Impact of Cryogenic Temperatures on Radiation-Induced Parameter Shifts in RADFETs

This paper investigates the impact of cryogenic temperatures on the degradation of key electrical parameters in commercial off the shelf p-channel Metal-Oxide-Semiconductor Field-Effect Transistors (MOSFET) dosimeters, RADFETs, caused by total ionizing dose (TID) effects. The parameters analyzed include carrier mobility (μ<italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">p</i>), threshold voltage (<italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">V_t</i>), and subthreshold swing (SS). While it is well known that cooling MOSFETs to cryogenic temperatures generally increases mobility, raises threshold voltage, and reduces subthreshold swing, limited research has explored how these effects are impacted by room temperature TID exposure. This study fills some of those gaps by examining the behavior of RADFETs irradiated with <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">60</sup>Co γ-rays up to 500krad(SiO<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub>), with irradiation performed at room temperature and subsequent testing conducted at temperatures ranging from 40K to 300K. A new model is proposed and TCAD simulations are performed to analyze and explain temperature effects on threshold voltage and mobility in irradiated devices. These findings provide critical insights into the performance and reliability of p-channel MOSFETS in combined radiation and cryogenic environments, particularly in space applications.