Transparency of thin metal films on semiconductor substrates

The transmittance of light into Si and GaAs through thin metal films has been calculated, both with and without anitreflection coatings. Reflection is the biggest optical loss for 100-Å-thick films, amounting to about 35% for the best metals. The transmittance can be increased from 60% to over 94% with the addition of AR coatings with indices of 2.1 or more. Ag, Cu, Au, and Mg are the most transparent films, while Al and Cr are the least transparent.