Noise-Suppressed High-Performance WSe2 Phototransistors Enabled by Optically Programmed Remote Contact Doping

Improving the sensitivity of two-dimensional semiconductor phototransistors requires increasing photocurrent while minimizing noise. However, conventional doping approaches often place charged dopants in or near atomically thin channels, introducing charge scattering, trap states, and noise that limit the signal-to-noise ratio. Here, we address this signal-noise trade-off in WSe2 phototransistors by using photoinduced charge trapping in patterned hBN to implement contact-selective remote doping. Under illumination with a negative gate voltage, trapped holes in hBN electrostatically n-dope WSe2 while remaining spatially separated from the transport channel. Patterned hBN confines the doping to selected regions, allowing the WSe2 near the metal electrodes to be remotely doped while leaving the channel undoped. This remote contact doping simultaneously suppressed the device noise by approximately 100-fold, reduced the effective density of electrically active traps by approximately 100-fold, and lowered the activation energy by 30-80 meV, indicating improved contact quality and more efficient carrier injection. As a result, the contact-doped phototransistors simultaneously exhibit enhanced responsivity of 99.7 A/W and a specific detectivity of 2.26 × 1011 Jones. These results establish optically programmed remote contact doping as a phototransistor-compatible contact-engineering approach to overcome the signal-noise trade-off in 2D phototransistors.