Impact of surface states and bulk doping level on hybrid inorganic/organic semiconductor interface energy levels

摘要

In applications, surface states and bulk doping concentration are important parameters of inorganic semiconductors, as they determine the bulk properties and substantially influence the properties of interfaces in devices, foremost the electron energy level alignment. In this work, we provide a qualitative model to describe the influence of surface state density and bulk donor concentration on the work function increase upon deposition of strong organic molecular acceptors onto the surface of n-doped inorganic semiconductors. This work function increase due to electron transfer to the molecular layer has two contributions: the formation of an interface dipole and a change of the near-surface space charge region inside the inorganic semiconductor, referred to as surface band bending. By using different surface preparation methods, we show how the surface state density limits the surface band bending change and enhances the interface dipole, both measured independently by photoelectron spectroscopy. In addition, we show that bulk donor concentration variation of the inorganic semiconductor has minor influence on the ratio of the two contributions to the work function change, at least for low to moderate donor concentrations up to 10(19) cm(-3). Published by AIP Publishing.