Reconfigurable Field‐Effect Transistor Technology via Heterogeneous Integration of SiGe with Crystalline Al Contacts

Abstract

Reconfigurable field‐effect transistors, capable of being dynamically programmed during run‐time, overcome the static nature of conventional complementary metal‐oxide semiconductors by reducing the transistor count and the circuit path delay. Thereby, SiGe and Ge are predicted to boost drive currents, switching speed and to reduce power consumption. Nevertheless, Ge‐based reconfigurable field‐effect transistor prototypes have so far fallen short in reaching both the promised performance due to interface instability to their contacts and gate oxides, as well as in reaching the current–voltage symmetry necessary for circuit applicability. Here, a top‐down fabricated SiGe‐based reconfigurable transistor technology is reported that is comprised of a vertical Si‐Si0.67Ge0.33 heterostructure enabling the envisioned high and symmetric on‐currents of both n‐ and p‐type operation. Monolithic integration with single‐elementary crystalline Al contacts alleviates process variability compared to conventional Ni‐silicide/Ni‐germanide contacts and introduces an ultra‐thin Si interlayer providing stability and equal injection efficiency of holes and electrons. The implementation of a three top‐gate transistor in combination with a hysteresis‐free Si/SiO2/HfO2 gate stack enhances polarity control and leakage current suppression to limit static power dissipation. Importantly, the obtained Al‐Si‐SiGe multi‐heterojunction and advanced reconfigurable transistor design is the first Ge‐based technology showing the envisioned stability and performance enhancements.

Accumulation of photoinduced carriers at the SiO2/Si interface observed through graphene transport

“…However, other approaches have been proposed to control n-or p-type behavior without introducing impurities. One approach is based on Si, Ge, or SiGe nanowire devices embedded on Si-MOS, [1][2][3][4][5][6][7][8][9] in which the conduction modes can be reconfigured reversibly between n-type and p-type. In nanowire devices, the voltage applied to the source/drain contacts modulates the height of the Schottky barrier, resulting in the injection of either electrons or holes depending on the polarity of the voltage.…”