| 1. |
- Beal, Jacob, et al.
(författare)
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Robust estimation of bacterial cell count from optical density
- 2020
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Ingår i: Communications Biology. - : Springer Science and Business Media LLC. - 2399-3642. ; 3:1
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Tidskriftsartikel (refereegranskat)abstract
- Optical density (OD) is widely used to estimate the density of cells in liquid culture, but cannot be compared between instruments without a standardized calibration protocol and is challenging to relate to actual cell count. We address this with an interlaboratory study comparing three simple, low-cost, and highly accessible OD calibration protocols across 244 laboratories, applied to eight strains of constitutive GFP-expressing E. coli. Based on our results, we recommend calibrating OD to estimated cell count using serial dilution of silica microspheres, which produces highly precise calibration (95.5% of residuals <1.2-fold), is easily assessed for quality control, also assesses instrument effective linear range, and can be combined with fluorescence calibration to obtain units of Molecules of Equivalent Fluorescein (MEFL) per cell, allowing direct comparison and data fusion with flow cytometry measurements: in our study, fluorescence per cell measurements showed only a 1.07-fold mean difference between plate reader and flow cytometry data.
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| 2. |
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- 2019
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Tidskriftsartikel (refereegranskat)
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| 3. |
- Kristanl, Matej, et al.
(författare)
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The Seventh Visual Object Tracking VOT2019 Challenge Results
- 2019
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Ingår i: 2019 IEEE/CVF INTERNATIONAL CONFERENCE ON COMPUTER VISION WORKSHOPS (ICCVW). - : IEEE COMPUTER SOC. - 9781728150239 ; , s. 2206-2241
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Konferensbidrag (refereegranskat)abstract
- The Visual Object Tracking challenge VOT2019 is the seventh annual tracker benchmarking activity organized by the VOT initiative. Results of 81 trackers are presented; many are state-of-the-art trackers published at major computer vision conferences or in journals in the recent years. The evaluation included the standard VOT and other popular methodologies for short-term tracking analysis as well as the standard VOT methodology for long-term tracking analysis. The VOT2019 challenge was composed of five challenges focusing on different tracking domains: (i) VOT-ST2019 challenge focused on short-term tracking in RGB, (ii) VOT-RT2019 challenge focused on "real-time" short-term tracking in RGB, (iii) VOT-LT2019 focused on long-term tracking namely coping with target disappearance and reappearance. Two new challenges have been introduced: (iv) VOT-RGBT2019 challenge focused on short-term tracking in RGB and thermal imagery and (v) VOT-RGBD2019 challenge focused on long-term tracking in RGB and depth imagery. The VOT-ST2019, VOT-RT2019 and VOT-LT2019 datasets were refreshed while new datasets were introduced for VOT-RGBT2019 and VOT-RGBD2019. The VOT toolkit has been updated to support both standard short-term, long-term tracking and tracking with multi-channel imagery. Performance of the tested trackers typically by far exceeds standard baselines. The source code for most of the trackers is publicly available from the VOT page. The dataset, the evaluation kit and the results are publicly available at the challenge website(1).
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| 4. |
- Tang, Ting-Ting, et al.
(författare)
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Impaired thymic export and apoptosis contribute to regulatory T-cell defects in patients with chronic heart failure.
- 2011
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Ingår i: PLoS ONE. - : Public Library of Science (PLoS). - 1932-6203 .- 1932-6203. ; 6:9, s. e24272-
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Tidskriftsartikel (refereegranskat)abstract
- Animal studies suggest that regulatory T (T(reg)) cells play a beneficial role in ventricular remodeling and our previous data have demonstrated defects of T(reg) cells in patients with chronic heart failure (CHF). However, the mechanisms behind T(reg-)cell defects remained unknown. We here sought to elucidate the mechanism of T(reg-)cell defects in CHF patients.
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| 5. |
- Adnane, Bouchaib, et al.
(författare)
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Mid/far-infrared detection using a MESFET with B-modulation doped Ge-dot/SiGe-well multiple stacks in the channel region
- 2004
-
Konferensbidrag (refereegranskat)abstract
- Multiple modulation-doped Ge-dot/SiGe-QW stack structures were grown using MBE, and processed as FET devices for mid/far infrared detection. From a non-optimized device, a broadband photoresponse has been observed in the mid-infrared range of 3-15 μm. A peak responsivity was estimated to be as high as 100 mA/W at T= 20 K. This work indicates that SiGE QD/QW structures using the lateral transport geometry can be a potential candidate for photodetectors operating in far-infrared range.
