Closed cycle chiller as a low cost alternative to liquid nitrogen in molecular beam epitaxy

The high cost of cooling the cryoshroud in a molecular beam epitaxy system has been greatly reduced by replacing liquid nitrogen (LN2) as a coolant with a silicone polymer heat transfer fluid cooled to as low as −80 °C by a closed cycle chiller. Gallium arsenide epitaxial layers have been grown with two different cooling configurations of the shroud: conventional LN2 cooling and cooling to −70 °C with the chiller. The partial pressure of water in the chamber is a factor of about 2.5 higher with the closed cycle chiller operating at −70 °C than with liquid nitrogen in the shroud. No significant difference is observed in the density of deep levels in the GaAs, as determined by deep level transient spectroscopy.

Closed cycle chiller as a low cost alternative to liquid nitrogen in molecular beam epitaxy Journal Articles