Phys 460 Lecture 20

( pdf version - 6 slides/page )
Monday, November 6, 2006
Lecturer: Richard Martin

No new homework

Reading: Kittel, Ch. 17, p 494-503, 507-11; Added material in notes

Start Part III: Semiconductor Structures
Outline

From previous lectures:
- Part I: Crystal Structures, Diffraction, Reciprocal Lattice, Crystal binding
  Phonons, Dispersion curves,Thermal properties
- Part II: Free electron gas, Energy bands for electrons in crystals
  - Bloch theorem, Bands E_kⁿ, gaps, metals vs. insulators
  - Semiconductors: effective mass, negative electrons and positive holes, doping
- Last time: Semiconductor devices - inhomogeneous semiconductors
  - Variations of band energies, p-n junctions
  - Rectification; Light-emitting diodes; Solar cells
  - Bipolar Transistor n-p-n p-n-p
Today: What is a semiconductor structure?
- Control semiconductor properties by voltages or material growth
- Heterostructure formed of different semiconductor materials
Created by Applied Voltages
- MOS structures
- Conducting channels near surfaces
- Controlled by gate voltages
- MOSFET transistors
Heterostructures created by material growth
- Layered semiconductors
- Grown with atomic layer control by “MBE”
- Confinement of carriers
- Confinement of light - lasers
- "Electron in a box"
- Quantum wells - electrons confined in one direction
Quantized Hall Effect
- Now international Standard of resistance
Next time: Quantum Dots
- electrons confined in all directions

Email clarification questions and corrections to rmartin@uiuc.edu
Email questions on solving problems to xin2@.uiuc.edu