  The boson-fermion (BF) model has been proposed to describe superconductivity
in short coherence length superconductors. In this work we use it to study
impurity induced inhomogeneities in high temperature superconductors (HTS) as
found in numerous scanning tunnelling measurements. The model has been
formulated in real space and solved with help of Bogolubov-de Gennes approach.
Disorder in the boson or fermion subsystem is directly coupled to the
superconducting order parameter and leads to severe changes of superconducting
properties like local order parameter and density of states. We present the
results for many impurities randomly distributed over otherwise clean and
periodic two-dimensional square lattice.
