Interface-induced heavy-hole/light-hole splitting of acceptors in silicon

TL;DR

This study investigates how the silicon surface influences the energy splitting of acceptor states, revealing a significant surface-induced effect that can enhance the development of silicon-based qubits.

Contribution

It provides experimental evidence of surface-induced heavy-hole/light-hole splitting in boron acceptors in silicon, supported by tight binding calculations, relevant for quantum computing applications.

Findings

Energy splitting exceeds 1 meV for acceptors within 2 nm of the surface

Surface proximity causes significant heavy-hole/light-hole degeneracy breaking

Results support tunable acceptor-based qubits with long coherence times

Abstract

The energy spectrum of spin-orbit coupled states of individual sub-surface boron acceptor dopants in silicon have been investigated using scanning tunneling spectroscopy (STS) at cryogenic temperatures. The spatially resolved tunnel spectra show two resonances which we ascribe to the heavy- and light-hole Kramers doublets. This type of broken degeneracy has recently been argued to be advantageous for the lifetime of acceptor-based qubits [Phys. Rev. B 88 064308 (2013)]. The depth dependent energy splitting between the heavy- and light-hole Kramers doublets is consistent with tight binding calculations, and is in excess of 1 meV for all acceptors within the experimentally accessible depth range (< 2 nm from the surface). These results will aid the development of tunable acceptor-based qubits in silicon with long coherence times and the possibility for electrical manipulation.