Solution-processed MoS₂ quantum dot/GaAs vertical heterostructure based self-powered photodetectors with superior detectivity

Abstract

The characteristics of a novel 0D/3D heterojunction photodetector fabricated using solution-processed colloidal MoS2 quantum dots (QDs) on GaAs is presented. MoS2 QDs with a dimension of ∼2 nm, synthesized by a standard sono-chemical exfoliation process with 2D layers have been used for the purpose. The microscopic and spectroscopic studies confirmed the formation of semiconducting (2H phase) MoS2 QDs. The photodetectors were fabricated using n-GaAs substrates with two different doping concentrations resulting in n–n heterojunctions between n-type 0D MoS2 QDs and bulk n-GaAs. The devices fabricated using GaAs with a higher doping concentration, showed an increase in the reverse current of the order of ∼102 upon illumination, while the same with a lower doping concentration showed an increase of the order of ∼103. All the heterojunction photodetector devices show a broadband operation over the visible wavelength range of 400–950 nm, with a peak responsivity of the devices being observed at 500 nm. The peak responsivity and detectivity are found to be ∼400 mA W−1 and ∼4 × 1012 Jones, respectively, even without any external applied bias, which are useful for self-powered photodetection. The results indicate that colloidal MoS2/GaAs based hybrid heterostructures provide a platform for fabricating broadband photodetectors by using highly absorbing MoS2 QDs, which may show the pathway towards next-generation optoelectronic devices with superior detection properties.

A review of molybdenum disulfide (MoS2) based photodetectors: from ultra-broadband, self-powered to flexible devices

“…The 0D/ 3D MoS 2 QDs/GaAs heterojunction photodetectors were fabricated using n-type GaAs substrates with varied doping concentrations which resulted in n-n heterojunctions between n-type MoS 2 QDs and bulk n-type GaAs. 431 The MoS 2 /GaAs heterojunction photodetectors operated between 400-950 nm and showed highest photoresponsivity of 400 mA W À1 and detectivity of 4 Â 10 12 Jones at 500 nm at zero bias voltage, which is a self-powered photodetection. Shi et al 432 integrated 0D InP@ZnS core-shell QDs with 2D bilayer MoS 2 to develop selfpowered hybrid phototransistors by using interdigitated Pt electrodes which acted as light collectors as well as plasmonic resonators.…”

Self-assembly of Au/MoS2 quantum dots core-satellite hybrid as efficient electrocatalyst for hydrogen production

“…MoS 2 quantum dots (QDs) with ultra-small sizes and many more active sites are beneficial for HER. Based on this, many methods including hydrothermal method [8][9][10], microwaveassisted synthesis [11], sono-chemical exfoliation [12] are developed to prepare MoS 2 QDs. However, MoS 2 QDs with ultra-small sizes are easy to aggregate and has poor conductivity, which seriously affects their electrocatalytic performance toward HER.…”

Photoluminescence and charge transfer in the prototypical 2D/3D semiconductor heterostructure MoS$_2$/GaAs

“…Layered transition metal dichalcogenides (TMDs) are among the most studied two-dimensional (2D) materials in the last decade. Their atomically-thin structure and physical properties have attracted attention not only because of their interesting fundamental physics but also due to their potential applications for ultra-thin technological devices [1][2][3][4][5][6][7][8] . Similar to graphene, these materials can be mechanically exfoliated to obtain single layers.…”

“…One interesting substrate for these monolayer materials is GaAs, a prototypical semiconductor which has been extensively studied and employed for electronics and optoelectronics applications that take advantage of its direct gap (1.42 eV at room temperature) and relatively high electron mobility (up to 8000 cm 2 V −1 s −1 at room temperature) 16 . The combination of the optical and electronic properties of TMDs and GaAs as a substrate has already shown promising results for implementation of solar cells 7 , with a power conversion efficiency of up to 9.03%, and photodetectors 3,5,6,17 , with a detectivity of up to 1.9 × 10 14 Jones. The success of these proof-of-concept studies urges the need to investigate in detail the properties of MoS 2 /GaAs heterojunctions, in order to further improve device quality 18 .…”

“…Most of the work done on MoS 2 /GaAs junctions so far employ n-doped GaAs 3,[5][6][7]18 . Nearly all of these works propose a type II band alignment for MoS 2 /n-GaAs.…”