| 1. |
- Chiragwandi, ZG, et al.
(författare)
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dc characteristics of a nanoscale water-based transistor
- 2003
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Ingår i: Applied Physics Letters. - : American Institute of Physics. - 0003-6951 .- 1077-3118. ; 83:25, s. 5310-5312
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Tidskriftsartikel (refereegranskat)abstract
- We demonstrate a nanoscale water-based transistor. The presented nanoscale water-based transistor relies on the controlled modification of the pH in deionized water through the base applied electric field. The dc characteristics are presented and studied with a focus on the influence of the base applied electric field, the base electrode design, and their proximity to the sensing emitter and collector nanoelectrodes. The demonstrated water-based nanoscale device is of interest for many bioelectrical applications due to the biocompatibility and the wide usage and presence of water in biological systems.
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| 2. |
- Jacob, A P, et al.
(författare)
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Cryogenic performance of ultrathin oxide MOS capacitors with in situ doped p(+) poly-Si1-xGex and poly-Si gate materials
- 2002
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Ingår i: Semiconductor Science and Technology. - : Iop Publishing Ltd. - 0268-1242 .- 1361-6641. ; 17:9, s. 942-946
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Tidskriftsartikel (refereegranskat)abstract
- A low-temperature electrical characterization of ultrathin oxide MOS capacitors with p(+) poly-Si1-xGex and poly-Si gate is performed. The investigated structures are suitable for future nano-scaled high speed MOSFETs. The aim of this study is to compare the low-temperature performance of poly-Si1-xGex and poly-Si gate MOS structures in the nanoscale channel length regime. Apart from the significant change in the flat band voltage, the result shows that all the poly-Si and poly-Si1-xGex gated MOS structures exhibit two centres of polarity change (zero-temperature coefficients) in capacitance. The second polarity change leads to an exclusive phenomenon in these structures. The low-temperature capacitance is found to be less than high-temperature capacitance at strong accumulation and this is in contrast to what has been observed so far in metal-gated capacitors. It is also observed that the temperature dependence of the tunnelling current is only on the oxide thickness and not on the gate material used.
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| 3. |
- Jacob, AP, et al.
(författare)
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Post-growth process relaxation properties of strained Cd0.92Zn0.08Te/Cd0.83Zn0.17Te quantum well heterostructures grown by molecular beam epitaxy
- 2004
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Ingår i: Journal of Vacuum Science & Technology B. - : American Vacuum Society; 1999. - 1071-1023 .- 1520-8567. ; 22:2, s. 565-569
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Tidskriftsartikel (refereegranskat)abstract
- The post-growth structural stability regarding relaxation and defect propagation in Cd0.83Zn0.17Te/Cd0.92Zn0.08Te/Cd0.83Zn0.17Te quantum well (QW) heterostructures grown on [001] oriented Cd0.88Zn0.12Te substrates at 300degreesC by molecular beam epitaxy is investigated. The investigated heterostructures were subjected to post-growth thermal treatment in an ambient atmosphere in a temperature range between 280 and 550degreesC for 3 It each. We have used high-resolution x-ray diffraction as the main characterization tool. High-resolution rocking curves as well as the powerful two-dimensional reciprocal space mapping were employed in both symmetrical as well as asymmetrical reflections. The results indicate that at a post-growth temperature cycle of 350degreesC for 3 h slight modification of the Cd0.83Zn0.17Te/Cd0.92Zn0.08Te barrier/QW heterointerface smoothness is affected. This indicates the onset of migration of Zn atoms at this post-growth temperature time cycle. At 450 degreesC, this effect is more pronounced and seen as the complete disappearance of thickness fringes. For higher post-growth thermal treatment at 550 degreesC for 3 h, a hi-fi relaxation level accompanied by Zn content reduction is observed. A reduction of the Zn content down to 0.11 fractional value in the thick Cd0.83Zn0.17Te barrier is attributed to Zn out diffusion and/or Zn precipitation. (C) 2004 American Vacuum Society.
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| 4. |
- Jacob, AP, et al.
(författare)
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Ultrathin oxynitridation process through ion implantation in a poly Si1-xGex gate MOS capacitor
- 2003
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Ingår i: Materials Science in Semiconductor Processing. - : Elsevier Science B.V., Amsterdam.. - 1369-8001 .- 1873-4081. ; 6:03-Jan, s. 37-41
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Tidskriftsartikel (refereegranskat)abstract
- Effect of temperature and time of heat treatment on the distribution of ion-implanted nitrogen in poly Si0.65Ge0.35 gate MOS samples was studied. Secondary ion mass spectrometry (SIMS) was used for the qualitative analysis of the nitrogen distribution. Rapid thermal processing was carried out for a temperature range of 950-1070degreesC for the redistribution of ions. The nitrogen implantation doses were 5 x 10(14) cm(-2), 2 x 10(15) cm(-2) and 5 x 10(15) cm(-2), all with an implantation energy of 50 keV. For a uniform distribution of nitrogen in the SiO2 region, an optimal temperature at a well calibrated time must be applied and this depends on the implantation dose. For medium and high concentrations the optimal conditions were 1050degreesC and 15s, and 1070degreesC and 15s, respectively. A uniform nitrogen distribution could be obtained throughout the SiO2 film. Prolonged heat treatment can cause degradation of the oxide layer and movement of the nitrogen and oxygen into the channel and the poly-Si0.65Ge0.35 layer.
