High-mobility capacitively-induced two-dimensional electrons in a lateral superlattice potential

Area of Science:

• Condensed Matter Physics
• Materials Science
• Semiconductor Nanostructures

Background:

• Lateral periodic potential modulation in two-dimensional electron systems can lead to exotic phenomena like graphene-like dispersion and Hofstadter butterfly.
• Conventional fabrication methods often introduce disorder, hindering the observation of these effects.
• Strong potential modulation is crucial for exploring novel quantum states in low-dimensional electron systems.

Purpose of the Study:

• To develop a novel fabrication process for imposing strong lateral potential modulation on capacitively induced two-dimensional electron systems.
• To preserve the host material quality during the fabrication of modulated heterostructures.
• To investigate the emergence of quantum phenomena with tunable electron density and high mobility.

Main Methods:

• Developed a novel fabrication process flow for Si/SiGe heterostructures.
• Utilized capacitive induction to create a two-dimensional electron system.
• Tuned electron density and measured mobility to analyze quantum oscillations.

Main Results:

• Achieved a wide electron density tunability (4.4 × 10^10 to 1.8 × 10^11 cm^-2) with a peak mobility of 6.4 × 10^5 cm^2/V·s.
• Observed sequential emergence of commensurability oscillations and magnetic-field-periodic quantum oscillations with increasing electron density.
• Successfully extracted the steepness of the imposed superlattice potential from the density dependence of quantum oscillations.

Conclusions:

• The novel fabrication process enables strong lateral potential modulation while maintaining high material quality.
• The observed quantum oscillations provide direct insight into the superlattice potential characteristics.
• This method opens avenues for exploring complex quantum phenomena in modulated two-dimensional electron systems.