Defect Structure of Cu-Rich and In-Rich Chalcopyrite CuInSe2 Films Grown on GaAS

Abstract

ABSTRACTUsing Transmission Electron Microscopy, we examine the defect structure of Cu-rich and In-rich CuInSe2 films grown by Molecular Beam Epitaxy on GaAs (100) substrates. A surprisingly high density of cation sublattice stacking faults on (001) planes are observed in the Cu-rich films. Because these stacking faults are extremely flat and extend thousands of Ångstroms over the surface, and because they are not observed in other, non-Cu-rich films, we argue that they are a consequence of a surface structural change during growth, induced by the excess Cu. Two other types of defects are also observed: near the CuInSe2/GaAs interface, there is a high concentration of dislocations, stacking faults and domain boundaries. In the In-rich films, stacking faults and twin-type defects on {112} planes extend throughout the thickness of the grown film.