Molecular Beam Epitaxy Systems and Procedures

Abstract

Until the advent of Gas Source Molecular Beam Epitaxy (GSMBE), a good working description for molecular beam epitaxy was that it was a growth method in which epitaxial layers are grown under high vacuum conditions by causing a thermal flux of atoms or molecules, that constitute the elemental components of the epitaxial layer, to impinge and react upon the heated surface of a single crystal substrate. The substrate surface is the template for epitaxy, therefore its temperature must be high enough that adsorbed atoms or molecules have sufficient mobility to move on the surface until they find appropriate growth sites, but not so high that evaporation or faceting to form low energy surfaces can occur. The MBE system is the aggregate of vacuum system, vacuum pumps, auxiliary analytical equipment, beam sources, sample introduction, manipulation and heating apparatus that make the achievement of these necessary growth conditions possible. These systems can be very similar for ESMBE and the GSMBE methods. In fact, in going from ESMBE to HSMBE the only necessary differences are in the pumping and the group-V beam sources. For this reason the discussion of the MBE apparatus starts in Sect. 4.1 with a description of conventional MBE growth chambers and their auxiliary apparatus.