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| 6. |
- Adnane, Bouchaib
(författare)
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Optical characterization of Silicon-based self-assembled nanostructures
- 2010
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This PhD thesis summarizes the work carried on the optical characterizations of some Si-based self-assembled nanostructures, particularly SiGe/Si quantum dots (QDs) and nanocrystalline (nc)-Si embedded in mesoporous silica (MS) using photoconductivity (PC), photoluminescence (PL), and photoluminescence excitation (PLE) measurements. The spectroscopic studies of SiGe/Si QDs grown on Si by molecular beam epitaxy revealed for the first time well-resolved PLE resonances. When correlated with numerical analysis, these resonances were directly related to the co-existence of spatially direct (inside the SiGe dot) and indirect (across the Si/Ge interface) recombination processes involving different dot populations selected by the monitored detection energy for PLE acquisition. The characteristics of these two transitions were further studied in detail by PLE (in some case implemented together with selective PL) on various samples, which contained either only one Ge dot layer or multiple Gedot/Si stacks, grown at substrate temperatures ranging from 430 to 580 °C; especially the temperature- and excitation power-dependence of the excitation properties. The results illustrated that the electronic structure of SiGe dots are influenced by size, Ge composition, as well as strain connected, and sometimes a mixed effect. Another attempt of the project was the fabrication of lateral transport mid-infrared photodetectors based on multiple Ge-dot/Si stacked structures. A broadband photoresponsivity of the processed multi-finger detectors was estimated to be about 90 mA/W over 3-15 μm range at 20 K, and the peaked photoresponse was measured at ~10 μm. The origin of the measured photocurrent, as elucidated by photoluminescence and photoluminescence excitation spectroscopies, was related to intersubband absorption of normal incidence infrared radiation corresponding to energies between the ground states of the heavy hole and the light hole in the valence band of the SiGe/Si QDs, and subsequent charge transfer to the Ge 2D wetting layer acting as a conduction channel. The absence of photocurrent in the energy range expected for a transition from the ground state to the first excited state of the heavy hole indicated that the holes in the SiGe dots behave essentially as 2D in character rather than a truly 3D confinement, where the transitions between heavy holes states are not allowed for TE polarized radiation (normal incidence). Finally, Si(or Ge) nanocrystals embedded in mesoporous silica samples prepared by spincoating and atomic layer chemical vapor deposition were optically investigated by means of PL with various excitation powers, together with several attempts using different post rapid thermal annealing processes. The shape and energy position of the PL spectra of the nc-Si embedded in MS samples and a reference MS template without nc incorporation were rather similar, but the luminescence was much more intense for those embedded with nanocrystals. This implies that the emission mechanism for MS samples with or without nc-Si could be the same, i.e., the light emission was governed by the surface properties of silica. The semiconductor nanocrystals played a role by sensitizing the luminescence emission through generating more photo-excited carriers. These carriers were then trapped in the defect state e.g. the interfacial oxygen defect sites and subsequently recombine to increase the PL intensity.
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| 7. |
- Adnane, Bouchaib, et al.
(författare)
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Origin of photoresponse at 8-14 μm in stacks of self-assembled SiGe/Si quantum dots
- 2009
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X.
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- A normal incidence photodetector operating at 8-14 μm is demonstrated using p-type δ-doped SiGe dot multilayer structures grown by molecular beam epitaxy on Si(001) substrates. Based on the experimental results of photoluminescence and photoluminescence excitation spectroscopies together with numerical analysis, the origin of the measured photocurrent was attributed to intersubband optical transitions between the heavy hole and light hole states of the valence band of the self-assembled SiGe dots and subsequent lateral transport of photo-excited carriers in the conduction channels formed by Ge wetting layers.
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| 8. |
- Adnane, Bouchaib, et al.
(författare)
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Photoluminescence excitation spectroscopy of self-assembled SiGe/Si quantum dots
- 2009
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Photoluminescence excitation (PLE) experiments are reported for various self-assembled SiGe/Si dot samples grown on Si(001) by molecular beam epitaxy at substrate temperatures ranging from 430 to 580 C. Two excitation peaks were observed, and the characteristics of the involved optical transitions were studied in detail by PLE (in one case implemented together with selective photoluminescence, SPL) on different samples containing either only one SiGe dot layer or multiple SiGe-dot/Si stacks. The temperature- and power-dependence of the excitation properties together with the results of six-band k.p calculations support the assignment of the observed PLE peaks to spatially direct and indirect transitions collected from two different SiGe dot populations.
