Semiconductor Materials » Exercise – 4
151. The addition of a very small quantity of aluminium to a silicon or germanium crystal makes it :
(a) A good conductor
(b) A good insulator
(c) P-type semiconductor
(d) N-type semiconductor
152. An intrinsic semiconductor at the absolute zero of temperature :
(a) Behaves like a semiconductor
(b) Behaves like an insulator
(c) Has a few free electrons and same number of holes
(d) Has a large number of holes and a few electrons
153. In a substance the conduction band and valence band are separated by a energy gap of the order of 1 eV, and there are at room temperature as money electrons in the conduction band as holes in the valence band. The substance is :
(a) An intrinsic semiconductor
(b) A p-type semiconductor
(c) A N-type semiconductor
(d) A doped semiconductor
154. The majority carriers of electricity in a p-type semiconductor are :
(a) Free electrons
(b) Holes
(c) Both electrons and holes
(d) Free ions
155. N-type semiconductor is obtained when silicon or germanium is doped by :
(a) Phosphorus
(b) Boron
(c) Aluminium
(d) Gallium
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