Self-Assembled Telecom Color Centers in Silicon and Their Growth Environment

TL;DR

This study explores how vacuum conditions during ultra-low-temperature epitaxial growth affect the formation and optical properties of silicon color centers, advancing their use in quantum photonics.

Contribution

It provides the first detailed analysis of how growth pressure and temperature influence silicon color center self-assembly and optical quality during epitaxial fabrication.

Findings

Growth pressure significantly affects the photoluminescence of SiCCs.

Lower growth pressures suppress background luminescence, improving optical quality.

Substrate temperature influences the self-assembly of specific SiCCs.

Abstract

Artificial atoms based on color centers in silicon (SiCCs) have recently emerged as promising candidates for highly integrable and scalable key components in photonic quantum technology, including telecom single-photon sources and spin memory devices. A novel all-epitaxial fabrication technique for SiCCs, based on ultra-low-temperature (ULT) molecular beam epitaxy (MBE), addresses limitations of conventional fabrication via ion implantation, such as vertical ion straggle and collateral crystal lattice damage. This method solely relies on self-assembly of SiCCs during kinetically-limited growth of (carbon-doped) Si(:C) at ULTs <~350{\deg}C. The latter requires an extraordinary pristine growth environment to prevent unintended defect formation caused by the incorporation of impurities from the background vapor; however, so far, no study has specifically addressed how exactly the vacuum conditions during epitaxy influence SiCC formation, their optical properties, and the quality of the surrounding crystal matrix. Here, we investigate the impact of the growth pressure and the substrate temperature on the self-assembly and photoluminescence (PL) properties of important SiCCs, such as W, G, G', and T centers. Further, we use PL and Doppler broadening variable energy positron annihilation spectroscopy to emphasize the role of the growth pressure in suppressing the luminescence background, which is crucial for advancing quantum photonics applications.