211. Germanium may be made p-type by adding acceptor impurities
A. during the normal-freezing process.
B. during the zone-refining process.
C. during the crystal-pulling process.
D. before purification begins.
212. A seed crystal is
A. a single crystal containing the donor or acceptor impurities.
B. a crystal in the liquid state.
C. a single crystal with a particular orientation.
D. a crystal formed by expitaxial growth.
213. An inert gas is pumped into the quartz tube during zone refining to
A. add acceptor impurities to the melt.
B. absorb impurities from the melt.
C. make melting occur at a lower temperature.
D. prevent the melt from absorbing impurities from the air.
214. Epitaxial growth is best suited for
A. growing single crystals several inches long.
B. obtaining polycrystalline germanium.
C. obtaining polycrystalline silicon.
D. growing very thin single crystals on a substrate.
215. Epitaxial growth is obtained by
A. freezing the melted semiconductor metarial.
B. melting and then refreezing the semiconductor material.
C. depositing the semiconductor material on to a heated surface.
D. pulling a solid from the liquid.
216. An epitaxial germanium film may be doped by
A. using hydrogen gas as a carrier.
B. using chlorine to form the vapor compound.
C. introducing the doping impurity as a vapor along with the germanium compound vapor.
D. adding the doping impurity to the melt.
217. Resistivity measurements are often used to determine
A. the lifetime of polycrystalline materials.
B. carrier concentration in intrinsic semiconductors.
C. carrier concentration in extrinsic semiconductors
D. carrier mobility
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