Selective Optical Switching of Interface-Coupled Relaxation Dynamics in Carbon Nanotube-Si Heterojunctions

By properly tuning the photon energy of a femtosecond laser pump, we disentangle, in carbon nanotube–Si (CNT/Si) heterojunctions, the fast relaxation dynamics occurring in CNT from the slow repopulation dynamics due to hole charge transfer at the junction. In this way we are able to track the transfer of the photogenerated holes from the Si depletion layer to the CNT layer, under the action of the built-in heterojunction potential. This also clarifies that CNT play an active role in the junction and do not act only as channels for charge collection and transport.