title: Hybrid light sensor based on ultrathin Si nanomembranes sensitized with CdSe/ZnS colloidal nanocrystal quantum dots.
abstract: We report the observation of a large enhancement of the wavelength-dependent photocurrent in ultrathin silicon nanomembranes (SiNM) decorated with colloidal CdSe/ZnS nanocrystal quantum dots (NQDs). Back-gated, field-effect transistor structures based on 75 nm-thick SiNMs are functionalized with self-assembled monolayers (SAMs) preventing surface oxidation and minimizing the surface defect densities. NQDs are drop cast on the active region of the device and the photocurrent is measured as a function of the excitation wavelength across the NQD absorption region. Photocurrent enhancement on the order of several hundred nA's is observed for NQD/SAM/SiNM devices compared to reference SAM/SiNM structures, with the device peak response closely correlated to the NQD absorption peak. We propose light-induced gating of the surface electrostatic potential and forward self-biasing of the FET channel as the two key mechanisms leading to the large photocurrent increase. Our findings open the possibility of employing silicon-nanocrystal hybrid structures for light sensing applications.
authors.affiliation: Department of Materials Science, The University of Texas at Dallas, Richardson, TX 75080, USA.
authors.forename: Weina
authors.initials: W
authors.lastname: Peng
authors.forename: Siddharth
authors.initials: S
authors.lastname: Sampat
authors.forename: Sara M
authors.initials: SM
authors.lastname: Rupich
authors.forename: Benoy
authors.initials: B
authors.lastname: Anand
authors.forename: Hue Minh
authors.initials: HM
authors.lastname: Nguyen
authors.forename: David
authors.initials: D
authors.lastname: Taylor
authors.forename: Brandon E
authors.initials: BE
authors.lastname: Beardon
authors.forename: Yuri N
authors.initials: YN
authors.lastname: Gartstein
authors.forename: Yves J
authors.initials: YJ
authors.lastname: Chabal
authors.forename: Anton V
authors.initials: AV
authors.lastname: Malko