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| 9. |
- Adnane, Bouchaib, et al.
(författare)
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Photoluminescence study of nanocrystalline-Si(Ge) embedded in mesoporous silica
- 2009
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Ingår i: Solid-State Electronics. - : Elsevier BV. - 0038-1101 .- 1879-2405. ; 53:8, s. 862-864
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Tidskriftsartikel (refereegranskat)abstract
- Photoluminescence (PL) properties of mesoporous silica (MS) samples incorporated with Si or Ge nanocrystals (nc) have been investigated with various excitation powers and post-RTA processes. The analysis of experimental results revealed a superlinear intensity dependence (m = 1.7) in the MS reference sample without nanocrystals, while a sublinear behavior (m = 0.8) is observed for the nc-Si in MS. It thus suggests the same recombination responsible for the luminescence at similar to 2.75 eV for both samples, but different kinetic limitations for the carrier transfer processes. Si nanocrystals play in this case an important role in generating more photo-excited carriers, enhancing the PL intensity.
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| 10. |
- Adnane, Bouchaib, et al.
(författare)
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Spatially direct and indirect transitions of self-assembled SiGe/Si quantum dots studied by photoluminescence excitation spectroscopy
- 2010
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Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 96:18, s. 181107-
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Tidskriftsartikel (refereegranskat)abstract
- Well-resolved photoluminescence excitation (PLE) spectra are reported for selfassembled SiGe dots grown on Si(100) by molecular beam epitaxy. The observation of two excitation resonance peaks is attributed to two different excitation/de-excitation routes of interband optical transitions connected to the spatially direct and indirect recombination processes. It is concluded that two dot populations are addressed by each monitored luminescence energy for the PLE acquisition.
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| 11. |
- Chen, P.Y., et al.
(författare)
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Synthesis design of artificial magnetic metamaterials using a genetic algorithm
- 2008
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Ingår i: Optics Express. - 1094-4087. ; 16:17, s. 12806-12818
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Tidskriftsartikel (refereegranskat)abstract
- In this article, we present a genetic algorithm (GA) as one branch of artificial intelligence (AI) for the optimization-design of the artificial magnetic metamaterial whose structure is automatically generated by computer through the filling element methodology. A representative design example, metamaterials with permeability of negative unity, is investigated and the optimized structures found by the GA are presented. It is also demonstrated that our approach is effective for the synthesis of functional magnetic and electric metamaterials with optimal structures. This GA-based optimization-design technique shows great versatility and applicability in the design of functional metamaterials. © 2008 Optical Society of America.
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| 12. |
- Cheng, M.H., et al.
(författare)
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Growth and characterization of Ge nanostructures selectively grown on patterned Si
- 2008
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Ingår i: Thin Solid Films. - : Elsevier Science B.V., Amsterdam.. - 0040-6090 .- 1879-2731. ; 517:1, s. 57-61
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Tidskriftsartikel (refereegranskat)abstract
- By utilizing different distribution of strain fields around the edges of oxide, which are dominated by a series of sizes of oxide-patterned windows, long-range ordered self-assembly Ge nanostructures, such as nano-rings, nano-disks and nano-dots, were selectively grown by ultra high vacuum chemical vapor deposition (UHV-CVD) on Si (001) substrates. High-resolution double-crystal symmetrical omega/2 theta scans and two-dimensional reciprocal space mapping (2D-RSM) technologies employing the triple axis X-ray diffractometry have been used to evaluate the quality and strain status of as-deposited as well as in-situ annealed Ge nanostructures. Furthermore, we also compare the quality and strain status of Ge epilayers grown on planar unpatterned Si substrates. It was found that the quality of all Ge epitaxial structures is improved after in-situ annealing process and the quality of Ge nano-disk structures is better than that of Ge epilayers; on planar unpatterned Si substrates, because oxide sidewalls are effective dislocation sinks. We also noted that the degree of relaxation for as-deposited Ge epilayers on planar unpatterned Si substrates is less than that for as-deposited Ge nano-disk structures. After in-situ annealing process,all Ge epitaxial structures are almost at full relaxation whatever Ge epitaxial structures grew on patterned or unpatterned Si substrates.
