Fermi level depinning at metal-organic semiconductor interface for low-resistance Ohmic contacts

This paper presents the direct evidence and successful demonstration of Fermi-level depinning at metal-organic semiconductor (M/O) interfaces by inserting an ultrathin interfacial Si₃N₄ insulator in between. The contact behavior is tuned from rectifying to quasi-Ohmic and to tunneling by varying the Si₃N₄ thickness within 0-6 nm. Detailed physical mechanisms of Fermi-level pinning/depinning responsible for the M/O contact behavior are clarified based on a proposed lumped-dipole model. Experimental results are in good agreement with the theory and model. This work represents a significant step toward the fundamental understanding of M/O interface properties and technological advancement of achieving low-resistance Ohmic contacts for organic electronic device (e.g. thin-film transistor) applications.