||Creating Carriers with Dopants|
|Density of States||An Analogy||The Fermi Function||Where are they?|
For a more visual explanation, take a look at the demo for donors. You will need Shockwave for your browser to run this. The Vectras should run the demo properly, but the Sun workstations will not. Also, for a better view, use the "full screen" option on your browser. After you're done viewing, use the "back" button on your browser to return to this page.
A semiconductor can also be doped with acceptors. These come from Column III of the periodic table and introduce energy states in the forbidden gap close to the valence band. Acceptors need one more electron to complete a bond. In other words, they lack an electron. This situation creates holes by trapping electrons from the valence band in the acceptor states and leaving behind positively charged voids, holes. This occurs easily because the energy that is needed to get from the valence band to the acceptor states is much smaller than the band gap energy. Free electrons are not created in this process unless the energy exceeds the band gap energy. The semiconductor is now p-type, which can be associated with positive carriers. It is doped with acceptors, making the hole the majority carrier. The minority carrier is the electron, since very few were created or even present. The bonding model can not be used to model these actions, but the band diagram can be used effectively.
To visualize acceptors take a look at the movie. You will need Shockwave installed for your browser in order for it to run. The movie should run properly on the Vectras but it will not run on the Sun workstations. Also, for a better view, use the "full screen" option on you browser. After you're done viewing, you will need to use the "back" button on your browser to return to this page.