A new time-dependent analytic compact model for radiation-induced photocurrent in epitaxial structures

Photocurrent generated by ionizing radiation represents a threat to microelectronics in radiation environments. Circuit simulation tools that employ compact models for individual electrical components (SPICE, e.g.) are often used to analyze these threats. Historically, many photocurrent compact models have suffered from accuracy issues due to the use of empirical assumptions, or physical approximations with limited validity. In this paper, an analytic model is developed for epitaxial diode structures that have a heavily-doped sub-collector. The analytic model is compared with both numerical TCAD calculations and the compact model described in reference [1]. The new analytic model compares well against TCAD over a wide range of operating conditions, and is shown to be superior to the older compact model [1]. The methods put forth in this paper could also be applied to model devices with similar physics, such as photonic and power devices.