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| 5. |
- Myrberg, T, et al.
(författare)
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Structural properties of relaxed Ge buffer layers on Si(001) : effect of layer thickness and low temperature Si initial buffer
- 2004
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Ingår i: Journal of materials science. Materials in electronics. - : Springer Science Business Media. - 0957-4522 .- 1573-482X. ; 15:7, s. 411-417
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Tidskriftsartikel (refereegranskat)abstract
- We have used the strain sensitive tool two-dimensional reciprocal space mapping (2D-RSM) and high resolution rocking curves (HR-RC) to assess the effect of the layer thickness and the influence of low temperature Si buffer on the properties of fully relaxed Ge on Si (0 0 1). The samples were grown by chemical vapor deposition in an ASM commercial reactor. As complementary measurements we have employed secondary ion mass spectrometry (SIMS) for chemical analysis, cross sectional transmission electron microscopy for quality assessment, and finally atomic force microscopy (AFM) for investigating the surface roughness. The investigated samples have a thickness ranging from 0.25 to 5.0 mum. In addition and for a 5.0 mum thick Ge layer, an initial low temperature Si (LT-Si) template was grown before the Ge epitaxy. The results indicate that high quality fully relaxed Ge layers have been achieved using the adopted growth procedure. Most of the improvement in crystalline quality was observed for Ge layers with thickness up to 1.5 mum. Above this thickness the observed crystalline quality improvement was negligible. The LT-Si buffer observed to be disadvantageous for pure relaxed Ge growth.
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| 6. |
- Willander, Magnus, et al.
(författare)
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Silicon germanium strained layers and heterostructures
- 2004
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Ingår i: Physica Scripta. - : Royal Swedish Academy of Sciences. - 0031-8949 .- 1402-4896. ; T114, s. 22-30
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Tidskriftsartikel (refereegranskat)abstract
- The integration of strained-Si1-xGex into Si technology has enhanced the performance and extended the functionality of Si based circuits. The improvement of device performance is observed in both AC as well as DC characteristics of these devices. The category of such devices includes field effect as well as bipolar families. Speed performance in some based circuits has reached limits previously dominated by III-V heterostructures based devices. In addition, for some optoelectronics applications including photodetectors it is now possible to easily integrate strained-Si1-xGex based optical devices into standard Silicon technology. The impact of integrating strained and relaxed Si1-xGex alloys into Si technology is important. It has lead to stimulate Si research as well as offers easy options for performances that requires very complicated and costly process if pure Si has to be used. In this paper we start by discussing the strain and stability of Si1-xGex alloys. The origin and the process responsible for transient enhanced diffusion (TED) in highly doped Si containing layers will be mentioned. Due to the importance of TED for thin highly doped Boron strained-Si1-xGex layers and its degrading consequences, possible suppression design methods will be presented. Quantum well p-channel MOSFETs (QW-PMOSFETs) based on thin buried QW are solution to the low speed and weak current derivability. Different aspects of designing these devices for a better performance are briefly reviewed. Other FETs based on tensile strained Si on relaxed Si1-xGex for n-channel and modulation doped field effect transistors (MODFETs) showed excellent performance. Record AC performance well above 200GHz for f(max) is already observed and this record is expected to increase in the coming years. Heterojunction bipolar transistors (HPTs) with thin strained-Si1-xGex highly doped base have lead to optimize the performance of the bipolar technology for many applications easily. The strategies of design and the most important designs of HBTs for optimum AC as well as DC are discussed in details. This technology is now mature enough and that is manifested in the appearance in the market nowadays. Si1-xGex based FETs circuits compatible with standard Si CMOS processes are soon expected to appear in the market. Finally, we briefly discuss the recent advances in Si1-xGex based infrared photodetectors.
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| 7. |
- Ye, L L, et al.
(författare)
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Structural roughness and interface strain properties in Si/SiO2/poly-Si1-xGex tri-layer system with ultrathin oxide
- 2003
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Ingår i: Journal of materials science. Materials in electronics. - : Springer Science Business Media. - 0957-4522 .- 1573-482X. ; 14:4, s. 247-254
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Tidskriftsartikel (refereegranskat)abstract
- We have explored the microstructure and local interface strain in the poly-Si1-xGex/SiO2/Si tri-layer system with ultrathin oxides. High-resolution transmission electron microscopy (HRTEM) and high-resolution X-ray diffraction rocking curves (HR-RC) and two-dimensional reciprocal space mapping (2D-RSM) were the main characterization tools. The poly-Si1-xGex/SiO2/Si structures have x=0, 0.2, and 0.35 for ultrathin oxides (2.0-3.0 nm). The result shows that for the adopted growth process, the poly grain size depends very strongly on the Ge concentration, and it increases with increasing Ge mole fraction. In turn, this increase of the grain size in the poly-Si1-xGex/SiO2/Si reduces the strain in the film, which then affects the interface strain at the lower SiO2/Si interface. In addition, the presence of defects at the SiO2/Si interface was found to be greater for samples with no local interface strain.
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