Fig. 2: Optical spectroscopy of V2 centre in a Schottky diode.

a Extracted linewidth and spectral PLE position of defect-1 marked with a red circle in (b) versus applied voltage (−150 V to + 20 V). Detuning follows a purely quadratic dependence yielding a perpendicular Stark tuning coefficient of −0.047 ± 0.006 \({{{\rm{GHz}}}}/{\left(\frac{{{{\rm{MV}}}}}{{{{\rm{m}}}}}\right)}^{2}\). Inset show both examples, broad PLE without bias and narrow PLE lines in the depleted case (voltage data point indicated with filled markers). Blue octagons show measurement of defect-2, which has a lifetime limited linewidth (calculation uses lifetimes from ref. ²⁷, see Supplementary Note 1 in Supplementary information) (b) Right: boundary of the depletion zone mapped by single defects (shown on the left) and simulated with COMSOL¹⁶ (red dashed line is the threshold for [e⁻] = 1 × 10¹² cm⁻³). The COMSOL simulation has been parametrically optimised, with best agreement for 2 μm deep colour centres and initial epi-layer doping concentration (green colour of inset) of [N] = 7 × 10¹³ cm⁻³, validating given sample properties. Substrate doping (yellow colour) is [N] =1 × 10¹⁷ cm⁻³. c Exemplary PLE measurements of defect from sample B with distinct splitting of the resonance intro three equally spaced lines (1,2,3), caused by a nearby charge trap, showing occasional charge trap ionisation and jumps between lines 2-3. Application of off-resonant (repump) laser results in motional averaging and a steady state charge distribution between lines 1-2, whereas negative bias applied to the diode stabilises the charge state of the trap and eventually narrows down the PLE line. d Inset: PLE of a V2 centre affected by a fast-switching two-level system (TLS) in its vicinity, again associated with a charge trap. Solid curves show the sum of all lines and highlight the change of the PLE priority with and without weak CW repumping. Mainfigure: time-resolved study of that TLS by tracking the second PLE intensity versus the duration of laser illumination (red: no excitation; orange: 20 μW off-resonant excitation; blue: 3 nW of resonant to V2 excitation). Depopulation of the corresponding TLS state (decrease in PLE intensity) by photo-induced reconfiguration, while recovery if no laser is applied. Single exponential fits have been used to plot the solid lines.