Raisul Islam

Renewable energy scenario of Bangladesh: Physical perspective

The looming energy crisis, heightened by the continuing depletion of fossil fuels, accentuates the need for deployment of renewable energy resources in Bangladesh, now more than ever before. Though hydrocarbon resources in the country are limited, the substantial availability of renewable energy sources in the form of solar, biomass, hydropower and wind energy offers opportunities of sustainable energy based development. Motivated by this auspice, the government of Bangladesh and different non-government organizations have been working towards the dissemination of renewable energy based technologies throughout the country. Though this diffusion of renewable energy sources is yet to assume extensive commercial dimensions and widespread implementations, the advancement has been significant in recent years. With the objective of reviewing this progress, this paper presents a comprehensive study of the contemporary renewable energy scenario in Bangladesh in terms of distribution, research and infrastructural development in the country. In addition to this, installed capacity has been calculated to assess the relative contributions of the five renewable energy sectors of Bangladesh.

On the distinction between triple gate (TG) and double gate (DG) SOI FinFETs: A proposal of critical top oxide thickness

Distinction between triple gate (TG) and double gate (DG) silicon-on-insulator (SOI) FinFETs is presented here on the basis of their electrostatic and transport characteristics. A study missing in previous works on DG and TG FinFETs is the characterization of these structures with respect to the variation of top oxide thickness. In fact an exact value of the top-oxide thickness that can differentiate DG FinFETs from TG ones has not been reported yet. From this perspective, electrostatic and transport characteristics of DG and TG FinFETs having sub-10 nm fin dimensions are investigated in this work as a function of the top oxide thickness. To duly incorporate the quantum-mechanical (QM) effects in such nanoscale regime of operation, the devices are simulated by self-consistently solving the coupled Schrödingers and Poissons equations. Simulation results suggest that DG and TG FinFETs can be differentiated by a parameter which we define in our work with respect to the surface potentials existing beneath the top and side gates. This finding in effect proposes a critical top oxide thickness of FinFET that can draw the distinction between its DG and TG variants. The results also indicate that deposition of top oxide layer beyond a limit does not bring about any significant change in the electrostatic and transport characteristic of DG FinFETs in the ballistic limit.

Quantum mechanical effect on determining threshold voltage of trigate FinFET using self-consistent analysis

The quantum definition based threshold voltage has been evaluated for triple-gate (TG) SOI FinFETs using self-consistent Schrödinger-Poisson solver. Although a new quantum definition of threshold voltage for multiple gate SOI MOSFETs has been provided in recent literature, in-depth analysis of quantization effects on threshold voltage calculation for highly scaled TG FinFETs is yet to be done. In this paper, the electrostatics of the device has been explored from a quantum mechanical point of view for variation in silicon film thickness in the sub 10nm regime. Also the self-consistent solver, which takes wave function penetration and other quantum mechanical (QM) effects into account, has been utilized here to establish the capacitance-voltage (C-V) characteristics and a modified approach has been proposed for threshold voltage calculation.

Potential future generation nanoscale MOS device: Trigate (TG) or Double Gate (DG) FinFETs?

Performance limit of Tri-Gate (TG) and Double Gate (DG) SOI FinFETs have been compared in terms of ballistic current which is calculated using a modified model shown for conventional MOSFET. Such a simple model for calculating ballistic current in nanoscale multigate MOSFETs is yet to be reported. Comparison of the ballistic current for different Si fin thicknesses reveals that for decreasing fin thickness, strong quantum mechanical confinement degrades the ballistic current. The simulation result presented here contradicts with the previously reported result that TG FinFETs show better performance than DG FinFET and reveals that DG FinFET shows slightly better performance below 5nm fin thickness. This result indicates that in terms of ballistic drive current the tri-gate device is not always favorable than double gate device especially when the device dimension is scaled down deeply.

