Abstract
In this thesis, the characteristics of 4H-SiC NPN BJTs with thermal effects are studied by simulation and measurement. The effects of device features and material properties on common emitter current gain are examined. The simulation results show that the recombination velocity at the surface of the emitter and the base, carrier lifetime in the base, and the location of the base contact have significant effects on the current gain. Simulation shows that current gain decreases at high temperatures due to the enhancement of p-type ionization percentage in the base and that Ron decreases due to reduction of mobility at high temperatures. Decreasing of current gain at high JC which results from Rittner effect, Kirk effect and saturation effect is discussed. Self-heating due to power dissipation in the device is simulated and compared with measurement. Finally, a SPICE DC equivalent circuit model with thermal effects included is constructed to model IV curves, Gummel-plot and thermal transients of fabricated devices.