Present Status of Radiometric Quality Silicon Photodiodes
R Korde, C Prince, N. Cunningham, Robert E. Vest, E Gullikson
Evaluation of five types of silicon photodiodes was undertaken to verify their suitability for absolute radiometry and also for their use as transfer standards in the spectral region from 1 nm to 1100 nm. Four types of photodiodes were fabricated for this study; these were the p-on-n photodiode, n-on-p photodiodes with silicon dioxide front window and n-on-p photodiodes with metal-silicide front window. Fabrication of photodiodes 100% internal quantum efficiency is demonstrated and their necessity for making absolute radiometric measurements with lowest possible uncertainty is pointed out. The linearity characteristics of these devices, as measured by the ac/dc method, are far superior to those of the P-on-n diodes fabricated for this work and also to those exhibited by p-on-n diodes widely used at present by the radiometric community. Results on the stability of the quantum efficiency of the fabricated diodes after exposure to intense radiation of 13 nm, 120 nm, 157 nm, 193 nm and 254 nm radiation will also be presented. Photodiodes with metal-silicide front window were the only devices stable when exposed to the intense beams of third generation synchrotrons and UV excimer lasers.