Abstract
While band gap and absorption coefficients are intrinsic properties of a material and determine its spectral range, response time is mainly controlled by the architecture of the device and electron/hole mobility. Further, 2D-layered materials such as transition metal dichalogenides (TMDCs) possess inherent and intriguing properties such as a layer-dependent band gap and are envisaged as alternative materials to replace conventional silicon (Si) and indium gallium arsenide (InGaAs) infrared photodetectors. The most researched 2D material is graphene with a response time between 50 and 100 ps and a responsivity of <10 mA/W across all wavelengths. Conventional Si photodiodes have a response time of about 50 ps with maximum responsivity of about 500 mA/W at 880 nm. Although the responsivity of TMDCs can reach beyond 104 A/W, response times fall short by 3–6 orders of magnitude compared to graphene, commercial Si, and InGaAs photodiodes. Slow response times limit their application in devices requiring high frequency. Here, we highlight some of the recent developments made with visible and near-infrared photodetectors based on two dimensional SnSe2 and MoS2 materials and their performance with the main emphasis on the role played by the mobility of the constituency semiconductors to response/recovery times associated with the hetero-structures.
Highlights
Photodetectors form vital components of many electrical and opto-electronic devices as they facilitate the conversion of light into an electric signal that can be processed by standard read-out electronics
We present the recent developments with a case study of two dimensional SnSe2 and MoS2 and their related hetero-structures as photodetectors with the main emphasis on the role of mobility, electrode spacing, and depletion width to response/recovery time
We have reviewed and analyzed the factors that influence the response time of photodetectors based on 2D SnSe2, MoS2 and their related hetero-structures in relation to their constituent carrier mobility, built-in electric field at the interface and compared the findings to graphene and conventional materials of Si and indium gallium arsenide (InGaAs)
Summary
Photodetectors form vital components of many electrical and opto-electronic devices as they facilitate the conversion of light into an electric signal that can be processed by standard read-out electronics. Despite the enormous strides made by researchers in the development of layered materials for opto-electronic nano-device applications with reported responsivity of >104 A/W [1,52,53,54], the response time does not compete with those of Micromachines 2020, 11, 750 the conventional photodetectors fabricated from graphene, Si, and InGaAs photodetectors. We present the recent developments with a case study of two dimensional SnSe2 and MoS2 and their related hetero-structures as photodetectors with the main emphasis on the role of mobility, electrode spacing, and depletion width to response/recovery time. We conclude by suggesting methods of designing fast response time photodetector devices taking into consideration the overall performance of the device
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