The δ(z) Doping Layer: Impurities in the 2-d World of Layered Systems

We consider a layer of dopant atoms embedded in a single atomic plane during epitaxial growth of a GaAs crystal. It is shown that the electronic states of this 6-layer are subbands of a V-shaped potential well. The subband levels are studied in magneto-transport and tunneling experiments. We discuss the case of a periodic sequence of layers, the role of valley-orbit effects, and central cell corrections.