Diodes are standard components in, for example, mixers and detectors, in particular within the microwave and millimeter ranges. A diode conducts current essentially in only one direction, and this takes place if the voltage to which the diode is subjected in this direction exceeds a given value. The value at which a diode starts to conduct current is called the threshold voltage of the diode.
The fact that a diode starts to conduct current only at a given voltage means that a given minimum power will be consumed simply for the circuit of which the diode forms part to function. It is, of course, desirable to reduce this power to the greatest possible extent.
A number of different solutions for reducing the threshold voltage in a diode are previously known. Such a solution is described in U.S. Pat. No. 4 839 709. This solution may be considered to provide a semiconductor structure that is especially optimized for diodes and is not directly compatible with a semiconductor structure that might include active components, which may be said to be a disadvantage.
U.S. Pat. No. 4 410 902 describes a diode with a low threshold voltage, intended primarily for mixer circuits. This diode construction also appears to provide a semiconductor structure that is not directly compatible with active components. Furthermore, the solution appears to give an asymmetrical so-called current-voltage characteristic, which may also be a disadvantage as it can lead to the generation of undesirable odd harmonic multiples of the mixer frequency.