Power semiconductor devices support the infrastructure of our society. They regulate power in electrical distribution systems, drive electric motors, and power telecommunications. Demand is increasing for fast high-power switching devices that can operate in harsh environments. The predominant silicon technology is limited to temperatures below 150ºC and is susceptible to damage in high radiation environments. The industry must look to other materials to fulfill these needs. Silicon carbide of the 4H polytype is an ideal candidate for the replacement of Si in devices designed for these demanding applications. SiC has a low susceptibility to damage from chemical and high radiation environments. High critical electric field, saturation electron drift velocity, and thermal tolerance parameters mean that fast high power-density devices may be fabricated and used to reduce the size, weight, and cooling requirements of power supplies and other electronic devices. These characteristics will result in smaller and more efficient electronics for aerospace applications, high-voltage power distribution, and hybrid/electric vehicles. To date, no active SiC switching devices are commercially available. The introduction of SiC MOSFETs, BJTs, IGBTs, and thyristors has been delayed as a result of poor device yield and performance instability.

In this research, the SiC bipolar junction transistor is the focus of study. The SiC BJT experiences a near 100% failure rate in terms of device reliability and performance stability. The electrical performance of these devices is shown to degrade as a function of use. It is the purpose of this work to analytically examine these degradation phenomena in order to understand the mechanism of degradation. 4H-SiC bipolar junction transistors of several different structure types and fabrication methodologies were supplied by Cree Inc. These devices were stressed and characterized in order to study the degradation of electrical device parameters. Also, material defect characterization was performed using electron beam induced current (EBIC) mode SEM and potassium hydroxide etching. Multiple physical phenomena were discovered to be responsible for the device performance degradation. Of these physical mechanisms, the primary focus lies with the development of two-dimensional 3C quantum well inclusions, called Shockley stacking faults, within the p-type base region of the devices.