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| 13. |
- Du, Chun-Xia, et al.
(författare)
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Efficient 1.54 µm light emission from Si/SiGe/Si : Er
- 2001
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Ingår i: Materials Science & Engineering. - 0921-5107 .- 1873-4944. ; 81:1-3, s. 105-108
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Tidskriftsartikel (refereegranskat)abstract
- Si/SiGe/Si:Er:O-heterojunction bipolar transistor (HBT)-type light emitting devices with Er3+ ions incorporated in the collector region have been fabricated using layered structures prepared by differential molecular beam epitaxy (MBE). Intense light emission at 1.54 µm has been observed at room temperature by hot electron impact excitation at rather low injection current and applied voltage. Separate controls of the injection current and bias voltage make it possible to perform detailed electroluminescence (EL) studies that can not be done with conventional Si:Er light emitting diodes (LEDs). Saturation of the EL intensity occurs at very low current densities indicating a 100-fold increase of the effective excitation cross-section for Si/SiGe/Si:Er:O-HBTs compared with Si:Er-LEDs. © 2001 Elsevier Science B.V.
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| 14. |
- Du, Chun-Xia, et al.
(författare)
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Electroluminescence studies of Er and SiO co-doped Si layers prepared by molecular beam epitaxy
- 2000
-
Ingår i: Optical materials (Amsterdam). - 0925-3467 .- 1873-1252. ; 14:3, s. 259-265
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Tidskriftsartikel (refereegranskat)abstract
- Er/O co-doped Si light emitting diodes (LEDs) have been fabricated using layer structures prepared by molecular beam epitaxy (MBE). The Er/O doping was realized by sublimation of elemental Er and silicon monoxide simultaneously with Si during MBE growth. Intense Er-related electroluminescence (EL) at 1.54 mu m was observed at room temperature from p(+)-SiGe/i-SiGe-Si/Si:Er/n(+)-Si LEDs by electron impact excitation under reverse bias. It has been found that the EL intensity was increased with increasing growth temperature of the Si:Er/O layer in the range of 430-575 degrees C. The electrical pumping power dependence of EL intensity has been studied. An excitation cross section value of similar to 1 x 10(-16) cm(2) was estimated based on the experimental data and model fitting. The EL decay behavior under various injection and bias conditions has been studied by time-resolved EL measurements. The overall luminescence decay time is found to strongly depend on the injection parameters. Two types of de-excitation mechanisms due to Auger energy transfer to free carriers introduced by either dopant ionization or carrier injection have been discussed. Both Auger processes play an important role in reduction of the EL intensity when there is a high density of carriers with excited Er ions. (C) 2000 Elsevier Science B.V. All rights reserved.
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| 15. |
- Du, Chun-Xia, et al.
(författare)
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Si/SiGe/Si : Er
- 2001
-
Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 78:12, s. 1697-1699
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Tidskriftsartikel (refereegranskat)abstract
- Si/SiGe/Si:Er:O heterojunction bipolar transistor (HBT) type light-emitting devices with Er3+ ions incorporated in the collector region have been fabricated using a layered structure grown by differential molecular-beam epitaxy. Electroluminescence measurements on processed light-emitting HBTs can be performed in either constant driving current mode or constant applied bias mode, which is an important advantage over conventional Si:Er light-emitting diodes. Intense room-temperature light emission at the Er3+ characteristic wavelength of 1.54 µm has been observed at low driving current density, e.g., 0.1 A cm-2, and low applied bias, e.g., 3 V, across the collector and emitter. © 2001 American Institute of Physics.
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| 16. |
- Du, Chun-Xia, et al.
(författare)
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Si/SiGe/Si : Er : O light-emitting transistors prepared by differential molecular-beam epitaxy
- 2001
-
Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 78:12, s. 1697-1699
-
Tidskriftsartikel (refereegranskat)abstract
- Si/SiGe/Si:Er:O heterojunction bipolar transistor (HBT) type light-emitting devices with Er3+ ions incorporated in the collector region have been fabricated using a layered structure grown by differential molecular-beam epitaxy. Electroluminescence measurements on processed light-emitting HBTs can be performed in either constant driving current mode or constant applied bias mode, which is an important advantage over conventional Si:Er light-emitting diodes. Intense room-temperature light emission at the Er3+ characteristic wavelength of 1.54 mum has been observed at low driving current density, e.g., 0.1 A cm(-2), and low applied bias, e.g., 3 V, across the collector and emitter. (C) 2001 American Institute of Physics.
