Semi-conductors Objectives Part 03

41 . E0 for silicon is 1.12eV and that for germanium is 0.72eV. Therefore, it can be concluded that the conductivity of silicon will be less than that of germanium at room temperature.

42 . The resistivity of a semiconductor decreases as the temperature increases.

43 . Semi-conductors have negative temperature coefficient of resistance.

44 . The process of deliberately adding impurity to a semi-conductor material is called doping.

45 . A doped semiconductor is called extrinsic semi-conductor.

46 . Before doping the semi-conductor, material is purified.

47 . Phosphorous is donor impurity element.

48 . Gallium is acceptor impurity.

49 . Antimony, Gallium and Arsenic have five valence electrons.

50 . Silicon has four valence electrons.

51 . Boron, Indium and Gallium have three valence electrons.

52 . Antimony has the highest atomic number.

53 . As the temperature of an intrinsic semi-conductor material is increased energy of the atom is increased.

54 . A vacancy is filled by a valance electron from the neighboring atom results in the movement of hole.

55 . Addition of a small amount of antimony to germanium will result in formation of p-type semiconductor.

56 . A donor type impurity must have only five valance electron.

57 . At room temperature when a voltage is applied to an intrinsic semiconductor electron moves towards positive terminal and holes towards negative terminal.

58 . The energy of the atoms of a semi-conductor material is increased when temperature is increased.

59 . The conduction band is a range of energies compounding to the energies of the free electrons.

60 . The forbidden energy gap in semiconductors lies between valance band and conduction band.