Text

theses

Power electronics systems require robust power switches to operate at high temperatures to meet the demand for smaller and higher power density systems. The improvement in material technology has made 4H–Silicon Carbide (SiC) a promising material for power electronics applications. This is because SiC has superior properties such as high electric breakdown field, high thermal conductivity and high bandgap. Compared to other devices made on SiC, such as BJTs and IGBTs, SiC gate turn-off thyristors (GTOs) are favorable devices for power electronic applications due to their ability to operate at high current and high voltage levels under high temperature, which is attributed to conductivity modulation in the drift layer of the device. Furthermore, SiC GTOs offer several advantages over Si thyristors and Si GTOs such as compactness, higher current density, faster switching, and higher temperature operation. This dissertation presents the design, fabrication and characterization of 4H-SiC GTOs, along with the study of the multistep junction termination extension (MJTE) for high power 4H-SiC devices. The physics-based MJTE design and optimization via numerical simulations has been studied. The 3-step MJTE with the maximum blocking voltage of 7630 V, which is 90% of the ideal breakdown voltage, has been demonstrated. The design of MJTE has been applied to the fabrication of GTOs. 0.1 cm2 4H-SiC greater than 6 kV GTOs have been demonstrated with MJTE utilized successfully. A relatively large area, high voltage 4H-SiC GTO that exhibits encouraging characteristic at the on- and off-state, low leakage current and high yield is presented. Initial pulse testing results shows that the fabricated GTOs can handle both the high current density and the high turn-off speed.

ETD_4922

Ph.D.

Includes bibliographical references

Includes vita

by Lei Lin

doi:10.7282/T3RF5S2Q

ETD doctoral

The author owns the copyright to this work.