| Summary: | Erbium-doped silicon (Er-doped Si) materials hold great potential for advancing Si photonic devices. For Er-doped Si, the efficiency of energy transfer (<i>η<sub>ET</sub></i>) from Si to Er<sup>3+</sup> is crucial. In order to achieve high <i>η<sub>ET</sub></i>, we used nonthermal plasma to synthesize Si quantum dots (QDs) hyperdoped with Er at the concentration of ~1% (i.e., ~5 × 10<sup>20</sup> cm<sup>−3</sup>). The QD surface was subsequently modified by hydrosilylation using 1-dodecene. The Er-hyperdoped Si QDs emitted near-infrared (NIR) light at wavelengths of ~830 and ~1540 nm. An ultrahigh <i>η<sub>ET</sub></i> (~93%) was obtained owing to the effective energy transfer from Si QDs to Er<sup>3+</sup>, which led to the weakening of the NIR emission at ~830 nm and the enhancement of the NIR emission at ~1540 nm. The coupling constant (<i>γ</i>) between Si QDs and Er<sup>3+</sup> was comparable to or greater than 1.8 × 10<sup>−12</sup> cm<sup>3</sup>·s<sup>−1</sup>. The temperature-dependent photoluminescence and excitation rate of Er-hyperdoped Si QDs indicate that strong coupling between Si QDs and Er<sup>3+</sup> allows Er<sup>3+</sup> to be efficiently excited.
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