Direct observation of significant hot carrier cooling suppression in a two-dimensional silicon phononic crystal

Finding hot carrier cooling suppression in new material structures is fundamentally important for developing promising technological applications. These phenomenona have not been reported for crystalline silicon phononic crystals. Herein, we experimentally design two-dimensional (2D) silicon samples consisting of airy hole arrays in a crystalline silicon matrix. For reference, the determined hot carrier cooling times were 0.45 ps and 0.37 ps, respectively, at probe wavelengths of 1080 nm and 1100 nm. Surprisingly, when the 2D structured silicon possessed the properties of a phononic crystal, significant suppression of hot carrier cooling was observed. In these cases, the observed hot carrier cooling times were as long as 15.9 ps and 10.7 ps at probe wavelengths of 1080 nm and 1100 nm, respectively, indicating prolongation by orders of magnitude. This remarkable enhancement was also observed with other probe wavelengths. The present work presents experimental evidence for hot carrier cooling suppression in 2D silicon phononic crystals and opens opportunities for promising applications.