SEMICONDUCTOR PHYSICS AND TECHNOLOGY

Aim of this course is to provide students with advanced knowledge of Physics of semiconductor materials and related technologies.

For what concerns the above subjects of Physics and Technologies of semiconductors, the course will promote the following skills:

- knowledge and understanding. Critical understanding of the most advanced developments of Modern Physics, both theoretical and experimental, and their interrelations, also across different subjects. Adequate knowledge of advanced mathematical and numerical tools, currently used in both basic and applied research. Remarkable acquaintance with the scientific method, understanding of nature, and of the research in Physics.

- applying knowledge and understanding. Ability to identify the essential elements in a phenomenon, in terms of orders of magnitude and approximation level, and being able to perform the required approximations. Ability to use analogy as a tool to apply known solutions to new problems (problem solving). Ability to plan and apply experimental and theoretical procedures to solve problems in academic or applied research, or to improve existing results.

- making judgements. Ability to work with increasing level of independence, also undertaking responsibility in planning and managing projects. Ability to convey own interpretations of physical phenomena, when discussing within a research team. Developing one's own sense of responsibility, through the choice of optional courses and of the final project.

- communication skills. Ability to discuss about advanced physical concepts, both in Italian and in English. Ability to present one's own research activity or a review topic both to an expert and to an non-expert audience.

- learning skills. Ability to acquire adequate tools for the continuous update of one's knowledge. Ability to access to specialized literature both in the specific field of one's expertise, and in closely related fields. Ability to exploit databases and bibliographical and scientific resources to extract information and suggestions to better frame and develop one's study and research activity.

Lectures (LIM slides available). Seminars.

Visit to research labs at DFA.

• Band structures and doping

Semiconductor structure and general properties - Bandgap formation - Energy band structure – Metals, insulators and semiconductors

Density of states and effective mass - Electons and Holes

Intrinsic semiconductor statistics - Mass action law - Acceptor and donors - Charge neutrality

Doped semiconductor statistics - Doping compensation - Thermal dependance of carrier density

• Electrical and optical properties

Conductance, scattering, mobility and thermal dependance - Einstein relation

Generation and recombination processes - Band-to-band recombination - Shockley, Read & Hall recombination - Experimental determination of carrier density and their mobility - Haynes Shockley experience

Free carrier absorption - Direct optical transition

Indirect optical absorption - Excitons - Light emission – Binary, ternary and quaternary semiconductors - Optical properties of heterostuctures and nanostructures

• Simple devices

Schottky diode

Metal/oxide/semicondutors systems - MOS capacitance - Flat band voltage

pn junction at equilibrium: band bending, depletion region, internal electric field

pn junction out of equilibrium: direct and inverse polarization, minority charge carriers injection and extraction, Shockley law: IV curve

pn junction: quasi Fermi level, CV curve, jnuction breakdown, transient behavior

Metal-oxide-semiconductor field-effect transistor (MOSFET)

• Semiconductor technologies

Moore Law, Lithography, Ion implantation, Thermal diffusion

SiC and power devices

Semiconductor sensors (definition, properties, mechanisms and nanostructures advantages). Semiconductor/gas interface: surface states, adsorption, chemoresistive effects.

Gas sensors based on semiconductors: adsorption kinetics, response times. UV sensors.

Semiconductor/liquid interface: Electrochemical cells, redox reactions, Nernst Equation, reference electrodes, electrical double layer.

Electrochemical techniques applied to semiconductors: ciclic and transient voltammetry, EIS (electrochemical impedance spectroscopy)

B. Sapoval, C. Hermann - Physics of Semiconductors - Springer-Verlag

S.M. Sze - Physics of Semiconductor Devices (3rd edition) - Wiley

L. Colombo - Fisica dei semiconduttori - Zanichelli

K. B. Oldham, J. C. Myland - Fundamentals of Electrochemical Science - Academic Press