SURFACE ELECTRONIC-STRUCTURE OF A STEP-WELL-BASIS SUPERLATTICE

Surface electronic structure of a semi-infinite polytype superlattice (SL) with period consisting of three different layers (the so-called s tep-well basis) is investigated using a transfer-matrix approach withi n an effective-mass approximation. Explicit analytical formulas for th e bulk dispersion relation as well as the energy expression and existe nce condition for surface states are given for arbitrary terminating m edium and their simplification for particular SL terminations by a sub strate identical to one of the SL constituents is discussed. Dependenc e of surface-state properties (i.e., its energy position and the degre e of localization) on SL parameters (i.e., layer thicknesses and poten tial barrier heights) and different surface configurations (depending on a sequence of SL layers approaching the surface as well as on the c hoice of substrate) is studied for a triple-constituent AlxGa1-xAs-bas ed SL. Additionally, surface-state wave functions are plotted in order to examine the associated space-charge distributions.