Response to ionizing radiation of different biased and stacked pMOS structures

- Thermal and dosimetry characterization of three models of low-cost commercial general-purpose MOSFETs and a RADFET.
- Photon beams, and build-up layers.
- Commercial transistors have been stacked and biased to increase the sensitivity.
- One of commercial transistor in the most sensitive configuration shows similar specifications than the RADFET in its standard configuration.

Different low-cost commercial general-purpose MOSFETs and a RADFET are subjected to ionizing photon beams for comparison. The main characteristics of the radiation response, such as sensitivity, reproducibility, and short-term fading, have been determined using traditional measurement algorithms and others previously developed by our research group. Several vertical and lateral p-channel transistor structures have been preliminarily analysed and the most promising device, the 3N163, has been fully characterized in different configurations (single and two stacked transistors, unbiased and biased during irradiation) and compared with ad-hoc transistors to detect ionizing radiation (RADFETs). Although all the transistors are reliable for photon dosimetry, the two-stacked configurations with the 3N163 model transistor show high sensitivities to 6 MV photon beams (33 ± 2 mV/Gy for the unbiased mode and 62 ± 3 mV/Gy for the biased mode). These values are similar to the 57.1 ± 0.7 mV/Gy of the analysed RADFET in unbiased mode. The uncertainty of the two-stacked configuration is comparable to the uncertainty obtained with the RADFET, but reproducibility is even better than in the latter. In contrast, RADFETs present the lowest short-term fading among the studied MOSFETs.