Simultaneous measurement of light and temperature by a single amorphous silicon sensor

In this work we propose the use of one single device (p-doped/intrinsic/n-doped amorphous silicon thin film diode) acting as both temperature and photo sensor. The two modalities are accomplished by applying two different bias conditions to the diode. In order to prove the correct device operation, we have analyzed the crosstalk effects of the temperature variation on light measurement and those of the light intensity variation on the accuracy in the temperature measurement. We found that the temperature variation induces an error lower than 0.55 pW/K in the light intensity measurement at 550 nm if the diode is biased in short circuit condition, while, an error below 1 Κ/μνν results in the temperature measurement, if a forward bias current higher than 25 μ&Agr;/cm2 is applied. The use of a single sensor for the simultaneous measurement of two different physical parameters increases the integration level in miniaturized system as, for example, in lab-on-chip devices, where optical detection is often required during a heat treatment of the analyte