According to the tunneling phenomenon of tunnel diode which one of the following is true?

• A Tunnel Diode is a heavily doped p-n junction diode.
• The tunnel diode shows negative resistance.
• Tunnel diode works based on Tunnel Effect.
• The p-type and n-type semiconductor is heavily doped in a tunnel diode due to a greater number of impurities.

Heavy doping results in a narrow depletion region. When compared to a normal p-n junction diode, tunnel diode has a narrow depletion width. Therefore, when a small amount of voltage is applied, it produces enough electric current in the tunnel diode. 

The depletion width is given as:

\(W=\sqrt{\dfrac{2{\epsilon}}{q}\left( \dfrac{1}{N_A}+\dfrac{1}{N_D}\right)V_J}\)

Where VJ = Vbi + VRB

Where NA and ND are doping concentrations. 

In heavily doping case-

 \(\rm\downarrow W \propto\dfrac{1}{\sqrt{doping\ connection}\uparrow}\)

As the width of the depletion layer reduces, charge carriers can easily cross the junction.

Charge carriers do not need any form of kinetic energy to move across the junction. Instead, carriers punch through the junction.

This effect is called Tunneling and hence the diode is called Tunnel Diode.