Ongoing Researches: Department of Electrical and Electronic Engineering

• Photovoltaic devices and systems
• Modeling, simulation and characterization of semiconductor devices
• Engineering education

• Electron transport in semiconductor nanostructures
• Electronics of 2D materials
• Strain engineering for improved performance of nano transistors
• Photovoltaics and solar cell

Research interests:

• Sensors & systems for personalized, preventive & proactive healthcare
• Micro and nanofluidic systems with applications in medical and environmental sciences.
• Micro & nanofabrication
• Silicon based nanoelectronics: Advanced silicon front end processes & devices
• Biomedical engineering and/or healthcare technologies
• Engineering of functional nano-materials
• Heterogeneous integration of silicon
• ZnO based nanodevices for healthcare, environmental control, aerospace & defence applications
• Classical/quantum mechanical simulation of nanodevices.

Research Grants Received and/or assisted:

• EPSRC, Feasibility of Novel Deca-Nanometer Vertical MOSFETs for Low-cost Radio Frequency Circuit Application Reference: EP/E012329/1, Value: £648,248, Role: Researcher, Funded.
• EPSRC, Silicon Nanowire Arrays for Viral Infection Markers (SINAVIM), Reference: EP/G061696/1, Value: £1,107,763, Role: Researcher co-investigator,
• TSB, Low cost Nanowire Diagnostic Platform, Value: £768, 421, actively participated on background results for proposal preparation. Funded.
• OIPT, Nanowires of Novel Materials Using Deposition & Etch: Value: £360, 000. Co-investigator,
• HEQEP sub-project knowledge transfer and capacity development of academic staff, Silicon nanowire biosensors for healthcare and environmental control, Value: 5,80,000 BDT. Principal investigator, This project is in collaboration with Southampton Nanofabrication Center, UK.

Research track record

1. Reaserch projects:

In Progess:

• Silicon nanowire biosensors for healthcare and environmental control: My current research is funded by CRT, EWU. The overall aim of this project is to perform a detail investigation of different types of silicon nanowire (SiNW) biosensors with the target to solve one of the key outstanding issues which is the determination of the required thickness, length, surface states and appropriate bias voltages of different types of nanowires for single moleculer level detection. Single crystal and polycrystalline silicon nanowires will be realized and the complicated relationship of nanowires’ electrical behavior with parameters like nanowire length, thickness, doping, bias polarity, interface states will be investigated using the industry standard Technology Computer Aided Design tool Silvaco. This project builds up a unique platform of international collaboration between CRT, EWU and Southampton Nanofabrication Center, UK which is known as one of the topmost nanofabrication facilities in Europe. The project will have unique access to experimental samples from Southampton Nanofabrication Center, University of Southampton, UK allowing calibration, physical explanation thereby would provide the necessary insight into the required parameters for the desired electrical characteristics, process condition for realizing nanowires of appropriate materials and applicable bias conditions so that nanowire biosensor designs are optimized.

Completed:

