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Numerical Methods For Partial Differential Equations

The Physics of Low-dimensional Semiconductors: An Introduction; J.H. Davies, Cambridge University Press, UK, ISBN 0-521-48491-X, $44.95

In this Letter we present the electrical and electro-optical characterization of single crystalline germanium nanowires (NWs) under tensile strain conditions. The measurements were performed on vapor–liquid–solid (VLS) grown germanium (Ge) NWs, monolithically integrated into a micromechanical 3-point strain module. Uniaxial stress is applied along the ⟨111⟩ growth direction of individual, 100 nm thick Ge NWs while at the same time performing electrical and optical characterization at room temperature. Compared to bulk germanium, an anomalously high and negative-signed piezoresistive coefficient has been found. Spectrally resolved photocurrent characterization on strained NWs gives experimental evidence on the strain-induced modifications of the band structure. Particularly we are revealing a rapid decrease in resistivity and a red-shift in photocurrent spectra under high strain conditions. For a tensile strain of 1.8%, resistivity decreased by a factor of 30, and the photocurrent spectra shifted by 88 meV...

Tuning the Electro-optical Properties of Germanium Nanowires by Tensile Strain

Due to resource constraints in wireless sensor networks and the presence of unwanted conditions in communication systems and transmission channels, the suggestion of a robust method which provides battery lifetime increment and relative security is of vital importance. This paper considers the secure communication in wireless sensor networks based on new robust adaptive finite time chaos synchronization approach in the presence of noise and uncertainty. For this purpose, the modified Chua oscillators are added to the base station and sensor nodes to generate the chaotic signals. Chaotic signals are impregnated with the noise and uncertainty. At first, we apply the modified independent component analysis to separate the noise from the chaotic signals. Then, using the adaptive finite-time sliding mode controller, a control law and an adaptive parameter-tuning method is proposed to achieve the finite-time chaos synchronization under the noisy conditions and parametric uncertainties. Synchronization between the base station and each of the sensor nodes is realized by multiplying a selection matrix by the specified chaotic signal which is broadcasted by the base station to the sensor nodes. Simulation results are presented to show the effectiveness and applicability of the proposed technique.

Secure communication in wireless sensor networks based on chaos synchronization using adaptive sliding mode control

The international technology roadmap of semiconductors (ITRS) is approaching the historical end point and we observe that the semiconductor industry is driving complementary metal oxide semiconductor (CMOS) further towards unknown zones. Today's transistors with 3D structure and integrated advanced strain engineering differ radically from the original planar 2D ones due to the scaling down of the gate and source/drain regions according to Moore's law. This article presents a review of new architectures, simulation methods, and process technology for nano-scale transistors on the approach to the end of ITRS technology. The discussions cover innovative methods, challenges and difficulties in device processing, as well as new metrology techniques that may appear in the near future.

State of the Art and Future Perspectives in Advanced CMOS Technology.

This study theoretically analyses the performance of multiple quantum well infrared photodetector mainly with the variation of active layer doping. However, the effect of temperature and applied bias has also been studied. Results show that the effect of doping on the responsivity is significant whereas on the dark current is less significant. Effect of temperature on the dark current is more significant compared with that of doping concentration. Moreover, concerning the detectivity of the device, choice of doping plays a significant role on the detector.

https://ietresearch.onlinelibrary.wiley.com/doi/epdf/10.1049/iet-cds.2017.0011

Effect of doping on the performance of multiple quantum well infrared photodetector

In this work, we have quantified the effects of dot size variability on the interband optical absorption spectra of interdiffused III–V quantum dot (QD) systems through analytical models which agree well with experimental data. The variability function induced due to inhomogeneous nature of dot size distribution has been considered to be Gaussian in nature, where individual dots have been assumed to be lens-shaped having inhomogeneous material composition inside the dot. This is necessary to consider any realistic interdiffused system. Such an assumption is not in line-up with the conventional methodologies reported earlier on the subject, where the QD composition was considered to be homogeneous, presenting an ideal or quasi-ideal situation which may be applicable only for dot structures in absence of interdiffusion. Moreover, for the first time, the effects of dot size variability and interdiffusion on the optical spectra of QD systems have been analysed in the same platform. The effects of dot size deviation, QD aspect ratio, core group III content inside the dot, standard deviation, and so on, on the optical absorption spectra have been demonstrated.

