Density of states of a terminated superlattice with periodically arranged δ -defects

Abstract

Surface electronic structure and the local density of states (LDOS) of a periodicallyδ-doped GaAs/AlxGa1−xAs superlattice (SL), terminated by an AlyGa1−yAs substrate, are investigated using the wave-function multi-matching procedure within an effectivemass approximation and a Green-function formalism based on factorization and direct techniques. The considered system is described in terms of a semi-infinite Kronig-Penneytype of model interleaved with a periodic array ofδ-function-like potentials, representing deep-center defect sheets. It is shown that the spectrum of surface-localized states and the corresponding space-charge distributions within particular SL minibands can be tailored by varying the terminating conditions (i.e., the substrate parameters) as well as the properties of inserted defects (i.e., the weight and position ofδ-potentials). In this respect, importance of a symmetric/nonsymmetric arrangement ofδ-dopants inside SL barriers and the related effect of miniband crossing/anticrossing are emphasized.