Optoelectronics of Multijunction Heterostructures of Transition Metal Dichalcogenides.
basic_science · Level V
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- Record sourced from PubMed, PMID 32083883.
- Also identified by DOI 10.1021/acs.nanolett.9b05212.
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Abstract
Among p-n junction devices with multilayered heterostructures with WSe<sub>2</sub> and MoSe<sub>2</sub>, a device with the MoSe<sub>2</sub>-WSe<sub>2</sub>-MoSe<sub>2</sub> (NPN) structure showed a remarkably high photoresponse, which was 1000 times higher than the MoSe<sub>2</sub>-WSe<sub>2</sub> (NP) structure. The ideality factor of the NPN structure was estimated to be ∼1, lower than that of the NP structure. It is claimed that the NPN structure formed a thinner depletion region than that of the NP structure because of the difference of carrier concentrations of MoSe<sub>2</sub> and WSe<sub>2</sub>. Hence, the built-in electric field was weaker, and the motion of the photocarriers was facilitated. These behaviors were confirmed experimentally from a photocurrent mapping analysis and Kelvin probe force microscopy. The work function depended on the wavelength of the illuminator, and quasi-Fermi level was estimated. The surface photovoltage on the MoSe<sub>2</sub> region was higher than that on WSe<sub>2</sub> because the lower bandgap of MoSe<sub>2</sub> induces more electron-hole pair generation.