Charge transport in semiconductors: electrons and holes
Intrinsic semiconductor
Electron in a semiconductor crystal can absorb energy became free
leaving a positively charged vacancy – “hole” .
n-type material: electrical current is a flow of the negatively charged electrons
As is a donor dopant or donor impurity for Si
p-type material: electrical current is a flow of the positively
charged vacancies – “holes”
Al is an acceptor dopant or acceptor impurity for Si
The law of mass action: intrinsic semiconductor
Intrinsic carrier concentration
Data from “Semiconductor devices:basic
principles” by J. Singh, Jon Wiley&Sons.
Inc.
Fermi level position: summary
Light absorption in semiconductors
Reduced density of states