SCEN103 Class 16
Bottom of page/
Introduction to Semiconductor Physics
Insulator or Semiconductor?
- Viewgraph of energy levels as a function of
atom separation for Group 4 elements
-- four valence electrons
- Model of crystal structure (Bring ball-and-stick model to class.)
-- covalent bonding to four nearest-neighbors
----- sharing of electrons
- Interactive Unit Cell
from Education Applets in Solid State Materials,
Center for Active Learning of Microelctronics and Photonics
at SUNY Buffalo
- Relative size of bandgap
-- the energy separation between valence and conduction bands
||(at room temp.)
||[helium] 2s2 2p2
||[neon] 3s2 3p2
||[argon] 4s2 4p2
|For comparison to photon energies, recall:
- Diamond is considered to be an insulator,
whereas Se, Si, and Ge are considered to be semiconductors.
- Diamond is transparent to visible light, Si and Ge are not;
can be explained with relative band gap energies.
-- optical absorption; energy or photon is absorbed by electron and
-- (Examine wafer of silicon.).
- In general, thermal electrons still cannot "jump" bandgap in pure
semiconducting materials; however
- Photons of sufficent energy can "promote" conduction electrons.
Top of page/
Back to SCEN103 Home Page.
Comments, suggestions, or requests to email@example.com.
Last updated Jan. 28, 1998.
Copyright George Watson, Univ. of Delaware, 1996.