Review of recent studies on nanoscale electrical junctions and contacts: Quantum tunneling, current crowding, and interface engineering

Abstract

The study of charge carrier transport at nanoscale electrical contacts is crucial for the development of next-generation electronics. This paper reviews recent modeling efforts on quantum tunneling, current crowding, and contact resistance across electrical interfaces with nanometer scale dimensions. A generalized self-consistent model for quantum tunneling induced electron transport in metal–insulator–metal (MIM) junctions is summarized. Rectification of a dissimilar MIM junction is reviewed. A modified two-dimensional (2D) transmission line model is used to investigate the effects of spatially varying specific contact resistivity along the contact length. The model is applied to various types of electrical contacts, including ohmic contacts, MIM junction based tunneling contacts, and 2D-material-based Schottky contacts. Roughness engineering is recently proposed to offer a possible paradigm for reducing the contact resistance of 2D-material-based electrical contacts. Contact interface engineering, which can mitigate current crowding near electrical contacts by spatially designing the interface layer thickness or properties, without requiring an additional material or component, is briefly reviewed. Tunneling engineering is suggested to eliminate severe current crowding in highly conductive ohmic contacts by introducing a thin tunneling layer or gap between the contact members. Unsolved problems and challenges are also discussed.

Interfacial Properties of the SnO/κ-Ga2O3 p-n Heterojunction: A Case of Subsurface Doping Density Reduction via Thermal Treatment in κ-Ga2O3

“…Nowadays, a major fraction of consumer and industrial electricity is processed by power electronic devices and instruments; therefore, the role of high-power electronics, and inherent losses, becomes increasingly important. − Current power electronics face many technical challenges such as heat dissipation and overheating, limitations of the operation voltage, etc. − There are also problems associated with the bad electrical contact that can lead to higher energy consumption or device breakdown due to the current crowding effect and localized overheating . It is important to note that about 13% of electricity is wasted in switching and conversion by conventional devices; therefore, development of new approaches and materials in high power electronics is an urgent and fundamental task.…”

“… 5 − 9 There are also problems associated with the bad electrical contact that can lead to higher energy consumption or device breakdown due to the current crowding effect and localized overheating. 10 It is important to note that about 13% of electricity is wasted in switching and conversion by conventional devices; 9 therefore, development of new approaches and materials in high power electronics is an urgent and fundamental task. Ultrawide band gap semiconductors have emerged as good alternative for high power/low loss electronics.…”

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“…Quantum mechanical tunneling is a good candidate solution. , A tunneling device has an ultrathin potential barrier so that electrons can penetrate the potential barrier. Thus, it can show high operating speed, a sub–60 mV/decade subthreshold swing, low operating voltage, and high current efficiency. − Usually, an oxide material or a semiconductor is used as the tunneling barrier. − However, in this case, some issues still remain, such as electron trap and scattering due to the defects in the barrier. This easily degrades the electrical properties of the device.…”