Zenerilmiötä

Zenerilmiö, also known as the Zener effect or the tunnel effect in semiconductor diodes, describes the phenomenon where a diode can conduct current in the reverse direction when subjected to a sufficiently high reverse voltage. This effect is distinct from avalanche breakdown. In a Zener diode, the diode is specifically designed with a high doping concentration in its p-n junction. This high doping results in a very narrow depletion region. When a reverse voltage is applied, the electric field across this narrow depletion region becomes very strong. This intense electric field can pull electrons directly from the valence band of the semiconductor material on one side of the junction to the conduction band on the other side, even without the need for thermal excitation. This quantum mechanical tunneling of electrons is the basis of the Zener effect. The voltage at which this occurs is known as the Zener voltage. Zener diodes are intentionally manufactured to operate in this reverse breakdown region, and their Zener voltage is relatively stable over a range of reverse currents. This characteristic makes them useful for voltage regulation and as voltage reference elements in electronic circuits. The Zener effect is temperature-dependent, with the Zener voltage generally increasing with temperature for voltages above approximately 5.6 volts, and decreasing for voltages below 5.6 volts due to the interplay with the avalanche effect.