The Tunnel Diode | Construction | Esaki diode.
The Tunnel Diode
The width of depletion layer of a pn junction depends on the amount of doping. In a conventional pn junction diode the impurity concentration is about 1 part in 10⁸ and the width of the depletion layer is of the order of 5 microns and the potential barrier does not allow the majority carriers to flow from p to n or n to p. But if the impurity concentration is greatly increased (~1 part in 10³), then depletion layer becomes very small (~ 100 Angstrom) and the characteristics of the device is completely changed. Such a diode is called tunnel diode, also referred to as the Esaki diode, named after its inventor.
Construction
A tunnel diode is usually made of germanium or gallium arsenide because of high electron mobility and reasonable energy gap. It is a junction diode. Both p and n sides are very heavily doped (degenerate semiconductors) with impurities so that each region has high conductivity.
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