21. In “p” type material, minority carriers would be:
(a) holes (b) dopants (c) slower (d) electrons
Answer
Answer : (d)
Explanation
Explanation : The purpose of p-type doping is to create an abundance of holes. In the case of silicon, a trivalent atom (typically from Group 13 of the periodic table, such as boron or aluminium) is substituted into the crystal lattice. The result is that one electron is missing from one of the four covalent bonds normal for the silicon lattice. Thus the dopant atom can accept an electron from a neighboring atom’s covalent bond to complete the fourth bond. This is why such dopants are called acceptors. The dopant atom accepts an electron, causing the loss of half of one bond from the neighboring atom and resulting in the formation of a “hole”. Each hole is associated with a nearby negatively charged dopant ion, and the semiconductor remains electrically neutral as a whole. However, once each hole has wandered away into the lattice, one proton in the atom at the hole’s location will be “exposed” and no longer cancelled by an electron. This atom will have 3 electrons and 1 hole surrounding a particular nucleus with 4 protons. For this reason a hole behaves as a positive charge. When a sufficiently large number of acceptor atoms are added, the holes greatly outnumber thermal excited electrons. Thus, holes are the majority carriers, while electrons become minority carriers in p-type materials. Let us discuss.
555555555556. In what state is a silicon diode if the voltage drop across it is about 0.7 V? (a) No bias (b) Forward bias (c) Reverse bias (d) Zener region
55555555553. Ionization within a P-N junction causes a layer on each side of the barrier called the: (a) junction (b) depletion region (c) barrier voltage (d) forward voltage
PN Junction Diode » Exercise - 121. Which one is the valid statement with respect to PN junction diode ? (a) Under forward bias, the electrons from P region & holes from N region drift towards the junction (b) A junction diode cannot be used as a switch in electrical circuits (c) Depletion capacitance is voltage independent (d) Diffusion current of minority carriers is proportional to the concentration gradient
555555555523. A P-N junction mimics a closed switch when it: (a) has a low junction resistance (b) is reverse biased (c) cannot overcome its barrier voltage (d) has a wide depletion region
55555555558. When is a P-N junction formed? (a) in a depletion region (b) in a large reverse biased region (c) the point at which two opposite doped materials come together (d) whenever there is a forward voltage drop
555555555556. In what state is a silicon diode if the voltage drop across it is about 0.7 V? (a) No bias (b) Forward bias (c) Reverse bias (d) Zener region