Terahertz photoconductivity and photocarrier dynamics in graphene–mesoporous silicon nanocomposites

We investigate the photocarrier and charge transport dynamics in graphene-mesoporous silicon nanocomposites using optical pump-terahertz probe technique. These nanocomposites were made from a free-standing mesoporous silicon membrane covered with graphene-like coating. The temporal decay of the differential transmission data reproduced using a bi-exponential function show decay times of 74 ps and 730 ps in the uncoated mesoporous film. These decay times were significantly reduced to 5 ps and 25 ps in graphene-mesoporous silicon nanocomposites, respectively. A capture/recombination model was also proposed to describe the decay dynamics in these nanomaterials. The complex frequency-dependent photoconductivity data were well reproduced with a modified Drude-Smith model that considers diffusive restoring currents [1]. Our results show that the effective mobility is preserved in all the nanocomposites despite the increase in carrier confinement with graphene deposition temperature. The relatively high mobility and low photocarrier recombination time in these nanocomposites make them good candidates for the fabrication of pulsed terahertz devices.
.[1] T. L. Cocker, D. Baillie,M. Buruma, L. V. Titova, R. D. Sydora, F. Marsiglio, and F. A. Hegmann, Phys. Rev. B 96, 205439 (2017)