Xue W (2023)
Publication Language: English
Publication Type: Thesis
Publication year: 2023
Devices based on 4H-SiC have not only played a significant role in power electronics but have also shown remarkable potential in quantum applications. Currently, these devices are demonstrating astonishing capabilities in the field of quantum technology. Silicon vacancies located within 4H-SiC, for instance, can effectively serve as efficient quantum dots. However, it cannot be ignored that other types of defects present in 4H-SiC also impact silicon vacancies. For instance, the presence of fixed charges in the vicinity of the silicon vacancies can lead to the broadening of the excitation spectrum. Additionally, the emission wavelength can fluctuate over time due to mobile charges, thereby constraining the further development of quantum applications.
In this master's thesis, an in-depth exploration of the defect landscape in 4H-SiC-based devices is investigated using the powerful technique of deep-level transient spectroscopy (DLTS). By characterizing the defects under different processing conditions, their behaviour and impact on device performance could be uncovered. Epitaxial 4H-SiC layers will be used to fabricate a range of devices, including MOS capacitors prepared using diverse oxidation processes such as plasma-enhanced chemical vapor deposition (PECVD), low-pressure chemical vapor deposition (LPCVD), and various thermal oxidation methods. Additionally, Schottky capacitors will be fabricated based on dry thermal oxidation MOS capacitor to comprehensively investigate the defect landscape. Before conducting the DLTS experiments, certain electrical connection issues about the series resistance of chuck and natural oxide of polysilicon were also addressed. This was primarily achieved by ensuring the closeness of the two spots of silver glue and employing Focused Ion Beam (FIB) with Platinum deposition. This successful approach resulted in the alignment of the C-V curves obtained from DLTS with those obtained from standard C-V experiments. During DLTS measurements, new defect levels ON1 and ON2 originated from excess carbon are found to be introduced through thermal oxidation, along with the observation of silicon vacancies. Similar new defects were observed in LPCVD MOS capacitors, resembling those introduced during thermal oxidation, but they are most probably not the same defects because there will be no excess carbon in LPCVD process, so they are suspectable to be some intrinsic defects or caused by some residuals from LPCVD process. Additionally, various defects were identified in the Schottky diode capacitors including silicon vacancy.
Furthermore, high-dose and low-dose electron irradiation will also be utilized. After electron irradiation, an increase in the concentration of defects related to carbon vacancies in the Schottky diode capacitors can be observed. However, this phenomenon has not been observed in the MOS capacitors.
APA:
Xue, W. (2023). Investigation of defects in 4H-SiC and the SiC/SiO2 interface using DLTS measurements (Master thesis).
MLA:
Xue, Weidong. Investigation of defects in 4H-SiC and the SiC/SiO2 interface using DLTS measurements. Master thesis, 2023.
BibTeX: Download