Dot size variability induced changes in the optical absorption spectra of interdiffused quantum dot systems

This paper focuses on the potential of compressive strained group IV quantum well (QW) structure in photo sensitive devices specially photodetectors. Direct absorption characteristic in compressive strained SiGe/GeSn QW is determined with the help of Schrodinger equation. The Schrodinger equation for Г-valley, Heavy hole band and Light hole band is solved by finite difference method (FDM). Due to compressive strain, heavy hole (HH) band pushes upwards and light hole (LH) band lowers on addition of Sn concentration. Absorption coefficient of QW is evaluated by using Fermi’s golden rule. Result shows that significant absorption is obtained in short wave infrared range. HH to conduction band transition provides greater absorption than LH to conduction band transition. Result also shows that compressive strained GeSn become direct band gap in nature for Sn concentration greater than 0.15 (15 %).

Theoretical Analysis of Direct Transition in SiGe/GeSn Strained Quantum Well Structure by Finite Difference Method

Background & objectives Jharkhand is one of the highly malaria endemic states in India and experiencing vast ecological and human-induced changes over the years. These changes have provided more favourable conditions for malaria transmission in the region. The present study was carried out to find out the distribution and prevalence of anopheline vector and non-vector species in District Ramgarh of Jharkhand state. Methods Daytime indoor resting adult female anopheline mosquitoes were collected from four subcentres comprising of eight study villages in District Ramgarh. The collections were made from fixed as well as random human dwellings and cattlesheds on fortnightly basis using manual aspiration method from January to December 2012. Mosquito identification was done by using standard identification keys. Results A total of 18,875 anophelines belonging to 19 species were collected. Of these, 61.87% were vector species (An. culicifacies, An. fluviatilis and An. annularis). Of total vector collection, 57.44% was observed in Gola block and 42.55% in Ramgarh. An. culicifacies was predominant species followed by An. fluviatilis and An. annularis in the study area. Out of 19, eight anopheline species exhibited successional changes in their composition over the period of years. Statistical analysis revealed positive correlation between meteorological variables and man hour density in case of An. culicifacies, whereas these were negatively correlated in case of An. fluviatilis and An. annularis. Interpretation & conclusion The study revealed the prevalence of three recognised malaria vector species (An. culicifacies, An. fluviatilis and An. annularis) in high density throughout the year in this area, which indicates possibility of widening of malaria transmission window in the presence of malaria parasites. The shifting of anopheline species in Ramgarh also indicate alteration in ecological, environmental and sociological conditions, which necessitate routine monitoring on ecology and successional changes of vector species as well as malariological survey for management and adoption of appropriate vector control strategies in this area.

Anopheline mosquitoes in District Ramgarh (Jharkhand), India.

The Group IV Photonics (GFP) which include an alloy of Si, Ge & Sn that gives a direct bandgap material (GeSn, SiGeSn) in near and mid-IR region used as an active material in photonics devices. The multiple quantum well SiGeSn/GeSn transistor laser structure is considered in this paper and performance parameters are evaluated for the same. The result shows that the threshold base current density (2.6 kA/cm2) for the proposed device initially decreases with increasing number of quantum well (QW) and later on it saturates. The current gain and output photon density of the device decreases and increases respectively, with increasing number of QW.

Mukul K. Das

Papers

Effect of doping on the performance of multiple quantum well infrared photodetector

Dot size variability induced changes in the optical absorption spectra of interdiffused quantum dot systems

Theoretical Analysis of Direct Transition in SiGe/GeSn Strained Quantum Well Structure by Finite Difference Method

Anopheline mosquitoes in District Ramgarh (Jharkhand), India.

Performance analysis of GeSn-alloy-based multiple quantum well transistor laser