Novel silicon carbide devices for high power and high temperature applications.

摘要

Silicon Carbide (SiC) offers great promise in high power, high temperature applications. This research focuses on the development of SiC devices, specifically the two most important devices in semiconductor power electronics: SiC Schottky diodes and PN junction diodes.; A novel Schottky diode named MOSSD is presented and experimental results show that MOSSD exhibits significantly lower leakage currents and high breakdown voltages compared to the conventional Schottky diode with the same footprint area. The accumulation layer formed beneath MOS structure helps spread the forward current laterally. Thus, MOSSD makes no serious sacrifice in forward current characteristics. To decrease the forward voltage drop of the lateral Schottky diode, a novel structure named ACCU-LSD is proposed and fabricated. The accumulation layer provides a current channel with low specific on state resistance. The accumulation layer contribution depends on the forward bias, operational temperature and the oxide film thickness. Because of their excellent electrical characteristics, MOSSD and ACCU-LSD are promising Schottky diode structures for high power and high temperature applications. In this work, it has been demonstrated that high temperature annealing can improve the Schottky diode characteristics by suppressing the leaky secondary diode, caused by the heterogeneous barrier height.; Power P+PN+ diodes were fabricated and forward conduction performances were measured and compared to identical P +NN+ diodes. Results show that P+PN + diodes exhibit a non-linear behavior at room temperature and higher forward current density above a certain forward bias compared to P +NN+ diodes. The superior forward performance of the P+PN+ diode is attributed to its high injection efficiency and low carrier recombination. Ideal ohmic contacts in the SiC PN junction are also demonstrated for the first time in this research, and forward electrical characteristics are investigated systematically.; This research work also investigates the electrical performance comparison between N and P type Schottky diodes; a novel technique to obtain thick oxide film on SiC is invented and characterized. Finally, two novel wafer designs for high voltage applications are simulated.