## Pre-requisite modules

## Co-requisite modules

- None

## Prohibited combinations

Occurrence | Teaching cycle |
---|---|

A | Autumn Term 2019-20 to Spring Term 2019-20 |

This module covers the fundamental concepts relevant for the understanding of the physical properties of semiconducting materials, their applications in microelectronics, energy harvesting and opto-electronics as well as the principles of interaction between light and matter. The skills obtained throughout this course are of great importance in society and economy, which are both increasingly driven by the application of electronics in all walks of life.

*Physics and Applications of Semiconductor Devices (100 hrs)*

Based on the models developed in Quantum Mechanics, Statistical Mechanics as well as in Solid State Physics (Solid State Physics I and II), this course discusses the links between our fundamental understanding of electronic states in materials and the application of this understanding in micro- and optoelectronics as well as detector-physics. It will cover and revisit vital concepts such as crystal symmetries and defects, band structures, phonon dispersion, the interaction of charge carriers with external fields and the effect on the electronic and optical properties. Experimental techniques to synthesize semiconductors and to study their physical properties will be discussed for some of the most prominent semiconductor materials such as Si, GaAs, GaN and Ge.

A large part of this course will focus on the application of these concepts and techniques for well established and novel devices such as transistors, metal oxide semiconductor field effect transistors (MOSFETs), light emitting diodes/laser diodes and particle detectors.

*Lasers and Atom-light Interactions (100 hrs)*

An introduction of the basic features of lasers is first given leading to a more general discussion on the interaction of light with atoms. The properties of laser cavities are investigated, leading to a description of the stable operating range for cavities and the associated mode structures. The quantum mechanics of the atom-radiation interaction are considered in the semi-classical limit (treating the radiation field classically) to determine transition probabilities. Some of the spectroscopic background for the description of plasma emission processes important in astrophysical and laboratory plasmas is presented.

*Physics and Applications of Semiconductor Devices*

At the end of this part of the module the students will be able to

- describe the relevance of the crystal structure and atomic bonds for the fundamental electronic properties
- apply the band structure model and effective mass concept to determine band gap width and mobility of charge carriers
- identify the important transport and scattering processes at work in semiconductors (drift, diffusion, generation, recombination, thermionic emission, tunnelling and ionisation)
- calculate the temperature dependence of the ionisation of dopant states and charge carrier concentrations
- distinguish the relevant electron-hole recombination processes and the role of majority and minority charge carrier for these processes
- quantitatively describe the experimental determination of the charge carrier concentrations and transport properties of semiconductors (e.g. Hall resistance and Haynes-Shockley experiment)
- describe the impact of defects on these properties
- understand the physics of p-n junctions (charge densities, potential distribution, charge carrier transport processes) and their relevance for their application in electronic devices
- correlate the theoretical description of p-n junctions with experimental techniques to determine their physical properties
- distinguish the main building blocks for the semiconductor based devices discussed in this course
- describe the underlying principles of microelectronic, optoelectronic and detector devices.

*Lasers and Atom-light Interactions*

- describe the basic components of a laser and the principles of laser operation.
- describe and apply matrix methods to establish stability requirements for laser cavities.
- describe beam propagation in a laser cavity in terms of solutions of Maxwell’s equations.
- derive Planck’s radiation law from a consideration of radiation modes in a cavity.
- determine the relationship between Einstein’s
*A*and*B*coefficients. - determine a general formula for laser gain
- by applying perturbation theory to the problem of light interacting with an atom in the semi-classical limit, determine in a general way the selection rules for radiative transitions.
- determine line shape formula for radiative and Doppler line broadening.
- describe how collisional-radiative processes control light emission from plasmas.
- Describe the physics behind selected (laser-based) plasma diagnostics

**Lecture notes**

Full notes should be taken based on material presented in the lectures of this module.

Please note, students wishing to take this module should have taken either Statistical Mechanics & Solid State II (PHY00049H) or (NS) Solid State II - PHY00060H.

**Syllabus**

*Physics and Applications of Semiconductor Devices*

Physics of Semiconductors

o Lattice properties (elastic properties, phonon dispersion)

o Electronic band structure and densities of states in semiconductors

o Fundamental electronic transport properties of semiconductors

o Interaction of semiconductors with radiation

o Structural defects (point, line, planar and volume defects) and their impact on the transport properties

Characterization of semiconductors

o Electronic properties: Four probe measurements, I-V characterisation

o Structural and chemical characterisation: X-ray diffraction and spectroscopy, electron microscopy

Applications

o Microelectronic devices (bipolar transistors and MOSFETs)

o Detectors (CCDs, X-ray detectors)

o Solar cells

o Optoelectronic devices (diodes, lasers)

*Light and Matter*

__Lasers and light in laser cavities__

Simple laser cavity parameters – gain, threshold gain, longitudinal modes.

Matrix methods for paraxial optics. Stability criterion for laser cavities.

Directionality and spreading of an electromagnetic beam. Beam propagation. The cylindrically symmetric solution. Transverse modes.

Gaussian beams in a cavity. The ‘ABCD’ rule. Cavity mode frequencies.

Density of modes in a three-dimensional cavity. Quantisation of the field energy. Planck’s law.

The Einstein A and B coefficients. Lines shapes and laser gain. Rate equations for a four level laser.

__Interaction of electromagnetic radiation with atoms or molecules__

The effect of electromagnetic radiation on an atom or molecule.

The interaction Hamiltonian in the semi-classical limit.

Transition probabilities and selection rules.

The macroscopic theory of absorption. Radiative broadening. Doppler broadening.

Collisional radiative processes in plasmas. The Saha equation. Coronal equilibrium.

Task | Length | % of module mark |
---|---|---|

University - closed examinationLasers and Atom-Light Interactions |
1.5 hours | 50 |

University - closed examinationPhysics and Applications of Semiconductor Devices |
1.5 hours | 50 |

None

Task | Length | % of module mark |
---|---|---|

University - closed examinationRe-assessment: Lasers and Atom-Light Interaction |
1.5 hours | 50 |

University - closed examinationRe-assessment: Physics and Applications of Semiconductor Devices |
1.5 hours | 50 |

Marks for the individual exams received from supervisor. Detailed model answers provided online.

Sze SM: *Semiconductor Devices: Physics and Technology*, Wiley

Loudon R: *The quantum theory of light* (Oxford Science)

Verdeyen JT: *Laser electronics* (Prentice Hall)

Tallents, G.J: *An Introduction to the atomic and radiation physics of plasmas *(CUP)