7.5 Development of a Compact NH_3 Jet - NH_3 Jet Performance Compared to
Leak Valve
The jet performance was compared to a leak valve in terms of flux intensity
versus gas load on the system. The leak valve was placed about 6'' from
the substrate compared to 20'' for the NH_3 jet. It was found that the
gas load on the system for typical `fluxes' of 5x10^-6 torr is only about
4 times larger using the leak valve than using the NH_3 jet. It should
be emphasized though that the leak valve was much closer to the substrate
than the jet. The data were obtained by comparing the background pressure
in the growth chamber with the cryoshroud in the growth chamber switched
off using the NH_3 jet and the leak valve. A useful comparison between
a supersonic jet and a leak valve is also provided in the concluding section
of the chapter on jet theory.
So far no data was obtained in comparing the jet to a leak valve in
terms of growth rate and crystal quality. Initial results indicate that
the jet does not increase the growth rate by any significant amount. Future
experiments are planned comparing the growth rate and crystal quality of
jet and leak valve grown material, as well as the dependence on jet parameters,
especially the nozzle temperature To. These experiments will be performed
as soon as the jet independent growth rates are determines and a more fundamental
understanding of the growth process is achieved.
Table of Contents