• Silicon nanowire arrays for viral infection markers: My most recent research project is an UK Grand Challenge Project for Healthcare engineering using heterogeneous integration of silicon nanowires & bio-nanotechnology which was honoured with £1.3 Million by Engineering & Physical Sciences Research Council (EPSRC), UK. This is a multidisciplinary research project in which I was a Researcher Co-investigator, Peter Ashburn as Principal Investigator and co-investigators were from the School of Medicine, Chemistry, Sociology and Electronics of the University of Southampton. The aim of this research is to develop silicon nanowire biosensors with cost-effective electronic detection, into a robust user platform for large-scale biomarker diagnostics for a personalized, proactive and preventative healthcare. I have successfully developed a generic top-down fabrication approach for polysilicon nanowire fabricatio. The polysilicon is deposited by PECVD and a special anisotropic dry etch process is used to create rectangular nanowires. The whole process does not require any expensive lithography which just uses mature microelectronics (linewidths of >3mm) and thin film technology, offering a very low cost technology. A successful integration of functional biological molecules is achieved on these nanowires and the quantification of the immobilized biological complexes is done upon application of electric field which demonstrated a commercial route for nanowire biosensor fabrication. This has created an exciting opportunity for research on low cost diagnostic platform through a second phase of grant from TSB, UK. I have actively participated on this follow up proposal preparation.
• Nanowires using novel materials for smart biosensors, aerospace and defence companies and photonic applications:I have also participated on a collaborative research on realising nanowires using novel materials with Prof. Peter Ashburn and Dr. Chong in Southampton which has been awarded with £360, 000 from Oxford Instrument Plasma Technology (OIPT). As a starting, remote plasma atomic layer deposition (ALD) was used to successfully grow ZnO layer with a resistivity of 1 kΩ.cm and an estimated carrier concentration of ~ 6×10¹⁹cm^-3. We have extensively studied the stoichiometry of our grown ZnO layer and the quality of the layer was assessed by fabrication of staggered bottom gate thin film transistors (TFT). Recently we have successfully fabricated rectangular ZnO nanowires using my generic generic top-down fabrication approach of deposition and etch in mature microelectronics (linewidths of >3mm). Currently we are investigating the ZnO nanowires developed by the aforementioned technology and a follow up proposal is also prepared which aims to realize stable p-type ZnO layer and junction less ZnO nanowire transistors. This research has several promises for exploitation. On one side ZnO nanowires are attractive for realising smart gas sensors for healthcare & environmental control, on the other hand this research will lead to a paradigm shift in wide bandgap semiconductor devices and lead to new fields of research into zinc oxide pn diodes, photonic devices, MOSFETs, MESFETs, bipolar transistors and power devices with obvious applications in aerospace/defence companies and display companies for transparent electronics.
• Silicon based nano CMOS devices: I also worked on a Engineering & Physical Sciences (EPSRC), UK funded research project (£648,248) aimed at investigating non-classical vertical MOSFETs for a viable route for improving the RF performance of mature CMOS technologies which exploits the lithography independent short channel definition technique of vertical MOSFETs. Several innovations came out of this research solving the problems of overlap capacitance, short channel effects and source/drain series resistances in these devices. We are the first group to realize a silicidation technology for surround gate vertical MOSFETs which was successfully integrated with a Fillet Local Oxidation (FILOX) process. In this way, a world record f_T of 20 GHz was achieved for Si based nMOS devices for 0.5µm lithography offering a low cost route for improving the RF performance of mature lateral CMOS These inventions have attracted attention of several semiconductor industries.
• Engineering of smart nano-materials: My PhD research was a project of SINANO which aimed to strengthen European scientific and technological excellence in the field of Si-based nanodevices. This research focused on thin layer of amorphous silicon deposition and engineering its morphology by crystallization for transistor-in-grain technology and/or large area electronics. Two novel methods of low temperature crystallization of amorphous silicon were developed during this research. One method used fluorine during metal induced lateral crystallization (MILC) of amorphous silicon which delivered dramatically increased lateral crystallization distance (65%) and a high quality silicon layer. I also identified a new amorphous silicon crystallization phenomenon which originated from the perimeter of the germanium layer during low temperature anneal and excellent grain localization was achieved without any metal contamination. The developed methods of devising poly-silicon have a considerable commercial potential for some other applications like thin film solar cells, mass production of high quality silicon nanowires for bio-sensors & obviously for post scaling of CMOS using 3D integration.
• Simulation & compact model development: I also got an extensive experience of process/device simulation using SILVACO & SYNOPSIS TCAD tools and Matlab, C++ environment through several simulations which I undertook in the past. Simulation of vertical MOSFETs to study the device behaviour during transition from partial to fully depleted operation in vertical MOSFETs and simulation of PIN diode for a proposed novel multiplexed near field Terahertz microscope were carried out. A theoretical study on the quantum phenomena in deep sub micron MOSFETs with high-K dielectrics was also done. This Quantum mechanical modelling of MOS devices with high-K dielectrics was one of the earliest theoretical investigations of this type of structures.

Key research achievements

• Demonstrated a wafer scale nanowire biosensor platform using mature microelectronics (linewidths of >3mm) and thin film technology, offering the prospect of manufacturability in a very low cost technology which attracted attention of industries like Sharp, Aptamer Solutions, Applied Nanodetecto and BAE Systems, UK. The technology was presented as Innovative Engineering Solutions for Healthcare in a BBC, UK interview in the year of 2011 [4].
• Invention of two novel methods of low temperature crystallization of amorphous silicon for transistor-in-grain technology and/or large area electronics.
• Silicidation for surround gate vertical MOSFETs with integration of Fillet Local Oxidation (FILOX) process which delivered a world record f_T of 20 GHz for Si based nMOS devices that employed only 0.5µm lithography.
• Developed a generic technique of nanowire definition [4, 6] using Oxford Instruments equipments which created collaborative research with OIPT and the University of Southampton was honoured with a £360,000 contract from OIPT for nanowire growth in some other technologically important materials for smart nanosensor and advanced electronic/photonic realization.

Expertise

A. Simulation:

• 2D/3D process and device simulations: In particular semiconductor devices like Nanowire bio-sensors, planar and vertical MOSFETs, TFTs, nanowire transistors, etc using Silvaco & SYNOPSIS TCAD tools.
• 2D/3D electromechanical static & dynamic simulation system by using ANSYS-ISE and Conventorware-COMSOL platforms.
• Atomistic simulation of charge-transfer phenomena between chemical species & biomolecules and Si surfaces using ab-initio packages SIESTA and Virtual Nano Lab.
• Chip layout/mask design and design verification of VLSI devices using SILVACO & SYNOPSIS TCAD tools, Cadence, L-EDIT and Microwind tools.
• VLSI circuit performance evaluation using Pspice/Orcad tools and mixed mode simulation platform of SILVACO TCAD tools.
• Modelling quantum transport in mesoscopic structures: Developed a coupled Schrodinger and Poisson solver which is capable of simulating transport phenomena in nanodevices like deep sub-micron and nanowire MOSFETs.

