Epitaxial growth of 4H-silicon carbide by CVD for bipolar power device applications

Wenzhou Chen, Purdue University

Abstract

Silicon carbide (SiC) has shown significant promise for a wide range of electronic device applications which cannot be achieved by traditional semiconductors. Epitaxial growth of 4H-SiC is the essential technology for any device applications based on this polytype. Among many device structures, bipolar power devices are attractive because of lower forward voltage drop and potential for high-temperature applications. Therefore, epitaxial growth of 4H-SiC by chemical vapor deposition (CVD) technique for bipolar power device application will be studied in this work. In this dissertation, material issues associated with the development of 4H-SiC bipolar power devices are identified to be: (1) reduction of basal plane dislocation (BPD) densities and (2) improvement of epilayer minority carrier lifetimes. Both issues will be investigated extensively in this research. Epitaxial growth of 4H-SiC is performed using horizontal hot-wall CVD technique on both Si-face and C-face substrates. Low BPD densities are achieved on 4° off-angle Si-face epilayers. Nitrogen-induced step-bunching and defect generation are identified on C-face epilayers and low surface defect densities are achieved. High-purity epilayers with long minority carrier lifetime are obtained on Si-face epilayers. Correlation between the deep-level trap density and C/Si ratio is established. High-voltage 4H-SiC pin diodes are fabricated on both 4° and 8° off-angle Si-face epilayers. The performance of fabricated pin diodes has been evaluated by various techniques. The forward voltage degradation of the pin diodes is discussed in details. Devices with minimal forward voltage drift are achieved on 4° off-axis epilayers with very low BPD density.

Degree

Ph.D.

Advisors

Capano, Purdue University.

Subject Area

Electrical engineering

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