Semi-conductors Objectives Part 02
21 . Phosphorous element does not have three valence electrons.
22 . Indium element does not have five valence electrons.
23 . Silicon and Germanium have four valence electrons.
24 . The total energy of an electron in an atom will be maximum when it is in an orbit farthest from the nucleus.
25 . Silicon has four valance electrons.
26 . A germanium atom has two electron orbits.
27 . If an electron moves through a potential difference of 500V, the energy possessed by it will 500eV.
28 . One electron volt is equivalent to 1.6×10-19 joules.
29 . The forbidden energy gap for silicon is 1.12eV.
30 . The forbidden energy gap for germanium is 0.72eV.
31 . Free electrons exist in conduction band.
32 . The forbidden energy gap between the valence band and conduction band will be least in case of metals.
33 . The forbidden energy gap between the valence band and conduction band will be wide in case of insulators.
34 . An insulator will conduct when the voltage applied is more than the break down voltage and temperature is raised very high level.
35 . A semi-conductor in its purest form is called intrinsic semi-conductor.
36 . At absolute zero temperature a semi-conductor behaves like an insulator.
37 . When atoms are held together by the sharing of valence electrons they form a covalent bond.
38 . An electron in the conduction band has higher energy than the electron in the valance band.
39 . When an electron breaks a covalent bond and moves away, a hole is created.
40 . E0 for silicon is 1.12eV and that for germanium is 0.72eV. Therefore, it can be concluded that less number of electron hole pairs will be generated in silicon than in germanium at room temperature.