134. Semiconductor materials have bands.
A. ionic
B. covalent
C. mutual
D. metallic
135. The maximum number of electrons which the valence shell of an atom can have is
A.6
B.8
C.18
D.2
136. Silicon has Z = 14. It outermost orbit is
A. partially filled
B. half filled
C. completely occupied
D. empty
137. Major part of the current in an intrinsic semiconductor is due to
A. conduction-band electrons
B. valence-band electrons
C. holes in the valence band
D. thermally-generated electron
138. Conduction electrons have more mobility than holes because they
A. are lighter
B. experience collisions less frequently
C. have negative charge
D. need less energy to move them
139. Doping materials are called impurities because they
A. decrease the number of charge carriers
B. change the chemical properties of semiconductors
C. make semiconductors less than 100 percent pure
D. alter the crystal structures of the pure semiconductors
140. Current flow in a semiconductor depends on the phenomenon of
A. drift
B. diffusion
C. recombination
D. all of the above
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