High-Speed, High-Sensitivity Optoelectronic Device with Bilayer Electron and Hole Charge Plasma

Analogous to a drop exciting a wave in a reservoir that is detected more rapidly than the drop's transport by current flow, charge plasma confined in a semiconductor can transfer energy, hence respond much faster than the electric field-induced carrier drift current. Here we construct an optoelectronic device in which charge reservoirs respond to excitation with a speed that is impossible to achieve by transport of charge. In response to short optical pulses, this device produces electrical pulses that are almost 2 orders of magnitude shorter than the same device without the charge reservoirs. In addition to speed, the sensitivity of this process allowed us to measure, at room temperature, as low as 11 000 photons. These micro plasma devices can have a range of application such as optical communication with a fraction of a microwatt power compared to the present tens of milliwatts, ultrasensitive light detection with cryogenic cooling, photovoltaic devices capable of harvesting dim light, THz radiation detectors, and charged particle detectors.