Al–Ge–Al Nanowire Heterostructure: From Single‐Hole Quantum Dot to Josephson Effect

Abstract

Superconductor–semiconductor–superconductor heterostructures are attractive for both fundamental studies of quantum phenomena in low‐dimensional hybrid systems as well as for future high‐performance low power dissipating nanoelectronic and quantum devices. In this work, ultrascaled monolithic Al–Ge–Al nanowire heterostructures featuring monocrystalline Al leads and abrupt metal–semiconductor interfaces are used to probe the low‐temperature transport in intrinsic Ge (i‐Ge) quantum dots. In particular, demonstrating the ability to tune the Ge quantum dot device from completely insulating, through a single‐hole‐filling quantum dot regime, to a supercurrent regime, resembling a Josephson field effect transistor with a maximum critical current of 10 nA at a temperature of 390 mK. The realization of a Josephson field‐effect transistor with high junction transparency provides a mechanism to study sub‐gap transport mediated by Andreev states. The presented results reveal a promising intrinsic Ge‐based architecture for hybrid superconductor–semiconductor devices for the study of Majorana zero modes and key components of quantum computing such as gatemons or gate tunable superconducting quantum interference devices.

Understanding the Electronic Transport of Al–Si and Al–Ge Nanojunctions by Exploiting Temperature-Dependent Bias Spectroscopy

“…Nanowire (NW)-based Schottky barrier (SB) metal–semiconductor–metal (MSM) heterostructures are highly interesting for emerging applications in nanoelectronics , and quantum electronics , that take advantage of their unique physical, electrical, and photonic as well as plasmonic properties. , Having such a MSM structure allows to electrostatically tune the metal–semiconductor junctions as well as the channel’s energy landscape through its implementation in a SB field-effect transistor (SBFET) . In this respect, undoped SBFETs show a certain degree of ambipolar charge carrier injection of electrons and holes into the channel, enabling dedicated “More than Moore” paradigms, e.g., reconfigurable FETs (RFETs). , Importantly, the source/drain contact metal is of high relevance in defining the charge carrier injection capabilities.…”

“…Nanowire (NW)-based Schottky barrier (SB) metal–semiconductor–metal (MSM) heterostructures are highly interesting for emerging applications in nanoelectronics 1 , 2 and quantum electronics 3 , 4 that take advantage of their unique physical, electrical, and photonic as well as plasmonic properties. 5 , 6 Having such a MSM structure allows to electrostatically tune the metal–semiconductor junctions as well as the channel’s energy landscape through its implementation in a SB field-effect transistor (SBFET).…”

High aspect ratio arrays of Si nano-pillars using displacement Talbot lithography and gas-MacEtch

“…In addition, high aspect ratio pillar arrays are used in photodiodes [15], CMOS [16], X-ray wavefront sensors [17] and 3D neutron detectors [18]. Silicon nanowires in field effect transistors can be used as active components in platforms for quantum computing experiments [19,20]. Nanostructures open opportunities for labeling and optical-based detection of biological species offer advantages compared with conventional organic molecular dyes widely used today.…”

Relaxation Delay of Ge‐Rich Epitaxial SiGe Films on Si(001)

“…Ge‐rich epitaxial SiGe films grown on Si(001) surfaces hold great potential for various applications if the critical thickness for both plastic and pronounced elastic relaxation could be expanded beyond the state of the art, while maintaining a low surface roughness and a high crystal quality of the epilayer. These applications include novel microelectronic devices based on robust planar flat‐film technology such as hole‐gas field‐effect transistors, [ 1 ] Josephson field‐effect transistors, [ 2 ] and negative differential resistance devices based on the Gunn–Hilsum effect. [ 3,4 ] In photonics and optoelectronics, the realization of thick but pseudomorphic and Ge‐rich Si 1− x Ge x films could enable the implementation of double heterostructures [ 5 ] to advance the present, fully group‐IV‐based room temperature light‐emitting devices [ 6 ] or photodetectors.…”