International Radiation Detectors, Inc.

Performance Characteristics

A less than 1% change in the 254 nm responsivity was observed when UVG photodiodes were subjected to the following accelerated testing.

Thus, it is clear that UVG-series diodes possess excellent long term stability as well as radiation hardness.

Reponse uniformity of UVG diodes over 10 mm x 10 mm active area was within +/- 0.5% when scanned with a 254 nm photon beam of 1 mm diameter and is shown in Figure 1.

Fig. 1: Uniformity of UVG-100 photodiode at 254 nm.

Fig. 2 shows the temperature dependence of the diode responsivity at 254 nm. Typically the responsivity was found to increase by 0.045% per degree celsius. Note that this responsivity dependence on temperature is less than that reported by other manufacturers of UV-enhanced photodiodes. As the diode does have 100% internal collection efficiency, we believe that the temperature dependence of the responsivity is caused by an increase in the quantum yield with higher temperatures and also partly by the change in surface reflectance.

Fig. 2: Change in 254 nm responsivity of UVG photodiodes with temperature.

Fig. 3 shows temperature dependence of the shunt resistance. The shunt resistance was found to decrease by a factor of 2 for every 7.5°C rise in temperature.

Fig. 3: Change in shunt resistance of UVG photodiodes with temperature.

As UVG diodes are windowless devices, they are supplied with protective epoxy on their wire bonds. Hence, these devices need to be operated near room temperature, i.e., one can not heat these devices for out gassing purpose nor cool them to reduce the noise. This is necessary to avoid generation of stress on the wires because of difference in the Thermal Coefficient of Expansion (TCE) between the wire and the epoxy.

If necessary, UVG series diodes can be provided without epoxy on the wire bonds or with a UV transmitting window like fused silica or magnesium fluoride.