Semiconductor diode
A diode made of semiconductor components, usually silicon. The cathode,which is negatively charged and has an excess of electrons, is placedadjacent to the anode, which has an inherently positive charge, carrying anexcess of holes. At this junction a depletion region forms, with neitherholes nor electrons. A positive voltage at the anode makes the depletionregion small, and current flows; a negative voltage at the anode makes thedepletion region large, preventing current flow.
A diode made of semiconductor materials, usually silicon, with a positive to negative flow of current.
The fundamental property of a diode is its tendency to conduct electric current in only one direction. When the cathode is negatively charged relative to the anode at a voltage greater than a certain minimum called forward breakover, then current flows through the diode.
If the cathode is positive with respect to the anode, is at the same voltage as the anode, or is negative by an amount less than the forward breakover voltage, then the diode does not conduct current.
This is a simplistic view, but is true for diodes operating as rectifiers, switches, and limiters. The forward breakover voltage is approximately six tenths of a volt (0.6 V) for silicon devices, 0.3 V for germanium devices, and 1 V for selenium devices.