Nanoscale Diodes Without p-n Junctions

The p-n junction cannot be implemented at the nanoscale because the doping is very often a detrimental effect. The doping could change dramatically the properties of a nanomaterial such as graphene or single-walled carbon nanotubes. Therefore, we will present two graphene diodes without a p-n junction. The first is based on the dissimilar metals having workfunction below and above the graphene workfunction and playing the role of a Schottky diode. The second diode is a ballistic graphene diode having a trapezoidal-shape where the rectification is achieved only by the geometry of the device. 1. Graphene Schottky Diodes Based on Graphene The Schottky diode is the second electronic device as importance after transistors. The Schottky diodes due to their abrupt nonlinear I-V characteristics are used in any electronic circuit where nonlinearities are needed i.e. in multipliers, mixers, detectors. Schottky diodes are well-known in semiconductors where metal such as Mo, Pt, or Au or metallic alloys and a semiconductor (e.g. Si, GaAs), are producing a Schottky barrier [1]. When new nanomaterials have attained a certain degree of maturity new Schottky diodes were developed using nanoparticles, nanowires, and nanotubes. Also geometrical diode via carving parallel channels in 2 DEG devices are used to detect THz waves at room temperature [2]. In principle, the CNT Schottky diodes are implemented with the help of asymmetric contacts [3] and this principle is used even to diodes operating at THz frequencies[4]. However, the impedance of a single CNT is greater than 6.5 kΩ which is a huge mismatch since 50 Ω is used for RF instrumentation. This is a problem for all nanomaterials enumerated above and there are not straightway methods to solve this. In the case of CNTs, many parallel CNTs could reach 50 Ω, but the process is not fully reproducible.