Table of Contents

# Atomic, Molecular & Optical Physics

## 2012 PH682: Optical Properties of Semiconductors

A graduate course taught by the Department of Physics at Oregon State University. In 2012 the course is being taught by Prof. Ethan Minot during Week 6 - Week 10 of Winter term. The module is offered biyearly.

## Calendar

Day | Topic | Reading | Summary | Assignments | |
---|---|---|---|---|---|

1 | M 2/13 | Below bandgap effects | A&M Ch27 | Cyclotron resonance (A&M p570). CNT anisotropic THz absorption. Plasma reflectivity edge at tens of THz. Absorption via lattice vibrations at tens of THz. | HW #1 |

2 | W 2/15 | Below bandgap effects | Optical properties in the transparency window: Frequency dependent dielectric constant, birefringence, non-linear optical materials | ||

3 | F 2/17 | Absorption | Pankove Ch3 | Direct bandgap semiconductor: density of directly associated states, absorption coefficient (inverse of penetration depth) | hw1soln.pdf |

Day | Topic | Reading | Summary | Assignments | |

4 | M 2/20 | Absorption | Exciting electrons across an indirect bandgap. Absorption coefficient for indirect transitions. Intro to excitons. Exciton Rydberg | HW #2 | |

5 | W 2/22 | Excitons | Experiments probing free excitons: Excitons generated by resonant absorption, excitons generated by ħω > E_g. Exciton Rydberg in 2-dimensional system. | ||

6 | F 2/24 | Excitons, Light emission processes | fox_5.3.2.pdf | day6_2012.pdf: Tightly bound excitons. Radiative recombination and photoluminescence spectra. Excess carrier radiative recombination lifetime. | hw2soln_2012.pdf |

Day | Topic | Reading | Summary | Assignments | |

7 | M 2/27 | Light emission processes | Exciton spontaneous emission lifetime in a bulk crystal | HW #3 | |

8 | W 2/29 | Light emission processes | S&T p515 | Quasi-Fermi Level. Measurements of exciton lifetimes. Purcell factor tunes spontaneous emission lifetime. | |

9 | F 3/2 | Laser Diodes | Ch 17 S&L, §5.43 Fox | Waveguiding and restricted recombination region, quantum efficiency, quality factor of laser cavities | hw3solns2012.pdf |

Day | Topic | Reading | Summary | Assignments | |

10 | M 3/5 | Laser Diodes | S&T p732 | Laser diode: population inversion, incremental gain coefficient, gain guiding. Quantum Cascade Laser, worksheet to guide discussion of the quantum engineering | HW #4 |

11 | W 3/7 | Photovoltaics | A&M Ch 29 | day11_2012.pdf: Best research efficiency, motivate derivation of Schockley-Queisser limit (intro to SQ limit). Deriving the ideal diode equation: generation currents and recombination currents, calculate reverse bias saturation current for a real example. | |

12 | F 3/9 | Photovoltaics | day12_2012.pdf: Ideal diode under illumination: Short circuit current and open circuit voltage, calculating V_OC based on ideal diode curve, choosing material thickness, choosing load resistance, fill factor, reason for concentrating the sunlight. | hw4solns_2012.pdf, hw4_qcl_question.pdf | |

Day | Topic | Reading | Summary | Assignments | |

13 | M 3/12 | Photovoltaics | Dr. Cohen's 2010 Presentation | day13_2012.pdf: Calculating maximum possible V_OC using Quasi-Fermi level concept, the solar spectrum and the room temperature blackbody background (the argument used by Schockley-Quisser), overview of the rest of S-Q argument Schockley-Queisser's 1961 article, final result of the S-Q argument | HW #5 |

14 | W 3/14 | Photovoltaics | Discussion of ways to beat the S-Q limit. | ||

15 | F 3/16 | Photovoltaics | Guest Lecture: Dr. Robert Kykyneshi (thin-film photovoltaics) | hw_5_2012.pdf |

## Syllabus

Below bandgap effects

- Spectra of dielectric function and of complex index of refraction
- Kramers-Kronig relations
- Microscopic description of polarizability
- Birefringence, Kerr rotation, Faraday effect, Voigt effect
- The electron gas plasma resonance
- Ensemble of uncoupled oscillators – classical and quantum

Interband excitations and emissions

- Band-to-band transitions
- Absorption cross-section
- Exciton models (Wannier and Frenkel)
- Exciton & defect state spectroscopy (including excited states & triplet/singlet)
- Excitons in low-dimensional systems
- Electron-hole plasma
- Semiconductor Bloch equations (intro)

Phonons

- Raman scattering
- Phonon polaritons
- Brillouin scattering

Semiconductor lasers

- pn junctions
- non-radiative transitions
- tunable alloys
- Purcell effect
- cavity QED
- quantum cascade laser

Photovoltaics

- Optimal bandgap and Shockley–Queisser limit
- Thin film solar cells