Bottom-gated epitaxial graphene suitable for half-integer quantum metrology ?

TL;DR

This study demonstrates a buried gate in epitaxial graphene on SiC that effectively modulates carrier concentration at intermediate temperatures, enabling quantum Hall effects relevant for quantum metrology.

Contribution

It introduces a nitrogen-implanted buried gate in epitaxial graphene that functions at 40-80K, advancing control over carrier density for quantum applications.

Findings

Effective carrier modulation at 40-80K

Observation of half-integer quantum Hall effect at 4K

Gate efficiency diminishes below 40K due to channel freezing

Abstract

We demonstrate that the carrier concentration of epitaxial graphene devices grown on the C-face of a SiC substrate is efficiently modulated by a buried gate. The gate is fabricated via the implantation of nitrogen atoms in the SiC crystal, 200 nm below the surface, and works well at intermediate temperatures: 40K-80K. The Dirac point is observed at moderate gate voltages (1-20V) depending upon the surface preparation. For temperatures below 40K, the gate is inefficient as the buried channel is frozen out. However, the carrier concentration in graphene remains very close to the value set at T\sim 40K. The absence of parallel conduction is evidenced by the observation of the half-integer quantum Hall effect at various concentrations at T\sim 4K. These observations pave the way to a better understanding of intrinsic properties of epitaxial graphene and are promising for applications such as quantum metrology.