title: Hybrid graphene-quantum dot phototransistors with ultrahigh gain.
abstract: Graphene is an attractive material for optoelectronics and photodetection applications 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 ∼10(-2) A W(-1). Here, we demonstrate a gain of ∼10(8) electrons per photon and a responsivity of ∼10(7) A W(-1) 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 quantum-dot layer. The device, with a specific detectivity of 7 × 10(13) Jones, benefits from gate-tunable sensitivity and speed, spectral selectivity from the short-wavelength infrared to the visible, and compatibility with current circuit technologies.
authors.affiliation: ICFO-Institut de Ciencies Fotoniques, Mediterranean Technology Park, 08860 Castelldefels, Barcelona, Spain. gerasimos.konstantatos@icfo.es
authors.forename: Gerasimos
authors.initials: G
authors.lastname: Konstantatos
authors.forename: Michela
authors.initials: M
authors.lastname: Badioli
authors.forename: Louis
authors.initials: L
authors.lastname: Gaudreau
authors.forename: Johann
authors.initials: J
authors.lastname: Osmond
authors.forename: Maria
authors.initials: M
authors.lastname: Bernechea
authors.forename: F Pelayo
authors.initials: FP
authors.lastname: Garcia de Arquer
authors.forename: Fabio
authors.initials: F
authors.lastname: Gatti
authors.forename: Frank H L
authors.initials: FH
authors.lastname: Koppens
mesh_terms: D004583:Electrons; D006108:Graphite / Q000737:chemistry*; D017785:Photons; D045663:Quantum Dots
chemical_list: D006108:Graphite