Study of W centers formation in silicon upon ion implantation and rapid thermal annealing

The recent demonstration of optically active telecom emitters in silicon has paved the way for realizing industrial-scale silicon-based solid-state quantum photonic platforms. The scientific community has been pursuing the implementation of novel single-photon devices for quantum technology applications by introducing extrinsic impurities inside the silicon lattice upon ion implantation. Here we report the optical characterization through single-photon microscopy of intrinsic W centers in high-purity silicon substrates upon carbon implantation and subsequent rapid thermal annealing. The photoluminescence investigation of their emission properties at cryogenic temperatures allowed us to identify the effects of the post-implantation thermal treatment in the formation of telecom quantum emitters based on interstitial silicon clusters upon the introduction of an extrinsic atomic species.

I. Introduction

Recently it has been demonstrated that silicon can host optical defects with single-photon emission in the near IR [1] . Notably, the W centre is a tri-interstitial complex characterized by a sharp zero phonon line (ZPL) at 1218 nm (1.018 eV) [2] . It is considered to have a trigonal geometry, and five defective alternative configurations of the centre have been proposed so far. Based on classical molecular dynamics (CMD) simulations and density functional theory (DFT) calculations, the so-called I ₃ -V complex is the most energetically favourable candidate [3] . Furthermore, it has been recently demonstrated that the W center can be isolated at the single-photon emitter level, thus offering an enticing platform for integrated silicon photonics based on native defects. In this perspective, the manufacturing of single-photon sources based on W centers at the wafer scale relies on the technological capability of their controlled placement in high-purity silicon substrates. For this goal, mature ion implantation techniques are required to deliver single impurities with high spatial resolution. On the other hand, highly efficient post-implantation processes play a crucial role in enabling their optical activation upon conversion into stable lattice defects. So far, W-centre photoluminescence emission optimization has been studied upon silicon implantation to create self-interstitial defects [4] . However, the increasing interest in the scientific community for realizing novel deterministic silicon-based single photon sources has been pursued by introducing different impurities in the silicon lattice [5] . Therefore, this work investigates the suitability of ion implantation for the fabrication of W centres. The study relies on C keV ion implantation and subsequent multiple-step rapid thermal annealing processes. In this way, these results offer insight into the concurrent kinetics factors involved in incorporating carbon impurities.