Density of states of a superlattice with a δ defect in the subsurface region

The effect of a spatially and strongly confined (δ-like) defect layer on the electronic properties of a semi-infinite superlattice (SL) is investigated, with emphasis placed on local density-of-states (LDOS) modifications at the SL end. The SL energy spectrum and the LDOS distributions, calculated within a modified Kronig–Penney type of approach, are studied for variable δ-defect parameters (i.e. its strength and position with respect to the SL surface) and different SL terminating conditions (depending on the choice of substrate). The possibility of a dramatic redistribution of extended states forming the SL minibands as a result of a single δ-defect sheet insertion in the subsurface SL region is indicated and discussed in detail.