The tunnel diode is a p-n Junction device that operates in certain region of I - V characteristic by the tunneling of electrons through potential barrier of the junction. The tunnel diode consist of two degenerate semi-conductors.
Ip = peak current
IV = valley current
Vp = peak voltage
Ip/IV = figure of merit for tunnel diode
Vp/Vf = measure of voltage spread between two positive resistance region.