Elucidating the photoresponse of ultrathin MoS₂ field-effect transistors by scanning photocurrent microscopy

The mechanisms underlying the intrinsic photoresponse of few-layer (FL) molybdenum disulfide (MoS₂) field-effect transistors are investigated via scanning photocurrent microscopy. We attribute the locally enhanced photocurrent to band-bending-assisted separation of photoexcited carriers at the MoS₂/Au interface. The wavelength-dependent photocurrents of FL MoS₂ transistors qualitatively follow the optical absorption spectra of MoS₂, providing direct evidence of interband photoexcitation. Time and spectrally resolved photocurrent measurements at varying external electric fields and carrier concentrations establish that drift-diffusion currents dominate photothermoelectric currents in devices under bias.