Tunnel diode is the P-N junction device that exhibits negative resistance. It is also known as 'Esaki Diode'.
- It consists of a p-n junction with highly doped regions.
- Because of the thinness of the junction, the electrons can pass through the potential barrier of the dam layer at a suitable polarization, reaching the energy states on the other sides of the junction.
- The current-voltage characteristic of the diode is represented in Figure 1.
- In this sketch Ip and Up are the peak, and Iv and Uv are the valley values for the current and voltage respectively.
- The form of this dependence can be qualitatively explained by considering the tunneling processes that take place in a thin p-n junction.
Theory Of Tunnel Diode:
- For the degenerated semiconductors, the energy band diagram at thermal equilibrium is presented in Figure 2.
- In Figure 3 the tunneling processes in different points of the currentvoltage characteristic for the tunnel diode are presented:
- In Fig. 3a, the thermal equilibrium situation corresponding to point 1 from the Fig. 1 diagram presented; in this case the electrons will uniformly tunnel in both directions, so the current will be null.
- At a direct polarization, a non-zero electron flow will tunnel from the occupied states of the conduction band of the n region to the empty states of the valence band from the p region.