Actually not only do some diodes have silver, many have a variety of PM's used in their construction. Here's a few of the more common ones:



1) Gunn Diodes use gold for one of the terminal connections. Gold is used because of its relative stability and high conductivity
2) Photodiodes can use gold nanoparticles, gold plated pins and/or package and silver
3) Laser Diodes have gold wires and a gold and/or gold plated conatiner
4) Light Emitting Diodes all have a gold bonding wire. depending on their color they can also contain indium
4) Zener Diodes can contain germanium and/or selenium. Many of them have gold plated leads
5) Gold (or platinum) doped diodes contain gold doped semiconductor or platinum doped semiconductor, gold leads, gold bonding ribbon wire, glass sealed enclosure and/or a gold plated enclosure. Many of them are sought after as collectibles

Rectifiers are similar to diodes and generally used for devices 1 amp and over. They also have a variety of PM's used in their construction. here are a few of the more common ones;

1) Silicon Controlled rectifiers contain tungsten and/or molybdenum
2) Triode for alternating current (TRIAC's) contain gallium and/or indium
3) Bridge Rectifiers (four or more diodes in a bridge circuit) may contain (depending on their package) barium, germanium, selenium, strontium and/or gallium
4) Shockley Diodes can have gold leads and/or a gold or gold plated container
5) Tunnel Diodes can have gold leads and/or a gold or gold plated container

There are others but these are the most common ones