semiconductors Flashcards
semiconductor
a substance who’s resistivity is between that of a good conductor and a good insulator
valence electrons
electrons on the outer shell of an atom that are involved in bonds with other atoms
conduction electron
at room temp some valence electrons get enough thermal energy to break free from their covalent bonds
holes
when an electron breaks free from a covalent bond it leaves behind a hole in the atom which is pos.
intrinsic conduction
conduction in a pure semiconductor ie due to an equal amount of holes and electrons moving. electrons move from neg. to pos. and holes move the opposite direction
n-type semiconductor
this is where the impurity added produces more free electrons available for conduction e.g phosphorus and silicon. majority charge carriers are electrons, minority are holes
p-type semiconductor
impurity added produces extra holes which are available for conduction e.g. boron in silicon. majority charge carriers are holes
extrinsic conduction
this is where increased conduction in a semiconductor is due to the addition of impurities
p-n junction
piece of semiconductor with part of it doped p-type and the rest doped n-type
depletion layer
region at both sides of a p-n junction that contains no free majority charge carriers. it behaves as an insulator
junction voltage
this is the p.d. that exists accross a p-n junction caused by holes and electrons moving accross the junction when it was formed
forward biased
p-n junction that conducts current. p-type connected to pos. terminal and n-type connected to neg. terminal.
current flows once e.m.f. is greater than junction voltage
reverse biased
p-n junction that does not conduct current. p-type connected to neg. terminal and n-type connected to pos. terminal.
voltage of the battery increases the depletion layer hence increasing insulation preventing conduction
