Spin coherence of near-surface ionised $^{125}$Te$^+$ donors in silicon

TL;DR

This study demonstrates that near-surface $^{125}$Te$^+$ donors in silicon maintain long spin coherence times, with optical control of charge states, making them promising for quantum technology applications.

Contribution

It introduces $^{125}$Te$^+$ donors as a new near-surface spin system with extended coherence times and demonstrates optical control of their charge and spin states.

Findings

Spin coherence times exceed 1 ms at zero field.

Surface band-bending enables ionisation of Te donors.

Optical illumination controls Te donor charge states.

Abstract

Impurity spins in crystal matrices are promising components in quantum technologies, particularly if they can maintain their spin properties when close to surfaces and material interfaces. Here, we investigate an attractive candidate for microwave-domain applications, the spins of group-VI Impurity spins in crystal matrices are promising components in quantum technologies, particularly if they can maintain their spin properties when close to surfaces and material interfaces. Here, we investigate an attractive candidate for microwave-domain applications, the spins of group-VI $^{125}$Te$^+$ donors implanted into natural Si at depths as shallow as 20~nm. We show that surface band-bending can be used to ionise such near-surface Te to spin-active Te$^+$ state, and that optical illumination can be used further to control the Te donor charge state. We examine spin activation yield, spin linewidth, relaxation ($T_1$) and coherence times (\ttwo) and show how a zero-field 3.5~GHz `clock transition' extends spin coherence times to over 1~ms, which is about an order of magnitude longer than other near-surface spin systems.