is a thermionic emission current. Due to thermal agitation some of carriers which have energy equal to or larger than the conduction band energy at the metal-semiconductor interface, contributing to the current flow.
In Schottky barrier diode the current is based only on majority charge carriers. The frequency range goes to up 5 THz useful for high-speed switching applications. This is due to the low forward voltage and short reverse recovery time of the order of Pico farads. The diode conversion efficiency