10.9 GaN Growth Investigations - Search for Oscillations
Several attempts were conducted in the search for GaN growth oscillations,
so far unsuccessfully. Currently this is believed to be due to the insufficient
surface quality of the samples. Also, the equipment used to monitor oscillations
was faulty and was fixed only recently. Another important issue seems to
be instabilities in the RHEED gun used, causing it to oscillate under certain
conditions, as well as what might be charging effects which could be due
to both the sample (insulating) and equipment in the chamber not properly
grounded. Those issues are currently addressed and significant progress
had been made. It should be mentioned that so far no group has observed
RHEED oscillations on any III-Nitride system. Ones RHEED oscillations are
detected it would be a significant step forward in terms of being able
to deduce crystal quality (amplitude) and growth rates (frequency) directly
during growth without having to perform lengthy post growth characterizations
every time a sample is prepared, as well as being able to conveniently
conduct several experiments on the same sample.
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