Tiêu đề 14.Semi-conductor-Electronics-f.pdf ✅

Physics Smart Booklet 2

Physics Smart Booklet 4 Differences between intrinsic and extrinsic semiconductors Sl. No. Intrinsic Semiconductor Extrinsic Semiconductor 1. Pure Ge or Si crystal is known as intrinsic semiconductor. The semiconductor with specific impurities in controlled quantities is known as extrinsic semiconductor. 2. Conductivity is low. Conductivity is high. 3. At any given temperature, the number of electrons is always equal to the number of holes. The number of electrons and holes are always unequal. Differences between p-type and n-type semiconductor Sl. p-type n-type 1. A p-type semiconductor is obtained by doping a trivalent impurity like B or Al with intrinsic semiconductor. An n-type semiconductor is obtained by doping a pentavalent impurity like P or As with intrinsic semiconductor. 2. Majority charge carriers are holes and minority charge carriers are electrons. Majority charge carriers are electrons and minority charge carriers are holes. 3. The impurity atom accepts the electron from valence band and contribute to increased conductivity. The impurity atom donates an electron to conduction band and contributes to increased conductivity. 4. The acceptor impurity energy level is close to the valence band. The donor impurity energy level is close to the conduction band. p-n junction or semiconductor diode (unbiased) The charge depletion region has a thickness of about one-tenth of a m and the junction voltage is about 0.3 V for a germanium diode and 0.7 V for a silicon diode at 20 C. Biasing of a p-n junction or (Semiconductor) diode Forward bias n Depletion region − + + + + + + + + + − − + p-n junction diode under forward bias W → width of depletion region p n − + + + + + − − − − W V0 (a) (b) (c) Barrier potential (a) without battery (b) low batter voltage (c) high battery voltage