Band alignments in the Cu(In,Ga)(S,Se)(2) alloy system determined from deep-level defect energies

The composition dependence of defect energies in polycrystalline Cu(In1-xGa x)(Se1-ySy)(2) chalcopyrite semiconductor thin films is investigated by adm ittance spectroscopy. Alloying CuInSe2 with S increases the energy of the d ominant acceptor from 300 meV to approximately 380 meV in CuIn(Se0.4S0.6)(2 ), whereas in the alloy system Cu(ln(1-x)Ga(x))Se-2, the acceptor energy re mains unchanged over the whole composition range 0 less than or equal to x less than or equal to 1. Using the acceptor energy as a reference, we extra polate the valence-band offsets Delta Ev = -0.23 eV for the combination CuI nSe2/CuInS2 and Delta Ev = -0.04 eV for CuInSe2/CuGaSe2.