Band lineup at an organic-inorganic semiconductor heterointerface: perylenetetracarboxylic dianhydride/GaAs(100)

We present a photoemission study of the electronic properties of an interface between the organic semiconductor; 3, 4, 9,10 perylenetetracarboxylic dianhydride (PTCDA) and n-type GaAs(100). We examine the evolution of the interface electron distribution as a function of PTCDA overlayer thickness. The highest occupied molecular orbital level of PTCDA is measured at 0.7±0.1 eV below the GaAs valence band maximum. The PTCDA ionization potential is measured at 6.4±0.15 eV. The discrepancy between the band alignment deduced from photoemission and transport measurement suggests that interface states or polarization effects play a role in determining the transport properties of the organic-inorganic heterojunction diodes.