An atomistic view on the Schottky barrier lowering applied to SrTiO3/Pt contacts

Abstract

The interface between a metal and a semiconductor is known as Schottky contact and a key factor in semiconductor technologies. Those interfaces normally build an energetic barrier, which is responsible for the exponential current voltage dependence. Analytical models often describe the right trend for the description of the Schottky barrier height, but fail to predict the barrier properties quantitatively correct. To overcome this problem atomistic and quantum mechanical approaches are required such as the here applied density functional theory combined with the non-equilibrium Greens function method. So far, these methods have rarely been applied to wide band gap metal oxides, which leads to a lack in the understanding of oxide electronics. The presented study deals with the image force induced Schottky barrier lowering of a SrTiO3/Pt interface as a model system for wide band gap metal-oxide Schottky contacts. The Schottky barrier lowering is investigated for the case of different doping concentrations/positions and for different voltages. From a defect chemical point of view, oxygen vacancies act as donors in many metal oxides and dominate the electronic conduction in oxide electronics. Consequently, we investigated the Schottky barrier lowering induced by oxygen vacancies. The second doping mechanism is achieved in the sense of classical doping using Nb impurities, which form a conventional n-type donor. The atomistic simulation reveals the Schottky barrier lowering effect for both type of dopants. The results are compared to a standard analytical model regarding the Schottky barrier lowering.