Wide-bandgap semiconductors can sustain high temperatures and high power operation in various important applications such as transistors, light-emitting diodes, and lasers. Although in embryonic stage, one can expect such a resilience in GaN resonant tunneling diodes (RTDs) and superlattices as well with distinct applications. Because of the negative differential conduction, the double barrier resonant tunneling structures could be the basis for new high-power coherent microwave sources operating in W-band and terahertz. In this paper, recent progress in wide-bandgap semiconductor RTDs is discussed.