Specific features of the nonradiative relaxation of Er$^{3+}$ ions in epitaxial Si structures

The specific features of the nonradiative relaxation of Er$^{3+}$ ions in Si:Er layers grown by sublimation molecular-beam epitaxy (SMBE) are studied. In Si:Er/Si diode structures containing precipitation-type emitting centers, a resonance photoresponse at the wavelength $\lambda\approx$ 1.5 $\mu$m is observed, which is indicative of the nonradiative relaxation of Er$^{3+}$ ions via the energy back-transfer mechanism. Saturation of the erbium-related photocurrent is for the first time observed at high temperatures. This allows estimation of the concentration of Er centers that undergo relaxation via the above-mentioned back-transfer mechanism ($N_0\approx$ 5 $\cdot$ 10$^{16}$ cm$^{-3}$). In terms of order of magnitude, the estimated concentration $N_0$ corresponds to the concentration of optically active Er ions upon excitation of the Si:Er layers by means of the recombination mechanism. The features of the nonradiative relaxation of Er$^{3+}$ ions in Si:Er/Si structures with different types of emitting centers are analyzed.