Publication: Fast response photogating in monolayer MoS_2 phototransistors
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Publication Date
2021
Authors
Vaquero, Daniel
Clericò, Vito
Salvador Sánchez, Juan
Chico Gómez, Leonor
Meziani, Yahya M
Díez, Enrique
Quereda, Jorge
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RSC
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Abstract
Two-dimensional transition metal dichalcogenide (TMD) phototransistors have been the object of intensive research during the last years due to their potential for photodetection. Photoresponse in these devices is typically caused by a combination of two physical mechanisms: the photoconductive effect (PCE) and photogating effect (PGE). In earlier literature for monolayer (1L) MoS_2 phototransistors, PGE is generally attributed to charge trapping by polar molecules adsorbed to the semiconductor channel, giving rise to a very slow photoresponse. Thus, the photoresponse of 1L-MoS_2 phototransistors at high-frequency light modulation is assigned to PCE alone. Here we investigate the photoresponse of a fully h-BN encapsulated monolayer (1L) MoS_2 phototransistor. In contrast with previous understanding, we identify a rapidly-responding PGE mechanism that becomes the dominant contribution to photoresponse under high-frequency light modulation. Using a Hornbeck-Haynes model for the photocarrier dynamics, we fit the illumination power dependence of this PGE and estimate the energy level of the involved traps. The resulting energies are compatible with shallow traps in MoS2 caused by the presence of sulfur vacancies.
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©2021 RSC
We acknowledge financial support from the Agencia Estatal de Investigacion of Spain (Grants PID2019-106820RB, RTI2018-097180-B-100, and PGC2018-097018-B-I00) and the Junta de Castilla y Leon (Grants SA256P18 and SA121P20), including funding by ERDF/FEDER. J. Q. acknowledges financial support from MICINN (Spain) through the programme Juan de la Cierva-Incorporacion. We are also thankful to Mercedes Velazquez for her help with the photoluminescence and Raman characterization and to Adrian Martin-Ramos for his assistance on the development of the photocurrent measurement setup.