Removal of threading dislocations from patterned heteroepitaxial semiconductors by glide to sidewalls

We have shown that threading dislocations can be removed from patterned heteroepitaxial semiconductors by glide to the sidewalls, which is driven by the presence of image forces. In principle, it should be possible to attain highly mismatched heteroepitaxial semiconductors which are completely free from threading dislocations, even though they are not pseudomorphic, by patterned heteroepitaxial processing. There are two basic approaches to patterned heteroepitaxial processing. The first involves selective area growth on a pre-patterned substrate. The second approach involves post-growth patterning followed by annealing. We have developed a quantitative model which predicts that there is a maximum lateral dimension for complete removal of threading dislocations by patterned heteroepitaxy. According to our model, this maximum lateral dimension is proportional to the layer thickness and increases monotonically with the lattice mismatch. For heteroepitaxial materials with greater than 1% lattice mismatch, our model predicts that practical device-sized threading dislocation-free regions may be realized by patterned heteroepitaxial processing.     

Design and Analysis of InGaN-GaN Modulation Doped Field-Effect Transistors (MODFETs) for Over 60 GHz Operation

A Modulation-Doped Field-Effect Transistor (MODFET) structure realized in InGaN-GaN material system is presented for the first time. An analytical model predicting the transport characteristics of the proposed MODFET structure is given in detail. Electron energy levels inside and outside the quantum well channel of the MODFET are evaluated. The two-dimensional electron gas (2DEG) density in the channel is calculated by self-consistently solving Schrödinger and Poisson's equations simultaneously. Analytical results of the current-voltage and transconductance characteristics are presented. The unity-current gain cutoff frequency (f _T) of the proposed device is computed as a function of the gate voltage V _G . The results are compared well with experimental f _T value of a GaN/AlGaN HFET device. By scaling the gate length down to 0.25 μm the proposed InGaN-GaN MODFET can be operated up to about 80GHz. It is shown in this paper that InGaN-GaN system has small degradation in f _T as the operating temperature is increased from 300°K to 400°K.     

Radiation resistance of MBE-grown GaInP/GaAs-based solar cells

Proton irradiation-based degradation characteristics for molecular beam epitaxy (MBE) grown Ga_0·51In_0·49P/GaAs single-junction tandem solar cells of n/p configuration are reported. The cells were irradiated with 3-MeV protons up to fluences of 10¹³ cm⁻². The cells were characterized with current–voltage (I–V) measurements at AMO conditions, and with spectral measurements. The damage coefficient for the GaAs cells was calculated using numerical modelling by the PC-1D program, and the result was compared with the InP damage coefficient. By using the ‘displacement damage dose’ approach, the degradation characteristics were compared with the published data for InP and GaAs/Ge solar cells. In addition, these MBE results were compared with the radiation behavior of metal-organic chemical vapor deposition (MOCVD)-grown Ga_0·51In_0·49P/GaAs single-, and double-junction solar cells of p/n configuration. © 1998 John Wiley & Sons, Ltd.     

APuML: An Efficient Approach to Detect Mobile Phishing Webpages using Machine Learning

Wireless Personal Communications - The recent trend in wireless technology has been tremadously increased the demand of higher frequency bands from every corners of the mobile technology. As next...     

Analysis and design considerations of a load and line independent zero voltage switching full bridge DC/DC converter topology

The analysis and design of a zero voltage switching (ZVS) full bridge DC/DC power converter topology is presented in this paper. The converter topology presented here employs an asymmetrical auxiliary circuit consisting of a few passive components. With this auxiliary circuit, the full bridge converter can achieve ZVS independent of line and load conditions. The operating principle of the circuit is demonstrated, and the steady state analysis is performed. Based on the analysis, a criterion for optimal design is given. Experiment and simulation on a 350-400 V to 55 V, 500 W prototype converter operated at 100 kHz verify the design and show an overall efficiency of greater than 97% at full load.     

