Hybrid graphene–quantum dot phototransistors with ultrahigh gain

Graphene is an attractive material for optoelectronics1 and
photodetection applications2–6 because it offers a broad spectral
bandwidth and fast response times. However, weak light
absorption and the absence of a gain mechanism that can generate
multiple charge carriers from one incident photon have
limited the responsivity of graphene-based photodetectors to
∼1022 AW21. Here, this group demonstrate a gain of ∼108 electrons
per photon and a responsivity of∼107 AW21 in a hybrid photodetector
that consists of monolayer or bilayer graphene covered
with a thin film of colloidal quantum dots. Strong and tunable
light absorption in the quantum-dot layer creates electric
charges that are transferred to the graphene, where they
recirculate many times due to the high charge mobility of
graphene and long trapped-charge lifetimes in the quantumdot
layer. The device, with a specific detectivity of 731013
Jones, benefits from gate-tunable sensitivity and speed,
spectral selectivity from the short-wavelength infrared to the
visible, and compatibility with current circuit technologies.

more information: Gerasimos Konstantatos et al.  nature nanotechnology, DOI: 10.1038/NNANO.2012.60.