ABSTRACTWe review Gas Source Molecular Beam Epitaxy of the GaAs/AlGaAs system. Among the growing number of condensed matter discoveries in materials grown by this approach we describe within resonant tunneling structures. This example serves to demonstrate the high quality quantum well formation and suppressed rate of dopant segregation that occurs during the GSMBE approach. We find a physical basis to quantify the latter growth effects when dopant segregation is viewed in two new ways. First, the broken translational symmetry created by the surface leads to dopant motion (as segregation) that otherwise is not allowed in the crystal interior (as diffusion). Secondly, dopants can dimerize on the crystal surface and this ultimately dictates how the rates of incorporation and segregation proceeds. The manner in which growth creates or destroyes covalent bonds of dopants on semiconductor surfaces thus presents new opportunities to improve dopant control.
