Origin of photoresponse in black phosphorus photo-transistors

TL;DR

This paper investigates the mechanisms behind photocurrent generation in multilayer black phosphorus transistors, revealing thermally driven processes dominate and significantly enhance photoresponse compared to graphene.

Contribution

It identifies thermoelectric and bolometric effects as the main photoresponse mechanisms in black phosphorus transistors, highlighting their spatial extent and impact on device performance.

Findings

Photocurrent is dominated by thermally driven thermoelectric and bolometric effects.

Photo-thermoelectric current can originate up to a micrometer from contacts.

Photo-responsivity exceeds that of graphene by two orders of magnitude.

Abstract

We study the origin of photocurrent generated in doped multilayer BP photo-transistors, and find that it is dominated by thermally driven thermoelectric and bolometric processes. The experimentally observed photocurrent polarities are consistent with photo-thermal processes. The photo-thermoelectric current can be generated up to a $\mu$m away from the contacts, indicating a long thermal decay length. With an applied source-drain bias, a photo-bolometric current is generated across the whole device, overwhelming the photo-thermoelectric contribution at a moderate bias. The photo-responsivity in the multilayer BP device is two orders of magnitude larger than that observed in graphene.