International Radiation Detectors, Inc.

Quantum Yield

Recently, 1 cm² active area UVG-100 diodes were used to determine quantum yield (number of electron-hole pairs generated per absorbed photon) of silicon in 254 nm to 160 nm spectral region [1]. Quantum yield in this region has been determined for the first time and can be seen in figure1 from 320 nm to 150 nm.

Fig. 1:Internal quantum efficency of UVG photodiodes

This quantum yield knowledge now makes possible development of trap detectors for absolute flux determination in applications like deep UV lithography, and photorefractive and phototherapeutic keratectomy. Owing to their 100% collection efficiency, the external quantum efficiency of UVG-series photodiodes can be calculated in the UV and short wavelength visible (about 160 nm to 600 nm) as the product of the internal quantum efficiency times one minus the reflectance of the photodiode. The internal quantum efficiency can be taken from figure 1 and the reflectance can be measured or calculated. Figure 2 shows the measured reflectance from 150 nm to 1100 nm for the UVG series photodiodes with 70 nm oxynitride front window.

Fig. 2: Typical reflectance of UVG series photodiodes.

References:

1] L.R. Canfield et. al. "Absolute Silicon Photodiodes for 160 nm to 254 nm Photons"

Metrologia, Vol. 35, 329-334 (1998)