Higher potential energy hole lower potential energy

Info iconThis preview shows page 1. Sign up to view the full content.

View Full Document Right Arrow Icon
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: acing is such that there is significant overlap of the orbitals, electrons will be exchanged between adjacent atoms Ashcroft & Mermin, “Solid State Physics” 11 sp3 Hybridiza[on and Lajce Periodic Poten[al sp3 hybrid form, and electrons “feel” the periodic potential of the crystal lattice 12 Depic[on of Bands in Real Space Increasing Electron Energy 0 Electrons (0K) 4N States Conduction Band Distance in “Device” (Real Space) Increasing Hole Energy Valence Band 4N Electrons (0K) 4N States 13 Depic[on of Bands in k- Space Momentum Space p = k 14 Detailed Band Structure: Si and GaAs 15 AlGaAs Band Structure We have names for the different minima in k-space: Γ,L,X,K 16 Inferring Poten[al & Kine[c Energy From Band Diagrams “k” Space E “Real” Space Electron Higher Potential Energy Electron Lower Potential Energy Hole Higher Potential Energy Hole Lower Potential Energy Comments: •  The location of the band edge is an indication of the potential energy •  The location above (or below for holes) the band edge is an indication of kinetic energy 17 Energy Band Picture or 19 Defini[ons Conduction Band Nx4 States •  no(T>0oK) e Ec E e e Thermal Excitation •  g Ev e e ee e ee ee e e e po e Valence Band: Nx4 electrons occupy Nx4 states at 0oK •  Insulator: no electrons are present in the conduc2on band at T=0oK and the energy gap is large (Eg > ~10 eV). Virtually no electrons can be thermally excited from the valence band to the conduc2on band at T=300oK. Semiconductor: no electrons are present in conduc2on band at T=0oK and the energy gap is smaller (~0.1< Eg < ~5 eV). Some electrons are thermally excited from the valence band to the conduc2on band at T=300oK. Metal: Some electrons are present in the conduc2on band at T=0oK and the conduc2on band...
View Full Document

Ask a homework question - tutors are online