ORNL-2106 - the Molten Salt Energy Technologies Web Site

ANP PROJECT PROGRESS REPORT
IIOV -60-
atom as it travels through the lattice result in the
formation of lattice vaccncies and interstitial
atoms. Since the germanium lattice is fairly open,
the interstitial atoms can diffuse readily through
the crystal. Because of the high dielectric con-
stant of germanium, the interstitial atom is ionized
at room temperature, and hence its diffusion should
be influenced by the presence of an electric field.
Fields of the order of tenths of a volt per micron
are available in the barrier region of a diode, and
the conductivity of the diode is extremely sensitive
to changes in carrier concentration in the region
of the barrier.
A 1N38A point-contact germanium rectifier was
exposed for 5 min in hole 51-N of the ORNL
Graphite Reactor. After removal from the reactor
the rectifier was biased in the forward direction
246
Fig. 4.2.16. Transistor Test Circuit.
‘0
at 0.7 v in order to remove the potential gradient
in the barrier region. The measured current was
low because of radiation damage. The unit was
then placed in an oil bath to maintain a constant
temperature of about 250C for six days. At the
end of the six-day period there had been no
observable change in the current passing through
the sample at 0.7-v bias. The bias was removed
for 2 hr, then restored. When the bias had been
restored, it was noted that the current had in-
creased by about an order of magnitude. After
eight days in the biased condition, the current had
not changed.
When the bias was removed, an electric field
was established at the barrier to cause the relative
interstitial atoms to diffuse from the barrier region.
This removal of interstitial atoms from the p-type
.
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