Analytical Determination of Unipolar Diode Losses in Power Switching and Perspective for Ultra-Wide Bandgap Semiconductors

Ultra-wide bandgap (UWBG) materials have exciting potential for power electronics applications due to their high breakdown electric fields. However, current UWBG diodes that achieve high breakdown fields tend to have higher turn-on voltage, counteracting the benefits to conduction losses that UWBGs are supposed to offer. The added losses from increased turn-on voltage are explored in this work, accounting for conduction losses as well as hard and soft-switching losses with respect to thermal limitations. It is shown that turn-on voltage of 2V or more prohibits UWBG diodes from achieving lower overall efficiency than incumbent technologies like 4H–SiC at typical voltage and frequency operating conditions, offering perspective on the applications under which UWBGs can offer a practical benefit and the importance of efficient thermal management, low turn-on voltage device topologies, and soft-switching converter topologies.