Simulation of Reconfigurable Field-effect Transistors: Impact of the NiSi2-Si Interfaces, Crystal Orientation, and Strain


Simulation of Reconfigurable Field-effect Transistors: Impact of the NiSi2-Si Interfaces, Crystal Orientation, and Strain

Fuchs, F.; Schuster, J.; Gemming, S.

Reconfigurable transistors (RFETs) can be switched between electron and hole current by changing the polarity of the gate potential. This allows a much higher functionality and hence, logic operations can be realized with fewer transistors. The device performance of such a transistor is strongly dominated by the contact physics.
In this work, the electron transport across the NiSi 2 -Si interface is studied using the NEGF formalism and density functional theory, which allows us to consider the atomic structure of the interface. A new model is then presented which relates the electron transport through the interface to the transfer characteristic of an RFET. The model is compared to experimental data, which shows very good agreement, especially with respect to the ratio between electron and hole current (left figure).
Based on the model, different structure variations at the interface and their consequences on the device performance are discussed. It is demonstrated that best symmetry between electron and hole current is achieved for the <110> crystal orientation, which is much worse for <100> orientation (right figure). This makes the <110> orientation advantageous for RFETs. Also the influence of strain generated parallel to the interface plane is investigated (right figure). It is shown that strain can be used to tune the symmetry in case of <110> crystal orientation even further. This is entirely different for the <100> crystal orientation, where the highest electron currents are observed for all strain states. In this state, the electron currents are about three orders of magnitude higher than the hole currents. A detailed discussion of these differences based on work function and band structure analysis will be given in our contribution.

Keywords: reconfigurable transistor; RFET; density functional theory; metal-semiconductor interface

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Publ.-Id: 25391