Line Tunneling Dominating Charge Transport in SiGe/Si Heterostructure TFETs

• Published in: IEEE transactions on electron devices 2016-11, Vol.63 (11), p.4173-4178
• Main Authors: Blaeser, Sebastian, Glass, Stefan, Schulte-Braucks, Christian, Narimani, Keyvan, von den Driesch, Nils, Wirths, Stephan, Tiedemann, Andreas T., Trellenkamp, Stefan, Buca, Dan, Mantl, Siegfried, Qing-Tai Zhao
• Format: Article
• Language: English
• Subjects: Activation energy E_{a}; band-to-band-tunneling (BTBT); counter-doped pocket; Doping; Ions; Junctions; line tunneling; Logic gates; point tunneling; selective and self-adjusted silicidation; Silicon germanium; small(er) bandgap E_{g}; strained SiGe; TFETs; Tunneling; tunneling FET (TFET)
• ISSN: 0018-9383; 1557-9646
• DOI: 10.1109/TED.2016.2608383

This paper provides an experimental proof that both the ON-current ION and the subthreshold swing SS of Si(Ge)-based tunneling FETs (TFETs) drastically benefit from device architectures promoting line tunneling aligned with the gate electrical field. A novel SiGe/Si heterostructure TFET is fabricated, making use of a selective and self-adjusted silicidation, thus enlarging the area for band-to-band-tunneling (BTBT) in a region directly underneath the gate. In addition, a counter-doped pocket within the SiGe layer at the source tunnel junction is introduced in order to sharpen the corresponding doping profile and, consequently, to shorten the resulting tunneling length. Experimental analysis of activation energies E α identifies BTBT, dominating the drain current Id in the SiGe/Si heterostructure TFET over a wide region of the gate voltage V g , thus reducing parasitic influence of Shockley-Read-Hall recombination and trap-assisted tunneling. Both a relatively high ION = 6.7 μA/μm at a supply voltage V DD = 0.5 V and an average SS of about 80 mV/decade over four orders of magnitude of I d were achieved.