Year: 2020
Type: article
Abstract: Indian researchers have demonstrated thermoelectric rectification in a graphene self-switching diode (GSSD) on a SiO2 /Si substrate. An applied bias leads to a change in the potential profile and effective channel width of the GSSD, resulting in a diode with current-voltage (I-V) characteristics. The GSSD presented in Electronics Letters exhibits a high Seebeck coefficient (S ) of 200 μV/K, a voltage detection sensitivity and noise equivalent power (NEP) of 97.964 V/W and 0.6064 nW/Hz1/2 respectively. Graphene is something of a buzzword in the scientific community and has been suggested for usage in a wide variety of applications including drug delivery, lightweight computing components, and solar cells. Graphene, comprising of a two-dimensional (2D) sheet of pure carbon arranged is hexagonal patterns, in an excellent electrical and thermal conductor, owing to the presence of delocalised electrons in its structure. Single layer graphene in particular has the interesting property of a zero energy bandgap and high carrier mobility, making it suitable for usage in low power THz detectors. Aran Kuymar Singh (far right) and research group at Department of Electronics and Comm. Engg. Punjab Engineering College, Chandigargh, India. Thermal measurement setup with a variable heat source at cathode and voltage source at anode, with cathode grounded. Lattice temperature profile of device at 475 K. In recent years the development of ever-smaller devices, such as fin field-effect transistors (FinFETs), three-terminal junctions, ballistic rectifiers and carbon nanotubes, has been the main way of maintaining Moore's law as it approaches saturation. Amongst these nanoscale devices, the self-switching diode (SSD), developed in 2003 by Song et al. has been fabricated using a range of semiconductor materials. The electrical characteristics of the SSD are similar to a conventional semiconductor diode (i.e allowing the flow of current in one direction only) but the way in which it does this is more akin to a field effect transistor (FET). SSDs have been proposed as thermoelectric rectifiers over other novel devices due to their high responsivity, low NEP and their ability to work in the THz frequency range due to low parasitics. Additionally, SSDs have generally simple structures in comparison to other similar devices and can therebefore be easily fabricated by using exfoliated graphene. Although there is a wealth of literature surrounding SSDs, there has not, until now, been an intensive thermal analysis of SSDs and an evaluation of their suitability as a thermoelectric rectifier. The work of Singh et al. presented in Electronics Letters is the first work to present a detailed analysis of GSSDs working as thermoelectric rectifiers. Moreover, the authors have produced a discussion on the Seebeck effect in their fabricated device. The Seebeck effect is that, when a temperature gradient is present across a device, an electrical voltage is generated between two contact points. The phenomenon is dictated by the Seebeck coefficient (S ) of the device material. In GSSDs the S value is observed to approach a value of 200 μV/K when VBG = 0 V, making them suitable thermoelectric rectifiers for energy harvesting processes. As the device is highly sensitive, the GSSD can function when exposed to heat that would otherwise be considered ‘wasteful’ – from other electrical devices for example. This presents an interesting potential for this device to power other electrical components that only require a small voltage. Since their initial development in 2009, research into SSDs has come a long way. In the formative years only group III-V heterojunction devices were developed, but with the improvements in technology of novel 2D materials like graphene, MoS2, and others, much more capable and high performance devices are being fabricated and designed. Researchers have adapted SSD technology to develop geometric diodes, which can also work into the high microwave frequency range. In particular, the group of Singh et al. has also utilised different materials such as III-V heterostructures and graphene to design and develop this technology, with technical guidance from Prof. Aimin Song, University of Manchester (UK), the inventor of the SSD. In the next 10 years, with the development of high frequency technologies like 5G, SSDs may be a suitable candidate to replace Schottky and other high frequency diodes due to their superior performance and ease of fabrication. They can be further utilised in designing numerous types of other novel circuits, such as bridge rectifiers, logic gates and more. Additionally, the room temperature detection of microwave and THz signals, and SSD's capability as a THz emitter, as envisaged by numerical simulations, may lead to the development of a compact, cost-effective THz system in near future, which is something that Singh et al. are keen to pursue.
Source: Electronics Letters
DOI: 10.1049/el.2020.2745
Author: anonymous
Language: English
Subfield: Materials Chemistry
Field: Materials Science
Domain: Physical Sciences
Open Access status: bronze
OpenAlex ID: W4206783727