Temperature-dependent photoconductivity in two-dimensional MoS2 transistors

The photoconductivity in monolayer MoS2 back-gate transistors is studied as a function of temperature and pressure. The photocurrent increases linearly with the light intensity up to a maximum responsivity of & SIM;30 A/W in air. Time-resolved photocurrent measurements confirm that the photoresponse is dominated by the photogating effect. The device shows slow photoresponse with two-time constants that are attributed to the photobolometric effect and the desorption of adsorbates, respectively. An enhancement of the photocurrent is observed above room temperature and below the atmospheric pressure, that is, when the photoinduced desorption of adsorbates such as O2 and H2O molecules is facilitated. Indeed, the light-induced removal of adsorbates from the surface of MoS2 enhances the n-doping level and the current of the channel. Moreover, at lower pressures, the reverse mechanism of re-adsorption in dark conditions is suppressed and results in a persistent photocurrent. The study clarifies the photocurrent relaxation dynamics and unveils the key role of surface adsorbates in the optoelectronic properties of monolayer MoS2 and other similar 2D materials.

Automated summary

The photoconductivity of monolayer MoS2 back-gate transistors is investigated with respect to temperature and pressure. The photocurrent shows linear increase with light intensity, reaching a maximum responsivity of approximately 30 A/W in air. The photocurrent enhancement is observed at elevated temperatures and reduced pressures, which can be attributed to the desorption of adsorbates such as O2 and H2O molecules, leading to an increase in the n-doping level and channel current.