B. Nanofabrication:

Around nine years of in hand micro & nano fabrication experience in the nanofabrication facility of the University of Southampton and Electrum Laboratory, KTH, Sweden. In particular, processing and process development experience in:

• Dry etching experience with Applied Materials Precision 5000 Mark II, Oxford RIE 80+ and Plasmalab ICP etcers. CHF₃, CF₄and Ar/O₂ based anisotropic oxide and nitride etch; HBr, Cl₂ and SF₆, O₂, C₄F₈ based anisotropic PolySilicon and Silicon etch; BCl₃, Cl₂, SF₆, N₂ based anisotropic Al/TiW metal etch etc.
• Experience in operating Bruce/Tempress LPCVD and diffusion furnaces for nitride, LTO, TEOS, amorphous/polysilicon layer deposition, oxidation and annealing.
• Extensive experience in photo resist coating, exposition using XLS 7500/2145 i-line stepper, EVG 620 manual and automatic aligners and developing.
• Rapid thermal processing using Mattson 100 RTP Systems.
• Metal evaporation using Provac PAK 600/700 Coating System and sputtering using Magnetron ET sputter.
• Various wet processing (isotropic/anisotropic wet etch of nitride, oxide and silicon, surface cleaning and different wet etch techniques to characterise the grain growth in amorphous silicon) & lift off using SSE tool.

C. Characterisation:

DC and RF characterisation of VLSI devices, in particular planar and vertical MOSFETs; acquired at the Southampton Nano Fabrication Centre, University of Southampton, UK.

• Operation of manual Microtech prober/semiautomatic Summit 12000B-AP probe station for transistor and chip measurements.
• Operation of Agilent 4155C Semiconductor Parameter Analyser, Agilent 4279A 1MHz CV meter, Agilent B1500A semiconductor device analyzers and Agilent 8361A microwave vector network analyzer.

Structural characterisation of semiconductor materials:

• Extensive experience in SEM (Scanning Electron Microscope) microscopy and sample preparation; performed at the Electron Microscopy Centre of the University of Southampton; instruments used: JSM 6500F/7500F thermal field emission scanning electron microscope and Hitachi FEG-SEM.
• Surface analysis with SIMS (Secondary Ion Mass Spectrometry), performed at LSA (Loughborough Surface Analysis Ltd.)
• Silicon surface profiling using Alphastep 200 Automatic Step Profiler and LOT KLA-Tencor alpha-step IQ stylus surface profiler.
• Thin layers thickness measurements using LOT Woollham M2000D ellipsometer.
• X-ray diffraction, performed at the Department of Chemistry, University of Southampton, Southampton, UK.
• Raman Spectroscopy using Renishaw in Via Reflex Spectrometer system.
• Atomic force microscopy (AFM) using Veeco Multimode Nanoscope V Scanning Probe Microscope and Veeco Caliber Scanning Probe Microscope.
• Surface characterization by Nomarski Differential Interference Contrast (DIC) Imaging.

General computing skills:

Research webpage: [Khan SLR Group]

• Solar cells, solar farm, bifacial PV, agro-PV, 
• Paper bsed biosensors, non-invasive biosensors

• Photonics
• Stimulated Brillouin Scattering
• Image Processing
• Renewable  Energy

1. Power Converters 

2. Electric Vehicle Systems

3. Renewable Energy Systems

4. Power Supply Design

5. Deep Learning based Energy Forecasting

• Non-destructive Inspection
• Systems Modeling
• Pattern recognition
• Video Analysis
• Image processing
• Parallel Processing

• Non-destructive Inspection
• Pattern recognition
• Image processing
• Machine Learning
• Deep Learning

• RESEARCH GATE_PROFILE
• Image Processing
• Computer Vision
• Artificial Intelligence
• Computer Networks Security
• Machine Learning
• Deep Learning
• Internet of things
• Robotics 

• Photovoltaics
• Perovskites
• Photonics
• Thin Films
• Nano-fabrication

• Novel Spintronic & Neuromorphic Devices
• Spike Neural Networks (SNN)
• Spin Optoelectronics & Photonics
• FSO & CPDM based Fiber Optics

• Machine Learning
• Artificial Intelligence
• Microstrip Patch Antenna Design
• STT_MRAM characteristic and application
• Bio-inspired photonics
• IoT
• Photonic Bandgap Device design and application

• Wireless Communication

• Machine Learning

• Biomedical Engineering

MDM Group: https://sites.google.com/view/mems-group/home

Summary: MEMS, BioMEMS, Nanofabrication, Thin-film Solar cell, MEMS Resonator, Epitaxy, Heterostructure, Sensors and Actuators, Underwater energy harvesting, Brain-computer interface, Neural Sensing.