Schottky effect

The Schottky - effect causes the reduction of the electron work function of a metal surface by a high electric field strength in the outer space. This effect ( metal-semiconductor contacts), such as Schottky diodes with hot cathodes (metal - vacuum interface ) and Schottky contacts. The effect was named after the German physicist Walter Schottky.

Explanation

For simplicity, a metal surface is observed in the first vacuum. An electron in distance induced positive charge to the metal surface. The attractive force between the induced charge and the electron corresponds exactly to the force between the electron and an equal positive charge and is called mirror mirror or image force.

With the dielectric constant. The potential energy of the electron results from the work that needs to be done to bring the electron up by:

( The work is negative because the attractive force between the electron and the image charge acts in the direction of integration. )

A linear potential profile of a homogeneous field in the outer space is superimposed on the image force potential to

If the external field is very strong, it leads already within the short range of the mirror force to a lowering of the potential. With increasing field strength, the maximum of the potential curve moves closer to the surface,

And thus drops from to

For an electric field of strength gives the and what would quadruple at 1000 Kelvin about the current strength of the Schottky emission ( see Edison Richardson effect). In general, the Schottky effect increases the current intensity of the thermal emission by a factor.

Higher field strength must be taken into account as the tunnel effect, because the width of the barrier is no longer large compared to the wavelength of the electrons. In the tunneling current is considerably even in cold electrode, see field emission.

The above principle also applies to the metal - semiconductor interfaces. The "external" field exists in this case, even with short-circuited terminals, namely, the space charge region in the semiconductor material ( having a dielectric constant to be considered in the formulas ).

• Electrodynamics
• Solid State Physics
• Semiconductor electronics