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| 17. |
- Duteil, F., et al.
(författare)
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Er/O doped Si1-xGex alloy layers grown by MBE
- 2001
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Ingår i: Optical materials (Amsterdam). - 0925-3467 .- 1873-1252. ; 17:1-2, s. 131-134
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Silicon-based light emitting diodes (LEDs) containing an Er/O-doped Si1-xGex active layer have been studied. The structures were grown by molecular beam epitaxy (MBE), with Er and O concentrations of 5 × 1019 and 1 × 1020 cm-3, respectively, using Er and silicon monoxide sources. The microstructure has been studied by X-ray diffraction (XRD) and cross-sectional transmission electron microscopy, and it is found that Er/O-doped Si0.92Ge0.08 layers of high crystalline quality, can be obtained. Electroluminescence (EL) measurements have been performed on reverse-biased Er/O doped diodes both from the surface and from the edge and the emission at 1.54 µm associated with the Er3+ ions has been studied at 300 K and lower temperatures. To evaluate the possibility to use a Si1-xGex layer for waveguiding in Si-based optoelectronics, studies of the refractive index n of strained Si1-xGex as a function of the Ge concentration have been done by spectroscopic ellipsometry in the range 0.3-1.7 µm. At 1.54 µm the refractive index increases monotonically with the Ge concentration up to n = 3.542 for a Ge concentration of 21.3%. © 2001 Elsevier Science B.V.
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| 18. |
- Duteil, F., et al.
(författare)
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Luminescence and microstructure of Er/O co-doped Si structures grown by MBE using Er and SiO evaporation
- 2000
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Ingår i: Materials Science in Semiconductor Processing. - 1369-8001 .- 1873-4081. ; 3:5-6, s. 523-528
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Tidskriftsartikel (refereegranskat)abstract
- Er and O co-doped Si structures have been prepared using molecular-beam epitaxy (MBE) with fluxes of Er and O obtained from Er and silicon monoxide (SiO) evaporation in high-temperature cells. The incorporation of Er and O has been studied for concentrations of up to 2×1020 and 1×1021 cm-3, respectively. Surface segregation of Er can take place, but with O co-doping the segregation is suppressed and Er-doped layers without any indication of surface segregation can be prepared. Si1-xGex and Si1-yCy layers doped with Er/O during growth at different substrate temperatures show more defects than corresponding Si layers. Strong emission at 1.54µm associated with the intra-4f transition of Er3+ ions is observed in electroluminescence (EL) at room temperature in reverse-biased p-i-n-junctions. To optimize the EL intensity we have varied the Er/O ratio and the temperature during growth of the Er/O-doped layer. Using an Er-concentration of around 1×1020 cm-3 we find that Er/O ratios of 1:2 or 1:4 give higher intensity than 1:1 while the stability with respect to breakdown is reduced for the highest used O concentrations. For increasing growth temperatures in the range 400-575 °C there is an increase in the EL intensity. A positive effect of post-annealing on the photoluminescence intensity has also been observed.
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| 19. |
- Elfving, Anders, et al.
(författare)
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Asymmetric relaxation of SiGe/Si(110) investigated by high-resolution x-ray diffraction reciprocal space mapping
- 2006
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Ingår i: Applied physics letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 89, s. 181901-1--181901-3
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Tidskriftsartikel (refereegranskat)abstract
- Strain relaxation of SiGe/Si(110) has been studied by x-ray reciprocal space mapping. To get information about the in-plane lattice mismatch in different directions, two-dimensional maps around, e.g., (260) and (062) reciprocal lattice points have been obtained from Si0.8Ge0.2/Si(110) samples, which were exposed to different annealing conditions. The in-plane lattice mismatch was found to be asymmetric with the major strain relaxation observed in the lateral [001] direction. This was associated with the formation and propagation of dislocations oriented along [10]. The relaxation of as-grown structures during postannealing is thus different from relaxation during growth, which is mainly along [10].
