First Principal Study of 2D Lateral and Vertical Heterostructures Built by 2D Polar Binary Compounds: SiC, GeC, and SiGe


Fri, 06 Aug 2021, 02:00 pm - 03:00 pm
Gradute Thesis Defense Spring 2021
Safia Abdullah R. Alharbi
University of Lousiville


 Heterostructures are the building blocks of the most advanced semiconductor devices being developed and produced. They are essential elements of the highest-performance optical sources and detectors and are being employed in high-speed and high-frequency digital and analog devices. Also, they have been found to be used in a variety of specialized applications, such as heterojunction bipolar transistors (HBT), field-effect transistors FETs, Photodetectors, Light emission devices LED, photovoltaic, and photocatalysis. 

We will propose to conduct a systematic study on lateral and vertical heterostructures, which are constructed by 2D polar binary compounds including flat SiC and GeC sheets, as well as the bulked SiGe sheet. A sharp interface is the key feature of lateral heterostructure, which may lead to unique optical and electrical transport properties. The weak van der Waals (vdW) interlayer interaction, on the other hand, is the key feature of vertical heterostructure, even though it is weak and small, but it has crucial effects on the electronic structure. 

A systematic computational calculation based on f Density Functional Theory (DFT) method will be carried out by focusing on roles played by the interface, the strain, the confinement, the electrostatic interlayer and vdW interactions, etc. on the structural and electronic properties of 2D lateral and vertical heterostructures. Our preliminary studies on the 2D SiC/GeC lateral heterostructures showed that band gap of the combined system exhibits different nature with different interfaces, the mismatch induced biaxial strain widens the band gap at the GeC domain, and narrowed the band gap at the SiC domain, independent of the size of the domain. The confinement effect, on the other hand, could also tune the band gap by controlling the size of the domains. Furthermore, our preliminary study on 2D SiC/GeC and BN/BN vertical heterostructures have revealed that the interlayer species ordering (e.g., C-Ge (Si-C) or Si-Ge (C-C)) can trigger the electrostatic interlayer bonding which plays a key role in stabilizing 2D SiC/GeC vertical heterostructures. The 2D BN vdW bilayer heterostructures, however, is stabilized solely by the vdW interaction. These keys finding form the basis of the current in-depth exploration of 2D polar binary compounds heterostructures.

Proposed work including 2D SiC/SiGe and GeC/SiGe lateral and vertical heterostructure will be addressed. Our work will unveil significant differences between 2D lateral and vertical heterostructures.