| Due to its superior physical and electrical properties, silicon carbide (SiC) forms the most attractive alternative to silicon in fabricating devices for high-voltage, high-power density, high-temperature, and high-frequency applications. Currently, the basic device structures of interest for SiC are concentrating on MOSFETs, which are popular in silicon. SiC MOSFETs, however, suffer from the low channel electron mobility and the immaturity of the gate oxide and dielectric technology in general. The high electric fields in the case of SiC, one order of magnitude higher compared to silicon, make the requirements set on the MOSFET gate difficult to meet as long as there are no mature alternatives to SiO2. Therefore, it is essential to develop power devices not requiring critical gate dielectric for SiC.; This thesis presents the design, optimization and performance prediction of four gate-oxide free power device structures in 4H-SiC by way of two-dimensional device simulations using the 4H-SiC physical parameters extracted from the most recent published literatures. They are 4H-SiC NPN BJT, 14kV 4H-SiC normally-off planar vertical-JFET (P-VJFET), 1.7kV to 14kV 4H-SiC normally-off trenched-and-implanted vertical-JFET (TI-VJFET), and 450V 4H-SiC normally-off trenched-and-implanted static induction transistor (TI-SIT). For the first time, the temperature coefficient of the common-emitter current gain of 4H-SiC NPN BJT is studied systematically. Both P-VJFET and TI-VJFET structures are novel device structures and proposed for the first time.; Based on this thesis research, some exciting preliminary experimental results have been obtained by SiCLAB, ECE Department of Rutgers University, including the first 10kV 4H-SiC normally-off TI-VJFET with an effective specific on-resistance of 130mO-cm2 and the first 4H-SiC normally-off TI-VJFET with a blocking voltage (VBR) of 1726V and a specific on-resistance (Ron,sp) of 3.6mO-cm 2, corresponding to a VBR2/ Ron,sp value of 827MW/cm2, which represents a substantial improvement over the best reported results for the SiC JFETs. The analyses of the experimental results by performing device simulations are also presented in this thesis.; These four device structures do not require critical gate dielectric so that they are supposed to be able to fully utilize the advantages of SiC as a wide-bandgap semiconductor. They could become the popular device structures in the future SiC industry. |
