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Chapter 10: Q68E (page 470)

Question: The diagram shows the energy bands of a tunnel diode as the potential difference is increased. In this device high impurity atom density causes the occupied donor and unoccupied acceptor levels to spread into impurity bands which overlap respectively the n-type conduction- and the p-type valence bands. In all unbiased diodes, the depletion zone between the n-type and p-type bands constitutes a potential barrier (see Section 6.2) but in the tunnel diode it is so thin that significant tunnelling occurs. The current versus voltage plot shows that unlike a normal diode significant current begins to flow as soon as there is an applied voltage—before the bias voltage is Egap /e. It then decreases (so called negative resistance) before again increasing in the normal way. Explain this behavior.

Short Answer

Expert verified

Answer

The tunneling effect of the diode has been explained.

Step by step solution

01

Given data 

Tunnel diode to be used.

02

Definition of Tunnel diode

Tunnel diode is a diode is a type of diode which is heavily diode at the junction.

The tunnel diode has negative coefficient of resistance.

As the voltage increases across the diode the current through the diode decreases.

03

Draw the diagram and explain the tunneling effect 

The given diagram is shown in Figure 1.

Tunnel diode is a diode is a type of diode which is heavily diode at the junction.

The tunnel diode has negative coefficient of resistance.

As the voltage increases across the diode, the current through the diode decreases.

As soon as the tunnel diode is forward biased, the current flows through the narrow junction barrier.

The electrons in the n-type region get aligned to the holes in the region, and a large amount of current flows through the diode.

The case when the voltage across the diode is increased the barrier potential starts to increase because of accumulation of the holes and the electrons at the junction this decrease the current through diode.

But when the voltage is increased further the current again starts to increase and diode is normal this is known as the tunneling effect.

Therefore, the tunneling effect of the diode has been explained.

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