Backward diode can be used in high speed switching applications.

The backward diode is a special form of tunnel diode in which the tunneling phenomenon is only incipient, and the negative resistance region virtually disappears.

Since it has low capacitance and no charge storage effect, and a strongly nonlinear small-signal characteristic, the backward diode can be used as a detector up to 40 GHz.

In semiconductor devices, a backward diode (also called back diode) is a variation on a Zener diode or tunnel diode having a better conduction for small reverse biases (for example -0.1 to -0.6 V) than for forward bias voltages.

When used in the reverse direction, tunnel diodes are called back diodes (or backward diodes) and can act as fast rectifiers with zero offset voltage and extreme linearity for power signals (they have an accurate square law characteristic in the reverse direction).