The Enhanced Low Dose Rate Effect (ELDRE) 4.1 Discovering the ELDRE

4.1 Discovering the ELDRE In 1991 Enlow and coworkers made a comparative study between traditional crystalline emitter transistors (BJTs) and polysilicon emitter transistors (PETs) [1]. The work was intended to study the difference in radiation response of these technologies; indeed at this time large amounts of data were available for crystalline transistors, while very little attention had been paid to the emerging polysilicon technology. Previous works on BJTs had shown that ionizing radiation damage does not depend upon the dose rate (rad/s) for a given total dose (rad), for dose rates above 10 rad/s. Now for the sake of care Enlow and co. tried to explore a wide range of rates (1.1, 16 and 300 rad/s). They noticed that in few cases decreasing dose rate below 10 rad/s, the damage increases. This would be a fairly astonishing result, because even if it would not contradict other studies on the subject, it would be not intuitive. In Fig. 4.1a and 4.1b two examples of the dose rate effect observed are shown. It is easy to recognize that the low dose rate (LDR) on Silicon emitter transistors (enhancement factor 2) is within the measurement error, meaning that probably we are facing a simple misunderstanding. Nevertheless the poly-emitter measurements are clearer and the EF is about 4 to 7.