Internal Loss Analysis and Visualization of 4H-Silicon Carbide Power Diodes: Free Energy Loss Analysis Under the Static Condition

Loss visualization and analysis of 4H-silicon carbide (4H-SiC) power diodes were performed using the free energy loss analysis (FELA) method that was originally developed for photovoltaic cells. The FELA approach features several advantages, including the direct expression of loss in W/cm$^{2}$, representation of each electron- and hole-induced loss, and internal loss visualization by calculating the free energy at each point. Four 4H-SiC power diodes, including two PiN diodes, a Schottky barrier diode (SBD), and a junction-barrier Schottky diode (JBSD), were evaluated. The PiN diodes exhibited significant Joule losses owing to the inherently high recombination heating associated with these bipolar devices. In contrast, the SBD e$^-$-induced Joule loss, whereas h$^+$-induced Joule and recombination losses were negligible for this unipolar device. The JBSD exhibited a high allowable current density with low self-heating and was determined to be the best power diode. The FELA visualization of the e$^-$-induced Joule loss of this device revealed that the SBD interface, particularly the p$^+$-region, is the dominant source of Joule loss. Applying FELA to reversed characteristics revealed several insightful device phenomena and which physics were responsible for the loss in different situations.