Sharief F. Babiker

Complete Monte Carlo RF analysis of "real" short-channel compound FET's

A comprehensive RF analysis technique based on ensemble Monte Carlo (EMC) simulation of compound FETs with realistic device geometry is presented. Y-parameters are obtained through Fourier transformation of the EMC transients in response to small changes in the terminal voltages. The terminal currents are statistically enhanced and filtered to allow for reliable y-parameters extraction. Improved analytic procedure for extracting the intrinsic device small-signal circuit components is described. As a result, stable y-parameters and reliable circuit components can he extracted for the whole range of device operation voltages. Parasitic components like contact and gate resistances are included in the y-parameters at a post processing stage to facilitate the forecast of the performance figures of merit of real devices. The developed RF technique has been applied in the EMC simulation of pseudomorphic HEMTs (pHEMTs) fabricated at the Glasgow Nanoelectronics Research Center. Good agreement has been achieved between the simulated and measured small-signal circuit components and performance figures of merit.

Simple approach to include external resistances in the Monte Carlo simulation of MESFETs and HEMTs

The contact and external series resistances play an important role in the performance of modern 0.1-0.2 /spl mu/m HEMTs. It is not possible to include these resistances directly into the Monte Carlo simulations. Here we describe a simple and efficient way to include the external series resistances into the Monte Carlo results of the intrinsic device simulations. Examples of simulation results are given for a 0.2 /spl mu/m pseudomorphic HEMT.

Internet of things based smart environmental monitoring using the Raspberry-Pi computer

This paper proposes an approach to build a cost-effective standardized environmental monitoring device using the Raspberry-Pi (R-Pi) single-board computer. The system was designed using Python Programming language and can be controlled and accessed remotely through an Internet of Things platform. It takes information about the surrounding environment through sensors and uploads it directly to the internet, where it can be accessed anytime and anywhere through internet. Experimental results demonstrated that the system is able to accurately measure: temperature, humidity, light level and concentrations of the carbon monoxide harmful air pollutant. Its also designed to detect earthquakes through an assembled seismic sensor.

Strain engineered pHEMTs on virtual substrates: a Monte Carlo simulation study

Monte Carlo simulations are used to investigate the influence of various strain conditions on the performance of pseudomorphic High Electron Mobility Transistors (pHEMTs) with low In content InxGa1-xAs channels (x<0.3) grown on strain relief graded buffers, commonly referred to as ‘virtual’ substrates. Strain engineering can be achieved by varying the composition of the graded InxAl1-xAs buffers to control the type and magnitude of strain induced in the channel. It is shown that devices with relaxed (lattice matched) and tensile strained channels provide better RF performance compared with conventional compressively strained pHEMTs on standard GaAs substrates. It is argued that strain engineering in GaAs based devices with low In content in the channel makes it possible to achieve RF performance comparable to that of InP based pHEMTs, whilst improving device breakdown characteristics and avoiding the fabrication problems associated with fragile InP substrates.

New evidence for velocity overshoot in a 200 nm pseudomorphic HEMT

It is believed that significant velocity overshoot effects are responsible for the high performance of Pseudomorphic HEMTs (PsHEMTs) with InGaAs channels grown on GaAs substrates. The expected overshoot is associated with the low effective mass in the channel and the large ¿ - L separation and is clearly demonstrated in numerous Monte Carlo simulations. Average electron velocities well in excess of 3.0×107 cm/s have been predicted. However, average electron velocities extracted form transconductance measurements of such devices are much lower, typically in the range 1.5 - 2.0×107 cm/s. Although there are some explanations in the literature for why such discrepancies exist in the extracted effective velocity they are based on Monte Carlo simulation itself without direct links to real fabricated and measured devices. In this paper we analyse for the first time real device measurements by using Monte Carlo and drift diffusion simulations. We obtain clear evidence that the average velocity in the channel of 200 nm PsHEMT fabricated in the Nanoelectronics Research Centre of Glasgow University exceeds 3.0×107 cm/s.

Tactile web navigator device for blind and visually impaired people

Blind or visually impaired people have limited or no access to the internet. This paper presents a low cost tactile web navigator device aimed at enabling blind people to have feasible internet accessibility. This navigator design includes a microcontroller that communicates with the browser software proxy transcoder server running on a PC to acquire the text from a web page. The text is subsequently displayed using an array of solenoids giving the required tactile sense. The visually impaired user then uses his/her tactile sense to recognize the text in Braille language. This device also provides an English character mode. Many navigation functions like loading a webpage address, clicking on links and entering data (E-mails, passwords, etc) have been provided. The navigator was tested by volunteer blind users with excellent results. The cost of the implementation is an impressive ∼12% of the commercial Braille displays.

Shot Noise in Single-Electron Tunneling Systems: A Semiclassical Model

In this paper, shot noise in single-electron tunneling circuits is studied using a semiclassical approach based on the master equation formalism where the transport through the circuit is modeled as sets of sequential stationary Poisson processes. Analytical expressions for the distribution of time between tunnel events and the resulting power spectral density S(f) are derived. The model is then used to investigate the correlated transfer of electrons and fluctuations in homogeneous long arrays of tunnel junctions.

Comparative study on the speed of DC motor using PID and FLC

The main purpose of this paper is to control the speed of a DC motor using two techniques, via PID Controller and Fuzzy Logic Controller (FLC). A system model is implemented for PID and FLC controllers along with a model for a DC motor using MATLAB Simulink. The performance of the two techniques is evaluated and compared in terms of the settling time (Ts) and maximum overshoot under different load conditions. PID controller is shown to give a good response and small rise time, but higher overshoot and settling time. Fuzzy Logic Controller is found to provide better performance as compared to PID controller in terms of settling time and percentage overshoot and a better control of the DC motor due to the fact that FLC required no tuning and human manipulations are reduced.

Shot Noise Suppression in Single Electron Transistors

Shot noise in a single electron transistor coupled to a dissipative environment is studied. The evolution of the charging process is modeled using classical circuit equations. The distribution of time between tunnel events in the presence of series coupling resistances is derived and used in modeling the stochastic tunneling processes. It is shown that resistive series elements result in a suppression of the Fano factor, below the theoretical 0.5 limit.

Controlling the CNC machine using microcontroller to manufacture PCB

The Printed Circuit Boards (PCB) has made an enormous contribution in the Electronic devices industry, this paper will present a robust cost effective method of controlling a specific designed machine to manufacture the PCBs. Computer Numerical Control (CNC) machine will be used and controlled by an innovative controlling method which converts the CNC machine language (G Code) into a form of C programing language functions in addition to this there is an electronic circuit consisting of a microcontroller chip and motors drivers. The user just needs to draw the pattern of the circuit diagram using any available electronic circuit Simulation software and the machine will automatically respond and draw the desired circuit diagram on the PCB board. As a result of using this controlling method such machines will be affordable for electronics engineering students during project implementations as well as electronics entrepreneurs.