Quantum dots in InAs nanowires induced by surface potential fluctuations

Area of Science:

• Semiconductor Nanowire Physics
• Quantum Dot Phenomena
• Advanced Materials Science

Background:

• Back-gated Indium Arsenide (InAs) nanowire field-effect transistors are crucial for quantum device research.
• The origin of intrinsic quantum dots, not defined by external electrodes, remains incompletely understood.
• Previous explanations for intrinsic quantum dot formation present unresolved questions.

Purpose of the Study:

• To investigate the formation and characteristics of intrinsic quantum dots in InAs nanowires.
• To elucidate the physical mechanisms responsible for the spontaneous emergence of these quantum dots.
• To explore the tunability of quantum dot behavior through electrostatic gating and material doping.

Main Methods:

• Fabrication and characterization of back-gated InAs nanowire field-effect transistors.
• Recording detailed stability diagrams at ultra-low electron temperatures (below 200 mK).
• Analysis of device characteristics to determine quantum dot number, size, and connectivity (series/parallel).

Main Results:

• Intrinsic quantum dots were observed and characterized in the InAs nanowire devices.
• Stability diagrams provided insights into quantum dot properties and interconnections.
• The most probable origin identified for these dots is potential fluctuations at the nanowire surface.
• Devices demonstrated tunability into various Coulomb blockade regimes using gate voltage and doping levels.

Conclusions:

• Potential fluctuations on the InAs nanowire surface are the likely cause of intrinsic quantum dot formation.
• Electrostatic gating and doping offer effective control over quantum dot behavior and device regimes.
• This research contributes to a deeper understanding of quantum phenomena in nanowire-based electronic devices.