices for future high-speed applications. We present results obtained with a single-pixel amplitude modulator. We discuss the status of our work on a 128x—128-pixel ternary SLM. This SLM will run at 10 kHz and have one low-reflectance level and two high reflectance levels with a phase difference of Ï€. We also present a study of the relation between the coding domain and the structural design of modulators.
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| 6. |
- 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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| 7. |
- Malm, Hedda, et al.
(författare)
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Recent developments in type-II superlattice detectors at IRnova AB
- 2012
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Ingår i: INFRARED TECHNOLOGY AND APPLICATIONS XXXVIII, PTS 1 AND 2. - : SPIE-INT SOC OPTICAL ENGINEERING. - 9780819490315
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Konferensbidrag (refereegranskat)abstract
- A mid wave infrared type-II superlattice focal plane array with 320x256 pixels, 30 mu m pitch and 90 % fill factor was fabricated in house, using a conventional homojunction p-i-n photodiode design and the ISC9705 readout circuit. High-quality imaging up to 110 K is demonstrated with the substrate fully removed. The absorber is 2 mu m thick, and no antireflection coating was used, so there is still room for significant improvement of the quantum efficiency, which is in the 40 % range. Studies of the dark current vs. temperature behavior indicate that the device is limited by Shockley-Read-Hall generation from the depletion region. The activation energy of this dark current component is 0.13 eV, suggesting an unidentified recombination center positioned halfway into the 0.24 eV bandgap. Furthermore, we report on detectors with 100 % cut-off at 13 mu m. The dark current density at 60 K and -50 mV bias is 2x10(-4) A/cm(2). Quantum efficiency, NETD and BLIP temperature are also calculated. Position-sensitive photocurrent measurements on mesa-etched superlattice material were made at low temperatures using a focused laser spot. The lateral diffusion length for holes was extracted and is reported.
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| 8. |
- Pettersson, Håkan, et al.
(författare)
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Quantum Dots-in-a-Well Infrared Photodetectors-Electronic Structure and Optical Properties
- 2010
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Ingår i: Bulletin of American Physical Society. - : American Physical Society.
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Konferensbidrag (refereegranskat)abstract
- Quantum dots-in-a-well (DWELL) infrared photodetectors is a new class of nanophotonic devices with the potential of significantly increasing the performance and reducing the cost of infrared detectors. Here we present a comprehensive study of DWELL photodetector structures using a variety of optical techniques (PL, PLE, and PC). Complementary tunnel capacitance measurements support the electronic structure obtained from the optical measurements. A detailed energy level scheme based on the experimental findings is presented and compared to theoretical modeling. The presented work show the importance of combining different electrical and optical techniques to obtain a consistent model of complicated quantum structures which is crucial for the development of future nanophotonic devices.
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