ELECTROCHEMICAL ETCHING OF SIC MATERIALS AND MODIFICATION OF PROPERTIES

Abstract

With the development of semiconductor physics and technology, the third-generation semiconductor, silicon carbide (SiC), has been developed for several decades, and a mature industry and market have been built up. For optoelectronic applications, SiC is an attractive material, because of its wide energy band gap. Due to the indirect band gap and high cost of fabrication, the real applications are not as good as III-V materials such as GaN. However, from the aspect of sustainability, the reservoir of group III elements such as Ga is quite limited, which cannot satisfy the increasing demand for products such as LEDs and displays. In this situation, SiC is in abundance and must play a significant role in the future. This thesis focuses on the electrochemical etching strategy of SiC materials, exploring the effects of surface reconstruction and modification on their properties. In Chapter 4, a comprehensive study of electrochemical etching is provided by characterizing the surface with SEM, including the reaction mechanism, key parameters, and usage of different etchants with the relationships in between. Apart from that, a highly reflective porous structure was achieved by adjusting the etching parameters with dilute HF. The reflectivity was successfully explained by multilayer interference effects and shows the potential to be applied as optical reflectors and sensors. Besides, surface chemistry and size results were studied with XPS, Raman and XRD to provide a better understanding of the effects of etching. In Chapter 5, a simple strategy for selective etching of patterns was proposed assisted with surface scratching. The applied forces during scratching were explored with the ability to adjust the width of the pattern as observed by SEM and AFM. The formation mechanism is explained by the redistribution of electric field due to the amorphization, which is checked by TEM and theoretically verified by simulation modeling.