Generation of photovoltage in graphene on a femtosecond time scale through efficient carrier heating

TL;DR

This study demonstrates that graphene can generate photovoltage in under 50 femtoseconds through efficient carrier heating, enabling ultrafast broadband photodetectors and precise measurement of femtosecond laser pulses.

Contribution

It provides the first measurement of photovoltage generation time in graphene at under 50 femtoseconds, highlighting ultrafast carrier heating as a key mechanism.

Findings

Photovoltage generation in graphene occurs faster than 50 femtoseconds.

Graphene exhibits constant spectral responsivity between 500 and 1500 nm.

Carrier heating in graphene is highly efficient and ultrafast.

Abstract

Graphene is a promising material for ultrafast and broadband photodetection. Earlier studies addressed the general operation of graphene-based photo-thermoelectric devices, and the switching speed, which is limited by the charge carrier cooling time, on the order of picoseconds. However, the generation of the photovoltage could occur at a much faster time scale, as it is associated with the carrier heating time. Here, we measure the photovoltage generation time and find it to be faster than 50 femtoseconds. As a proof-of-principle application of this ultrafast photodetector, we use graphene to directly measure, electrically, the pulse duration of a sub-50 femtosecond laser pulse. The observation that carrier heating is ultrafast suggests that energy from absorbed photons can be efficiently transferred to carrier heat. To study this, we examine the spectral response and find a constant spectral responsivity between 500 and 1500 nm. This is consistent with efficient electron heating. These results are promising for ultrafast femtosecond and broadband photodetector applications.