To modulate electrical or optical properties of a semiconductors, impurities are added to a pure (intrinsic) semiconductor. This process is called “doping” and is done during the production.
In a pure silicon lattice and especially at low temperatures there are very few free electrons. This is because Si atom has 4 electrons at its outer shell and they are forming bonds with the 4 neighboring atoms.
A donor atom is an impurity atom with 5 electrons in its outer shell such as arsenic (As), phosphorus (P), or bismuth (Bi). Click on any Si atom to replace it with a donor atom. Why does the donor atom becomes positively charged? What about the overall charge in the lattice? Is it positive, negative, or zero?
An acceptor atom is an impurity atom with 3 vallance electrons. Click on any Si atom to replace it with an acceptor atom. Why does the acceptor atom becomes negatively charged? What about the overall charge in the lattice? Is it positive, negative, or zero?
We can now focus on electrons and holes (mobile charges) and ionized donor and accepter atoms (fixed charge). In practice, we don’t normally use both dopants. Can you say why?
Scroll back to add more acceptor doping or donor doping if you like.
So far, we were assuming that the temperature was relatively low and the thermal generation of electron-hole pairs was negligible. What happens at higher temperatures such as room temperature?
Use the slider to add donor atoms and wait till we reach equilibrium again.
Compared to intrinsic Si, what happens to the hole population when you n-dope? Why?
Donor Density (per cm3):
Each time you change the doping, the simulation is reset.
What about p-doping?
Acceptor Density (per cm3):
What if you use both n-doping and p-doping?
Donor Density (per cm3):
Acceptor Density (per cm3):