Self consistent simulation for C-V characterization of sub 10nm Tri-Gate and Double Gate SOI FinFETs incorporating quantum mechanical effects

Capacitance-Voltage (C-V) characteristics of Tri-Gate (TG) and Double Gate (DG) Silicon-on-Insulator (SOI) FinFETs having sub 10nm dimensions are obtained by self consistent method using coupled Schrodinger-Poisson solver taking into account quantum mechanical effects. Though self-consistent simulation to determine current and other short channel effects in these devices have been demonstrated in recent literature, C-V characterization is yet to be done using self-consistent method. We investigate here the C-V characteristics of the devices with the variation of an important process parameter, the silicon film thickness. The gate inversion capacitance should be higher in TG FinFET than that of DG FinFET because of the presence of thick oxide layer under the top gate of DG FinFET. Simulation results validate this phenomenon with an indication that drive current tends to increase with an increase in the number of gates.

Segmentation and 3D visualization of volumetric image for detection of tumor in cancerous brain

Development of an accurate three dimensional (3D) model of human skull showing the shape and relative position of a tumor inside the cancerous brain is crucial for taking pre-surgical or pre-therapy measures. This paper presents a new method for automatic segmentation of volumetric image which is a collection of series of spatially distributed slice images of a cancerous brain. The proposed method provides a 3D visualization in order to identify the position, shape, and size of a tumor inside the brain of a skull. Each of the images of the series is segmented using a level-based segmentation method using the histogram of image intensities. Such a segmentation of single image in the series results in spurious regions which may cause misleading 3D shapes of tumors. In order to obtain an accurate 3D model of the tumor inside the brain, both the intra- and inter-slice area-based thresholds are exploited for removing the spurious regions from the initially segmented images. The proposed segmentation scheme not only removes the false regions regarding the segmentation of tumor, but also effectively maintains the size and shape of the original tumor. Extensive experimentations on a number of volumetric images reveal that the proposed method can provide minimum volumetric noise in the extraction process of a tumor as compared to the recently introduced vector flow method.

Battery Chemistry Detection Algorithm Implementable with Intelligent Systems: A Step towards the Development of a Novel Charger Applicable for Multi-Chemistry Environment

This paper introduces a theory for the development of a fully automated multiple chemistry battery charger. This can be possible through the detection of battery chemistry. The paper presents an algorithm to differentiate between Ni based, Li-ion and Sealed Lead Acid (SLA) batteries through the analysis of voltage profile during charging and discharging periods. The algorithm was implemented and tested in an intelligent charger capable of charging aforementioned types of batteries without any prior identification of battery type from the user. This industrially viable solution for developing multiple chemistry charger can easily be incorporated in any embedded system using minimum input and circuit arrangement connected to the battery.

Prospect of charge enhancement by increasing top oxide thickness of silicon-on-insulator fin field effect transistors

The variation of electrostatic and transport characteristics of silicon-on-insulator fin field effect transistors (FinFETs) having sub-10 nm fin dimensions is investigated with the variation of top oxide thickness. Capacitance voltage and ballistic transport characteristics of double gate (DG) and triple gate (TG) FinFETs are obtained by self-consistently solving the coupled Schrodinger’s and Poisson’s equations. Performance enhancement can be obtained in terms of both on-state current and inversion capacitance by increasing the top oxide thickness of highly scaled FinFETs. The work suggests limiting values of the device parameter to differentiate the DG and TG variants of FinFET.

A physically based compact model for eigenenergy in in rich In 1−x Ga x As MOSFETs using modified Airy function approximation

We propose a compact model for calculating the quantized energy levels in InGaAs MOSFETs with Al2O3 gate dielectric. The model is based on the modified Airy function approximation, originally developed for Si nano-MOSFETs. The parameters of the model are extracted from numerical results calculated by self-consistent solution of one-dimensional Schrödinger and Poisson equation including the effect of wave function penetration into the gate dielectric. It is found that the compact model parameters are not sensitive to the variations in the In content in the channel layer and to the substrate doping density. Therefore, constant values of the parameters are proposed for both electrons and holes.

A physically based compact model for FinFETs on-resistance incorporating quantum mechanical effects

On-resistance is a term that occurs during high frequency switching. In this paper, the analysis of the on-resistance of FinFETs including quantum mechanical effect (QME), contact resistance, accumulation layer resistance, drift resistance and channel resistance is presented. Specific on resistance of FinFET is considered to be the series equivalent of contact resistance, drift resistance, accumulation layer resistance, channel resistance etc. Quantum mechanical effect changes the threshold voltage and thus change on current. So, this effect is considered in resistance modeling.