Photosensitive device with electric shutter

A photosensitive device which can be configured to provide an electrical response when Illuminated by electromagnetic radiation incident on the device, comprising:

• at least one substantially horizontal, electrically conducting gate electrode which defines a first region on a substrate surface,
• a substantially horizontal layer of ambipolar two-dimensional material which overlies or underlies the at least one gate electrode across the first region,
• an insulating layer between the at least one gate electrode and the layer of ambipolar two-dimensional material across the first region,
• a substantially horizontal layer of photoactive semiconducting material which is in contact with and forms a junction with the layer of ambipolar two-dimensional material across the first region,
• a control unit configured to apply a gate voltage to the gate electrode and to measure the electrical response of the photosensitive device from the ambipolar two-dimensional material,
• wherein the photoactive semiconducting material and the ambipolar two-dimensional material are configured so that
• there is a non-screening gate voltage interval where an interface voltage at the junction between the photoactive semiconducting layer and the ambipolar two-dimensional material can be changed by applying to the gate electrode a gate voltage which falls within the non-screening gate voltage interval,
• the non-screening gate voltage interval comprises a flat-band gate voltage at which the interface voltage is zero, a depletion gate voltage range where the interface voltage is nonzero, and a charge-neutrality gate voltage at which the ambipolar two-dimensional material is at its charge-neutrality point,
• the depletion gate voltage range and the charge-neutrality gate voltage lie on the same side of the flat-band gate voltage on a gate voltage axis.