Silicon nanowires (NW) are considered possible candidates for more-than-Moore and beyond-Moore electronic applications. In this work, Si and metallic NiSi2 NWs as well as NiSi2/Si/NiSi2 longitudinal NW heterostructures are fabricated and investigated electrically to conceive novel transistor and circuit architectures. Silicon-NWs are grown by Au-catalyzed chemical vapor deposition following the vapor-liquid-solid growth mechanism. Segments of these Si-NWs are transformed into metallic ones by a longitudinal volume diffusion process. Single-crystalline NiSi2 NW segments are formed along the Ni diffusion path by an epitaxy limited solid-state reaction. The resulting interfaces have a sharpness of at most a couple of nanometers. Schottky barrier field effect transistors (SBFET) were fabricated by a NiSi2 encroachment from both NW ends, confining a pristine Si segment, which constitutes the active region, in between. The intruded metallic NiSi2 segments act as extended source and drain regions providing nanometer scale Schottky contacts. Initially, a common back-gate steers the FET. The NiSi2 NW electrodes strongly enhance the gate field at the Schottky junction, efficiently adjusting the width of the Schottky barriers and tuning the current injection. Accordingly, the transistor operation is controlled by switching between thermionic emission and tunneling through the Schottky contacts. To boost device functionality, this transport mechanism is used to independently control the charge carrier injection through each Schottky junction. With a multiple gate structure the Si energy bands are bent locally at the S/D-junctions in such a way that either electron or hole injection dominates. Simultaneously, the other type of carriers can be blocked effectively. By applying this method the control over polarity of NW SBFETs was achieved. The same SBFETs can be programmed to operate either as a p- or n-type devices depending on the biasing of the individual top-gates. With this method first dopant-free logic circuits have been achieved.
Silicon nanowires (NW) are considered possible candidates for more-than-Moore and beyond-Moore electronic applications. In this work, Si and metallic NiSi2 NWs as well as NiSi2/Si/NiSi2 longitudinal NW heterostructures are fabricated and investigated electrically to conceive novel transistor and circuit architectures. Silicon-NWs are grown by Au-catalyzed chemical vapor deposition following the vapor-liquid-solid growth mechanism. Segments of these Si-NWs are transformed into metallic ones by a longitudinal volume diffusion process. Single-crystalline NiSi2 NW segments are formed along the Ni diffusion path by an epitaxy limited solid-state reaction. The resulting interfaces have a sharpness of at most a couple of nanometers. Schottky barrier field effect transistors (SBFET) were fabricated by a NiSi2 encroachment from both NW ends, confining a pristine Si segment, which constitutes the active region, in between. The intruded metallic NiSi2 segments act as extended source and drain regions providing nanometer scale Schottky contacts. Initially, a common back-gate steers the FET. The NiSi2 NW electrodes strongly enhance the gate field at the Schottky junction, efficiently adjusting the width of the Schottky barriers and tuning the current injection. Accordingly, the transistor operation is controlled by switching between thermionic emission and tunneling through the Schottky contacts. To boost device functionality, this transport mechanism is used to independently control the charge carrier injection through each Schottky junction. With a multiple gate structure the Si energy bands are bent locally at the S/D-junctions in such a way that either electron or hole injection dominates. Simultaneously, the other type of carriers can be blocked effectively. By applying this method the control over polarity of NW SBFETs was achieved. The same SBFETs can be programmed to operate either as a p- or n-type devices depending on the biasing of the individual top-gates. With this method first dopant-free logic circuits have been achieved.
