Dual dielectric silicon metal-oxide-semiconductor field-effect transistors as radiation sensors

A new design for radiation-sensing field-effect transistors (RADFETs) is presented, involving the use of very thick silicon nitride layers deposited on top of a high-quality thermal silicon dioxide. In contrast to previous RADFET fabrication procedures, no attempt was made to introduce hole traps into the thermal oxide. Instead the trapping layer at the nitride oxide interface was used to store the positive charge which forms the basis for operation of the RADFET. Data is presented which shows hole transport in the thermal oxide. Models explaining the field dependence of the response and the saturation behavior of the dual dielectric device are given. These RADFETs are more stable than any previously described in the literature and have a sensitivity of 86 μV/rad dose at room temperature.