SEMICONDUCTORS AND SUPERCONDUCTORS

Aim of this course is to provide students with advanced knowledge of Physics of semiconductor materials and superconducting materials and some devices based on them.

Semiconductors (3 CFU)

• Band structures

Semiconductor structure and general properties - Fermi Gas - Band structure – Metals, insulators and semiconductors - Density of states and effective mass - Electons and Holes – Electronic propreties of defects and impurites - Equilibrium charge carriers density - Acceptor and donors - Mass action law - Thermal dependance of carrier density - Conductance, scattering, mobility and thermal dependance

• Generation, recombination and diffusion processes

Non-equilibrum conditions - Injection and extraction of minority carriers – Diffusion current - Generation and recombination processes - Band-to-band recombination - Shockley, Read & Hall recombination - Auger recombination - Lifetime – Experimental determination of carrier density and their mobility - Haynes Shockley experience - Einstein relation

• Optical properties

Free carrier absorption - Direct and indirect optical transition - Excitons - Light emission – Binary, ternary and quaternary semiconductors - Optical properties of heterostuctures and nanostructures

• MOS devices

Metal/oxide/semicondutors systems - MOS capacitance - Flat band voltage - Channel conductance –Metal-oxide-semiconductor field-effect transistor (MOSFET) - Volatile and non volatile memories

Superconductors (3 ECTS)

• Basic phenomena and phenomenological theories

Vanishing resistance and Meisser effect. Magnetic flux quantization. Gorter Casimir model. Electrodynamics of superconductors: London phenomenological theory. Ginzburg Landau theory.

• Mircoscopic Bardeen-Cooper-Schrieffer (BCS) theory

Cooper pairs. Origin of the attractive interaction and “s-wave pairing” - BCS ground state. Energy bands and superconducting gap, density of states - Finite temperature effects: critical temperature - Penetration depth – Electron tunneling and Cooper-pair tunneling – Josephson effect – Josephson effect in the presence of magnetic field: Superconducting Quantum Interference Devices (SQUID).

• Special topics

Josephson effect in mesoscopic junctions – Superconducting artificial atoms - Introduction to high-temperature superconductivity - The Lawrence Doniach model - d-wave pairing.

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

S.M. Sze - Physics of Semiconductor Devices - Wiley

Michael Tinkham - Introduction to Superconductivity: Second Edition - Dover Books on Physics