Software‐defined network‐enabled opportunistic offloading and charging scheme in multi‐unmanned aerial vehicle ecosystem

Unmanned aerial vehicles (UAVs) are autonomous fliers, which can play different roles in modern day applications. In one of the important role, UAVs can act as aerial data forwarding nodes for communication range enhancement in remote areas. UAVs form a web of drones, which can be geo‐distributed across a large area to serve various applications. However, the two major contradicting challenges with respect to multi‐UAV networks are channel congestion and flight time enhancement. The use of effective data transmission techniques to handle congestion can lead to higher battery dissipation, which in turn end up in the reduction in flight time. However, it is utmost necessity to provide an effective framework, which can provide a viable solution for handling congestion in multi‐UAV networks while enhancing the flight time of UAVs. To handle these issues, software‐defined network (SDN)–enabled opportunistic offloading and charging scheme (SOOCS) in multi‐UAV ecosystem is designed in this paper. In this scheme, an opportunistic offloading scheme is proposed, which uses an SDN‐based control model to handle congestion issues. Apart from this, an opportunistic energy‐charging scheme is designed, wherein the UAVS can either replenish their batteries using solar plates or they can wirelessly charge energy from charging points deployed at various geo‐distributed locations. The proposed scheme is evaluated using a simulation‐based study over the realistic deployment of charging points in Chandigarh City, India. The results obtained show the superiority of SOOCS over other variants of its category in terms of end‐to‐end delay, throughput, and hand‐over latency.     

A multilayered mobility management scheme for auto-configured wireless IP networks

The convergence of wireless and IP has led to the need for IP to handle mobility. The Mobile IP protocol was developed to facilitate IP mobility. However, it has a number of shortcomings for dynamically auto-configured networks. Mobility protocols like Mobile IP with Location Registers (MIP-LR) and Session Initiation Protocol (SIP) have been developed to address some of its shortcomings. Micromobility protocols like Cellular IP have been developed to address other shortcomings of Mobile IP. We present a new integrated mobility management scheme that advantageously combines the strengths of SIP and MIP-LR with the benefits of a micromobility management protocol similar to Cellular IP. A prototype implementation of our scheme is explained, and lessons learned in the prototyping process are presented.     

Fabrication and Circuit Modeling of NMOS Inverter Basedon Quantum Dot Gate Field-Effect Transistors

This paper presents the fabrication of a negative-channel metal–oxide–semiconductor (NMOS) inverter based on quantum dot gate field-effect transistors (QDG-FETs). A QDG-FET produces one intermediate state in its transfer characteristic. NMOS inverters based on a QDG-FET produce three states in their transfer characteristic. The generation of the third state in the inverter characteristic makes this a promising circuit element for multivalued logic implementation. A circuit simulation result based on the Berkley simulation (BSIM) circuit model of the QDG-FET is also presented in this paper, predicting the fabricated device characteristic.     

Efficient dissemination of personalized information using content-based multicast

There has been a surge of interest in the delivery of personalized information to users (e.g., personalized stocks or travel information), particularly as mobile users with limited terminal device capabilities increasingly desire updated and targeted information in real time. When the number of information recipients is large and there is sufficient commonality in their interests, as is often the case, IP multicast is an efficient way of delivering the information. However, IP multicast services do not consider the structure and semantics of the information in the multicast process. We propose the use of Content-Based Multicast (CBM) where extra content filtering is performed at the interior nodes of the IP multicast tree; this will reduce network bandwidth usage and delivery delay, as well as the computation required at the sources and sinks. We evaluate the situations in which CBM is advantageous. The benefits of CBM depend critically upon how well filters are placed at interior nodes of the IP multicast tree and the costs depend upon those introduced by filters themselves. Further, we consider the benefits of allowing the filters to be mobile so as to respond to user mobility or changes in user interests and the corresponding costs of filter mobility. The criterion that we consider is the total network bandwidth utilization. For this criterion, we develop an optimal filter placement algorithm, as well as a heuristic that executes faster than the optimal algorithm. We evaluate the algorithms by means of simulation experiments. Our results indicate that filters can be effective in substantially reducing bandwidth. We also find filter mobility is worthwhile if there is marked large-scale user mobility. We conclude with suggestions for further work.