Optically induced dynamics of muonium centers in Si studied via their precession signatures

We studied the influence of the optical excitation on three muonium centers ${\mathrm{Mu}}_T^0$, ${\mathrm{Mu}}_{\mathit{BC}}^0$, and ${\mathrm{Mu}}_{\mathit{BC}}^{+}$ in high resistivity silicon. These investigations were carried out on the spin precession signature of each center as a function of temperature. It is found that photoexcitation resulted in significant enhancements of the depolarization rates of the precession signals as the three muonium centers underwent interactions with photogenerated free carriers. The results are described by a three-state model involving transitions between ${\mathrm{Mu}}_T^0$, ${\mathrm{Mu}}_{\mathit{BC}}^0$, and ${\mathrm{Mu}}_{\mathit{BC}}^{+}$ as well as spin exchange processes.

Figure 1

Schematic diagram of the $\mu \mathrm{SR}$ cryostat for the optical excitation experiment. The incoming ${\mu }^{+}$ can be polarized to be either transverse or longitudinal to the applied magnetic field direction.

Figure 2

(Color online) Typical $\mathrm{TF}\text{−}\mu \mathrm{SR}$ spectra for ${\mathrm{Mu}}_{\mathit{BC}}^{+}$ in a field of $0.1\mathrm{T}$ and $\approx 260\mathrm{K}$ (a) in the dark and (b) under illumination. The circles are the experimental data and the solid lines are the fits as described in the text.

Figure 3

(Color online) Typical $\mathrm{LF}\text{−}\mu \mathrm{SR}$ spectra for ${\mathrm{Mu}}_{\mathit{BC}}^0$ in a field of $\approx 0.2\mathrm{T}$ and $\approx 64\mathrm{K}$ (a) in the dark and (b) under illumination. The circles are the experimental data and the solid lines are the fits as described in the text.

Figure 4

(Color online) Typical $\mathrm{TF}\text{−}\mu \mathrm{SR}$ spectra for ${\mathrm{Mu}}_T^0$ in a field of $\approx 1\mathrm{mT}$ and $\approx 269\mathrm{K}$ (a) in the dark and (b) under illumination. The circles are the experimental data and the solid lines are the fits as described in the text.

Figure 5

The three-state model of muonium in Si under photoexcitation. The notation is described in more detail in the text.

Figure 6

Relaxation rates of the precession signals of (a) ${\mathrm{Mu}}_{\mathit{BC}}^0$, (b) ${\mathrm{Mu}}_{\mathit{BC}}^{+}$, and (c) ${\mathrm{Mu}}_T^0$. The open and solid circles are data in the dark and under illumination, respectively. The solid lines are the simulations using the three-state model and the parameters listed in Table. . (The power of the lamp is 200, 100, and $80\mathrm{W}$ for ${\mathrm{Mu}}_T^0$, ${\mathrm{Mu}}_{\mathit{BC}}^0$, and ${\mathrm{Mu}}_{\mathit{BC}}^{+}$, respectively.) The inset in (b) shows the amplitude of the ${\mathrm{Mu}}_{\mathit{BC}}^{+}$ signal as a function of temperature.

Figure 7

Temperature dependence of the longitudinal field relaxation in an applied field of $0.1\mathrm{T}$ under illumination. The solid line represents the simulation using the model of Fig. 5 and the parameters in Table .