What is a Schottky barrier diode (SBD)?

A Schottky barrier diode (SBD) is a type of diode that has a junction formed between a semiconductor (typically an n-type semiconductor) and a metal such as platinum (Pt), molybdenum (Mo), or titanium (Ti), instead of a pn junction.
SBDs are designed to exploit a Schottky barrier created by a difference between the work function of a metal (i.e., the energy needed to remove an electron from the surface of a metal) and the electron affinity of a semiconductor. (In the case of an n-type semiconductor, a Schottky barrier is created only when a metal has a higher work function than the n-type semiconductor.)
SBDs have lower forward voltage than pn junction diodes because SBDs use a metal-semiconductor junction with a lower potential barrier than the pn junction.
The pn junction diode is a bipolar device in which both electrons and holes act as donors whereas the SBD, which is typically composed of an n-type semiconductor and a metal, is a unipolar device in which only electrons act as donors. Therefore, SBDs have no reverse recovery charge due to residual minority carriers, which is a matter of concern when using pn junction diodes. However, due to the electrostatic capacitance that exists between terminals, there is a reverse recovery time, although it is slight compared to pn junction diodes.

The low forward voltage and short reverse recovery time of SBDs make them suitable for high-speed switching applications.
Silicon SBDs withstand only several tens of volts whereas some SiC SBDs using wide bandgap semiconductor provide a withstand voltage of more than 600 V.