The tunnel diode is that the contact device that exhibits negative resistance. which implies once the voltage has accumulated the current through it decreases. Classically, a carrier ought to have the energy a minimum of equal to potential-barrier height to cross the junction.But according to physical science, there’s the finite probability that it’ll penetrate through the barrier for a thin breadth. This development is termed tunneling and so the man of science Diode is believed as Tunnel Diode.
Electron Tunneling within the tangency
- When the p and n region is very doped, the depletion region becomes very skinny (~10nm).
- In such a case, there’s a finite probability that electrons can tunnel from the natural phenomenon band of n-region to the valence band of p-region.
- During the tunneling, the particle ENERGY doesn’t AN change.
Tunnel Diode Operation
When the semiconductor is unbelievably extraordinarily doped (the doping is greater than No) the Fermi level goes on top of the physical phenomenon band for n-type and below valence band for p-type material. This unit is understood as degenerate materials.
Under forwarding Bias
Step 1: At zero bias there’s no current flow
Step 2: a little forward bias is applied. Potential barrier continues to be very high – no noticeable injection and forward current through the junction. However, electrons at intervals the natural phenomenon band of the n region will tunnel to the empty states of the valence band in p region. this could turn out a forward bias tunnel current.
Step 3: With a much bigger voltage the energy of the majority of electrons at intervals the n-region is capable that of the empty states (holes) at intervals the valence band of p-region; this could manufacture most tunneling current.
Step 4: because the forward bias continues to increase, the amount of electrons at intervals the n side that square measure directly opposite to the empty states at intervals the valence band (in terms of their energy) decrease. therefore decrease at intervals the tunneling current will begin.
Step 5: As loads of forwarding voltage is applied, the tunneling current drops to zero. however, the regular diode forwards current thanks to electron-hole injection can increase thanks to a lower potential barrier.
Step 6: With more voltage increase, the tunnel diode I-V characteristic is comparable thereto of a daily p-n diode.
Tunnel Diode Operation
Under Reverse Bias
In this case the, electrons at intervals the valence band of the p side tunnel directly towards the gift of the empty state at intervals the natural phenomenon band of the n side creating large tunneling current that may increase with the appliance of reverse voltage. The TD reverse I-V has cherished the Zener diode with nearly zero breakdown voltage.