Publikationsrepositorium - Helmholtz-Zentrum Dresden-Rossendorf

In contrast to conventional CMOS transistors, reconfigurable field effect transistors (RFETs) can be switched between n- and p-type behavior, which allows more compact and flexible circuit designs [1, 2]. Symmetry between n- and p-current is required and this can be achieved by strain engineering as experimentally demonstrated in Ref. [2]. However, a detailed understanding of the electron transport across the strained interface is not yet available and requires electronic models to capture all relevant transport mechanism.
We investigate the relation between strain and electron transport properties of planar interfaces between metallic NiSi 2 and semiconducting Si in <110> crystal orientation. We apply the non-equilibrium Green’s functions formalism together with density functional theory as implemented in Atomistix ToolKit [3] to calculate the transmission spectra. Using a modified version of the Landauer formula, we than obtain an expression for the current through the RFET and hence, the transfer characteristic can be investigated. A comparison between the calculated transfer characteristic using this model and experimental reference data [2] are performed. A very good agreement can be seen which verifies our model. However, in the experiment, the RFET was compressed during the oxidation process. Because the structure in the simulation was supposed to be unstrained, some pre-strain might be present in the simulation. We also study how strain, either applied perpendicular or parallel to the transport direction, alters the current. It can be seen that a small amount of strain is sufficient to change the ratio between n- and p-current and that symmetry can be achieved. Considering the above-mentioned pre-strain in the simulation, the general trend is also in agreement with experimental studies [1, 2].

[1] A. Heinzig et al., Reconfigurable Silicon Nanowire Transistors. Nano Letters 12, 119 (2012)
[2] A. Heinzig et al., Dually Active Silicon Nanowire Transistors and Circuits with Equal Electron and Hole Transport. Nano Letters 13, 4176 (2013)
[3] Atomistix ToolKit 15, QuantumWise A/S (www.quantumwise.com)