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| 20. |
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| 21. |
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| 22. |
- Elfving, Anders, 1976-
(författare)
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Near-infrared photodetectors based on Si/SiGe nanostructures
- 2006
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Two types of photodetectors containing Ge/Si quantum dots have been fabricated based on materials grown by molecular beam epitaxy and characterized with several experimental techniques. The aim was to study new device architectures with the implementation of Ge nanostructures, in order to obtain high detection efficiency in the near infrared range at room temperature.Heterojunction bipolar phototransistors were fabricated with 10 Ge dot layers in the base-collector (b-c) junction. With the illumination of near infrared radiation at 1.31 to 1.55 µm, the incident light would excite the carriers. The applied field across the b-c junction caused hole transport into the base, leading to a reduced potential barrier between the emitter-base (e-b) junction. Subsequently, this resulted in enhanced injection of electrons across the base into the collector, i.e., forming an amplified photo-induced current. We have therefore obtained significantly enhanced photo-response for the Ge-dot based phototransistors, compared to corresponding quantum dot p-i-n photodiodes. Responsivity values up to 470 mA/W were measured at 1.31 µm using waveguide geometry, and ∼2.5 A/W at 850 nm, while the dark current was as low as 0.01 mA/cm2 at –2 V.Metal-oxide field-effect phototransistors were also studied. These lateral detectors were processed with three terminals for source, drain and gate contacts. The Ge quantum dot layers were sandwiched between pseudomorphically grown SiGe quantum wells. The detector devices were processed using a multi-finger comb structure with an isolated gate contact on top of each finger and patterned metal contacts on the side edges for source and drain. It was found that the photo-responsivity was increased by a factor of more than 20 when a proper gate bias was applied. With VG above threshold, the measured response was 350 and >30 mA/W at 1.31 and 1.55 µm, respectively.Properties of Si/Si1-xGex nanostructures were examined, in order to facilitate proper design of the above mentioned transistor types of photodetectors. The carrier recombination processes were characterized by photoluminescence measurements, and the results revealed a gradual change from spatially indirect to direct transitions in type II Si1-xGex islands with increased measurement temperature. Energy dispersive X-ray spectrometry of buried Ge islands produced at different temperatures indicated a gradual decrease of the Ge concentration with temperature, which was due to the enhanced intermixing of Si and Ge atoms. At a deposition temperature of 730°C the Ge concentration was as low as around 40 %.Finally, the thermal stability of the Si/SiGe(110) material system, which is a promising candidate for future CMOS technology due to its high carrier mobility, was investigated by high resolution X-ray diffraction reciprocal space mapping. Anisotropic strain relaxation was observed with maximum in-plane lattice mismatch in the [001] direction.
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| 23. |
- Elfving, Anders, et al.
(författare)
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SiGe (Ge-dot) heterojunction phototransistors for efficient light detection at 1.3-1.55 µm
- 2003
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Ingår i: Physica E: Low-dimensional Systems and Nanostructures. - 1386-9477. ; 16:3-4, s. 528-532
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Tidskriftsartikel (refereegranskat)abstract
- The aim of this work is to develop a Si/SiGe HBT-type phototransistor with several Ge dot layers incorporated in the collector, in order to obtain improved light detectivity at 1.3–1.55 μm. The MBE grown HBT detectors are of n–p–n type and based on a multilayer structure containing 10 Ge-dot layers (8 ML in each layer, separated by 60 nm Si spacer) in the base-collector junction. The transistors were processed for normal incidence or with waveguide geometry where the light is coupled through the edge of the sample. The measured breakdown voltage, BVceo, was about 6 V. Compared to a p–i–n reference photodiode with the same dot layer structure, photoconductivity measurements show that the responsivity is improved by a factor of 60 for normal incidence at 1.3 μm. When the light is coupled through the edge of the device, the detectivity is even further enhanced. The measured photo-responsivity is more than 100 and 5 mA/W at 1.3 and 1.55 μm, respectively.
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| 24. |
- Elfving, Anders, et al.
(författare)
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Three-terminal Ge dot/SiGe quantum-well photodetectors for near-infrared light detection
- 2006
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Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 89, s. 083510-083513
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Tidskriftsartikel (refereegranskat)abstract
- A three-terminal metal-oxide-semiconductor field-effect transistor type of photodetector has been fabricated with a multiple stack of Ge dot/SiGe quantum-well heterostructures as the active region for light detection at 1.3–1.55 µm. Gate-dependent edge incidence photoconductivity measurements at room temperature revealed a strong dependence of the photoresponse on the gate voltage. At positive gate bias, the hole transport from the dots into the wells was improved, resulting in a faster response. The high photoresponsivity at negative VG, measured to be 350 mA W–1 at 1.31 µm and 30 mA W–1 at 1.55 µm, was ascribed to the photoconductive gain.
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| 25. |
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