The diagram shows the energy bands of a tunnel diode as the potential difference is increa...

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 depiction 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 tunneling 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 Egaple. It then decreases (so-called negative resistance), before again increasing in the normal way. Explain this behavior.