Conduction in materials and devices: A universal expression for transport

Abstract

The space-charge-limited-current spectroscopy is a consolidated technique for studying electrical properties of materials and devices. In general, the conduction in the material can be expressed as a single scaling law, relating the current with voltage and gap (or sample thickness) with different values for the exponents. However, some aspects of this technique remain obscure, especially when dealing with very thin (few nanometer) gaps and solids. Beyond this, abrupt transitions between different transport regimes are observed, whereas unusual space-charge-limited current behaviors are expected in out of 2D plane of 2D-material-based heterostructures. Therefore, there is a need for a universal model to describe the current–voltage characteristic curves, including different conduction mechanisms as well as smooth transitions between them. This goal, pursued for decades without substantial success, is not achievable based on the mentioned simple scaling laws, requiring a new approach. In this work, we propose a universal model with the same underlying physics. A new function is considered which contains relevant information for transport and accounts for most of the fingerprints observed in experimental current–voltage curves of the most diverse set of physical systems, from materials to devices. This approach leads to the usual scaling laws for constant values of the transport function, whereas it is abandoned for the trap filling regime, although the same familiar higher slopes of current–voltage curves can be recovered. The model is used to fit the experimental curves of the most diverse materials and devices in order to show its applicability and accuracy.