Donor-bound-exciton strain microscopy in silicon devices

We explore the effects of stress on silicon donor bound exciton (D⁰X) transitions in bulk silicon and in microfabricated silicon devices. We first study D⁰X transitions in an isotopically purified silicon-28 bulk doped sample under controlled uniaxial stress, confirming the validity of existing models in the low strain (10⁻⁵) regime. We then demonstrate the localised photoconductive detection of a few thousand donors illuminated by a 1078 nm resonant laser with 4~μ m spot focused on a microfabricated device consisting of an implanted phosphorus layer between a pair of metallic contacts. We observe local variations in the strained exciton peak splitting from 10~μ eV to 200~μ eV, and obtain scanning microscopy stress maps in good agreement with finite-element-model thermal stress simulations. Our results suggest a potential use of donor bound excitons for in-situ stress sensing, and demonstrate pathways for the miniaturisation of D⁰X photoconductive detection.