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Investigation and development of novel electronic materials, devices and experimental techniques for their characterisation. This include studies of bulk and nano-structured semiconductors, transition metal oxides and polymers using physical, chemical, electrical and optical techniques.

Semi-insulating Czochralski silicon substrates for microwave devices
D. Jordan, Dr. K. Mallik, Jian Yang, Professor R.J. Falster**, Dr. C.H. de Groot*, Professor P. Ashburn*, Dr. P.R. Wilshaw, Dr. K. Strickland***, Dr. P. Osborne***
Silicon (Si) and silicon-germanium (Si-Ge) technology has now reached a point where silicon-based group IV-IV semiconductor devices are capable of operating at frequencies up to 100 GHz, approaching the frequencies of many III-V compound semiconductor devices. However, at these frequencies standard Si substrates grown by the Czochralski (Cz) technique become very difficult to use because of the high absorption of microwave power by background free carriers present in the substrate. This results in an unacceptable degradation of the circuit performance. Thus, the performance of silicon radio frequency (RF) technology is limited to a large extent by the properties of the Si substrate used. Furthermore, this substrate-dependent restriction in the potential uses of Si will become increasingly important in coming years as even faster Si-based devices are developed. The availability of semi-insulating Cz-Si substrates would remove this limitation, and hence lead to a paradigm shift in the RF technology by extending the reach of Si-based technologies through to higher frequencies. The aim of this project is to search for suitable deep level compensating impurities and determine the processing conditions required to produce semi-insulating handle wafers for application in RF SOI. It brings together the expertise of the University of Oxford in characterisation and diffusion of deep level impurities and that of the University of Southampton in high frequency measurements and device fabrication. The project is actively supported by close involvement of a multinational wafer manufacturer, MEMC, who will deliver the starting material and of a UK/EU RF device manufacturer, Plessey Electronics, who will fabricate passive and active microwave devices on the novel high-resistivity substrates. Potentially useful initial results obtained by us include observation of resistivity ca. 500kohm-cm in Au-doped Cz-Si wafers where there has been at least a ten-fold increase in the resistivity, and effectiveness of the SiO2 diffusion barrier to Au diffusion at 1000 C. (*University of Southampton, **MEMC Electronic Materials, ***Plessey Semiconductors.) (Funded by the EPSRC.)

1 public active projects

D.M. Jordan, R.H. Haslam, K. Mallik and P.R. Wilshaw, The Development of semi-insulating silicon substrates for microwave devices, To be published in the Journal of Electrochemical Marterials.

J. Yang, J.R. Hyde, J.W. Wilson, K. Mallik, P.J.A. Sazio, P. O’Brien, M.A. Malik, M. Afzaal, C.Q. Nguyen, M.W. George, S.M. Howdle, and D.C. Smith, Continuous Flow Supercritical Chemical Fluid Deposition of Optoelectronic Quality CdS, To be published in the Advanced Materials.

M. Roos, V. Baranauskas, M. Fontana, H. J. Ceragioli and A.C. Peterlevitz, K. Mallik and F. T. Degasperi, Electron field emission from boron doped microcrystalline diamond, Applied Surface Science 253, 7381 (2007).

K. Mallik, C.H. de Groot, P. Ashburn and P.R. Wilshaw, Observation of resistivity enhancement in Czochralski silicon by deep level Mn doping, Applied Physics Letters 89, 112122 (2006).

L.H. Chong, K. Mallik, C.H. de Groot and R. Kersting, The structural and electrical properties of thermally grown TiO2 thin films, Journal of Physics Condensed Matter 18, 645–657 (2006).

L.H. Chong, K. Mallik, and C.H. de Groot, Fowler-Nordheim tunnelling in TiO2 for room temperature operation of the vertical metal insulator semiconductor tunnel transistor (VMISTT), Microelectronic Engineering 81, 171-180, (2005).

K. Mallik, R.J. Falster, and P.R. Wilshaw, Schottky diode back contacts for high frequency capacitance studies on semiconductors. Solid-State Electronics 48, 231-238 (2004).

D. Stowe, S. Galloway, S. Senkader, K. Mallik, R.J. Falster, and P.R. Wilshaw, Room temperature near-bandgap luminescence from ion-implanted silicon. Physica B 340-342, 710-713 (2003).

