Analysis of single- and double-barrier tunneling diode structures using ultrathin CaF2/CdF2/Si multilayered heterostructures grown on Si

Abstract

The current–voltage (I–V) characteristics of single-barrier and double-barrier tunneling diode structures using CaF2/CdF2/Si ultrathin multilayered heterostructures grown on Si substrates have been theoretically analyzed and their material parameters, such as the conduction band discontinuity (ΔEC) at the heterointerface and effective mass (m*), have been evaluated by fitting simulation with the measured I–V characteristics. ΔEC between the ultrathin (1–3 nm) CaF2 and Si layers and m* for CaF2 were found to be 1.5–2.3 eV and 0.3–1.0m0, respectively. A clear thickness dependence of these parameters was observed, and the deviations of m* and ΔEC were approximately 30–50%, which probably originated from the thin layer thicknesses in atomic order. Using the estimated values derived from the single-barrier tunneling diodes, m* for CdF2 was also estimated to be 0.36m0 by fitting simulation of double-barrier diodes. These results will contribute to clarifying the design principle of tunneling devices with CaF2 and enhancing quantitative studies on electron transport in atomically thin multilayered heterostructures.