Near-Infrared Photodetectors Based on Hybrid Graphene-Colloidal PbSe Quantum Dots
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MRS Advances © 2020 Materials Research Society DOI: 10.1557/adv.2020.256
Near-Infrared Photodetectors Based on Hybrid Graphene-Colloidal PbSe Quantum Dots Wafaa Gebril1, Haider Salman2 and M. Omar Manasreh2 1)
Microelectronics and Photonics graduate program, University of Arkansas, Fayetteville, AR 72701, U.S.A.
2)
Department of Electrical Engineering, University of Arkansas, Fayetteville, AR 72701, U.S.A.
ABSTRACT
Photodetectors based on a hybrid structure of graphene sensitized with lead selenide (PbSe) colloidal quantum dots (QDs) effective in the near-infrared (NIR) region with high responsivity were investigated. Colloidal PbSe nanocrystals were synthesized via a hot injection method. The bandgap of the synthesized nanocrystals was determined to be 0.68 eV by measuring their optical absorbance spectrum. Photodetectors based on PbSe QDs were investigated to examine their functionality. These devices were characterized by measuring the current-voltage curves in the dark and light and the spectral response spectrum. A photodetector was fabricated using a multilayer mechanically exfoliated graphene on a Si/SiO2 substrate with a PbSe QDs layer on top. A responsivity and detectivity of 1265A/W and 3.4 *1010cm.Hz0.5/W respectively were calculated based on current-voltage measurements.
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INTRODUCTION Graphene is the first discovered two-dimensional layered material in 2004 [1], [2]. It is structured of a monolayer of carbon atoms arranged in a hexagonal lattice [1], [3]. Graphene has attracted great attention in the field of photodetection because of its unique properties compared to conventional semiconductors [4], [5]. The ultrahigh carrier mobilities make graphene a great candidate for high-speed photodetectors [2], [6], [7], also, its zero-band gap enables a wide range absorbance of the energy spectrum [4], [5]. However, graphene’s low light absorption around (2.3%) of the incident light limited its photodetection applications and directed research attention to overcome that [5], [8]. On the other side, colloidal quantum dots (QDs) semiconductors have shown very high light absorption besides their cost-effective growth, and tunable bandgaps over a wide range of wavelengths [9]. Their films nevertheless suffer from relatively poor carriers mobilities [10], [11]. Hybrid photodetectors of graphene and other nanostructured materials have been reported to improve the performance of graphene-based photodetectors [5], [12]– [15]. Infrared photodetectors of graphene decorated with colloidal lead sulfide (PbS) QDs were found to achieve high photoresponsivity [11]. Lead selenide (PbSe) colloidal QDs have emerged as an excellent absorber for optoelectronics [16]. Compared to PbS QDs, PbSe QDs have a much larger exciton Bohr radius that insures reaching stronger quantum c
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