Silicon-Impurity Defects in Calcium Fluoride: A First Principles Study

With the emergence of novel nanoelectronic devices based on 2D materials, the need for suitable dielectrics has become apparent in recent years. One particular promising candidate for future device dielectrics is calcium fluoride (CaF2) due to its inert surface and the possibility to form a quasi van der Waals (vdW) interface with 2D semiconductors like molybdenum disulfide (MoS 2 ). In this work we explore silicon-impurity defects in CaF 2 , which is typically grown on Si(111), and their potential relevance for device reliability using density functional theory. Defect parameters describing the charge trapping behavior of these defects within a nonradiative multiphonon theory are provided to be used in future TCAD simulations. We show that Si-impurity defects can act as amphoteric charge traps and hence might play a role in the observed hysteresis and bias temperature instability in Si/CaF 2 /MOS 2 gate stacks.