Electric Field Dependent Photocurrent Decay Length in Single Lead Sulfide Nanowire Field Effect Transistors

We determined the minority carrier diffusion length to be $\sim $1 $\mu $m in single PbS nanowire field effect transistors by scanning photocurrent microscopy. PbS nanowires grown by the vapor-liquid-solid method were p-type with hole mobilities up to 49 cm$^{2}$/Vs. We measured a photo-response time faster than 14 $\mu $s with near-unity charge separation efficiency at the contacts. For the first time, we also observed a field dependent photocurrent decay length, indicating a drift dominant carrier transport at high bias.