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VA: Fachverband Vakuumphysik und Vakuumtechnik

VA 1: Cryogenic Vacuum Pumping

VA 1.1: Hauptvortrag

Montag, 14. März 2011, 10:00–10:40, HSZ 101

Cryogenic pumping for the fabrication of highest-purity semiconductors — •Werner Wegscheider — Laboratorium für Festkörperphysik, ETH Zürich, 8093 Zürich, Switzerland

Cryogenic capture pumps based on closed-cycle gaseous He refrigerators are extensively used in semiconductor industry due to their high pumping speed resulting in short pump down times of vacuum chambers. For highest-purity growth of semiconductor heterostructures, where molecular beam epitaxy (MBE) is the method of choice, background vacuum levels below 1E-12 mbar have to be reached. This requirement presents a major challenge for the design of such a MBE system in which cryogenic capture pumps are exclusively used. I will present the outline and results of a GaAs based MBE system which was specifically designed for the fabrication of highest-mobility two-dimensional electron gases. The performance of these structures, which represent the key ingredient for so-called high-mobility transitors (HEMTs), depends critically on the purity of the growing material and thus on the vacuum level in the growth chamber.