Process-induced anomalous current transport in graphene/InAlN/GaN heterostructured diodes

Graphene and III-nitride semiconductors are promising materials platforms for the development of high-frequency, high-power electronic devices. Successful integration of these materials, however, requires a detailed understanding of the electrical properties of the graphene/III-nitride interface. In this work, we investigate the interfacial charge carrier transport across the graphene/InAIN interface. We show that at room temperature the leakage current in these devices is well described by the Fowler-Nordheim tunneling relation. Temperature-dependent measurements between 100 K and 400 K, however, show that as temperature decreases, the leakage current increases. This observation cannot be explained by Fowler-Nordheim or other standard conduction mechanisms (thermionic emission, Poole-Frenkel emission, trap-assisted tunneling). It is proposed that device processing, specifically polymer residue contamination, affects the interfacial coupling between graphene and the InAIN substrate, resulting in the observed anomalous current transport. Evidence for such a mechanism is provided by Raman spectroscopy and temperature-dependent atomic force microscopy studies.