Quantum Emitter Formation Dynamics and Probing of Radiation-Induced Atomic Disorder in Silicon

Near-infrared color centers in silicon are emerging candidates for on-chip integrated quantum emitters, optical-access quantum memories, and sensing. We access ensemble G-color-center formation dynamics and radiation-induced atomic disorder in silicon for a series of megaelectronvolt proton-flux conditions. The photoluminescence results reveal that the G centers are formed more efficiently by pulsed-proton irradiation than by continuous-wave proton irradiation. The enhanced transient excitations and dynamic annealing within nanoseconds allows optimization of the ratio of G-center formation to nonradiative defect accumulation. The G centers preserve narrow line widths of about 0.1 nm when they are generated by moderate pulsed-proton fluences, while the line width broadens significantly as the pulsed-proton fluence increases. This implies vacancy or interstitial clustering by overlapping collision cascades. The tracking of G-center properties for a series of irradiation conditions enables sensitive probing of atomic disorder, serving as a complementary analytical method for sensing damage accumulation. Aided by ab initio electronic structure calculations, we provide insight into the atomic disorder induced inhomogeneous broadening by introducing vacancies, silicon interstitials, and oriented strain fields in the vicinity of a G center. A vacancy leads to a tensile strain and can result in either a red shift or a blue shift of the G-center emission, depending on its position relative to the G center. Meanwhile, $\mathrm{Si}$ interstitials lead to compressive strain, which results in a monotonic red shift. High-flux and tunable ion pulses enable the exploration of the fundamental dynamics of radiation-induced defects as well as methods for the optimization of G-center formation and qubit synthesis for quantum information processing.

Figure 1

(a) An example of the PL spectra of G centers created by one, five, 20, and 100 shots of $7.9\pm 1.6\times {10}^{10}$ protons per ${\mathrm{cm}}^2$ per pulse, respectively, with a laser pump power of 0.3 mW. (b) A comparison of the integrated PL intensity of G centers generated by $7.9\pm 1.6\times {10}^{10}$ protons per ${\mathrm{cm}}^2$ per pulse (labeled as pulse A, black dot), $6.9\pm 1.6\times {10}^9$ protons per ${\mathrm{cm}}^2$ per pulse (labeled as pulse B, red dot), and a cw proton (blue dot), with the proton fluence varying from ${10}^{11}{\text{cm}}^{-2}$ to ${10}^{14}{\text{cm}}^{-2}$.

Figure 2

(a) The time-resolved PL of G centers created by pulsed-proton ($7.9\pm 1.6\times {10}^{10}$ protons per ${\mathrm{cm}}^2$ per pulse) irradiation by varying the number of shots from one to 100, respectively. (b) The time-resolved PL of G centers created by cw proton irradiation with the fluence varying from $1\times {10}^{11}{\text{cm}}^{-2}$ to $1\times {10}^{14}{\text{cm}}^{-2}$. (c) The effective PL decay time extracted using single-exponent fitting of the experiments as a function of the proton fluence by using a pulse of $7.9\pm 1.6\times {10}^{10}$ protons per ${\mathrm{cm}}^2$ per pulse (black dots), $6.9\pm 1.6\times {10}^9$ protons per ${\mathrm{cm}}^2$ per pulse (red dots), and cw proton irradiation (blue dots and dashed lines as guides to the eye). (d) The corresponding transient PL intensity at initial delay as a function of the proton fluence by using pulsed and cw proton irradiation.

Figure 3

(a) A comparison of a normalized zero-phonon-line spectrum of G centers generated by 100 shots (black) and one shot (gray) of $7.9\pm 1.6\times {10}^{10}$ protons per ${\mathrm{cm}}^2$ per pulse and cw $1\times {10}^{13}$ protons per ${\mathrm{cm}}^2$. (b) A comparison of the proton-fluence-dependent line width (full width at half maximum) of G centers generated by irradiation with $7.9\pm 1.6\times {10}^{10}$ protons per ${\mathrm{cm}}^2$ per pulse, $6.9\pm 1.6\times {10}^9$ protons per ${\mathrm{cm}}^2$ per pulse, and cw protons.

Figure 4

(a) The shift of the ZPL transition energy versus the distance between the GCB and the perturbing defect, where the defect is a vacancy (blue circles) or a silicon self-interstitial (red cross). (b),(c) Histograms of the ZPL shift due to (b) vacancies and (c) self-interstitials for the region marked by the green box in (a).

Figure 5

(a),(b) The ZPL shift versus the strain for the (a) $x$ and (b) $z$ directions. (c),(d) The distribution of combined ZPL shifts for (c) a uniform selection of $<x,y,z>$ strain vectors and (d) a distribution biased in the $<001>$ direction.