Abstract:
Interdigital heterobarrier metal–semiconductor–metal (MSM) structures are proposed as ultrafast photodetectors of visible radiation. Vertical photocarrier drift in MSM diode structures provides the simplest way of reducing the active region of a detector to a submicron size and of considerably shortening the response time without a significant loss of the radiation coupling efficiency. External electrooptic sampling was used to determine the subpicosecond (half-amplitude duration 0.6 ps) electrical response of a detector built into a coplanar microwave transmission line. Under a bias voltage of 1 V and for an optical excitation energy of 10 pJ per pulse the change in the photodiode voltage amounted to 40% of the bias voltage, which makes these diode structures sufficiently efficient and extremely fast detectors of optical radiation.