William Angerer - Department of Physics and Astronomy - University ...

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Krypton len laeer
dewar
chopper
compUler
m cnochromeler
Figure 4.10: Experimental setup for photoluminescence from GaNj.-\'1203
pIe was placed in a Janis Research Company dewar model8DT Supervaritemp. ),;"ote.
the GaN sample was mounted in the dewar for both the 293 K and 82 K photoluminescence
measurements. This dewar consists of an inner jacket, which was filled
with liquid nitrogen to a level just below the sample during the low temperature
measurement, and an outer jacket, which was filled with liquid nitrogen to the top
of the dewar during the low temperature measurement. The sample was mounted in
the optical fin of the dewar, which consists of four glass windows through which light
can propagate. Prior to cooling the dewar with liquid nitrogen, we purged the inner
jacket with gaseous nitrogen for ",,10 minutes to remove any moisture in the inner
jacket. This process was a necessary step in the experimental process to prevent water
vapor from freezing on the GaN sample and clouding the optical fin, thus impeding
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