K. Mallik, R.J. Falster, and P.R. Wilshaw, “Semiinsulating” silicon using deep level impurity doping: problems and potential. Semiconductor Science and Technology 18, 517-524 (2003).

S.E. Booth, C.D. Marsh, K. Mallik, V. Baranauskas, J.M. Sykes, and P.R. Wilshaw, Fabrication of nanocrystalline aluminium islands using double-surface anodization, Journal of Vacuum Science and Technology B 21, 316-318 (2003).

P. Misra, P. Bhattacharya, K. Mallik, S. Rajagopalan, L.M. Kukreja, K.C. Rustagi, Variation of bandgap with oxygen ambient pressure in Mg x Zn1-xO thin films grown by pulsed laser deposition, Solid State Communications 117, 673-677 (2001).

K. Mallik, Nonlinear doping of the collector in avalanche transistors to improve the performance of Marx bank circuits, Review of Scientific Instruments 71, 1853-1861 (2000).

K. Mallik, The theory of operation of transistorized Marx bank circuits, Review of Scientific Instruments 70, 2155-2160 (1999).

K. Mallik, and T.S. Dhami, Optical absorption spectra of lead iodide nanoclusters, Physical Review B 58, 13055-13059 (1998).

A. Chatterjee, K. Mallik, and S.M. Oak, Principles of operation of avalanche transistor-based Marx bank circuits: A new perspective, Review of Scientific Instruments 69, 2166-2170 (1998).

U.N. Roy, K. Mallik, and L.M. Kukreja, Reflectivity of cadmium sulphide nanocrystal films grown by the Langmuir-Blodgett technique, Applied Physics A 67, 259-261 (1998).

S. Dhar, K. Mallik, and M. Mazumdar, Electron traps in GaAs:Sb grown by liquid phase epitaxy, Journal of Applied Physics 77, 1531-1535 (1995).

K. Mallik, and S. Dhar, Dominant traps in liquid phase epitaxial GaAs, studied by controlled doping with indium and antimony, Physica Status Solidi (b) 184, 393-402 (1994).

K. Mallik, S. Dhar, and S. Sinha, Photoluminescence and photocapacitance study of GaAs:In and GaAs:Sb layers grown by liquid phase epitaxy, Semiconductor Science and Technology 9, 1649-1653 (1994).

S. Dhar, K. Mallik, and B.R. Nag, Characteristics of indium doped GaAs layers grown by liquid phase epitaxy with indium content in the range (0.3-7) x 10¹⁹ cm^-3, Journal of Applied Physics 69, 3578-3582 (1991).

Production of Semi-Insulating Silicon for High Frequency Devices
P R Wilshaw / Kanad Mallik

This project will provide an opportunity to research the making of semi-insulating (resistivity of 10-100kohm-cm) silicon-on-insulator (SOI) substrates grown by the Czochralski technique for microwave monolithic integrated circuits (MMIC). This has been identified as a novel substrate material in the ITRS Roadmap and has the potential to bring about a paradigm shift in the semiconductor industry.

The research involves enhancement of the resistivity of SOI handle wafers by doping with transition elements, which introduce deep impurity levels in the silicon energy band gap. Another challenging aspect of the research is to confine these dopants to the handle wafer by use of diffusion barriers. The work will provide an excellent opportunity to get training and gain experience in a wide range of experimental skills in modern semiconductor science and technology. For example:

• Transition element doping techniques, including ion implantation and diffusion.
• Characterization techniques like, deep level transient spectroscopy (DLTS), secondary ion mass spectroscopy (SIMS), Auger electron spectroscopy (AES), X-ray photoelectron spectroscopy (XPS), and microwave absorption measurements.
• Some of the characterisation experiments will involve training in high vacuum techniques and cryogenics.
• Semiconductor device fabrication using photolithography.
• Working in semiconductor-grade cleanrooms in Southampton and Oxford.
• There is also scope for numerical modelling work concerning the electronic properties of semiconductors and microwave device simulation.

The student will work in a team involving members of the Department of Materials, Oxford, the Electronic Engineering Department, Southampton, a multi-national Si wafer manufacturer, and a UK/EU semiconductor device manufacturer.

Also see homepages: Kanad Mallik Peter Wilshaw

Also see a full listing of New projects available within the Department of Materials.