Radiation sensitive detector based on field-effect transistors

Resumo

The possibility of developing radiation detectors based on field-effect transistors (FET) is investigated. Transistor saturation current is chosen as an informative parameter for modeling. Experimental results show that the drain saturation current of the FET with p-n junction as a gate is decreasing after irradiation. In metal-oxide-semiconductor (MOS) FETs during radiation-induced defect formation two effects are competing, therefore the result of radiation influence is highly dependent on the electro-physical properties of transistors before irradiation and on the absorbed radiation dose. It is shown that saturation current increases with absorbed radiation dose for all the transistors with low electron concentration in a channel above certain levels of absorbed radiation. While the opposite effect is observed for high electron concentration in a channel, i.e. the saturation current drops. Obtained dependences of the drain saturation current of FET on the irradiation dose facilitated development of simple detector design for low levels of radiation. The bridge circuit is used in the radiation sensor to minimize the effect of temperature fluctuations. The sensitivity of the detector is enhanced several times with the help of two pairs of FETs with the opposite sign of radiation sensitivity.