Dielectric properties of nc-Si/CaF2 multi quantum wells

Admittance measurements were performed on nc-Si/CaF2 multi quantum wells (MQWs) with 50 periods, over the temperature range 75–320 K. Nominal CaF2 thickness in each bilayer was in the range of 1.4–2.8 nm and Si thickness was equal to 1.6 nm. The structure exhibited capacitive behavior, similar to that of a metal–insulator–semiconductor (MIS) structure. All the experimental results indicate that carrier injection takes place, leading to charge build-up within MQWs. This charge is able to move under electric fields, forming a reversible space charge. Its transport is strongly temperature dependent. From the conductance–voltage characteristics two carrier exchange mechanisms were identified and they will be discussed.