Junction diode

(electronics) A semiconductor diode in which the rectifying characteristics occur at an alloy, diffused, electrochemical, or grown junction between n-type and p-type semiconductor materials. Also known as junction rectifier.

A semiconductor rectifying device in which the barrier between two regions of opposite conductivity type produces the rectification. Junction diodes are used in computers, radio and television, brushless generators, battery chargers, and electrochemical processes requiring high direct current and low voltage. Lower-power units are usually called semiconductor diodes, and the higher-power units are usually called semiconductor rectifiers. See also Semiconductor.

Junction diodes are classified by the method of preparation of the junction, the semiconductor material, and the general category of use of the finished device. By far the great majority of modern junction diodes use silicon as the basic semiconductor material. Germanium material was used in the first decade of semiconductor diode technology, but has given way to the all-pervasive silicon technology, which allows wider temperature limits of operation and produces stable characteristics more easily. Other materials are the group III–V compounds, the most common being gallium arsenide, which is used where its relatively large band-gap energy is needed.

In silicon units nearly all categories of diodes are made by self-masked diffusion, as shown in illus. a. Exceptions are diodes where special control of the doping profile is necessary. In such cases, a variety of doping techniques may be used, including ion implantation, alloying with variable recrystallization rate, silicon transmutation by neutron absorption, and variable-impurity epitaxial growth. The mesa structure shown in illus. b is used for some varactor and switching diodes if close control of capacitance and voltage breakdown is required. See also Electronic switch; Ion implantation; Rectifier.

High-speed diffused silicon diodes. (a) Mesaless structure. (b) Mesa structure.