what is a semiconductor? describe 2 main types of semiconductors and contrast their conduction mechanism.
Answers
what is a semiconductor? describe 2 main types of semiconductors and contrast their conduction mechanism.?
Semiconductors are substances with conductance in the
intermediate range of 10 −6 to
10 4 ohm −¹ m −¹.
(i) n-type semiconductor: In this semiconductors, increase in conductivity is due to negatively charged electrons. For example, Si or Ge (group 14 elements) doped with P or As (group 15 elements containing 5 valence electrons).Out of five valence electrons of group 15 elements, 4 valence electrons form covalent bonds with four neighboring Si or Ge atoms and the remaining fifth electron becomes de-localized and increases the conductivity of doped Si or Ge.
(ii) p-type semiconductor. In this semiconductors, increase in conductivity is due to positively charged holes. For example, Si or Ge (group 14 elements) doped with B, Al or Ga (group 13 elements containing 3 valence electrons). In presence of electric field, electrons move toward the positively charged plate through electron holes. However, it appears as if the electron holes are positively-charged and are moving towards the negatively-charged plate.